Anesthesia Quiz One to Midterm

What is EMLA cream (Euthetic Mixture of Local Anesthetics)?

2.5% lidocaine + 2.5% prilocaine, used for IV cannulation, blood sampling. Must be applied under occlusive bandage for 45-60 min to obtain skin desensitization. Up to 2 hour duration

Where is halothane metabolizeD?

20 - 25% in the liver

What is the onset of action for proximal paravertebral blocks?

20 minutes

How is lipid rescue done?

20% lipid emulsion component of parenteral nutrition. Used successfully in cardiac arrests due bupivacaine intoxication. 1 ml/kg every 3-5 min (max 3 ml / kg) followed by 0.25 ml / kg /min

How can minute volume be estimated?

200 ml / kg / min (10 ml / kg * 20 breaths / min)

What is medical air?

21% O2, 79% N2 (purified and dehumidified)

What is the standard size of a common gas outlet?

22 mm

At what dose is bupivacaine cardiotoxic?

4 - 5 mg / kg. Do not inject more than 3 mg / kg in dogs and 2 mg / kg in cats

What is the duration of action of bupivacaine?

4 - 6 hours

At what dose is ropivacaine cardiotoxic?

5 mg / kg. Do not inject more than 3 mg / kg in dogs and cats

What is Etonox?

50% O2, 50% N2O

What is the intracellular pH?

6.9

What does each E-cylinder contain?

680 L of oxygen when filled to 145 bar

What is the extracellular pH?

7.4

At what dose is lidocaine cardiotoxic?

8 - 16 mg / kg. Do not inject more than 6 mg / kg in dogs and 4 mg / kg in cats

What is the minimum size for using a rebreathing system?

>5 kg (5 - 10 kg: pediatric system)

What is the Mapleson classification of breathing systems?

A (Lack, Magill), D (Bain), E (Ayre's T-Piece), and F (Jackson-Rees T-Piece)

What is CO2 absorbent / soda lime?

A base that neutralizes an acid. The reaction produces heat, change in pH (color change), and water

What is nociceptive pain characterized by?

A high stimulus threshold. Intensity and duration are proportional to the stimulus

What is the critical length for local anesthetics?

A minimum of 3 - 5 nodes of Ranvier need to be blocked

What is neuroplasticity?

Ability of the nervous system to change or adapt in response to internal and external stimuli (multiple minor sensory, single major sensory events might change stimulus response)

What does preemptive analgesia do?

Abolition of afferent nociception, significant anesthetic and analgesics sparing effect

What is absent in non-rebreathing systems?

Absence of unidirectional valves and CO2 absorber

What is necessary for perception of acute pain?

Activation of both Adelta and C fiber

How is pain classified according to time?

Acute or chronic

How can local anesthetics cause neurotoxicity?

Additives / preservatives

How is visceral pain transmitted?

Adelta and C fibers (ratio 1:10). Organs, tendons, generalized. Respond to stretch, ischemia, and dilation

How is somatic pain transmitted?

Adelta and C fibers (ratio 1:2). Bones, muscles, localized. Responds to mechanical, thermal, and chemical stimuli

What is spinal anesthesia?

Administration of local anesthetic in the subarachnoid space

What is epidural anesthesia?

Administration of local anesthetic inside the epidural space

What is the differential blockade affected by?

Affected by fiber diameter, length exposed to drug, myelination, frequency of stimulation, drug concentration, drug properties

What do inhalant anesthetics do to cardiac output?

All decrease CO, decrease contractility. HR effect varies depending on agent and species

What do inhalant anesthetics do to arterial blood pressure?

All decrease blood pressure, mostly because of decrease in SV and decrease in SVR. N2O produces either no change or modest increase in BP

What occurs in the non-rebreathing system (semi-open / open)?

All previously exhaled gases are removed from the breathing system

What can local anesthetic toxicity cause?

Allergic reactions and methemoglobinemia

What does a vaporizer do?

Allows controlled evaporation of a liquid anesthetic, dilution of the anesthetic vapor in a carrier gas, delivery of a range of concentration of vapor. Specific for each agent

What is true about metabolism of desflurane?

Almost no metabolism, but more likely to produce CO

What is tidal volume?

Amount of air inhaled and exhaled during a normal breathing cycle

What is minute-volume?

Amount of air moved into and out of lungs per minute

What is methemoglobin?

An oxidized form of hemoglobin that has almost no affinity for oxygen

What is pain?

An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage

What is N2O used for?

Analgesia. Never given without oxygen

What does early expiration consist of?

Anatomical dead space gases

What is an E cylinder used for?

Anesthesia machine

What does the descending inhibitory nerve system consist of?

Antinociceptive (inhibitory) and pronociceptive (facilitatory)

What is topical anesthesia?

Application of local anesthesia in mucous membranes (anesthetics cannot cross the epidermis)

What determines lipid solubility of local anesthetics?

Aromatic end

Where is a supraorbital nerve block palpated?

Around 5 - 7 cm dorsal to the medial canthus and in the center of an imaginary triangle formed by grasping the supraorbital process of the frontal bone with the thumb and middle finger and sliding medially

What factors do not change MAC?

Arterial blood pressure > 50 mmHg. Atropine, glycopirrolate. Duration of anesthesia. Gender. Hyperkalemia, hypokalemia. Metabolic acid-base change. PaO2 >40 mmHg. PaCO2 15-90 mmHg

What are the characteristics of protein binding of local anesthetics?

Associated with duration of action (only unbound drug is active)

Where is a distal paravertebral block done?

At the distal end of the transverse processes

What does a facial nerve block block?

Auriculopalpebral nerve, supraorbital frontal nerve, and dorsal / ventral buccal nerves

What should be avoided with peripheral nerve blocks?

Avoid intraneural injections

What should be avoided with epidurals?

Avoid loss of hind limb motor function. Careful with cranial spread of local anesthetics

What optional accessories are there for rebreathing circle systems?

Bag / ventilator switch, Positive End Expiratory Pressure (PEEP) valve, respiratory gas sensor or connector, airway pressure sensor or connector, filter / heat moisture exchanger, heater / humidifier, and spirometer

What do vaporizers compensate for?

Barometric pressure. No need to adjust the dial

What do you need to be aware of with infiltration anesthesia?

Be aware of accidental intravascular injection

What are the determining factors of perception memory?

Behavior pattern, environmental, expectation of pain, and intensity of painful events

How does lipid rescue work?

Believed to withdraw the LA from tissues and sequester them in the vascular compartment

How is pain classified according to etiology?

Benign / adaptive (hand in fire), malignancy (neoplasias), post-surgical), degenerative (osteoarthritis)

What are the endogenous opioids?

Beta endorphins, dynorphins, and enkephalins

What does prevention of stress response do?

Better immune system activity, reduction of opioid usage

What is immobility with inhalational anesthetics the result of?

Binding to proteins. Result of multiple cell receptors and ion target modulations. GABAa, glycine, K+ channels, Ca2+, Na+ channels, and NMDA

What does the activated charcoal canister do?

Binds chlorinated and fluorinated anesthetics. Does not bind N2O or CO2. Must be weighed regularly to check if exhausted. Position so that holes on the bottom are not occluded

What are the techniques of peripheral nerve blocks?

Blind, nerve stimulator (only if motor nerve), and ultrasound

What is tonic / constant block?

Blockade obtained on unstimulated nerves

What does it mean if blood-gas coefficient is high?

Blood acts as a sink so changes are slower

What determines solubility of inhalant anesthetics?

Blood-gas partition coefficient and oil-gas partition coefficient

What color are nitrous oxide and Entonox cylinders?

Blue

Why are Tuohy needles better for epidural anesthesia than spinal needles?

Blunt tip, better pop feelin, designed to protect dura mater, less risk of dura and nerve damage, facilitates introduction of epidural catheter in a cranial direction

What is CO2 used for?

Body cavity insufflation

How is tidal volume calculated?

Body weight (kg) * 10 - 15 ml / kg

What does boiling point do with altitude?

Boiling Point reduces with altitude

Why does desflurane need a special vaporizer?

Boiling point is close to room temperature

Where are inverted L blocks done?

Bordering caudal aspect of 13th rib, ventral aspect of transverse processes of lumbar vertebrae. Very simple to perform

What is a breathing system?

Both the apparatus and the mode of operation by which the medical gases and inhalational agents are delivered to the patient

What cardiovascular signs are seen with local anesthetic toxicity?

Bradycardia, arrhythmias, hypotension

What is rebreathing?

Breathing in air that was just expelled from the lungs

What does it mean since the reservoir bag is compliant?

Buffers pressure rise. Generally located near APL valve

What is the longest-acting local anesthetic?

Bupivacaine

What local anesthetics are cardiotoxic at high doses?

Bupivacaine and ropivacaine

What is ropivacaine similar to in terms of onset and duration of action?

Bupivacaine. Higher safety profile

When are lumbosacral epidurals used?

C-sections, anesthesia abdomen, hind limb, with opioids also for thorax and thoracic limb

What does a brachial plexus block affect?

C6-T1 spinal nerves from distal humerus. Suprascapular, subscapular, musculocutaneous, radial, axillary, median and ulnar nerves. Nerve stimulator, ultrasound guided

What is the order of presentation of local anesthetic toxicity?

CNS signs (might not be observed in anesthetized patients), respiratory system depression, and cardiovascular system depression. Valid for most amide types of local anesthetics, but bupivacaine will cause cardiovascular depression first

How do you calculate FGF for a non-rebreathing system?

