Inhalational Anesthetics Flashcards by Hugo Siu

What are the 2 factors that determine the depth of inhalation anesthetics?

Concentration
-> Partial pressure
Solubility

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What are the 2 factors determines the rate of induction of inhalation anesthetics?

Physico-chemical properties of drug
- Solubility
Hemodynamic and pulmonary function

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What happens when the anesthetic agent has low solubility?

Low solubility
-> Blood is rapidly saturated
–> Transfer to other compartment ( e.g. Brain )
—> Faster onset
—> Deeper depth

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What does a high Blood/Gas Partition mean to Blood solubility?

High blood/gas partition = high blood solubility

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What does higher blood solubility mean to the rate of change in depth of anesthesia?

Higher blood solubility
-> Slower the rate of change in depth of anesthesia

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Match the following

Desflurane
Isoflurane Ultrashort acting
Enflurane
Halothane Short acting
Sevofllurane
Nitrous oxide Long acting
Methoxyflurane
Diethyl ether

Long acting
-> Diethyl ether
-> Methoxyflurane

Short acting
-> Halothane
-> Enflurane
-> Isoflurane

Ultrashort acting
-> Sevoflurane
-> Desflurane
-> Nitrous oxide

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What do we have to remember about methoxyflurane is very slow?

Methoxyflurane is very slow
- Induction
- Recovery
- Changes in anesthetic depth

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What is nitrous oxide used for during induction?

Nitrous oxide facilitates the induction

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What is nitrous oxide effect called?

2nd gas effect

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Why is Sevoflurane used in avian & small animals?

Rapid induction & recovery

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What is MAC short for?
What does it mean?

Minimal alveolar concentration
-> 50% of patients don’t feel pain

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The “higher” or “lower” the MAC, the more potent the anesthetic agent?

The lower the MAC
-> The more potent the anesthetic agent

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How many times of the MAC is required for surgical anesthesia?

1.2 - 1.5 times the MAC

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The “higher” or “lower” the lipophilicity, the more potent the anesthetic agent?

The higher the lipophilicity
-> The more portent the anesthetic agent

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4 Factors that decrease MAC

Hypo ( anything )
-> Hypotension
-> Anemia
-> Hypothermia
-> Hypoxia
-> Hypothyroidism

Metabolic Acidosis
-> Kidney problems

Old Age

Pre med

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2 Factors that increase MAC

Hyperthermia
-> Increase metabolic rate of brain

Hyperthyroidism

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6 Factors that do not affect MAC

Duration of Anesthesia

Species
-> Difference are negligible

Sex

PaCO2
-> 14 - 95 mmHg

PaO2
-> 38 - 500 mmHg

Hypertension

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Which of the following are Epileptogenic?

a) Methoxyflurane
b) Halothane
c) Enflurane
d) Sevoflurane

c) Enflurane

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Are IHs potent “Vasodilators” or “Vasoconstrictor”?

IH
-> Potent vasodilators
–> Increase cerebral blood flow
—> Increase intracranial pressure

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Does IH “Excites” or “Depress” cardiopulmonary function [ in a dose - dependent manner ]?

Depress cardiopulmonary function

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What type of receptor reflex activity does IH inhibits?

Baroreceptor

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What are 3 IH advantages?

Accurate control for anesthetic depth
-> During induction

Inhalant can be eliminated quickly
-> Through ventilations
–> Not metabolism

High - inspired oxygen can be provided

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What are 3 IH disadvantages?

Not suitable for dogs
-> Healthy
-> W/o pre med

Pungent smell [ Isoflurane & Desflurane ]
-> Causes animal to hold their breath
–> Slow down induction

Pollutes work environment

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Is IH suitable for ‘small’ or ‘big’ animals?

Small animals
&
Weakened Dogs & Cats
Dogs & Cats w/ strong pre med

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What happens if healthy animals aren't giving pre med before IH?

Excitement

Is 'Sevoflurane' or 'Isoflurane' better for Mask induction?

Sevoflurane -> Induction --> Quicker --> Smoother

What animals are suitable for Chamber induction?

Small & Intractable animals

What is the advantage of Chamber induction?

