Anesthesia - Chapter 8

Equipment for Endotracheal Intubation

Three endotracheal tubes of slightly different diameters, Two-foot length of IV tubing or rolled gauze to secure tube, Gauze sponge to grasp tongue, Syringe to inflate cuff, Good light source, Stylette for narrow diameter tubes, Lidocaine for injectable solution or gel to control laryngospasm (cats), and a larygnoscope with appropriate blade

TIVA

Total IntraVenous Anesthesia

Propofol

the most commonly used ultra-short acting/TIVA agent

3 factors that affect Delay Time

1) Patient's respiratory drive, 2) Agent used and carrier gas flow rate, & 3) Type and volume of breathing circuit

Drugs used for IV injection/Ultra-Short-acting Agent

1) Propofol!!!, 2) Methohexital, 3) Thiopental sodium, 4) Etomidate

5 types of Drugs Used for Premed/Sedation

1) Tranquilizers (Ace), 2) Alpha-2-Agonists (Dexmed), 3) Opioids (Hydrom), 4) Dissociatives (Ketamine), 5) Anticholinergics (Atropine)

1) rapid induction, 2) good control over both increases and decreases in anesthetic depth, and 3) rapid recovery

3 dynamic elements of both IV and inhalant administration include

1) conducts air or anesthetic gases directly fro oral cavity to trachea, 2) bypasses the nasal passages and pharynx, 3) can be connected to an anesthetic machine to maintain anesthesia

3 facts to know endotracheal intubation

General Anesthesia with IM induction

Anesthetic depth gradually increases, peaks, and gradually decreases; After injection, the anesthetist has little control over anesthesia

Inhalation Induction

Anesthetic induction using a facemask or induction chamber

ill, pediatric, or otherwise compromised animals

Anesthetic protocol is modified for

Use in animals in which IV injections are difficult; May need restraint equipment, blowpipe, or tranq gun

Benefits of IM induction

short to moderate length noninvasive procedures

TIVA & ultra short acting agents are used for

4 Desired Effects of Premed/Sedation

1) Sedation, 2) Cholinergic Blockade, 3) Analgesia, 4) Muscle Relaxation

IM induction

Anesthetic depth gradually increases, peaks, and gradually decreases

Isoflurane and Sevoflurane

Drugs used for Inhalant Induction

administer more anesthetic if adequate depth is not reached

During IM Induction of General Anesthesia, you may

1) calculated dosages, routes, and order of administration; 2) selected by the vet in charge; 3) calculate, check, and RECHECK drug doses, oxygen flow rates, and fluid administration rates

The protocol includes

Chamber Induction

Placing patient in a closed chamber infused with anesthetic gas; Patient is usually < 5-7 kg in body weight; Best used for small, aggressive patients; Examine chamber prior to use

Premedication or Sedation

Calms the patient and prepares the patient for anesthetic induction

How to minimize adverse effects of anesthesia:

Correct physiologic abnormalities prior to anesthesia, Base the protocol on the results of the patient's minimum database, Use a balanced protocol consisting of multiple agents, Double-check all injectable drug doses prior to administration, Label all syringes with the patient name, drug name, and drug concentration!!, Administer no more than the minimum dose needed to achieve the desired level of anesthesia, Administer all IV agents "to effect" unless told otherwise

Patient Preparation

Don't take shortcuts, Dont skip steps, Incomplete patient prep can result in life-threatening consequences

1) Mixture of equal volumes of ketamine and diazepam (or midazolam), 2) Propofol!!!, 3) Neuroleptanagesics, 4) Thiopental sodium, 5) Etomidate, (and various other combos containing dissociatives, tranquilizers, and opioids)

Examples of Drugs used for IV induction

Cautions of Mask Induction

Exposes personnel to waste anesthetic gas, Need adequate room ventilation; Patient struggling can lead to epinephrine release, Use only on calm or sedated patients; Longer induction period, Avoid in patients with poor respiratory function; Intubate immediately when possible to gain control of airway and ventilation; Always keep airway open, Dont occlude nostrils or compress airway or chest

smooth, gradual CNS depression with little apparent time spent in the excitement stage

IM induction results in

it can be administered if patient is too deep

If a reversal drug is available for the anesthetic agent during IM induction, it can?

Maintenance of General Anesthesia

Inhalant Agent, Repeated boluses of ultra-short-acting agents, Continuous Rate Infusion (CRI), Injectable agents, and Intramuscular injections

Equipment for Preparation

Intubation equipment (ET tube, rubber band, laryngoscope); Syringes, needles, drugs, fluids required; Equipment designed to prevent hypothermia (heating pad); Small anesthetic machine; Crash cart with emergency drugs and equipment

Low blood-gas solubility coefficient, which results in rapid passage through stage 2 anesthesia

Iso and Sevo have a?

(5) Influencing Factors of Anesthetic Recovery

Length of anesthetic period, Condition of patient, Type of anesthetic administered and route of admin, Patient body temp, and Patient breed

IV induction

Most common and takes animals through the excitement stage most rapidly

Gen Anesthesia using IV induction and Inhalant agent

Most commonly used method of inducing and maintaining anesthesia in small animals!!!

Gen Anesthesia using Inhalant agents

NOT an injection technique; Induction is faster than IM induction, but slower than IV induction; Anesthetist has control over depth of anesthesia and can make changes rapidly; Delay between time dial setting is changed and patient depth occurs

General Anesthesia with TIVA & USAA

Patient is induced to effect; Additional boluses are administered every 3-5 minutes as needed to maintain surgical anesthesia

General Anesthesia with TIVA by CRI

Patient is induced to effect; Anesthesia is maintained by constantly infusing small amounts of anesthesia via a syringe pump, slows down and moderates changes in depth as seen with bolus administration

2% injectable Lidocaine or Lidocaine gel, Adequate depth of anesthesia, Wait for glottis to open before intubating, Don't force the tube!!!!

Prevention of Laryngospasm

Mask Induction

Require skillful restraint to prevent patient or operator injury; Dont restrict chest excursions or the airway; Fit mask prior to induction; Mask obscures muzzle and eyes normally used for monitoring; Need higher oxygen flow rates than with ET tube

1) minimum patient database, 2) patient physical status, and 3) procedure

Selecting anesthetic protocol takes into account what 3 things

Complications of Chamber Induction

Stress, trauma, vomiting, airway blockage; Hard to monitor patient; Exposes personnel to waste anesthetic gas; Epinephrine release, prediposes patient to cardiac arrythmias and hypotension

Laryngospasms

This is common in cats!!, swine, and small ruminants in light plane of anesthesia; Makes intubation very difficult, Larynx is easily damaged; May lead to cyanosis or hypoxemia

Endotracheal Tube

This is placed in the patient's airway after general anesthesia induction

General Anesthesia with IV injection and Ultra Short-acting Agent

This technique is used for short procedures, less than 10 mins of anesthesia; Drug is given to effect; Anesthetic depth rapidly increases then gradually decreases; Anesthetist controls peak effect and can increase depth by administering more anesthetic agent

USAA

Ultra Short Acting Agent

increase depth but CANNOT decrease depth if excessive

Using TIVA and ultra-short acting agents, anesthetist can

young animals, aggressive animals, wild animals, and captive animals in zoos

examples of animals to use IM induction