Calculate tidal volume, calculate minute volume, use the circuit factor. FGF = minute volume * circuit factor

What are the characteristics of the flowmeter?

Calibrated for each gas. Tapered tube(s) with graduations to mark flow. Rotating bobbin. Flow control valve (needle valve, close gently)

What adverse effects does nitrous oxide have?

Can cause malignant hyperthermia, teratogenic, hematologic dysfunction, negative environmental effects, and flammable

What happens when isoflurane is used with dry soda lime?

Can lead to CO formation

When can N2O diffusion hypoxia occur?

Can occur following termination of N2O if patient is allowed to breath room air. Prevented by having patient breathe 100% oxygen for a minimum of 3 - 5 minutes

What happens if soda lime is not exchanged in time when using desflurane, enflurane, and isoflurane?

Carbon monoxide (more problematic with baralyme (withdrawn from the market))

What are some common characteristics of halogenates?

Cardiovascular depression, cardiac output reduction, direct myocardial depression, peripheral vasodilation, impairment of tissues' autoregulation mechanisms, and CNS depression (reduction of sympathetic tone). Mostly dose-dependent depression of any body system

What are the essential parts of an anesthesia machine?

Carrier gas source (hanger yoke / pipeline), pressure regulator, flowmeter, oxygen flush valve, vaporizer mounting bracket, and common gas outlet

What are the indications for retrobulbar and peribulbar nerve blocks?

Cataract (phacoemulsification), keratectomy, globe wounds / foreign body, and enucleation)

How is a Bier block done?

Catheterization of the vein, exsanguination and placement of a tourniquet, injection of lidocaine (no epinephrine - ischemia)

What species have laryngospasm?

Cats, pigs, camels, and rabbits

Where are epidurals done?

Caudal epidural (sacro-coccygeal or 1st intercoccygeal junction)

What does ropivacaine cause?

Causes lower motor blockade at clinical doses (different association with Na, K, Ca channels)

What happens when inhalant anesthetics cause a >1 MAC loss of cerebrovascular autoregulation?

Cerebral vasodilation, increase CBF and ICP, decreased CPP, uncoupling perfusion and CMRO2. CO2 further affects autoregulation

What should be done before using a vaporizer?

Check level of liquid anesthetic, check that the filling port is closed, check that the dial turns easily, and check if properly mounted

How can local anesthetics be anti-arrythmics?

Class Ib agents (membrane stabilizing agents) - interfere with Na channels and affect phase 0

What should be done in preparation for epidurals?

Clinical exam, sedation with alpha 2 adrenergic agonists, clipping, aseptic preparation, SQ injection of 2 - 3 mL lidocaine 2% or mepivacaine 2% (25 gauge needle)

What are examples of single-tubing systems?

Coaxial systems and parallel systems

What are the ester local anesthetics?

Cocaine, procaine, tetracaine, and benzocaine

What does exhausted soda lime appear like?

Color change (indicator dye - color depends on the brand). Consistency is hard granules

What safety features are in place to avoid accidental delivery of the wrong carrier gas?

Color coding and labeling, PISS, non-interchangeable screw thread system, and diameter index safety system and quick connect (pipeline) system

What are the characteristics of xenon?

Colorless, odorless noble gas. "Miracle inhalant" - stable, analgesic, safe for malignant hyperthermia, no metabolites, but very expensive. Only inhalant known to have gender dependent MAC (less in females). Will also move to closed gas spaces

What temperature do precision vaporizers have?

Compensated or not (bimetallic strip, expansion / aneroid bellows, supplied heat, rods, high specific heat capacity and metal construction - heat sink)

What happens if soda lime is not exchanged in time when using sevoflurane?

Compound A (nephrotoxic), high temperature, dry absorbents, high concentrations of sevoflurane

Where are nociceptive specific second order neurons found?

Concentrated on lamina I

What factors decrease MAC?

Concurrent anesthetics / analgesics / sedatives. N2O. Geriatric. Neonates. Hypothermia. Pregnancy. Severe hypoxemia (PaO2<40mmHg). Severe hypercapnia (PaCO2>90mmHg). Hypotension. Hyponatremia

What are the advantages of rebreathing systems?

Conservation of heat and moisture, less carrier gas waste, less anesthetic gas waste, gas flow can be changed, and less pollution by anesthetics

What is true since visceral pain doesn't have its own pathway?

Converges into somatic pathway and synapse with cells that also receive afferent from other nerves

What are the two points of injection per horn for dehorning / disbudding?

Cornual branch of the zygomaticotemporal nerve and cornual branches of infratrochlear nerve at horn base

What should be blocked for dehorning / debudding?

Cornual nerve (branch of lacrimal)

Why should the pop-off valve always be open?

Creates pressure in the system and can cause barotrauma to lungs and damage to cardiovascular system

What are the characteristics of PVC ET tubes?

Curved and semi-rigid (softened with body temperature), uncuffed models, high volume - low pressure

What is an H / J cylinder used for?

Cylinder bank

What noxious stimuli can lead to superficial pain?

Damage, threat of damage

What are the pharmacodynamics of inhalant anesthesias?

Decrease CMRO2, eq marked increase in ICP depending on recumbency but regional CBF maintained, and decreased blood flow to TL spine (may predispose to myelomalacia)

What can cause decreased removal from alveoli?

Decreased blood solubility of the anesthetic, decreased cardiac output

What do induction chambers do?

Deliver inhalant agent until animal loses consciousness. Continue anesthetic with mask / ETT. Has disadvantages

What are the essential functions of an anesthesia machine?

Deliver inhalational anesthetics safely and accurately, deliver oxygen, allow elimination of expired CO2 from breathing system/ prevent reinhalation, provide means for controlled ventilation

What does the O2 / flush button do?

Delivers oxygen at high flow (35 - 75 L / min). Bypasses vaporizer. Used to dump inhalant agents from the system or to do a leak test

What do enkephalins bind to?

Delta receptors

What do we know about inhalant anesthetics?

Depress the excitatory neurotransmission at cholinergic and glutamate receptors. Enhance inhibitory neurotransmission (GABAa receptors)

What are the two approaches for an auriculopalpebral block?

Depression caudal to the mandible, most dorsal point of zygomatic arch

What is seen during reduction of MV / hypoventilation?

Depression of ventilatory response to CO2, decreased ventilatory response to hypoxia / hypoxemia, depression of pulmonary hypoxic vasoconstriction, relaxation of respiratory muscles, bronchodilation (increase in dead space), airway irritation (desflurane > isoflurane > sevoflurane)

What is use-dependent / phasic blocks?

Depth of block increases with repetitive membrane depolarization

What does the oil-gas partition coefficient describe and correlate with?

Describes the ratio of a concentration of anesthetic in oil and gas phases at equilibrium. Correlates with the potency of an anesthetic drug (higher the solubility more potent the anesthetic)

What does a maxillary nerve block do?

Desensitization of the maxilla, premaxilla, paranasal sinuses, and sinus cavity

What does a transversus abdominus plane (TAP) block do?

Desensitizes T16 - T18 / L2

What does a distal paravertebral block do?

Desensitizes dorsal and ventral rami of the spinal nerves T13 - L2 +/- L3. No scoliosis and easier compared to proximal paravertebral. Less reliable effect and larger doses required

What does a proximal paravertebral block do?

Desensitizes the dorsal and ventral nerve roots T13 - L2 +/- L3. Causes scoliosis of the spine (muscle relaxation) and warming of skin

What does a supraorbital nerve block do?

Desensitizes the forehead, including the middle 2/3 of the upper eyelid. Facilitates minor surgical procedures of the nasal portion of the upper eyelid

What does a lacrimal nerve block do?

Desensitizes the lateral canthus, lateral aspect of the upper eyelid, lacrimal gland, local connective tissue, and temporal angle of the orbit

What does a mental nerve block do?

Desensitizes the lower lip, incisive and canine teeth

What does a zygomatic nerve block do?

Desensitizes the lower two thirds of the lower eyelid, skin, and connective tissue

What does the Peterson eye block do?

Desensitizes the nerves (optic, oculomotor, trochlear, abducent, and trigeminal nerves) responsible for sensory and motor function of all structures of the eye except the eyelid, that needs the addition of the auriculopalpebral block

What does an infraorbital block do?

Desensitizes the upper lip, the nostril, the roof of the nasal cavity, and the skin of the face rostroventral to the foramen, ipsilaterally

What are the characteristics of pKaof local anesthetics?

Determines speed of onset. High pKa is slow onset. Effect of the environmental pH

What occurs during central sensitization?

Development of or increases in spontaneous activity, reduction in threshold for activation by peripheral stimuli, and enlargement of their receptive fields (conversion of nociceptive-specific neurons to wide dynamic neurons that now respond to both innocuous and noxious stimuli)

What is true about spinal needles?

Different types. More blunt than hypodermic but less than Tuohy

What are the dual hemodynamic effects of nitrous oxide?

Direct myocardial depression and vasodilatory activity. Indirect CV stimulation neuraly mediated

What are the characteristics of laryngoscopes?

Direct visualization of the larynx and good illumination. Several models available. Patient positioning. Blade selection

How is ET tube placement verified?

Direct visualization, condensation of ET tube in each breath, reservoir bag moves with each breath, physiological chest movement when bag is inflated, and end tidal CO2

Where should the operator be during intubation?

