Part 4 General Anesthesia

what is it called when you Give preanesthetic sedatives to help reduce the dose of induction and maintenance agents?

"Balanced anesthesia"

when do we know that a patient is in stage 3 plane 4 anesthesia?

'Rocking" breathing pattern - increase in abdominal breathing, decrease in chest movement Decrease in effective ventilation Pupils are fully dilated and PLR's are absent Muscles are flaccid

what is stage 4 known as?

(Stops Breathing)

what happens to the patient during stage 2 of anesthesia?

-Animal may show signs of excitement such as paddling, vocalizing or struggling but these are involuntary movements = not conscious Stage II has also been called the "excitement phase"

what is Anesthesia?

-Comes from Greek word which means "without feeling" or "insensibility" -Defined as a "loss of sensation"

when under general anesthesia It is important to monitor the what?

-Heart rate -Pulse quality -Ventilation/respiratory rate -Mucous membrane color -CRT

A thorough patient evaluation includes:

-History -Physical exam findings -Lab data

what is the recovery stage of general anesthesia?

-Occurs after the maintenance period as soon as the concentration of anesthetic in the brain starts to decrease -Recovery is basically the reverse process of Induction - Reflex activity, muscle tone, and sensitivity to pain are regained as consciousness returns

During Maintenance the following occur:

-Skeletal muscle relaxation and cessation of movement -Further loss of protective reflexes, such as the palpebral (blink) -Mild respiratory and cardiac depression - depending on drug used

The components of a General Anesthetic Procedure include:

1. Preanesthesia 2. Induction 3. Maintenance 4. Recovery

How can we make anesthesia as safe as possible?

1.Thorough evaluation of the patient 2.Correct any pre-existing conditions 3.Use premeds 4.Double check drug dosages 5.Use minimum drug dosages 6.Intubate all patients 7.Closely monitor recovery

what is General Anesthesia?

A reversible state of unconsciousness

what is Surgical Anesthesia?

A specific stage of general anesthesia in which there is also sufficient analgesia and muscle relaxation to allow surgery to be performed without the patient feeling any pain or moving

what does ACVA stand for?

American College of Veterinary Anesthesiologists Monitoring Guidelines:

what does the animal look like when it is in stage 1 of anesthesia?

Animal is conscious but disoriented -May show struggling, urination, defecation, or other signs of fear or anxiety -Shows reduced sensitivity to pain -Respiration and heart rate are usually increased -Patient loses ability to stand and becomes recumbent -Stage 1 starts when Induction starts

what are some important notes about stages and planes of anesthesia

Appearance of stages vary with the anesthetic agent(s) used The patients don't read the textbooks! An animal can show signs of more than one stage/plane at same time It's up to the anesthetist to process this information and come to a conclusion

before administering any medication what do we have to double check?

Before administering any medication, double-check: Dosage calculation Drug concentration

what happens to the CRT, PLR, and eyes when an animal is in plane 3 stage 3 analgesia?

CRT increased PLR poor or absent Eyes central Pupils moderately dilated Reflexes absent Profound relaxation

how can General Anesthesia be achieved?

Can be achieved through the use of injectable and/or inhaled drugs

what is necessary when the animal reaches stage 4 anesthesia?

Cessation of respiration followed by circulatory collapse and death Immediate resuscitation necessary to save the patient's life Once animal enters this stage, it is almost impossible to recover

what can general anesthesia be characterized by?

Characterized by the loss of : - pain perception - memory - motor response to stimuli - reflex responses

what are the American College of Veterinary Anesthesiologists Monitoring Guidelines:

Class P1 and P2 patients should be monitored and recorded at least once every 5 minutes Class P3, P4, and P5 patients should be monitored and recorded continuously

what are examples of any correctable preexisting conditions that should be corrected before beginning anesthesia?

Dehydration Anemia Hypotension

what is stage 1 of anesthesia called?

Disoriented

how many planes does stage 3 of anesthesia have?

Divided into 4 planes (phases) of anesthesia, with each plane being deeper than the previous one

what is happening internally to cause the excitement response in stage 2 anesthesia?

During the "excitement phase" epinephrine is released which could cause cardiac arrhythmias or arrest

what is stage 2 of anesthesia also called?

Excitement

what is the general rule of thumb when we are giving drugs to effect?

Give half the calculated amount and wait 30-60 sec. If you need more then give half of what is left and wait another 30-60 sec If you still need more then give half of what is left and so on and so on.....

how can premeds help with reducing negative effects from occurring in general anesthesia

Give preanesthetic drugs that can protect the heart Give preanesthetic drugs to help reduce the dose of  induction and maintenance agents

what does giving to effect mean?

Give some of the drug and wait to see the effects, then give more and watch for the effects and when the desired effect is reached you stop giving the drug

what is the goal pertaining to stage 2 of anesthesia?

Goal is to get animal through Stage II as quickly as possible

what kind of vitals does the patient have during stage 2 of anesthesia?

