General Anesthesia Flashcards by Giselle Carter

what is the ultimate goal of anesthetic drugs

effect on brain: sedation and anesthesia

How well did you know this?

Not at all

Perfectly

what is FA and what is FI

FA: alveolar fraction
FI: inspiratory fraction

How well did you know this?

Not at all

Perfectly

why does FA differ from FI

because anesthetic is constantly being absorbed from the alveoli into the blood

How well did you know this?

Not at all

Perfectly

if the anesthetic vaporizer is set to 2%, what is FI

How well did you know this?

Not at all

Perfectly

elimination involves both _________ and _________

biotransformation (metabolism) and clearance

How well did you know this?

Not at all

Perfectly

what reflects the amount of anesthetic in the brain

alveolar concentration

How well did you know this?

Not at all

Perfectly

how do we measure alveolar concentration (and therefore amt of anesthetic in the brain)

end-tidal concentration

How well did you know this?

Not at all

Perfectly

what is the concept of dead space

the idea that not all anesthetic molecules are delivered to the alveoli (they can get caught up in the respiratory system)

How well did you know this?

Not at all

Perfectly

alveolar concentration depends on what 5 things

1) inspired concentration (FI)
2) alveolar ventilation
3) solubility of inhalational anesthetic
4) cardiac output
5) tissue capacity and blood flow

How well did you know this?

Not at all

Perfectly

what causes wasted ventilation

shallow breathing (dead space rebreathing)

How well did you know this?

Not at all

Perfectly

what is the order of inhalational anesthetics from lowest to highest BGPC (and therefore fastest to slowest induction/recovery)

desflurane
H2O
sevoflurane
isoflurane
halothane
methoxyflurane
ether

How well did you know this?

Not at all

Perfectly

are inhaled anesthetics soluble in the lipid or aqueous component of blood

lipid

How well did you know this?

Not at all

Perfectly

high solubility =

prolonged recovery and induction

How well did you know this?

Not at all

Perfectly

solubility can be expressed as ___/____

FA/FI

How well did you know this?

Not at all

Perfectly

describe how alveolar-venous tension difference influences amount of anesthetic in the brain

higher blood flow = faster uptake = decreased Fa = decreased amount in brain

How well did you know this?

Not at all

Perfectly

lower CO = (higher/lower) solubility

higher CO = (higher/lower) solubility

lower = higher solubility

higher = lower solubility

How well did you know this?

Not at all

Perfectly

normally, what percentage of CO goes to the brain in healthy animals

How well did you know this?

Not at all

Perfectly

what happens to the percentage of CO in the brain in animals in shock

it goes up to a very high percentage

How well did you know this?

Not at all

Perfectly

when there is low CO, (higher/lower) percentage of the CO goes to the brain

higher

How well did you know this?

Not at all

Perfectly

why do sick animals induce faster than healthy animals

they have less CO, so a higher fraction of the CO goes to the brain and the animal is induced faster

How well did you know this?

Not at all

Perfectly

brain concentration will not rise significantly until

alveolar concentration starts to rise

How well did you know this?

Not at all

Perfectly

anesthetic quantity in the blood is dependent on both

solubility and alveolar concentration

How well did you know this?

Not at all

Perfectly

once you turn off iso, what happens to inspiratory concentration and what happens to end-tidal concentration

inspiratory will drop to 0 and end-tidal will slowly decline as the animal eliminates the anesthetic through breathing

How well did you know this?

Not at all

Perfectly

do more or less soluble anesthetics have a higher degree of metabolism by the liver

more soluble

How well did you know this?