Directly in front of the patient, good visualization

What does a RUMM block affect?

Distal thoracic limb - mid radius, carpus and paw. Radial, ulnar, median and musculocutaneous. Nerve stimulator or ultrasound guided

What does a IVRA block affect in the thoracic limb?

Distal to elbow. Tourniquet <90 minutes

What does an IVRA nerve block affect in the pelvic limb?

Distal to hock. Tourniquet <90 minutes

What is N2O used to do?

Distention of gas-filled cavities (rumen, GDV, pneumothorax, ETT cuff, increased pressure in the middle ear). Magnitude of volume increase is influenced by PpandNO2, blood flow to the air-filled cavity, and duration of N2O administration

What should be done before an intratesticular block?

Do not forget to desensitize the skin incision site

Why does sevoflurane have a better margin of safety than other inhalants?

Does not impair cerebral autoregulation until >1.5 MAC

Where is the low pressure system?

Downstream of flowmeter to common gas outlet. Near atmospheric pressure

What resistance do precision vaporizers have?

Draw over, plenum

What are the cylinder sizes used for carrier gases in the US and EU?

E or J (H in the EU)

How can one lung intubation be done?

E-Z blocker or double lumen tubes

What are the possible complications of ET intubation?

ETT too long (endobronchial intubation - mechanical dead space), ETT too short (inadvertent extubation), cuff overinflated (tracheal damage / rupture or collapsed ET tube lumen), occlusion, obstruction and kinking, esophageal intubation, and laryngospasms / trauma

What are the characteristics of physiologic / nociceptive pain?

Early warning physiological protective system, essential for body integrity. The pain felt when touching something too hot, cold, or sharp

What is the ideal anesthetic?

Easily vaporized at or near room temperature. Non - flammable / non-explosive. Stable on storage (not degraded by heat or light). Does not react with materials of anesthetic breathing system or vaporizer. Does not readily diffuse through materials of anesthetic breathing system to pollute the operating environment. Compatible with CO2 absorbent. Non - toxic to tissues. Minimally metabolized; any metabolites should be non - toxic and inactive. Environmentally friendly; easily scavengeable. Non- irritant to mucous membranes; non-pungent, so that inhalation induction is not unpleasant. Induction of anesthesia and recovery from anesthesia should be excitement- free. Allows rapid control of anesthetic depth (low blood solubility). Some analgesia and muscle relaxation would be an advantage. Few cardiorespiratory side effects. No renal or hepatic toxicity. Inexpensive. Not requiring expensive vaporizer

What does reduced blood perfusion do with local anesthetics?

Enhances concentration of available drug in the premises of neuronal tissue, increases duration of action, and prolongs analgesics effects

How do you do a leak test of the anesthesia machine?

Ensure oxygen is connected and in enough quantity for the procedure and that vaporizer is full and fitted

What is the mechanism of action of local anesthetics?

Enters the cell through membranes or Na+ channels. Block voltage-gated Na+ channels. Reversible binding site at DIV-S6 of central pore, intracellular access only. Prevention of nerve conduction, block transduction at afferent nociceptor

How can adjuvants of local anesthetics have influence?

Epinephrine (1:200,000), bicarbonate, and baricity (spinal local anesthetics)

What does the intermediate chain of local anesthetics consist of?

Ester or amide

What is the localization of superficial pain?

Excellent

What is done in passive scavenging?

Exhaled gases are vented to distant site through long tubing. Expiratory effort and fresh gas flow push exhaled gases along tubing. Has activated charcoal canister

What are the characteristics of MAC?

Experimentally derived. Similar to ED50. Species- and anesthetic-specific. Different values within the same species (depends on the method used). Different MAC (MAC BAR > MAC immobility > MAC awake > MAC amnesia). Apneic index 1.5-3 MAC, CV collapse 2.7-3 MAC

What occurs in rebreathing systems / circle systems?

Expired gases (without CO2) returned to the patient. Can be full rebreathing (closed) or partial rebreathing (semi-closed - high or low flow)

What can neuronal ischemia cause?

Extra or intraneuronal hematoma or edema, leading to nerve damage

What are the clinical indications for an auriculopalpebral nerve block?

Eye exam (in association with topical anesthesia - removal of foreign bodies from the cornea), general anesthesia. Must apply artificial tears to protect the eye from accidental trauma or debris

What are the landmarks for the lateral approach to a retrobulbar block?

Facial crest, ramus of mandible, and caudal border of the orbital rim

What does better intra and postoperative pain control do?

Faster return to normal activities, easier discharge from the hospital

What does a femoral nerve block affect?

Femur from mid-diaphysis, medial posterior and anterior stifle, skin of dorsomedial tarsus, 1st digit. Nerve stimulator, ultrasound-guidedd

What are the key parts of a vaporizer?

Filling port, sight glass, dial or control knob, vaporization chamber, and bypass channel

How is the epidural space palpated?

First moveable joint. Up and down movement of tail should show dent

What CNS signs are seen with local anesthetic toxicity?

First sedation and nystagmus, followed by tonic-clonic seizures and comas

What is formaldehyde?

Flammable organic compound. Excessive heat and flammable metabolites means that CO2 absorbent cannister can spontaneously combust

What are the characteristics of silicone ET tubes?

Flexible and straight, may require a stylet, low volume - high pressure cuff

What vaporization do precision vaporizers have?

Flow over, bubble through, injection

What are the characteristics of plenum variable bypass vaporizers?

Flow over, variable bypass, out of circuit. Agent-specific, concentration-calibrated. Temperature compensated. Quantity is expressed in V% of the total mixture of gases

What are the characteristics of sevoflurane?

Fluorinated ether - increases stability and decreases potency (MAC 2.3% - 2.6%)

What are the characteristics of desfurane?

Fluorinated ether. Least potent (MAC 7 - 10%). Very low solubility in blood, so extremely fast onset and recovery. Expensive. Irritant to mucous membranes

When are laparotomies done in ruminants?

For rumenotomy, displaced abomasum, and C-sections

Where are opioid receptors found?

Found mainly in the laminae I and II. Post synaptic on the primary afferent and presynaptically second order neurons

What are the mandatory components of rebreathing circle systems?

Fresh gas inlet, inspiratory unidirectional valve, breathing tube (inspiratory and expiratory limbs), Y-piece, expiratory unidirectional valve, reservoir bag / breathing bag, pop-off valve, and CO2 absorber

Where is the mechanical dead space?

From Y-piece in rebreathing systems to incisors. Elbow connectors, length of ET tube (rostral to anatomical airway), mask, sampling connectors

Where is the high pressure system?

From cylinder to pressure regulator. Pressure regulator is in large cylinder bank

Where is the intermediate pressure system?

From pressure regulator to flowmeter

What are the inhibitors of spinal cord modulation?

GABA, opioids, alpha 2 agonists, adenosine, serotonin (5HT1), norepinephrine, and kainate

What are the characteristics of nitrous oxide?

Gaseous, very poorly soluble and very low potency (MAC 200 in dogs). Dual hemodynamic effects. Different CV effects depending on species, other drugs and predominance of direct or indirect effects

What should be done to ensure that an anesthesia machine is safe to use?

Gases switched n, vaporizer fitted and full, no leaks present and awareness of features

What does it mean if blood-gas coefficient is low?

Gases will exert a high partial pressure, so changes will be fast

What is windup not preventable by?

General anesthetics

What must be done in a lumbosacral epidural if the spinal cord is present?

Give a half dose

What do unidirectional / one-way valves do?

Give fresh gas toward patient during inspiration and take exhaled gas away from patient during expiration. Contribute to resistance to breathing. Must check movement and cleanliness

What are the facilitators of spinal cord modulation?

Glutamate (NMDA type), substance P (NK1), prostanoids, serotonin (5HT2), norepinephrine, Ach, ATP, and BDNF

What color are carbon dioxide cylinders?

Gray

What effect does CO have on anesthetic uptake?

Greater the CO, greater the amount of blood passing through the lungs carrying away anesthetic (delays alveolar rise in Panesthetic)

What color are oxygen cylinders?

Green or green and white

How is the cornual nerve located?

Halfway imaginary line between base of the horn and lateral canthus of the eye

What are the characteristics of halothane?

Halogenated alkane. Potent (MAC 0.9%). Intermediate solubility in blood. Degradation in light, pleasant, non-irritating odor

What are the characteristics of isoflurane?

Halogenated ether. MAC 1.2 - 1.7%. High potency. Dose-dependent vasodilation, respiratory depression

What is an example of an aliphatic hydrocarbon?

Halotane

What is the order of cardiac output reduction for halogenates?

Halothane > isoflurane >= sevoflurane > desflurane

What is the order of direct myocardial depression for halogenates?

Halothane >> isoflurane, sevoflurane > desflurane

What are the specific inhalant anesthetic agents?

Halothane, isoflurane, sevoflurane, desflurane, N2O, and xenon

What are the volatile liquid (vapor) anesthetics?

Halothane, isoflurane, sevoflurane, desflurane, enflurane, and methoxyflurane (analgesic)

What does perception have to involve?

Has to involve the cortex. If it doesn't it is only nociception

What are the health consequences of occupational exposure to inhalant anesthetics?

Headache, drowsiness, coordination difficulties, reproductive issues. Recommended exposure limits depend on the country. Periodic assessment

What do thermal receptors detect?

