Lec 16 - Inhalant Anesthetics (pt. 3) Study Guide

Dr. Johnson - Exam 2

What is the Minimum Alveolar Concentration (MAC)?

standard index of potency used to compare inhalants & predict effects → alveolar conc. in 50% of population that responds to supramaximal stimulus and 50% that do no

MAC is an index of what?

potency

What are the 3 variables that make MAC difficult to translate from research to clinical settings?

1. study only used healthy patients

2. MAC is an average (individual pt requirements will be different)

3. study measures spinal response (correlates w/ desired brain effect)

What is the MAC of Isoflurane and Sevoflurane?

iso = 1.3-1.6

sevo = 2.3-2.6

What 2 things increase MAC?

1. hyperthermia

2. CNS stimulants (amphetamines)

What 4 things decrease MAC?

1. pregnancy

2. hypothermia

3. extremes of age

4. other anesthetic agents (premeds, injectables)

What 7 things do NOT change MAC?

1. duration of anesthesia

2. gender

3. anticholinergics (atropine, glycopyrrolate)

4. normal pH

5. normal PaCO₂

6. normal PaO₂

7. normal blood pressure

What are the 4 potential beneficial clinical effects of inhalants in increasing order of dose.

1. unconciousness

2. muscle relaxation

3. loss of response to nociceptive input

4. loss of sympathetic response

What are the cardiovascular side effects of volatile anesthetics?

decreased CO (myocardial depression)

decreased SVR

both

What is the mechanism responsible for creating the cardiovascular side effects seen with volatile anesthetics?

dose dependent drop in blood pressure

What are the 2 respiratory side effects of volatile anesthetics?

1. decrease minute ventilation (RR x TV, primarily drop in TV)

2. decreased response to inc CO₂ (resp center in brainstem, apnea at high doses - apneustic center)

Cases of malignant hyperthermia typically present in which species/breeds?

usually white pigs → Landrace, Pietran, Poland China

What clinical signs are associated with malignant hyperthermia in pigs?

increased muscle activity/rigor

uncontrolled hyperthermia

uncontrolled CO₂

acidosis

arrhythmias

death

T/F: Modern inhalants are not metabolized by the body.

TRUE

T/F: Research clearly indicates that the regulatory limit for workplace exposure to waste anesthetic gases is <2 ppm.

FALSE — research is inconclusive (OSHA recommendations based on 1970’s NIOSH study)

T/F: If someone smells waste anesthetic gases, the exposure is much higher than 2 ppm.

TRUE

What population is at greatest risk for health problems due to exposure to waste anesthetic gases?

pregnant women