Chapters 60-99 Pharmacology

Question 1

Describe the unitary hypothesis of general anesthesia

Answer 1

AKA Meyer-Overton theory.

Based on correlation that increased lipid solubility = increased anesthetic potency

The anesthetic agents concentrate in the lipid membrane and change the fluidity of the membrane and/or act on membrane proteins and cause change in neurologic functioning

Question 2

What ion channels do sevo/des/iso act on?

Answer 2

potentiation of GABA and glycine receptors

Question 3

What ion channels does NO2 and xenon act on?

Answer 3

act like ketamine by antagonizing the excitatory NMDA receptors

Question 4

What specific brain structures do anesthetic agents inhibit?

Answer 4

1) inhibition of brainstem reticular formation–loss of consciousness
2) inhibitory effects at spinal cord reduce movement

Question 5

What are 3 major determinants of anesthetic gas uptake?

Answer 5

1) solubility (blood-gas coefficient)–the higher the blood-gas partition coefficient, the greater the amount of anesthetic dissolved in the blood at equilibrium, and causes delay in onset of anesthesia.
2) CO–changes in CO affect more soluble gases more.
3) partial pressure between alveoli and pulmonary vein–this includes the Fi of the agent and alveolar ventilation

Question 6

Increase or decrease MAC? Hypothermia

Answer 6

Decrease 4-5% for every 1 degree celcius

Question 7

Increase or decrease MAC? Age

Answer 7

highest in infants aged 3-6 months; decreases 6% for each decade of life

Question 8

Increase or decrease MAC? hyperthyroidism

Answer 8

Increase

Question 9

Increase or decrease MAC? Hypernatremia

Answer 9

increase

Question 10

If you have Right to Left shunt, how will this affect induction time and which agents (soluble versus insoluble) are more affected?

Answer 10

When a portion of the CO bypasses the lung it slows the induction because less anesthetic agent can be transferred from the alveoli to the blood. Impact of R–>L shunt is more pronounced in an insoluble agent.

Question 11

What is the limitation of uptake for highly soluble inhalation agents?

Answer 11

ventilation is the limiting factor

Question 12

What is the limitation of uptake for highly insoluble inhalation agents?

Answer 12

blood flow is the limiting factor

Question 13

If you have a LEFT to RIGHT shunt, how will this affect induction time and which agents (soluble versus insoluble) are more affected?

Answer 13

no significant change occurs in the speed of induction.

Question 14

Why are we concerned about N2O and airway fires?

Answer 14

While it is not flammable it will support combustion as easily as O2

Question 15

Does N2O have skeletal muscle relaxation properties?

Answer 15

No, only potent inhalation agents do

Question 16

What effects does N2O have on the respiratory system?

Answer 16

decreases TV, increases RR, reduces ventilatory response to hypoxia and hypercapnea

Question 17

What effects does N2O have CNS?

Answer 17

high concentrations cause increase cerebral blood flow

Question 18

What effect does N2O have on CVS?

Answer 18

slight myocardial depressant effect usually offset by sympathetic stimulation

Increases PVR

Question 19

How can N2O be toxic?

Answer 19

inactivation of methionine synthetase by oxidizing cobalt in Vit B12

Question 20

In neuro patients, when would N2O be an absolute contraindication?

Answer 20

2nd anesthetic within 3 weeks of undergoing open brain surgery, risk of having tension pneumocephalus because there is still significant air in the cranium

Question 21

Which of the agents is the least potent cerebral vasodilator?

Answer 21

Isoflurane