"Hands free" induction -> Safe --> Animal --> People

How many percentage of 'Isoflurane' & 'Sevoflurane' w/ O2 is used?

Isoflurane - 5% Sevoflurane - 8%

Until when are we safe to enter the Chamber?

Until animal losses its righting reflex -> Cannot stand straight

What are 4 advantages of IH for maintanence?

Protection of airway -> Intubated High - inspired O2 -> Maintains blood O2 content Easy control of depth of anesthesia Rapid recovery -> Ventilation elimination --> Not metabolism in Liver

Can pre med reduce maintenance concentration in IH?

Yes

What is the major elimination route of IH?

Respiration / Ventilation

What are the pharmacological effects of anesthetic action in these anatomic sites? - Spinal cord - Thalamocortical communication - Hippocampus

Spinal cord -> Immobilization Thalamocortical communication -> Unconsciousness Hippocampus -> Amnesia

What is the most potent IH?

Methoxyflurane

Up to how many % of Methoxyflurane is Metabolized?

Up to 50% -> Less elimination through Lungs

What is THE disadvantage of Methoxyflurane?

SLOWWW -> Induction -> Recovery

What does the metabolite of Methoxyflurane( F-, dichloroacetic acid...) do to kidney?

Kidney failure -> Irreversible

Does nitrous oxide smell bitter, sweet or spicyyy?

Sweet

Is N2O flammable?

No -> N2O --> Nonflammable gas

Is N2O a potent analgesic agent?

NOOO -> High MAC ( > 100% )

Does N2O provide Skeletal muscle relaxation?

What happens after discontinuation of N2O? Explain

Diffusion Hypoxia ( aka Dilutional hypoxia ) -> Discontinuation of N2O --> Concentration of gradient between Lungs & Alveolar circulation rapidly reverse ---> O2 dilution in Lungs ----> Hypoxia

If N2O has such high MAC, what is it used as instead?

Adjuvant

How many % of N2O + O2 can significantly reduce MAC for Halothane, Enflurane, Isoflurane? How many % of the amount of Primary IH is reduced in general using N2O as adjuvent?

70% N2O + O2 -> Significantly reduce MAC for --> Halothane --> Enflurane --> Isoflurane Reduces 25 - 30 % of the amount of Primary IA used

What is N2O 'Second gas effect'?

Low blood insolubility -> w/ High concentration --> Rapid uptake ---> Enhance uptake of Primary IH ----> Especially good for soluble IH

What is the 4 advantages for N2O?

Second gas effect Nonflammable Minimal effect on circulation Minimal effect on respiratory drive

What is the 4 disadvantages for N2O?

No skeletal muscle relaxation Weak anesthetic potency -> MAC > 100% Diffusion hypoxia Cannot be used a sole anesthetic agent

Does increased MAC of Halothane causes 'Increased' or 'Decreased' tidal volume in lungs *Tidal volume is the amount of air that moves in or out of the lungs with each respiratory cycle

Decreased

Up to how many % of Halothane is Metabolized?

Up to 25%

What is Halothane Hepatitis?

Metabolites of Halothane -> Trifluoroacetylated liver protein ( Tri | Fluoro | Acetylated ) --> Production of Antibodies against it ---> Halothane Hepatitis ( Immune response ) ----> 1 in 10,000 patients

Can halothane induce skeletal muscle relaxation?

Yes

What is the enzyme that metabolize Halothane into Trifluoroacetylated liver protein?

Cytochrome P450

What is Malignant hyperthermia?

Inhalation anesthetics ( Halothane, Isoflurane, Sevoflurane ) + Muscle relaxant ( Succinylcholine ) -> Uncontrolled released of Ca++ --> From SR ( Sarcoplasmic reticulum ) ---> Sustained muscle contraction ----> Hyperthermia

What is the treatment for Malignant hyperthermia?

Dantrolene -> Inhibits Ca++ release from SR Rapid cooling Provide supplemental oxygen Control lactic acidosis

How many F- are there in Enflurane?

Is Enflurane flammable?

No -> Not in room temperature --> So.. technically yes?

Does Enflurane has a pungent odor?

Yes

Up to how many % of Enflurane is Metabolized?