Heat and cold

What are armored ETTs?

Helical wire within the wall of the ETT. Prevents occlusion during extreme patient neck positioning. Useful for head, neck, and ocular procedures

What are the characteristics of amides?

Hepatic metabolism. Toxicity more likely to occur (delayed metabolization, accumulation)

What are the disadvantages of non-rebreathing circuits?

High gas flow requirement, more anesthetic gas waste, moisture and heat lost, inefficient (not economical) in larger animals), and gas flow varies with different systems

What safety profile does lidocaine have?

High safety profile

What safety profiles does mepivacaine have?

High safety profile

Why does desflurane require a special vaporizer?

Highly volatile. Low boiling point. Needs metal bottle (liquid under pressure)

What does an intraarticular nerve block affect in the pelvic limb?

Hip and stifle

What should the assistant do during intubation?

Hold patient's head and tongue, avoid pressure around the neck

What do vapor pressure and boiling point determine?

How to store and administer inhalant anesthetics

In which species is the efficacy of inhalant anesthetics demonstrated in?

Humans, vertebrate in general, invertebrates, protozoa, worms, and plants. Molecular mechanisms involving cellular components essential to life

What does a cervical paravertebral block affect?

Humerus, shoulder, distal scapula. Can be done blind, nerve stimulator (NS), US-guided. Low overall success and higher risk of complications

What will rebreathing CO2 result in?

Hypercapnia (high PaCO2 and ETCO2). Tachycardia, vasoconstriction, increased intracranial pressure, and cardiac arrhythmias

What factors increase MAC?

Hyperthermia. Pediatric. Catecholamine release. Hyperthyroidism. CNS stimulant drugs (morphine in horses). Hypernatremia and hyperosmolality. Higher altitude

What does nitrous oxide cause?

Increases PVR (if already pulmonary hypertension), short-lived analgesia via NMDA antagonism and modulation of noradrenergic and opioid R pathways. Not really MAC spearing effect in cats

How can concentration / dose of local anesthetics have influence?

Increases onset, increases efficacy, influences the volume administered, and effects on epidural blocks

What does lower solubility indicate?

Indicates faster speed of induction, recovery, and change of anesthetic depth

What does the pressure gauge do and what is it used for?

Indicates pressure in respiratory and breathing system. Used to check system for leaks and to check for correct pressure when doing mechanical / manual ventilation

What are the contraindications of epidural anesthesia?

Infection at site of puncture (dermatitis), neoplasia, septicemia (relative contraindication), severe hypovolemia / hypotension. coagulopathies, degenerative axonal disease, anatomic abnormalities (pelvic fracture➔ loss of landmarks) relative contraindication, lack of owner consent for epidural

What are some of the consequences of maladaptive pain?

Infection, impaired wound healing, sleep deprivation, anorexia, depression or aggression, altered locomotion, guarding, licking, self mutilation, and immobilization

What are silent / sleeping nociceptors activated by?

Inflammatory mediators (sensitizing soup). Responds to mechanical and thermal stimuli after activated

What are the characteristics of pathological / clinical pain?

Inflammatory pain (acute pain but still needs to be reduced), neuropathic pain (not protective, maladaptive, abnormal functioning of the nervous system). Must be treated

What happens when Na+ channels are activated?

Influx of Na+ ions, propagation of AP along nerve fiber

Why is waste anesthetic gas disposal important?

Inhalant anesthetic chronic exposure might promote formation of Alzheimer's disease

What do inhalant anesthetics do to cardiac rhythm?

Inhalants may increase myocardial automaticity (especially in ventricle). Halothane sensitizes the heart to catecholamine-induced arrhythmias (much less notable with modern inhalants)

What occurs during phase 1 of pain?

Initial adaptive (physiologic) pain

What are ring blocks?

Injection around an extremity (limbs / tails)

What are peripheral nerve blocks?

Injection of local anesthetic around a peripheral nerve. Small volume of local anesthetic can result in a large area of desensitization. Successful block depends on the precision

What are the side effects of halothane?

Inotrope negative, sensitizes myocardium to catecholamines (arrhythmias), hepatitis, malignant hyperthermia. Not commercially available

How is a lacrimal nerve block done?

Insert a needle percutaneously at the lateral canthus of the eye and direct it medially along the dorsal rim of the orbit

How is a maxillary nerve block done?

Insert the needle at a 90° angle to the head so that it enters the pterygopalatine fossa just caudal to the maxillary tuberosity. Alternative technique: Access the nerve via infraorbital foramen with a 14G catheter

What do non-rebreathing systems give good control of?

Inspired gas concentrations

What is a splash block?

Instillation of local anesthetic on open wound / surgical site before skin closure for post op analgesia

What is correct FGF integral to?

Integral to the correct function of the breathing system. Excess FGF is wasteful (O2 and volatile agent). Excess FGF potentiates hypothermia

What occurs during phase 2 (inflammatory pain)?

Intense noxious stimulus. Pain state persists after the termination of the stimulus. Tissue damage / inflammation. Firing threshold of Adelta and C nociceptive afferents reduced to non noxious stimuli. Activation of silent nociceptors. Secondary hyperalgesia (areas adjacent to the injury sites)

What do nociceptive specific second order neurons respond to?

Intense noxious stimulus. Responds only to Adelta and C fibers

What does a ultrasound-guided transversus abdominus plane / interfascial plane block affect?

Intercostal nerves (T11, T12), costoabdominal nerve (T13), cranial iliohypogastric nerve (L1), caudal iliohypogastric nerve (L2), and ilioinguinal nerve (L3)

What are the physicochemical properties of isoflurane?

Intermediate / fast onset and recovery. Intermediate solubility in blood. Pungent odor, irritates mucous membranes. Great stability

What are the thoracic peripheral nerve blocks?

Interpleural analgesia and thoracic paravertebral

How is infiltration anesthesia done?

Intradermal / subcutaneous injections adjacent to the area to be blocked

How are V-gel supraglottic devices used in rabbits?

Introduced blind with rabbit in sternal recumbency. Gentle placement until resistance felt. Position confirmed with capnography. 4 - 6 sizes

What does a mandibular block (inferior alveolar) do?

Ipsilateral anesthesia of the mandible and soft tissues, including all the teeth

Which inhalant anesthetic is least likely to produce hepatic injury?

Isoflurane

What are the predicted atmospheric lifetimes of inhalant anesthetics?

Isoflurane is 3.2 years, sevoflurane is 1.1 years, desflurane is 14 years, and N2O is 114 years

What are examples of ethers?

Isoflurane, sevoflurane, and desflurane

What is the order of peripheral vasodilation for halogenates?

Isoflurane, sevoflurane, desflurane >> halothane

What happens when pain is allowed to persist for days or weeks?

It is less responsive to treatment

What is true about the blood solubility of nitrous oxide?

It is much higher than nitrogen. Volume of N2O that can be transported to a closed gas space is many times the volume of N2 that can be carried away

What is true about sensing visceral pain?

It is not consciously sensed

What is true about referred pain in superficial pain?

It is the exception

What is true about referred pain in visceral pain?

It is the rule

What do dynorphins bind to?

Kappa receptors

What precautions should be used with a vaporizer?

Keep upright and never tip sideways, turn off after use, turn off if refilling while in use, and remember to turn it back on

What is the cranial part of the udder innervated by?

L1 and L2

What is the caudal part of the udder innervated by?

L3, L4, and perineal nerve

What contact do high volume cuffs have with the tracheal wall?

Large contact area

What is liquid oxygen useful for?

Large hospitals with high demand

What does activation of Abeta fibers lead to during peripheral sensitization?

Leads to secondary hyperalgesia in normal tissue around the injury and allodynia

What is the source of inhalant anesthetic exposure?

Leaks, forget to turn off flow when disconnecting patient, recovery, scavenge malfunction, mask, or chamber delivery

How much is isoflurane metabolized?

Less than 1%

What does the common gas outlet do?

Lets out the mixture of carrier and anesthetic gas at the preset concentration. Position depends on the machine. Allows for the attachment of a breathing system (circle, T-piece, etc.)

What local anesthetic has fast onset of action?

Lidocaine

What are the anti-arrhythmic local anesthetics?

Lidocaine and procaine

What drugs are used for local anesthesia in large animals?

Lidocaine, Bupivacaine, Ropivacaine, Mepivacaine, ad Procaine

What are the amide local anesthetics?

Lidocaine, prilocaine, mepivacaine, bupivacaine, ropivacaine, and levo-bupivacaine

What is malignant hyperthermia?

Life-threatening pharmacogenetic myopathy (RyR1 receptors in skeletal muscle). Reported in humans, dogs, cats, horses, and pigs. All contemporary volatile anesthetics can trigger (halothane >> others). Xenon can be safely used in patients with malignant hyperthermia

What does the APL / pop-off valve do?

Limits pressure build up within the system. Vents gas to the scavenging system. Screw down or spring loaded. Manual. Dangerous if improperly used

What is the Meyer-Overton rule?

Lipid theory. Lipid cell membrane as site of action

What do inhalant anesthetics do to pulmonary vascular resistance?

Little effect on pulmonary smooth muscle. N2O increase PVR if preexisting pulmonary hypertension

How is the Peterson eye block done?

Local anesthetic deposit at foramen orbitortundum

What is the modulated receptor hypothesis of local anesthetics?

