Inhalants Anesthesia Flashcards by Kate Guiremand

why use inhalant anesthesia

predictable effects (narcosis, muscle relaxation, not analgesic)

rapid adjustment of depth

minimal metabolism

economical

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vapor

gaseous state of a substance that is a liquid at ambient temp and pressure

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gas

exists in gaseous state a ambient temp and pressure

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N2O

low blood gas PC

mild analgesic

acumulates in clased gas spaces

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Xenon

expensive

mostly experimental at this time

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Dalton’s Law of partial pressure

total pressure of a gas mixture is equal to the sum of the partial pressure of the individual gases

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vapor pressure

pressure exerted by vapor molecules when liquid and vapor phases are in equilibrium

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vapor pressure is dependent on…

temperature

increases with increasing temp; inversely related to boiling point

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T/F desflurane is maintained in the gaseous form

True

blends with O2 to acheive vaporizer setting

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saturated vapor pressure

maximum administration percentage

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T/F vaporizers are needed to reduce the saturated vapor pressure to clinically useful doses

True

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anesthetic vapors dissove in

liquids and solids

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when is equalibrium reached

when the partial pressure of the anesthetic is the same in each phase

(partial pressure equal, but number of anesthetic molecules are not)

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what is solubility expressed as

partition coefficient

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what is the partition coefficient

concentration ratio of an anesthetic in the solvent and gas phase

describes the capacity of a given solvent to dissolve the anesthetic gas

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what is the most clinically useful number

blood gas partition coefficient

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what is the blood-gas partition coefficient

amount of an anesthetic in the blood vs. alveolar gas at equal partial pressures

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the anesthetic in alveolar gas represents…

brain concentration

this is the location of effect

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anesthetic dissolved in the blood is ppharmacologically…

Inactive

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low blood gas PC

less anesthetic dissolved in blood at equal patial pressure

(more in alveoli)

short induction and recovery - more clinically useful

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high blood gas PC

more anesthetic dissolved in blood at equal partial pressure

(less in alveoli)

long induction and recover

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the partial pressure in the brain is equal to

partial pressure in the aveoli

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how can PA be increased

increase the anesthetic delivery to alveoli

decrease removal from alveoli

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how can PI be increased

increase vaporizer setting

increase fresh gas flow

decrease breathing cicuit

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decrease removal from alveoli by

decrease blood solubilty of anethetic decrease CO - patients with low CO will have a faster rse of PA decrease alveolar-venous anesthetic gradient

T/F the higher the PI the more rapidly PA approaches PI

**True**

as uptake into blood decreases PI can be

decreased

anesthetic elimination requires

decrease in PA

how can you quickly decrease PA

turn off vaporizer disconnect patient and flush O2 turn up O2 flow increase ventilation (IPPV)

what is minimum alveolar concentration (MAC)

minimum alveolar concentration of and anesthetic that prevents movement in 50% of patients exposed to noxious stimulus

What is MAC used for

compare potency between agents inverse relationship (high MAC = low potency)

T/F: Alveolar concentration is NOT the same as the vaporizer setting

**True**

what increases MAC

hyperthermia hypernatremia drugs causing CNS stimulation

what decreases MAC

hypothermia hyponatremia drugs causing CNS depression MAP \<50 mmHg PaO2 \<40 mmHg PaCO2 \>95 mmHg pregnancy age

what are MAC multiples

used to describe dose of gas in relation to pharmacologic and physiologic effect 1.2-1.4 times MAC ensures immobility in 95% of patients

T/F MAC is additive

**True** (0.5 MACa) + (0.5 MACb) = 1 MACc

when is MAC important

changing gases in middle of a case usig N2O using partial intravenous anesthesia (PIVA)

cardiovascular effects of volatile anesthetics

CO, BP, SVR, contractility - decrease HR - no change to increase

when is there an increase in intracranial pressure

\>1 MAC

which doesnt suppress seizure activity

enflurane

renal effects of volatile anesthetics

decrease GFR and renal blood flow due to decreased CO renal failure

what is compound A

produced from sevoflurance breakdown in CO2 absorbent higher concentrations formed during: prolonged anesthesia, low fresh gas flow, desiccated absorbent

hepatic effects

reduce live blood flow and O2 delivery (decreased CO)

2 types of hepatotoxicity caused by halothane

increased liver enzymes "halothane hepatitis" - immune mediated, often fatal

which inhalant anesthetic is more likely to cause malignant hyperthermia

halothane

Tx of malignant hyperthermia

discontinue volatile anesthetic, flush with O2, switch to new circuit if possible provide 100% O2 administer dantrolene (muscle relaxant) fluids, active cooling

max administration of N2O

75% need at least 25% O2

CV effects of N2O

minimal CV and resp drepression

T/F N2O transfers to closed gas spaces

**True** GI tract, sinuses, middle ear, pneumothorax, GDV, cuff of ET tube avoid in disease states causing increased closed gas space

what is diffusion hypoxia

N2O administration is stopped, it diffuses quickly out of the blood into alveoli displaces O2 from alveoli if breathing room air → hypoxia

MAP with hypotension

\<60 mmHg (small) and \<70 mmHg (large)

what is the most appropriate and effective treatment for hypotension during inhalant anesthesia

turn down the vaporizer

if patient is light and hypotensive

add MAC-sparing drug then turn down vaporizer opioids, benzo, lidocaine, ketamine

definitition of hypoventilation

PaCO2 \>40 mmHg or EtCO2 \>45 mmHg

what can happen is pop off is closed

pneumothorax decreased CO

what signs are seen with stuck inspiratory-expiratory valves

rebreathing waveform on capnograph

what will you see with exhausted soda lime

rebreathing- waveform on capnograph

most common cause of laryngeal damage

from laryngoscope or stylet

tracheal tears are common in

cats

signs of tracheal tears

SQ emphysema pneumomediastinum and pneumpretroperitoneum

T/F inhalant anestheritics have a very low therapeutic index

**True**

what indicates inadequate cerebral blood flow for consciousness

low blood pressure MAP \<50 mmHg

partial pressure in the alveoli

PA =

gas delivery to alveoli - removal by the lungs