Inhaled anesthetics Flashcards by Meghan May

Therapeutic index for inhaled anesthetics

Very low therapeutic indices: LD50/ED50 values are 2-4!

How well did you know this?

Not at all

Perfectly

What determines the concentration gradient of inhaled anesthetics

Rather than a concentration gradient across a barrier, the partial pressure of the anesthetics determines transmembrane movement

How well did you know this?

Not at all

Perfectly

When is equilibrium of anesthetics reached

equilibrium is reached when partial pressures are the same, this is not necessarily equivalent to equal concentrations on each side of the membrane

How well did you know this?

Not at all

Perfectly

Measure of the solubility of the anesthetic in an aqueous versus gaseous environment

Blood:gas coefficent

How well did you know this?

Not at all

Perfectly

Low blood:gas partition coefficient results in

rapid equilibration in blood and relatively few molecules are required to raise its partial pressure

How well did you know this?

Not at all

Perfectly

rate of induction is______ related to the blood:gas partition coefficient

inversely

How well did you know this?

Not at all

Perfectly

recovery is ____ with a low blood:gas coefficient

quick

How well did you know this?

Not at all

Perfectly

with a low blood:gas PC, we need ____ amounts in the inspired ar

HIGH

How well did you know this?

Not at all

Perfectly

witha high blood:gas PC we need _____ amounts in inspired air

LOW

How well did you know this?

Not at all

Perfectly

induction and recovery are _____ with a high blood:gas PC

SLOW

How well did you know this?

Not at all

Perfectly

In a high fat:blood PC we see a _____ 1/2 life of drug

LONG

—cuases hangover bc more gets into brain

How well did you know this?

Not at all

Perfectly

Anesthetic concentration in the inspired air determines the gas pp in the air which affect:

ii) Also affects the partial pressure in the blood

also affects the rate of movement of gas into the blood

How well did you know this?

Not at all

Perfectly

The rate of transfer will increase as the concentration is _______ Therefore, rapid induction can be achieved with _________

increased

higher concentrations

How well did you know this?

Not at all

Perfectly

Pulmonary ventilation

Affects moderately blood soluble anesthetics _______ than low soluble agents

How well did you know this?

Not at all

Perfectly

Increased blood flow______ the rate of rise in arterial partial pressure
— Effect is most dramatic for moderately soluble anesthetics

slows

(the drug has less time to get into the blood)

How well did you know this?

Not at all

Perfectly

During induction, highly perfused tissues exert

the greatest effect and get most drug… like the brain

How well did you know this?

Not at all

Perfectly

Elimination is reverse of induction –________partition coefficient is the most important determinant

blood:gas

How well did you know this?

Not at all

Perfectly

_______anesthetics are eliminated fastest

Low solubility

How well did you know this?

Not at all

Perfectly

The longer the exopsure to a drug:

the more accumulation and the longer it takes to eliminate

How well did you know this?

Not at all

Perfectly

Anesthesia is achieved when

the brain partial pressure is equal to MAC

How well did you know this?

Not at all

Perfectly

Because the brain is well perfused, the partial pressures of the anesthetic in alveolar gas and in the brain become equal in a

short period of time

How well did you know this?

Not at all

Perfectly

NO net movement of gas at steady state:

Quick for gases with _____ blood:gas PC

LOW blood:gas

How well did you know this?

Not at all

Perfectly

steady state is Low for gases with _____ fat:blood PC

HIGH fat:blood

how is steady state determined in clinic

Equilibration occurs when the concentration of anesthetic in the inspired gas mixture is the same as the end-tidal (alveolar) concentration

Rate of elimination is dependent upon

blood: gas PC | - -Lowest will be eliminated the fastest

What determines the 1/2 life of anesthetic

the blood:fat PC bc the gas needs to get into the blood before it can be eliminated

For agents with low blood and tissue solubility, recovery is _____and unrelated to the length of anesthetic exposure

rapid

For agents with high blood and fat solubility, the recovery will be

a function of the duration of anesthetic administration (because of fat accumulation of the anesthetic)

Isoflurane (Forane®) Pharmacokinetics ______blood:gas PC and excreation

Moderate blood:gas partition coefficient--mod rates of induction and recovery 99% exreated unchanged from lungs

Clinical uses of isoflurane

inhalation anesthetic for incudction and maintenece but mostly for MAINTENENCE

Isoflurane is often used with NO to

reduce the amount needed

Respiratory Side effects of Isoflurane

Is an airway irritant, can cause coughing Decreases tidal volume and increases respiratory rate All volatile anesthetics are respiratory depressants and increase PaCO2.

CV side effcts of Isoflurane

Mycocardial depression; see decrease of BP Arrythmias (sensitizes heart to catecholamines) Cerebral vessel vasodialation = increase intracranial pressuer

very volatile at room temperature, requires special equipment to administer

Desflurane

Desflurane | blood:gas PC

Very low blood:gas partition coefficient; therefore very rapid induction and recovery

Can cause coughing and bronchospasm in awake patients so anesthesia is usually induced with intravenous agent

Desflurane

Desflurane cause coughing and bronchospasm in awake patients so anesthesia is usually

induced with intravenous agent

Produces direct skeletal muscle relaxation

Desflurane

Great for outpatient surgeries but cuases bronchospasm

Desflurane

CV effects of Desflurane

Mycocardial depression; see decrease of BP Arrythmias (sensitizes heart to catecholamines) Cerebral vessel vasodialation = increase intracranial pressuer

Respiratory effects of Desflurane

Is an airway irritant, can cause coughing Decreases tidal volume and increases respiratory rate All volatile anesthetics are respiratory depressants and increase PaCO2.

Has a very low blood:gas PC adn about 5% adminstered dose is metabolized to flouride ion in the liver

Sevoflurane

Issures with Sevoflurane metabolism

metabolized to fluoride ion that can cause renal damage and is degraded to compound A by administration apparatus that is nephrotoxic

Sevoflurane

Good for inpatient and outpatient and isn't a respiratory irritant

SEvoflurane

CV side of Sevoflurane

simular to isoflurane

Respiratory Sides of Sevoflurane

simular to iso but less respiratory depression

Very insoluble in blood and other tissues so results in a rapid equilibration; therefore, very rapid induction and recovery

Nitrous Oxide

Its rapid uptake from the alveolae results in the “concentration” of gases that are administered at the same time.

NO is a weak anesthetic because

weak anesthetic bc we can't get enough into air to produce MAC

Uses of NO

sedation and analgesia in 50% conc in inspired air and reduces conc of inhaled anesthetic dose needed.

Side effects of NO

contr: pneumothorax | negative ionotrope but also sympathomimetic with abuse liability

USed for induction and maintenence on inpatient | is slower and is an airway irritant

Isoflurane

Used for outpt, maintenence only and causes coughing and bronchospasm... given IV

Desflurane

Used for lots of stuff, induction and main.... but had fluoride ion and toxicity

Sevoflurane

Used in dentistry as adjunct and need oxygen dilution