Local anesthetic's high affinity for the channel in the open and inactivated states. Lipid-soluble form enters via the membrane, lipid-insoluble form enters through channel pore

Why is slow absorption of local anesthetics usually desired?

Local anesthetics act at the site of injection (locally)

What is the guarded receptor hypothesis of local anesthetics?

Local anesthetics bind to the receptor inside the channel with constant affinity, but channel must be open for access

What local toxicity do local anesthetics have?

Local effects - tissue irritation, allergic reactions (PABA metabolite), myotoxicity, chondrotoxicity. Mainly seen with ester-type local anesthetics

What are the uses of mepivacaine?

Local infiltration, epidural anesthesia, diagnostic anesthesia in horses

What are the uses of bupivacaine?

Local infiltration, epidural, and spinal anesthesia

What are the uses of lidocaine?

Local infiltration, epidural, spinal anesthesia, IV regional anesthesia. Topical: EMLA, patches. Desensitization larynx at intubation. Class I-b anti-arrhythmic. MAC sparing properties. Pro-kinetic. Systemic analgesia, anti-inflammatory, antiendotoxic

Where are wide dynamic range second order neurons found?

Located mainly on lamina V

What are the uses of tracheostomy tubes?

Long term ventilation (ICU), oral intubation will impede the procedure or access). Similar to ETTs. Cuff, tubing, connector. Tie to secure to the neck

What is the onset of action for bupivacaine?

Longer onset - 20 - 30 minutes

How is correct placement of LS epidural anesthesia confirmed?

Loss of resistance, pop sensation, hanging drop / running drip, nerve stimulation, ultrasound, x-rays / CT

What does low CO cause?

Low CO (alpha-2 agonists, myocardial failure, bradycardia, shock) causes increase in the rate of rise of the PA of the anesthetic. Inverse for anticipated elevated CO (excitement, hypermetabolic states)

What is the environmental impact of inhalant anesthetics?

Low compared to CO2, but significant contribution. Volatile agents are potent greenhouse gases. N2O has lesser short-term impact, but longer time period. Contribution to global warming (des > sevo > iso). Iso and N2O have ozone-depleting potential

What are the characteristics of visceral pain?

Low density innervation, diffuse presentation / poorly localized. Poor correlation between pathology and intensity of pain

What does a high oil-gas coefficient mean?

Low inhalant concentration needed to maintain anesthesia (low MAC)

What are the advantages of non-rebreathing circuits?

Low resistance to breathing, simple, light construction, no CO2 absorber required, inspired gas content similar to vaporizer setting, and can rapidly alter anesthetic depth

What safety profile does bupivacaine have?

Low safety profile

What helps to improve cuff seal?

Lubricant

What is the oil-has coefficient inversely proportional to?

MAC (minimum alveolar concentration)

What does the pressure regulator do?

Maintains high, intermediate, and low pressure systems

When should nasal intubation be done?

Mandible fractures, procedures in the oral cavity. Horses might tolerate the tube even when standing

What are the peripheral nerve blocks of the head?

Maxillary nerve, infraorbital nerve, mental nerve, and inferior alveolar nerve

What does a trigeminal nerve block block?

Maxillary, infraorbital, mandibular, and mental nerves

What is saturated vapor pressure?

Maximum concentration of molecules in the vapor state that exists for a given liquid at each temperature. No control over concentration of vapor

What may silent nociceptors contribute to?

May contribute to mechanical hyperalgesia in inflammation

What do pressure gauges do?

Measures the content of individual cylinders or pipelines (systems)

What is easy with rebreathing systems?

Mechanical ventilation

What does a saphenous nerve block affect?

Medial and cranial aspects of stifle. No quadriceps muscle paralysis. Only ultrasound guided

How are esters metabolized and excreted?

Metabolized in plasma (pseudocholinesterase) into water-soluble metabolites that are excreted via kidneys

How are amides metabolized and excreted?

Metabolized in the liver (CYP450) into water-soluble metabolites that are then excreted via the kidneys

What toxicity do anesthetic inhalants have on the kidneys?

Methoxyflurane has nephrotoxic potential - highly metabolized --> fluorine ion --> AKI. Sevoflurane biotransformation increases fluorine --> AKI (clinically unlikely). Compound A (sevo) is nephrotoxic in rats. Baralyme > soda lime

What is MAC?

Minimum alveolar concentration of an anesthetic at 1 atmosphere that produces immobility in 50% of subjects exposed to a supramaximal noxious stimulus (immobility)

What are the minimum and maximum times for Bier blocks?

Minimum of 20 - 30 minutes before onset, maximum of 1.5 hours for tourniquet application

What is the use of topical anesthesia?

Minor procedures (intubation, nasal cannulas, urinary catheter placement)

What is the duration of action of mepivacaine?

Moderate - 1 - 2 hours

How is needle / mechanical trauma prevented?

Monitor resistance to injection, use low stimulating currents, short bevel needles

What is needed to produce immobility and unconsciousness?

More halogenated. It is unlikely that an animal can be conscious but totally unable to move

When is blockade by local anesthetics more marked?

More marked at higher frequencies of depolarization. Sensory nerves have a higher firing rate

What is true about Tuohy needles?

More tactile information about location of tip - less likely to penetrate vessels / nerves. Curved tip

What opioids are used in large animals?

Morphine, used in epidural, intraarticular

What can needle / mechanical trauma with local anesthesia cause?

Most common cause of nerve injury after blocks

What are the complications of epidurals?

Motor block (postural instability / recumbency, hypoventilation), hemorrhage in epidural space, hypotension (local anesthetics), trauma to spinal cord and meninges nearly impossible), urinary retention (morphine), infection, and pruritis (morphine)

What do beta endorphins bind to?

Mu receptors

What must the inspired gas composition contain in rebreathing systems?

Must contain enough O2

How does N2O affect genetics?

N2O oxidizes cobalt from vitamin B12, which inhibits methionine synthase (implicated in formation of myelin and folic acid for DNA synthesis). Hematologic dysfunction, polyneuropathy, interference in myelin formation and DNA synthesis (teratogenesis), +/- vascular inflammation (chronic exposure)

What is the mechanism of action of centrally administered local anesthetics?

Na+ channels, K+ and Ca2+ channels - altered sensory processing. Substance P binding and evoked increase intracellular Ca2+. Glutaminergic transmission → decreased NMDA and neurokinin mediated transmission

How is FGF calculated for a rebreathing system?

Need to meet metabolic oxygen consumption (~7 ml / kg). However, some flowmeters cannot provide less than 200 ml / min and some vaporizers might require flow of at least 500 ml / min. Lower fresh gas flow required than non-rebreathing system

What does local toxicity with local anesthetics affect?

Neural, skeletal muscle, and chondrotoxicity

How is pain classified according to physiology?

Neuropathic or nociceptive (somatic or visceral)

What are the compressed gas anesthetics?

Nitrous oxide and xenon

Is visceral pain due to injury?

No

What is true about analgesia in auriculopalpebral blocks?

No analgesia, but does provide akinesia of the upper eyelid

What is true about maladaptive pain?

No consensus on the definition. Difficult to determine clinically when an adaptive pain becomes maladaptive. No protective purpose and difficult to treat

What do wide dynamic range second order neurons respond to?

Nociceptive and non-noxious stimuli

What is line block infiltration?

Nonspecific block (local block of tissue where incision is intended). Very simple and fast to perform. Large amount of local anesthetic needed

What is an inverted L block?

Nonspecific block (local block of tissue)

What neurotransmitters are inhibitory in the descending inhibitory nerve system?

Norepinephrine, serotonin, acetylcholine, GABA, and cannabinoids

What fibers are normally silent nociceptors?

Normally C fibers

What is true about red rubber ET tubes?

Not recommended

What is the pathology of visceral pain?

Not related to intensity

What is the recommended pressure in cuffs?

Not to exceed 25 cm H2O

When does sevoflurane impair autoregulation?

Not until >1.5 MAC

How is pain processing done?

Noxious stimulus (mechanical, chemical, thermal) undergoes transduction, transmission, modulation, projection, and perception

What occurs during transduction?

Noxious stimulus is turned into an electrical signal. Receptors detect innocuous and noxious information. Specialized nerve endings transform stimuli into electrical action potentials. These receptors vary in their sensitivity to mechanical, thermal, and chemical stimuli

What is low flow rebreathing system (20 - 40 ml / kg / min) used for?

O2 flow > patient's O2 consumption. 10 20 - 30 ml / kg / min. Surplus gas exits through APL valve. Careful with N2O (hypoxic gas mixture)

What makes up air pressure?

O2, N2, argon, H2O, and CO2

Where does amplification or inhibition of the nerve impulse occur during modulation?

Occurs mainly in the dorsal horn of the medulla. Can also happen in descending pathways

What does a sciatic nerve block affect?

Posterior and lateral stifle, tarsus and food. Nerve stimulator or ultrasound-guided

What is involved in the "sensitizing soup"?

Potassium ion, hydrogen ion, norepinephrine, histamine, bradykinin, serotonin, PGL, leukotrienes, Substance P

What complications can line block infiltration have?

Potential hematoma formation and pockets of local anesthetic, possible interference with wound healing

What are the reasons to provide local anesthesia?

Preemptive analgesia, better intra and postoperative pain control, prevention of stress response, and overall reduction in intra and postoperative complications

How is an ET tube selected?

Premeasure against patient (incisors to thoracic inlet). Gently palpate trachea and choose the biggest diameter tube without causing tracheal damage. Check the cuff

What are the uses of face masks?