HR and RR elevated, pupils dilated Reflexes are present and may be exaggerated Still able to chew and swallow Breathing may be irregular - animal may hold its breath (especially cats) Yawning common

Every anesthetized patient is at risk for:

Hypotension Hypoventilation Hypoxia Hypothermia

how will patients under stage 3 plane 1 react to painfull stimulus?

Increased heart rate Increased respiratory rate Movement

How are inhalant anesthetic drugs eliminated from the body?

Inhalation agents are excreted through the respiratory tract

why is it important that we intubate all patients undergoing general anesthetic?

Intubate all patients undergoing a general anesthetic. Allows us to oxygenate or ventilate ("bag") the patient Prevents aspiration and obstruction of airway

what are the HR, BP, mucous membranes, CRT, and RR like in stage 3 plane 4?

Marked decrease in HR and BP Pale mucous membranes Prolonged CRT In immediate danger of respiratory and cardiac arrest DANGER!!! We don't want to be here!!! This becomes an Emergency!!

what may you have to do when a patient reaches a stage 3 plane 3 anesthesia?

May have to assist respiration by "bagging

what is stage 3 plane 2 anesthesia called?

Medium depth of anesthesia

How are injectable anesthetic drugs eliminated from the body?

Most injectable drugs are broken down by the liver and excreted by the kidneys (in the urine)

do we always see stage 2 of anesthesia?

Most premedicated animals that are rapidly induced with IV drugs will appear to go directly from Stage I to Stage III without clinically showing any signs of Stage II. Animals that are "masked down" with a gas anesthetic are more likely to show excitement because it takes longer.

is the patient read for surgery in stage 3 plane 1?

Not ready for surgery yet!

what will cause a slight increase of HR or RR in a patient that is in stage 3 plane 2?

Painful stimuli may cause a slight increase in HR or RR, but patient is immobile and stays unconscious

is the patient conscious in stage 3 of anesthesia?

Patient is unconscious

what happens to the patients consciousness when they enter stage 2 of anesthesia?

Patient loses consciousness when they enter Stage II

what is Preanesthesia?

Period immediately preceding anesthesia when: -Patient data is collected -Patient is fasted -Adequate hydration is ensured -Preanesthetic drugs are administered

what are the vitals/reflexes of the animal when they are under stage 3 plane 1?

Respiration is regular PLR's decreased Gagging and swallowing reflexes depressed Involuntary movements cease Eyeballs rotate ventromedial Pupils become partially constricted Other reflexes such as palpebral present, but slower Unconscious but will respond to a painful stimulus by showing

what will the vitals/ reflexes be of a patient in stage 3 plane 2 anesthesia?

Slow PLR's, eyes ventral or ventromedial, pupils slightly dilated Respiration is shallow but regular 12-16 breaths/min in dogs, slightly higher in cats Heart rate and blood pressure mildly decreased Pedal and swallow reflexes absent Skeletal muscles relaxed

why must Dosages of barbiturates be altered for very fat or very thin patients?

Some of the barbiturates redistribute into the muscle and fat of the patient

when does stage 2 anesthesia end?

Stage II ends when the animal shows signs of muscle relaxation, slower respiration rate, and decreased reflex activity.

what is the maintenance stage of general anesthesia?

Stage after the induction period where sufficient anesthetic is supplied to keep the patient at an appropriate depth of anesthesia -When surgery or procedures are performed

how many stages of anesthesia are there?

Stages I to IV

is stage 3 plane 2 suitable for sugery?

Suitable for most surgical procedures

what is Induction?

The stage after the -preanesthetic stage when the animal leaves the normal conscious state and enters the anesthetized state -Induction agent may be administered by inhalation ("masking down") or by injection -Animal loses consciousness and loses protective reflexes, such as the ability to swallow or cough -May show an excitement phase before becoming anesthetized -Desirable to eliminate this excitement phase because it is - Unpleasant for the animal and the staff - Predisposes animal to cardiac arrhythmias

What is the anesthetist's goal?

To avoid excessive anesthetic depth while making sure the patient is not responding to the surgical stimulus

what are the characteristics of stage 3, plane 3 analgesia?

Too deep for most surgical procedures Significant depression of circulation and respiration often present RR<12/min and breaths are shallow Heart rate reduced, even with surgical stimulation Pulse strength reduced (decreased BP)

is stage 2 a good thing for the patient?

Unpleasant and potentially dangerous for the patient

do we use the same amount of induction and maintenance anesthetic when we are inducing all 20 kg dogs?

Use only the minimum dose of drug needed to achieve the desired level of anesthesia when both "inducing" an animal or "maintaining" it. Give injectable agents "to effect" **It doesn't necessarily take the same amount to induce every 20 kg dog!

what should we observe recovering patients carefully for?

Watch for: Vomiting Laryngospasm Seizures

when in doubt about the animal becoming too deep what should we do?

When in doubt as to whether or not a patient is too deep, it's better to decrease the amount of anesthetic being given (gas) or stop giving the anesthetic (injectable) and reevaluate the patient

what is stage 3 often called?

anesthesia

what is stage 3 plane one called?

light anesthesia

when can we place the endotracheal tube?

stage 3 plane 1

what is stage 3 plane 3 often called?

too deep