Lec 14 - Inhalant Anesthetics (pt. 1) Study Guide

Dr. Johnson - Exam 2

What are the advantages of inhalant anesthetics?

• predictable & rapid adjustment of effect (better control)

• part of a complete delivery system

  • precision vaporizer (simple), O₂ source, control of ventilation, CO₂ removal

• inexpensive after initial investment

What are the disadvantages of inhalant anesthetics?

• naroow therapeutic index (2-4)

• expensive initial investment

• don’t block nociceptive input → hyperalgesia

• side effects → cardiovascular, respiratory

What is the primary advantage of isoflurane over sevoflurane?

less expensive (sevo 10x more $$)

What is the primary advantage of of sevoflurane over isoflurane?

less soluble

Both isoflurane and sevoflurane are administered as what?

both are stored as a liquid and administered in a gaseous state

Why does an inhalant anesthetic with a high vapor pressure poses a risk to a patient?

can very rapidly administer a lethal dose to the patient

What is the clinically useful way to record the amount of inhalant being administered to a patient?

volume % = concentration of one gas in a mixture

administer anesthetic then observe to decide clinical effect

What is partial pressure?

the pressure exerted by one gas in a mixture of gases if occupying the space alone

What controls the clinical effect of inhalants on the patient?

partial pressure in the brain

How do changes in partial pressure can affect inhalant anesthetics & what is the clinical application?

lower partial pressure in the brain = less likely to be unconscious

anesthestic vaporizer setting IS NOT CHANGING

ex 1: surgery on top of a mountain = lower atm pressure = lower partial pressure

ex 2: surgery at sea level = higher atm pressure = higher partial pressure

What clinical property is dictated by the blood:gas solubility?

determines induction and recovery time!

What are the predicted clinical effects between 2 inhalants based on blood:gas partition coefficients (PC)?

more soluble = slower induction & recovery

ex 1: Sevo PC = 0.6 → less soluble = fast induction/recovery

ex 2: Iso PC = 1.4 → more soluble = slow induction/recovery

If given PC of 2 inhalants in relation to the blood:gas partition, what can you calculate?

how much time it takes to absorb (rate of induction/recovery)

What clinical property is predicted by the oil:gas solubility?

determines potency

What are the predicted clinical effects between 2 inhalants based on oil:gas partition coefficients (PC)?

more lipid soluble = more potent = less concentration required for clinical effect

*ex 1: Sevo PC = 50 → less potent = great conc. of drug required

ex 2: Iso PC = 99 → more potent = less conc of drug required

If given PC of 2 inhalants in relation to the oil:gas partition, what can you calculate?

concentration required to see clinical effect