Not at all

Perfectly

recovery depends on (3)

- movement from brain back to blood - movement from blood back to alveoli - removal from alveoli back to anesthetic circuit and eventually scavenging system

what are 4 properties of general anesthesia (what are 4 things we produce through inducing general anesthesia)

- muscle relaxation - hypnosis - amnesia - analgesia

what is analgesia

reduced or absent perception of pain, in a conscious state

T/F all analgesics are general anesthetics

You need to do a procedure on an animal and you think it might be painful... based on the procedure, what 3 options do you have to control the animal/the animals pain

1) physical restraint 2) sedation and local anesthesia 3) general anesthesia

what are the 3 ways to perform general anesthesia and what is most commonly done

- inhalational - total intravenous anesthesia (TIVA) - partial intravenous anesthesia (PIVA) PIVA most common

what are the 3 PHASES of anesthesia

1) pre-anesthetic 2) anesthetic 3) post-anesthetic

which of the following drugs are analgesics: (there are 3) - opioids - acepromazine - alpha-2 agonists - benzodiazepines - ketamine - alfaxalone

opioids, alpha-2 agonists, ketamine

which of the following drugs are NOT analgesics: (there are 3) - opioids - acepromazine - alpha-2 agonists - benzodiazepines - ketamine - alfaxalone

- acepromazine - benzodiazepines - alfaxalone

which of the following drugs are +/- at MAC reduction: - opioids - acepromazine - alpha-2 agonists - benzodiazepines - ketamine - alfaxalone

opioids and benzodiazepines

what are some benefits of pre-medicating your patients

- facilitates patient handling - lowers dose of induction anesthetic needed - lowers dose of inhalational anesthetic (MAC reduction) - smoother induction - smoother recovery (if still present in bloodstream during recovery) - +/- analgesia

what is the best route to premedicate

which of the induction drugs is the only analgesic

ketamine

which of the induction drugs is not a muscle relaxant

ketamine

which of the induction drugs always reduces MAC

ketamine and pentobarbital

what is neuroleptanesthesia

giving an opioid and a benzodiazepine to induce (only works for sick patients)

what induction anesthetic is good to induce on its own

propofol

what are examples of drug combinations that we can use to INDUCE a HEALTHY patient

- ketamine + diazepam/midazolam - propofol/alfaxalone + diazepam/midazolam - propofol alone - inhalational anesthetic

what are advantages of using IV drugs to induce

1) rapid control of airways 2) rapid induction 3) smooth recovery 4) rapid adjustment in depth of anesthesia

what are 4 disadvantages of injectable induction

1) have to restrain patient 2) depends on patients hepatic and renal function 3) cardiopulmonary depression if you inject into artery 4) prolonged recovery if used for maintenance of anesthesia

what are advantages of inhalant anesthetic

1) does not require IV access 2) rapid recovery with newer agents

what are disadvantages of inhalant

1) requires fancy equipment 2) dose-dependent cardiopulmonary depression 3) excitement 4) pollution 5) cancer

what are 5 intubation routes

1) orotracheal 2) nasotracheal 3) pharyngostomy 4) tracheostomy 5) laryngeal mask

what are 5 things we can use to monitor the depth of anesthesia

1) ocular signs (palpebral, eye position) 2) muscle relaxation, muscle reflexes 3) RR depth and pattern 4) HR and BP 5) pharyngeal and upper airway reflexes

reflexes differ based on

species and drugs used

rules for monitoring are (strict/not strict)

not strict

what animals need a longer time before extubating

brachycephalics

where is the highest rate of death in horses (what phase)

post-anesthetic (recovery) phase

what do we monitor in recovery

cardiorespiratory and temperature (TPR)

what types of things do we give in recovery

fluids, analgesia, sedation

a lower MAC means (more/less) response to pain

less

inhalant/injectable anesthetics stimulate what 2 receptors

GABA and glycine

what triggers the respiratory center and where is this center located

chemoreceptors (peripheral and central) detect O2 and CO2 in the blood; located in the medulla and pons

what triggers the cardiovascular center and where is this center located

triggered by signals from baroreceptors in the carotid sinus and aortic arch; located in the medulla

what is respiration

the total process of delivering O2 and removing CO2

what are the 3 processes involved in respiration

1) gas exchange in the lungs 2) movement of gas in the bloodstream 3) transfer of gases at the cellular level