Preoxygenation, oxygen supplementation during sedation, and ICU

What is vapor pressure?

Pressure (in mmHg or kPa) the vapor molecules exert on the walls of a closed system when liquid and vapor phases are in equilibrium (i.e. ability to evaporate)

What is in place to avoid pressure excess / fluctuations?

Pressure regulator

Why should leak tests be done with the anesthesia machine?

Prevent anesthetic gases from being released in the theater, ensure the patient is receiving the selected amount of inhalant anesthetic, ensure selected TV is delivered to the patient (IPPV)

What increases the risk of laryngospasms?

Previous or current neck / facial trauma, noisy respiration (stridor etc.), swellings or masses in pharyngeal area, inability to open mouth

What does nociceptive pain produce?

Produces a protective or adaptive response

What does local anesthetic do?

Produces a reversible blockade of the propagation of the action potential, to anesthetize a region of the body, with or without muscle paralysis, and are applied at target site

What is seen on an EEG during dose-dependent CNS depression?

Progressing to flat line

What occurs during transmission?

Propagation of the nerve impulse

What do chemical receptors detect?

Prostaglandins, lactic acid, leukotrienes, neurotransmitters, autocoid (histamine), cytokines, etc.

What affects distribution of local anesthetics?

Protein binding. Placental transfer limited for esters (rapid metabolism) and enhanced for amides (ion trapping)

How is blocked for laparotomies in ruminants?

Proximal paravertebral, distal paravertebral, inverted L, and line blocks. Neuraxial anesthesia

What is the onset of action for lidocaine?

Quick - 2 minutes

What onset does mepivacaine have?

Quick onset

What are the characteristics of esters?

Quickly metabolized by plasma esterases. Prone to hydrolysis (shorter duration of action). Metabolism not affected by liver dysfunction. Can induce allergic reactions (PABA). Rarely used in vet medicine

What nerves are blocked in a distal RUMM block?

Radial (in lateral), Median-Ulnar trunk (in medial), Musculocutaneous (in medial)

How can inhalant anesthetics have toxicity?

Reaction to strong bases in CO2 absorbents (KOH > NaOH). Carbon monoxide (des > iso >>> sevo), compound A (sevo), formaldehyde (sevo)

What is reduced with rebreathing systems?

Reduced cooling and drying of the animal

How is anesthetic eliminated?

Reduced partial pressure in the CNS allows return to consciousness. Metabolism (halothane 25%, iso <1%, sevo 3%)

How does resistance compare between non-rebreathing and rebreathing systems?

Reduced work of breathing / resistance in non-rebreathing systems

What are the effects of isoflurane on hepatic blood flow?

Reduces flow on hepatic portal vein, increases flow through hepatic artery, little change in perfusion. May result in improved oxygenation

What process is there in peripheral sensitization?

Reduction in activation threshold of the Adelta and C fibers, activation of silent nociceptors, and amplification of the nociceptive signal

How do inhalant anesthetics cause respiratory depression?

Reduction of MV via reducing Vt and / or RR (hypoventilation)

What happens if anesthetic is overfilled in a vaporizer?

Reduction of exposed area may drop vapor output or spillage into bypass chamber (overdose)

What do endogenous opioids lead to?

Reduction of neurotransmitter release from 1st order neuron and hyperpolarization of the second order neuron, which leads to reduction of action potential firing in the second order neuron (blocks the transmission of pain signal)

What are wide dynamic range second order neurons believed to be in charge of?

Referred pain

What is common with visceral pain?

Referred pain (upper arm and angina)

What does the blood-gas partition coefficient do?

Reflects the solubility of the anesthetic agent in blood

What are the indications for epidurals?

Regional anesthesia of pelvic viscera and genitalia. Treat rectal tenesmus. Surgical procedures: anal, perineal, vulva, bladder. Obstetric manipulations (prevent straining)

What is the pathology of superficial pain?

Related to intensity

What are the characteristics of lipophilicity of local anesthetics?

Relates with the potency (high lipid solubility → high potency). Some effect on the onset of action. Effect on the duration

What do inhalant anesthetics do to coronary blood flow?

Relatively weak coronary vasodilators. Myocardial protective effects against myocardial ischemia

What are the disadvantages of ET intubation?

Requires skills, requires equipment (tubes, laryngoscope), requires deeper plane of anesthesia, possible trauma to larynx, trachea, vocal folds, possible vagal stimulation, species-specific conditions: laryngospasm in cats

How is minute volume calculated?

Respiratory Rate x Tidal Volume

What respiratory signs are seen with local anesthetic toxicity?

Respiratory depression

What are the different states of Na+ channels?

Resting (closed), open state (depolarization), and inactive state (closed but can be activated - allows repolarization - H gates close)

How are the eyes and annexes blocked?

Retrobulbar and peribulbar blocks

What do local anesthestics do?

Reversibly block the transmission of action potential in the neuron axon by blocking voltage-gated sodium channels

What is the reservoir bag made of?

Rubber or plastic

How can neuraxial anesthesia be done?

Sacro-coccigeal epidural approach, lumbar, thoracolumbar, or thoracic epidural approach

What are precision vaporizers?

Safe and accurate volatile agent delivery systems

What are the benefits of being able to perform procedures on standing animals?

Safer (?), economical, easier access

What is equilibrium?

Same partial pressure in all the phases

How is waste anesthetic gas disposal done?

Scavenging-active or passive charcoal filters. Inhalant anesthetics are heavier than air

What are the consequences of windup?

Second-order neurons respond more vigorously to subsequent stimuli, which can lead to chronic pain. Reduced threshold and more neurotransmitter expression. Secondary hyperalgesia and allodynia

Why use airway devices?

Secure the airway, deliver inhalational anesthesia, deliver oxygen and other carrier gases, prevent environmental pollution, prevent aspiration of gastric contents

What are the main mechanisms of modulation?

Segmental inhibition, endogenous opioid system, and descending inhibitory / facilitatory nerve system

What do infratrochlear nerve blocks do?

Sensory block of medial canthus, lacrimal glands, nicitans, and connective tissue

What are nociceptors?

Sensory receptors of the peripheral somatosensory nervous system that is capable of transducing and encoding noxious stimuli

Which inhalant anesthetic is least likely to produce CO?

Sevoflurane

Why are hypodermic needles not suitable for epidurals?

Sharp and penetrate skin. Can cause nerve damage due to sharpness. No stylet - skin and cartilage are transferred into epidural space

Why are spinal needles not good for epidural anesthesia?

Sharp tip, designed to pierce dura mater (spinal anesthesia), risk of dura and nerve damage

What duration of action does lidocaine have?

Short

Where should nasal intubation be done?

Should be directed to the ventral nasal meatus

What should cuff pressure do?

Should be enough to "seal" the tracheal lumen and prevent air leaks

What is involved in the safe use of carrier gas cylinders?

Should be handled only by personnel trained in safe practices, cylinders should not be lubricated with oil, grease etc., no open flames, store in dry-clean, well ventilated / shaded areas, and store secure in upright direction

When should the O2 bypass / flush button not be used?

Should not be used when a patient is connected to a breathing system (increased risk of barotrauma)

What do intraarticular blocks affect in the thoracic limb?

Shoulder and elbow

What causes visceral pain?

Silent nociceptors induced by ischemia, hypoxemia, inflammation, distension, traction

What does the ideal breathing machine consist of?

Simple and safe, delivers the set gas / vapor mixture, suitable for all sizes of patient, efficient, sturdy, light, compact, easy removal of waste gases, and reusable

What is involved in the classical lock and key models of the mechanism of action for inhalant anesthetics?

Single atoms, diatomic elements (Nitrogen), inorganic molecules (N2O), hydrocarbons with different organic groups, endogenous by-products (CO2, ammonia)

What is levobupivacaine?

Single isomer of bupivacaine. Higher safety profile (less cardiotoxic)

What are the preparations of local anesthetics?

Single use vials for injection, sprays for topical application, drops for topical application, creams (EMLA) for skin desensitization, lidocaine skin patches

What are the contraindications for epidurals?

Skin alterations at the site of the injection, neoplasia in the area, poor cardiovascular function, anatomic abnormalities of the spinal column, coagulopathy, septicemia (relative contraindication), and lack of owner consent

What contact do low volume cuffs have with the tracheal wall?

Small contact area

When are induction chambers used?

Small mammals, exotics, and very fractious cats

What species can have a lumbosacral epidural?

Small ruminants, South American camelids, pigs

What fibers are more susceptible to local anesthetic?

Smaller, non-myelinized fibers are more susceptible than larger myelinized fibers

What is true about solubility of inhalant anesthetics?

Solubility in liquids and solids (fatty tissues) is different. Molecules move between two phases until equilibrium

Where do wide dynamic range second order neurons get input from?

Somatic and visceral input

How are V-gel supraglottic devices used in cats?

Species-specific. Introduced blind with cat in sternal recumbency. Cushion inflated once resistance felt to maintain position. Confirm placement with capnography. 6 sizes available

What specificity do precision vaporizers have?

Specificity for an agent or not

What is superficial pain innervated by?

Spinal

What is visceral pain innervated by?

Spinal and vagal

What are the sites of action of inhalant anesthetics?

Spinal cord (muscle relaxation - glycine receptors) and brain (hypnosis - GABAa receptors)

How are patients positioned for ET intubation?