2% metabolized

Can Enflurane causes renal failure?

Yes -> Too many F- --> Avoid long cases

Does Enflurane have 'slow', 'quite rapid' or 'rapid' onset and recovery, due to its intermediate solubility and high potency?

Quite rapid

Is Enflurane used for induction or maintenance of general anesthesia?

Maintenance**

Can Enflurane cause Seizure?

Yes -> Only when concentration > 3%

How many F- are there in Isoflurane?

Up to how many % of Isoflurane is Metabolized?

0.17% LOL

Is Isoflurane flammable?

No -> Not in room temperature

Does Isoflurane has a pungent odor?

Yes

What are the effects of Isoflurane on cardiovascular system?

Little effect

Can Isoflurane cause Seizure?

No -> Very good compared to Enflurane

Can Isoflurane cause Malignant hyperthermia?

Yes

Which of the following have well maintained cardiac output? - Halothane - Isoflurane - Enflurane

Isoflurane -> Little effect on cardiovascular system

What can enhance Isoflurane muscle relaxation?

Tubocurarine

Other than _______ procedures, reduced amounts of tubocurarine may be required?

Abdominal procedures?

What is the 5 advantages for Isoflurane?

Rapid & smooth adjustment of anesthetic depth No Hepatic & Renal toxicity -> Methoxyflurane --> Irreversible renal failure -> Halothane --> Halothane Hepatitis -> Enflurane --> Renal failure Little effect on cardiovascular system Relaxation of Skeletal muscle Arrhythmias is not unlikely -> Irregular heartbeats

What is the disadvantages for Isoflurane?

May cause Malignant hyperthermia

How many F- are there in Sevoflurane?

7 ==

Does Sevoflurane has a pungent odor?

Does Sevoflurane have 'slow', 'quite rapid' or 'rapid' onset and recovery,

Rapid onset & recovery

Does Sevoflurane cause airway irritation?

LEAST airway irritation -> Among other volatile anesthetic

Is Sevoflurane suitable for direct anesthesia induction?

Yesss -> Minimal airway irritation goodgood

Up to how many % of Sevoflurane is Metabolized?

3 - 5% metabolized

Is Sevoflurane's vapor pressure 'similar' or 'different' compared to Halothane and Isoflurane? If so, what vaporizer is recommended?

Similar -> Conventional, unheated vaporizer is fine

Does Sevoflurane form trifluoroacetylated liver protein?

No :D -> No Halothane Hepatitis

Can Sevoflurane cause Malignant hyperthermia?

Yes

Are Sevoflurane MAC decreased when pre med is used ?

Yes

What is the clinical usage for Sevoflurane

First - line ( Commonly chosen ) Excellent induction agent

How many F- are there in Desflurane?

Is Desflurane's vapor pressure 'similar' or 'different' compared to Halothane and Isoflurane? If so, what vaporizer is recommended?

Different -> Increased Vapor pressure --> Boiling in room temp. ---> Requires a special vaporizer ----> Temperature controlled vaporizer

Fluorination instead of Chlorination means that Desflurane has 'increased' or 'decreased' molecular stability?

Increased molecular stability

Up to how many % of Desflurane is Metabolized?

Too little there is no data .-.

Does Desflurane have 'increased' or 'decreased' potency compared to Isoflurane due to its Fluorination?

Decreased potency -> 5 times less than Isoflurane

Does Desflurane has a pungent odor?

Yes -> Less likely to be used for induction

What is the feature that separates Sevoflurane & Desflurane from all other IH?

Low solubility -> Rapid onset, recovery

Does Diethyl Ether 乙醚 have a 'quick' or 'slow' induction and recovery?

Slow induction & recovery

Is Diethyl ether has full spectrum of CNS depression?

Yes

What is the advantages of Diethyl Ether?

Muscle relaxation Analgesia Non - toxic metabolites

Why is Diethyl Ether no longer used in medical practices?

Flammable & Explosive Irritation -> Respiratory -> GI

Diethyl Ether was used in what animal for anesthesia?

Lab animal -> Mouse -> Rats

Inhalational Anesthetics Flashcards

(98 cards)