what is ventilation

the process of moving gases through the respiratory tract

does respiration or ventilation control O2 and CO2

ventilation

in an environment with no O2, what happens to ventilation and respiration

still ventilating because still moving air but not respirating because no O2

T/F ventilation is a part of respiration

what determines CO2 levels

minute ventilation (VE): RR x Vt

fill in the following: low VE = ______ventilation = ____ CO2 high VE = ______ventilation = _____ CO2

hypo; high hyper; low

why is it highly recommended to have a horse on a ventilator

depending on positioning, their organs can put pressure on the lungs and impact gas exchange

what is an issue with inhalant anesthetics and VE (think of Tainors graph)

when on inhalant anesthetic, the patient has a decreased ability to increase VE to compensate for higher CO2 (we may have to give breaths to counteract this)

physiologic dead space consists of:

anatomical and alveolar dead space

what does anatomical dead space consist of

air in the mouth, pharynx, larynx, trachea, bronchi and terminal bronchioles

what is alveolar dead space

air in the alveoli not participating in gas exchange (ex. due to atelectasis)

T/F PaCO2 = ETCO2

an animal that is panting/shallow breathing is ___________ but is not _______________-

ventilating; respirating

what is the consequence of panting/shallow breathing

less removal of CO2 from the lungs (may or may not impact O2 depending on FiO2)

what is the normal V/Q

0.8

V: Q:

V: Ventilation Q: CO or blood flow

what happens to V/Q when there is dead space

ventilating but not perfusing therefore V/Q = > 1

what happens to V/Q when there is a shunt

perfused but not ventilated therefore V/Q < 1

what are examples of a shunt

atelectasis, bronchoconstriction, complete small airway closure, vascular shunt

what pressure signifies relative hypoxemia and what pressure signifies absolute hypoxemia

relative: 80 mmHg absolute: 60 mmHg

what is hypoxemia

low FaO2

what are 5 causes of hypoxemia

- low PiO2 - V/Q mismatch - cardiac shunt - hypoventilation - diffusion barrier

what is PaO2 normally and under anesthesia

Normally: 93 mmHg Under anesthesia: 663 mmHg

what determines the amount of O2 available to tissues

Hg content and saturation

you never want to see under what number on a pulse oximeter why

95; corresponds with PaO2 of 80 (patient is starting to get hypoxemic)

one molecule of Hg can carry how many molecules of O2

how easily does each of the 4 oxygen molecules bind

first one hardest, gets easier for each subsequent molecule

hypoventilation is _____ dependent whereas hypoxemia is ____ dependent

CO2; O2

at rest, how what % of delivered oxygen is being used by cells

25%

T/F if you have an anemic patient you can prevent hypoxemia by delivering 100% oxygen

F; only a small portion of oxygen is dissolved in blood so without adequate Hb the patient will still be hypoxemic

most oxygen is removed from Hb on the arterial or venous side

venous

________ effect occurs in the lungs and ________ effect occurs in the tissues

Haldane; Bohr

oxygen delivery to tissues is highly dependent on

Cardiac Output (CO)

stroke volume is dependent on (3)

preload, afterload, contractility

what is preload

amount of blood present in the ventricles at the end of diastole

what is the effect of preload on cardiac output

increases CO to a certain point (volume), at which point the cardiac mm can no longer recoil effectively and the CO will decrease

what is contractility

ability of the heart to contract in the absence of any changes in preload or afterload

how can we "cheat" increasing contractility of the heart

by giving ionotropic drugs that act as B1 agonists: dopamine, epinephrine, dobutamine

what is afterload and what is the effect on CO

resistance to ventricular ejection; decreases CO

what is the effect of vasoconstriction on afterload and what drugs will do this

increases: a agonists

what is the effect of vasodilation on afterload and what drugs will do this

decreases; a antagonists and B2 agonists

BP depends on

CO and SVR (systemic vascular resistance)

CO depends on

HR and SV

oxygen delivery (DO2) depends on

cardiac output and CaO2

T/F if you see a good BP while monitoring anesthesia you can conclude that CO is also good as there is a correlation between CO and BP

F; not necessarily