Exam 2 - Inhalants

Question 1

what are the important physical properties of inhaled anesthetics

Answer 1

vapors not gasses
saturated vapor pressure
boiling point
solubility (partition coefficient)
minimal metabolism/biotransformation

Question 2

dose of inhaled anesthetics in units of pressure

Answer 2

% x 760 mmHg

Question 3

what is the MAC

Answer 3

minimum alveolar concentration: prevents gross purposeful movement in 50% of subjects exposed to a supramaximal noxious stimulus

Question 4

factors that increase MAC

Answer 4

hyperthermia
CNS stimulation (ephedrine)

Question 5

factors that decrease MAC

Answer 5

CNS depression
hypotension
hypothermia
age
severe hypoxia < 40 mmHg
severe hypercapnia > 95 mmHg

Question 6

what are the general side effects of inhaled anesthetics

Answer 6

decreased alveolar ventilation (increased PaCO2) - dose-dependent
decreased CO dose-dependent
increased cerebral blood flow (loss of autoregulation)
decreased renal blood flow and urine output

Question 7

what inhalant can boil at room temp (23.5 degrees C)

Answer 7

Desflurane

Question 8

what inhalant can cause nephrotoxicity by forming compound A when mixed with soda lime (baralyme)

Answer 8

Sevoflurane - worst metabolism

Question 9

what inhalant are at risk of causing apnea

Answer 9

Desflurane

Question 10

list the inhalants from most soluble to least based on partition coefficients

Answer 10

isoflurane (1.4) > sevoflurane (0.65) > desflurane (0.45)

Question 11

what is the formula for the time constant (t)

Answer 11

size of circuit (L) / flow rate (L/min)

Question 12

what is one time constant equivalent to

Answer 12

63% or 0.63%

Question 13

tidal volume of small animals

Answer 13

10-15 ml/kg

Question 14

describe a high partition coefficient in regard to solubility, induction/recovery and rate of rise in alveoli and brain

Answer 14

high solubility - wants to stay in vasculature
prolonged induction/recovery
slower rate of rise in alveoli and brain

Question 15

describe a low partition coefficient in regard to solubility, induction/recovery and rate of rise in alveoli and brain

Answer 15

low solubility - enter/exit to other organs
induction/recovery faster
faster rate of rise in alveoli and brain

Question 16

how does increased ventilation affect alveolar partial pressure (PAInhalant)

Answer 16

increased minute volume = faster change in PAInhalant

Question 17

how does higher cardio output affect alveolar partial pressure (PAInhalant)

Answer 17

higher CO = more anesthetic gas removed from alveoli

Question 18

how does higher solubility affect alveolar partial pressure (PAInhalant)

Answer 18

higher solubility = slower rate of change

Question 19

difference between semi-open, low flow and closed circuits

Answer 19

semi-open - high flow rate > 30 ml/kg/min

low flow - flow rate approx metabolic O2 consumption, 2-6 ml/kg/min

closed circuit - flow monitored continuously to keep circuit partially full

Question 20

how many time constants does it take to reach 1% anesthetic gas

Answer 20

3 time constants