Quiz 10

Question 1

MAC Amnesia

Answer 1

25% MAC in 50% population

Question 2

MAC intubation

Answer 2

130% MAC concentration required to prevent movement and coughing during endotrachial intubation

Question 3

Factors that increase MAC

Answer 3

• Hyperthermia
• Age: term infant to 6 months of age has the highest MAC requirement
• Chronic EtOH abuse
• Hypernatremia
• Drugs that increase CNS catecholamines cocaine, meth, etc.

Question 4

Factors that decrease MAC

Answer 4

Hypothermia: for every 1 deg. C drop in body temp – MAC decreases 2 to 5%
Preop medications
IV anesthetics, opioids
Neonate/Premature infants
Elderly
Pregnancy******
Acute EtOH ingestion
Lithium* on boards a lot
Cardiopulmonary bypass (CPB)
Hyponatremia
Alpha 2 agonists
Calcium channel blockers
Severe hypoxemia – PaO2 < 38 mmHg

Question 5

Factors that have no effect on MAC

Answer 5

Thyroid gland dysfunction*****
Duration of anesthesia
Gender
Hyperkalemia
Hypokalemia
Hypocarbia
Hypercarbia

Question 6

Halothane MAC

Answer 6

0.75

Question 7

Isoflurane MAC

Answer 7

1.15

Question 8

Sevoflurane MAC

Answer 8

2.05

Question 9

Desflurane MAC

Answer 9

6

Question 10

Alveolar uptake of agents

Answer 10

• Inspired concentration = concentration effect
• Alveolar ventilation – increased ventilation increases rate of rise of agent and speeds induction
• Anesthetic system – higher rates speed induction
• Uptake from alveolar space – depends on solubility, cardiac output, and alveolar/venous partial pressure difference

Question 11

The most important single factor in determining the speed of induction and the rate of emergence

Answer 11

Solubility

Question 12

Desflurane Blood:Gas coefficient

Answer 12

0.42

Question 13

N2O Blood:Gas coefficient

Answer 13

0.47

Question 14

Sevoflurane Blood:Gas coefficient

Answer 14

0.68

Question 15

Isoflurane Blood:Gas coefficient

Answer 15

1.4

Question 16

Halothane Blood:Gas coefficient

Answer 16

2.3

Question 17

N2O Properties

Answer 17

• good analgesic
• Can increase PONV
• Avoid use with closed gas spaces: PTX, complete bowel obstruction, inner ear, pneumocephalus, air embolism, intraocular bubbles,
• increases PVR especially in pts with pre-existing pulmonary HTN
• Nonflammable but an O2 source and supports combustion
• > 50% N2O given to pregnant rats for 24 hours increased skeletal abnormalities – inhibition of methionine synthesis which is needed for DNA synthesis, also may be secondary to impaired uterine blood flow
• Long term use can lead to peripheral neuropathy and megaloblastic anemia

Question 18

Halothane properties

Answer 18

• Dose dependent decrease in contractility, decreased BP & CO
• SVR and PVR stay normal
• Sweet odor, thymol preservative, previously most used for inhalation induction – children – vagal stimulation, may see bradycardia especially > 1 MAC – pretreat with atropine
• Sensitizes the heart to catecholamines, dysrhythmogenic, use epinephrine with caution

Question 19

Isoflurane/Desflurane properties

Answer 19

• Minimal decreases in contractility, decreased SVR, increases HR especially when rapidly increasing dose (norepinephrine)
• Coronary steal syndrome (ISO) – normal coronaries dilate and stenotic ones don’t so blood shunted away from diseased vessels

Question 20

Sevoflurane properties

Answer 20

• Nonpungent smell, good for inhalation induction, children – tolerate high levels within significant hemodynamic changes
• Rapid induction & emergence (occasional delerium in children)
• Can react with soda lime to form Compound A – nephrotoxic, brain, liver, increased formation with low FGF, high temp., [high agent], dry baralyme, long cases
• Keep Flows at least 2L / min.