Sternal or lateral (horses)

What do mechanical receptors detect?

Stress, stretching, compression, and crushing

Why aren't face masks recommended for anesthesia induction and maintenance / delivery of inhalant agents?

Stressful, can be unpleasant for the patient. No airway protection. Increased mechanical dead space. Inefficient delivery of anesthetics. Duration of induction. More anesthetic wasted. Difficult to control amount of anesthetic absorbed. Contamination of workspace (leakage)

What should be considered for mask / chamber inductions?

Stressful, environmental contamination, airway irritation, breath holding, +/- prolonged period of time with limited patient access. Not recommended for dogs and cats. 5.9x increase in odds of anesthetic related death when inhalants are used alone

What noxious stimuli can lead to visceral pain?

Stretch, inflammation, ischemia

What neurotransmitters are facilitatory in the descending inhibitory nerve system?

Substance P, glutamate, nerve growth factor, and prostanoids

What are the functions of the set of tubes connecting the patient to the anesthesia machine?

Supply supplementary oxygen, supply inhalational anesthetic agents, remove carbon dioxide from exhaled gas mixture, scavenge exhaled inhalational anesthetic agent, allows manual / mechanical ventilation, and provides the ability to monitor respiratory rate and effort

What do desflurane, isoflurane, and sevoflurane suppress?

Suppress drug-induced convulsive behavior

What are the indications for a femoral block inguinal approach?

Surgery / pain on distal femur, stifle, distal limb. used in combination with sciatic nerve block

What are the indications for a distal RUMM block?

Surgery / pain on elbow, mid radius / ulna, carpus

What are the indications for a lateral preiliac femoral block?

Surgery / pain on hip, femur, knee, or hind limb amputation

What are the indications for a brachial plexus block?

Surgery / pain on humerus (distally), elbow, radius / ulna, or carpus

What are the indications for a an ultrasound-guided serratus plane (interfascial plane) block?

Surgery / pain on lateral thoracic wall (1 - 7 intercostal spaces)

What are the indications for an ultrasound-guided quadratus lumborum / interfascial plane block?

Surgery of abdominal cavity and abdominal wall

What are the indications for an ultrasound-guided erector spinae / interfascial plane block?

Surgery of abdominal thoracic and abdominal wall, spinal surgery

What are the indications for an ultrasound-guided transversus abdominus plane / interfascial plane block?

Surgery of abdominal wall

What are the indications for great auricular and auriculotemporal nerve blocks?

Surgical procedures of ear canal and pinna. Potential for auriculopalpebral blockade

What are the indications for mental nerve blocks?

Surgical procedures of mandible and lower incisive teeth

What are the indications for inferior alveolar / mandibular nerve blocks?

Surgical procedures of mandible, lower lip, and lower dental arch. Possible complications include accidental block of the lingual nerve

What are the indications for maxillary nerve blocks?

Surgical procedures of maxilla, upper lip, hard and soft palates, and upper dental arch

What are the indications of infraorbital nerve blocks?

Surgical procedures of nose, upper lip, gingiva and incisor teeth, canine teeth, and 1st and 2nd premolar teeth

What are the indications for epidural anesthesia?

Surgical procedures on pelvis, hind limbs, abdominal cavity, and thoracic cavity

What can maladaptive / chronic pain result from?

Sustained noxious stimuli, such as ongoing inflammation

How can you speed up recovery with a non-rebreathing system?

Switch vaporizer off

How can you speed up recovery with a circle rebreathing system?

Switch vaporizer off, increase FGF, increase minute volume, and empty reservoir bag

How is local anesthetic toxicity treated?

Symptomatic (palliative), CPR if arrest, cardiovascular and / or respiratory support, steroids for allergic reactions, seizure control (diazepam or propofol), or lipid rescue (intralipid emulsion)

How is malignant hyperthermia treated?

Symptomatic treatment + dantrolene

What does a modified subcostal block affect?

T9 / T12 - T17 / T18

What is vaporizer performance affected by?

Temperature (unless compensatory mechanisms are included), flow, barometric pressure, pumping effect (manual or mechanic positive ventilation), anesthetic levels inside the vaporizer, and moving / tilting the vaporizer

What is boiling point?

Temperature at which vapor pressure of the liquid = atmospheric pressure (usually 760 mmHg, sea level)

What happens when a large volume of N2O is taken up form the alveoli into pulmonary capillary blood?

The concentration of gases remaining in the alveoli is increased. Increased P gradient between alveoli and pulmonary blood. Increased uptake of other gases. N2O will speed up induction of other inhalants

What is perception?

The final stage of the signaling process, where the integration, processing, and recognition of sensory information results in the subjective sensation of pain. Involves multiple areas of the brain

How is a mandibular block done?

The location of the mandibular foramen may be approximated using the intersection of a line passing vertically downwards from the lateral canthus of the eye and a line extending backwards from the table of the mandibular molar teeth. A 6 in (15.24 cm) 20-22 G needle is inserted at the ventral border of the ramus, just rostral to the angle of the mandible and then advanced to the location of the mandibular foramen. In that location, 15-20 mL of local anesthetic may be injected

How are infratrochlear blocks done?

The needle is inserted through the bony notch or the palpable irregularity on the dorsal rim of the orbit near the medial canthus

How are zygomatic nerve blocks done?

The needle is placed subcutaneously on the lateral aspect of the bony orbit and supraorbital portion of the zygomatic arch and 3-5 mL of local anesthetic are injected

What happens if no actual injury occurs with nociceptive pain?

The pain stops when the external stimulus is removed

What is nociceptive pain?

The physiologic process that results in the conscious perception of pain when carried to completion. Can be acute, adaptive, or protective pain

What is the law of partial pressures?

The total pressure of a mixture of gases is equal to the sum of the partial pressures of the component gases. Ptot = P1 + P2 + P3...

What is nociception?

The transduction, conduction and CNS processing of nerve signals generated by stimulation of the nociceptors. The physiologic process that leads to perception of pain. The sensory process by which noxious stimuli are transmitted to the brain

How can mixtures of different local anesthetics have influence?

Theory: combine the faster onset (lidocaine) with longer duration of action (bupivacaine). No scientific evidence. Might get the worst of the 2 worlds

What are the characteristics of C fibers?

Thermal, mechanical, and chemical stimuli. Lasts longer than the stimulus. Dull, burning, slow pain (2nd pain)

What is true about the cost of rebreathing systems?

They are economic

What is true about inherent memory pain or significant painful events?

They are harder to treat

What do Abeta fibers do?

They are large, myelinated, low threshold peripheral mechanoreceptors for touch sensation. Under normal circumstances, they are responsible for generating innocuous sensations

What are oxygen concentrators used for?

They compress room air and extract oxygen, providing concentrated oxygen flows in the range of 0.1 - 10 L. Use in anesthesia machine. Useful for patients in need of oxygen post-op. Max 95% oxygen

How do non-rebreathing systems eliminate CO2?

Through removing all expired gases from the system. Mechanical removal (high FGF)

How is an intratesticular block done?

Tip of needle on center of testicle. Inject until it feels turgid. Place the needle through caudal pole. Used for castration

What local signs are seen with local anesthetic toxicity?

Tissue irritation

What is true about hypodermic needles?

Tissue penetration with minimal resistance. Lack of layers feel

What happens during peripheral sensitization?

Tissue trauma leads to vasodilation, which leads to extravasion of inflammatory cells, which leads to release of mediators (primary hyperalgesia)

Why do you want to increase alveolar pressure?

To gain equilibrium with the CNS and increased alveolar delivery

How is flow read on a flowmeter?

Top end of the bobbin or middle of the ball

What are the regional anesthetic techniques from basic to advanced?

Topical anesthesia, local infiltration, IV regional anesthesia / Bier block, neuraxial anesthesia, peripheral / regional nerve blocks, and interfascial plane blocks

What does overinflation of a cuff cause?

Tracheal mucosa ischemia

What alpha 2 agonists are used in large animals?

Tramadol, ketamine, magnesium sulfate

What are the characteristics of Adelta fibers?

Type I and II. Heat and / or mechanosensitive . Sharp, fast, localized pain (first pain). Lasts until termination of the stimulus

How is systemic toxicity prevented?

Ultrasound, aspiration

What does alveolar gas do?

Undergoes gas exchange

Where are silent nociceptors found in large numbers?

Urinary bladder, distal colon, and knee joint

How can infections with local anesthetics be avoided?

Use aseptic technique in all blocks

How can you reduce the risk of laryngospasm?

Use of laryngoscope (opens the airway), appropriate anesthetic plane, desensitization of the larynx (lidocaine)

What is infiltration anesthesia used for?

Useful for small skin lesions / lacerations. Can be used next to skin incisions at the beginning or at the end of the surgery

What is the resistance in rebreathing systems due to?

Valves and CO2 absorber (increased work of breathing)

What are the types of vaporizers?

Variable bypass and heated blender

What output regulation do precision vaporizers have?

Variable bypass, measured flow

What is the differential blockade?

Vasodilation > sensory > motor

What do lateral preiliac femoral blocks affect?

Ventral branches of spinal nerves L4, L5, and L6

What are the characteristics of supra-glottic airway devices (V-gel)?

Veterinary-specific laryngeal masks (rabbit and cat models). Can be re-used up to 40 times and re-sterilized between uses. Require good airway monitoring. Alternative to tracheal intubation

What is apparatus dead space?

