anesthesia maintenance and recovery

what are the 2 different ways we can maintain sedation/anesthesia?

1. IV- with continuous rate infusion/total intravenous anesthesia

2. inhalant, with volatile agents (using the anesthetic machine)

which is the better option for maintaining anesthesia- IV or inhalants?

inhalant- because it administers both O2 and gas. however, it is more expensive

what part of the anesthetic machine gives O2 to the patient?

flowmeter

which part of the anesthetic machine gives anesthetic gas to the patient?

vaporizer

what is the pathway of volatile agents to the patient (starting from the anesthetic machine)?

anesthetic machine → lungs → alveoli→ blood → body → brain

what is the pathway of volatile agents being eliminated from the body?

brain → body → blood → alveoli → lungs → anesthetic machine

the administration and elimination of volatile agents depends on _____

ventilation

what physiological component is necessary for the absorption and elimination of gas?

good alveolar perfusion

the pharmacokinetics of the volatile agents may be altered when _____ is impaired

ventilation or perfusion

if we have a good control of _______, we will have a good control of anesthesia

ventilation and BP

what are the 3 anesthetic gases we use in vet med?

isofluorane

sevoflourane

desfluorane

are the vaporizers good for use with any volatile agent, or are they specific to a certain type?

they are each specific for a certain type of gas.

we cannot use a vaporizer with a gas that it is not meant for.

what is the MOA of the volatile agents?

they affect the GABA receptors

if a gas is more soluble, will there be a slower or faster induction/recovery?

SLOWER

a less soluble gas will have a _____ (longer/shorter) induction and recovery time?

shorter

which- isofluorane, sevofluorane, or desfluorane, is the most soluble?

isofluorane

which- isofluorane, sevofluorane, or desfluorane, is the least soluble?

defluorane

anesthetic gases are eliminated via :

exhalation

are most volatile agents metabolized?

no, most are eliminated unchanged

why must be be careful not to remove the endotracheal tube too early?

because the patient will then exhale gas, and it can intoxicate the staff

what is MAC?

minimal alveolar concentration- it is the minimum amount of gas that reaches the alveoli at which 50% of animals do not move in response to a painful stimulus

how can we tell if a sedated animal is feeling pain?

the heart rate increases

which animals- small or large- need a higher concentration of anesthetic gas?

small- because they have a faster metabolism

is it a good idea to put a higher MAC into the anesthetic machine just in case the animal needs a heavier sedation?

no- we NEVER put more than necessary. begin at the advised MAC and then can increase/decrease little by little if needed.

does a patient with tachycardia need a higher or lower MAC?

higher

a patient with hyperthermia requires a __________ (higher/lower) MAC

higher

we should _______ (increase/decrease) the MAC for a patient with hyperthyroidism

increase

an animal with hypertension requires a ________ (higher/lower) MAC

higher

what patient factors might lead us to need to increase the amount of anesthetic gas?

increased cardiac output (tachycardia)

hyperthermia

hyperthyroidism

hypertension

what patient factors might lead us to need to decrease the amount of anesthetic gas?

hypothermia

drugs

pregnancy

hypothyroidism

should we increase or decrease the amount of anesthetic gas given to the patient if they are pregnant?

decrease

if a patient is hypothermic, how do we adjust the level of anesthetic gas given (increase or decrease)?

decrease

a patient with hypothyroidism should be given ______ (more/less) anesthetic gas

less

what are the 3 main physiological effects of volatile agents?

CNS depression

CV depression

respiratory depression

how do volatile agents impact the cardiovascular system?

depression:

vasodilation

hypotension

decreased cardiac output

bradycardia

which volatile gas is the most potent?

isofluorane

______% of isofluorane is metabolised by the patient

0.2

which volatile agent has a very strong smell? is this an advantage or disadvantage?

isofluorane

this is advantageous because it can tell us when there is a leak or a bad intubation

which anesthetic gas is marked in purple?

isofluorane

______% of sevofluorane is metabolised by the patient

2

does sevofluorane have a stong odor?

no

what volatile gas is labeled in yellow?

sevofluorane

what color label does sevofluorane have?

yellow

what is the problem with mixing sevofluorane with the old absobants?

it produces component A, which is nephrotoxic

this is not a problem anymore because the new absorbants do not do this

which anesthetic gas is blue?

desfluorane

which volatile agent is gas at room temperature, so cannot be simply opened and has to be placed directly onto the vaporizer?

desfluorane

what color is desfluorane labeled with?

blue

which volatile agent requires an electric vaporizer?

desfluorane

which volatile agent has a very high MAC?

desfluorane (7-9%)

which volatile agent is a pollutant, and can intoxicate the air in the room if there is a leakage?

desfluorane

which volatile gas has the fastest speed of action?

desfluorane

(because it is the least soluble)

which is the cheapest volatile agent?

isofluorane

which volatile agent is the least potent?

desfluorane

which volatile agent is most metabolized?

sevofluorane

do patients have a fast or slow recovery from anesthetic gas?

fast, because it is quickly eliminated through exhalation (it only takes around 5 minutes)

how long does it take for a patient to recover from anesthetic gas?

around 5 minutes

can volatile agents accumulate in the body?

yes, in adipose tissue

so, overweight animals have a slower recovery

what are the advantages and disadvantages of using volatile gases (inhalants) for anesthetic maintenance?

advantages: easy to control the depth of anesthesia, fast recovery, airway control

disadvantages: CV and respiratory depression, expensive, pollution, anesthetists may breathe the gas

with inhalants, is it easy to control the depth of anesthesia?

yes

what is "recovery" from anesthesia?

the process of going from unconscious to conscious

why are complications common during the recovery stage of anesthesia?

because there are less monitors and we need to physically monitor the patient. there is also less staff caring for the patient.

what are the potential complications we might experience during the recovery phase of anesthesia?

dysphoria

vocalizations

pain

if the recovery is longer than normal, what problems can this cause in the patient?

hypoglycemia

hypothermia

hypotension

impairment of the metabolism of other drugs

electrolyte disturbances