Volume of breathing system that may contain exhaled gas that could be rebreathed during the subsequent breath

What is anatomical dead space used for?

Warming and humidification

How is O2 content (L) calculated?

Water capacity (L) * pressure (bar)

What does the amine end of local anesthetics determine?

Water solubility

When are cats more prone to developing methemoglobinemia?

With prilocaine and benzocaine use

What color are medical air cylinders?

Yellow

Is superficial pain due to injury?

Yes

How are partition coefficients calculated?

[Anesthetic]tissue1/[Anesthetic]tissue2 or [Anesthetic]Solvent1 /[Anesthetic]Solvent2

What are the indications for a sciatic block?

surgery / pain on stifle, tibia, and distal parts. When combined with femoral nerve block, get anesthesia of entire pelvic limb (distal to mid femur)

How can tidal volume be estimated?

~10 - 15 ml / kg

What does the pumping effect of vaporizers cause?

Increased resistance to flow through vaporizer / bypass chamber. Elongated flow passage into inlet / outlet

What are the disadvantages of rebreathing systems?

Increase resistance to breathing, problem for small animals, soda lime needs replacing, bulky, and slow changes in anesthetic depth at low flow

What does adding epinephrine and other vasoconstrictors to local anesthetics cause?

Increased duration of action and decreased tissue blood flow

What are the characteristics of retrobulbar blocks?

1 injection point, increased risk of nerve or eye damage, increased risk of spinal injection, increased risk of hemorrhage

How many PSI in 1 bar?

14.5

How much O2 is left approximately in a E-cylinder if the pressure gauge shows 600 psi?

193 liters

What is high flow rebreathing system (40 - 100 ml / kg / min) used for?

1st 10 minutes for denitrogenation, anesthesia induction, until patient is at stable anesthetic plane

Where are epidurals done in cattle?

1st moveable joint between 1st and 2nd coccygeal vertebrae

What is the oxygens metabolic rate for rebreathing systems?

2 - 10 ml / kg / min (minimal fresh gas flow)

What percent of sevoflurane is metabolized?

2 - 5%

What are the characteristics of peribulbar blocks?

2 injection points, reduced risk of nerve or eye damage, reduced risk of spinal injection, reduced risk of hemorrhage

What is hyperalgesia?

Increased or exaggerated response to a non-painful stimulus at primary or secondary site of injury. Nociceptors respond at lower threshold

What are the side effects of epidural anesthesia?

Hypoventilation ➔ respiratory muscle paralysis, hypotension, Horner's syndrome & hypoglycemia ➔ sympathetic blockade, Shiff-Sherrington-like reflexes, muscular twitches, convulsions, coma ➔ toxic level of local anesthetics, hind limb paresis, tail / perineum permanent anesthesia, accidental spinal anesthesia, infection / granuloma, hematoma

How can't bupivacaine be administered?

IV

How is lidocaine administered?

IV

How can teats be blocked?

IV, into the cistern, ring blocks, and into the teat canal wall

How large are reservoir bags?

Ideally 4 - 6x the tidal volume. 0.5 - 1 L in cats, 0.5 - 3 L in dogs, and 25 - 30 L in horses

How may propofol have advantages over volatile agents?

If hypercapnia cannot be prevented when attempting to preserve cerebral autoregulation

When is it difficult to localize the anatomical references for a proximal paravertebral block?

If the animal has a thick muscle layer

What anatomical landmarks are used for LS epidural anesthesia?

Iliac crests, medial sacral crest, and spinous process of L7

Where is the proximal paravertebral nerve block done?

Immediately after emerging from the intervertebral foramina

What is halothane hepatitis?

Immunogenic phenomenon - massive hepatic necrosis. Reductive metabolism - subclinical and self-limiting hepatic dysfunction

Why is sevoflurane in plastic bottles?

Impurities in the glass can lead to hydrofluoric acid, which combines with glass to form silicon fluoride (volatile, pungent, and highly toxic)

Where should carrier gas cylinders be placed?

In a cylinder manifold / bank or in the anesthesia machine (back up oxygen source and transport of anesthetized patients)

What location do precision vaporizers have?

In or out of circuit

Where does modulation occur?

In the spinal cord

When does infiltrative local anesthesia have reduced efficacy?

In tissues that are inflamed / infected. Edema / swelling after line block might interfere with surgical field. Possible delayed wound healing

What does N2O cause with the liver?

Inactivation of vitamin B12 dependent enzyme methionine synthase in liver (folic acid metabolism) which can lead to development defects in fetuses

How can there be systemic toxicity with local anesthesia?

Inadvertent IV or IA injection

What analgesia does line block infiltration have?

Incomplete analgesia and no muscle relaxation of deep layers of abdominal wall

What analgesia do inverted L blocks have?

Incomplete analgesia and no muscle relaxation of deep layers of the abdominal wall. Large amounts of local anesthetic needed

What can cause systemic toxicity with local anesthetics?

Incorrect dose / volume, inadvertent IV administration. Affects CNS, respiratory, and cardiovascular

What factors affect uptake of inhalant anesthetics?

Increase in inspired fraction (Fi) of the anesthetic (vaporizer setting, FGF), increase in alveolar ventilation, and decreased removal from alveoli

What can cause increase in alveolar ventilation?

Increase in minute ventilation, decrease in dead space ventilation

What do changes in the threshold and activation kinetics of NMDAR and AMPAR following nociceptive inputs lead to?

Increase of membrane excitability, synaptic facilitation, and central sensitization

What does reduction in the release or activity of GABA and glycine following nociceptive inputs lead to?

Increase of membrane excitability, synaptic facilitation, and disinhibition, central sensitization

What do changes in the trafficking of AMPA receptors in the membrane following nociceptive inputs lead to?

Increase of membrane excitability, synaptic facilitation, disinhibition, and central sensitization

What is hyperesthesia?

Increased sensitivity to stimulus

How is a line-block done?

On / around incision site. Wound infusion catheters

What drugs are used for epidurals?

Opioids, local anesthetics, and alpha 2 agonists

What are the additional parts of the anesthesia machine?

Oxygen failure alarm, overpressure valves, emergency air-intake valves, and nitrous oxide cut-out devices

What is the carrier gas?

Oxygen, N2O, medical air, CO2, or Entonox

What can cause allergic reactions with local anesthetics?

PABA (esters), adverse reactions to epinephrine-containing local anesthetics mistaken as allergic reactions

What are thinly myelinated (A delta) and unmyelinated (C) fibers used for?

Pain and temperature

What is allodynia?

Pain due to a stimulus that does not normally provoke pain

What occurs during phase 3 (neuropathic pain)?

Pain initiated or caused by a primary lesion or dysfunction or transitory perturbation in the peripheral or central nervous system. Includes changes in function as well as damage to a nerve as possible causes of pain. Lack of correlation between injury and pain. Still poorly understood

What is acute pain?

Pain that is alleviated when the stimulus is removed or with healing. Tends to be self limiting

What is chronic pain?

Pain that persists beyond the expected healing time, when nonmalignant in origin. Can be with low levels of pathology that are insufficient to explain the presence and / or extent of pain

What factors need to be considered when choosing the breathing system?

Patient size and respiratory capability, mode of ventilation (spontaneous or IPPV), requirement for economy of use of oxygen and anesthetic gases / vapors, accuracy of flowmeter / vaporizer for low flow, expected length of procedure, heat / moisture preservation, sterilization of equipment after the procedure, location of surgery (eg mouth/head --> "Circuit drag"), and ease of scavenging (location of pop-off valve)

What are the target sites of local anesthetics?

Perception, modulation, transmission, and transduction. Target is axons of Adelta and C fibers (sensory nerves)

What nerves are blocked for equine reproductive procedures?

Perineal and pudendal nerves, caudal epidural, and intratesticular

What are the characteristics of neuropathic pain?

Peripheral nervous system damage. Burning, stabbing pain. Similar characteristics to inflammatory pain

What are the characteristics of inflammatory pain?

Peripheral tissue damage. Poorly localized (secondary hyperalgesia), allodynia, hyperalgesia, initiates peripheral and central sensitization

What is central sensitization / windup?

Phenomenon when a repeated stimulus (with no change in strength) causes an increase in response from dorsal horn neurons mediated by the release of excitatory neuromediators

What does the site of injection of local anesthetics determine?

Physicochemical properties (pKa drug - pH tissue), drug-tissue binding, tissue blood flow, intrinsic drug properties (ability to cause vasodilation)

What is PISS?

Pin index safety system. Holes on the cylinder valve must match with pins on the yoke or pressure regulator. Primarily used in small cylinders attached to the anesthesia machine

What are the physicochemical properties of sevoflurane?

Pleasant smell ("fruity"). Non-irritant for the mucous membranes. Fast onset / recovery. Low solubility

What are the characteristics of TEC 3 vaporizers?

Plenum, flow over, variable bypass, out of circuit, temperature compensated, agent specific

What are the characteristics of Desflurane TEC 6 vaporizers?

Plenum, injection, measured flow, out of circuit, temperature compensated, agent specific, power supply

Why should dehorning be avoided in adult ruminants?

Pneumonized in cattle

What is the localization of visceral pain?

Poor

How is an epidural confirmed to be in the correct place?

Pop feeling when penetrating ligamentum flavum, negative pressure (hissing sound), hanging drop), and loss of resistance (5 mL air, 5 mL saline)