General Anesthetics

Question 0

What is MAC?

Answer 0

‘Minimum alveolar concentration’
Concentration of inhaled agent at which 50% of pts will NOT move in response to surgical incision
Directly related to agents olive oil solubility

Question 1

What are 2 ways to increase alveolar concentration of inhalant?

Answer 1

1. Increase ‘dialed in’ concentration (I.e. partial pressure of agent)
2. Increase ventilation

Question 2

What are the 3 volatile anesthetics? Rank in order of potency.

Answer 2

Isoflurane- most potent, gold standard
Sevoflurane- less soluble/potent
Desflurane- least soluble/potent

Question 3

What are some side effects of isoflurane and the others in its class?

Answer 3

Airway irritation; dose dependent CNS depression, increase in cerebral blood flow and intracranial pressure; dose dependent decrease in systemic BP; decrease in respiratory function; relaxes skeletal muscle; malignant hyperthermia

Question 5

What barbiturate is used to induce general anesthesia? Mechanism?

Answer 5

Methohexital-

GABAa agonist, NMDA antagonist; produces hypnosis and sedation but anti- analgesic

Question 6

Propofol- mechanism and therapeutic use

Answer 6

GABAa agonist, NMDA antagonist; rapid onset/offset

Anti-emetic at low doses, induction/maintenance general anesthesia; sedation in ICU

Question 7

What are the side effects of Propofol?

Answer 7

Propofol infusion syndrome-
Usually assoc with concurrent catecholamine and glucocorticoid infusion (impaired fatty acid oxidation?); metabolic acidosis, rhabdomyolysis, renal failure, bradycardia, death

Question 8

Etomidate- mechanism and therapeutic use?

Answer 8

GABAa agonist (D-isomer)
Hypnosis, no analgesic activity
-used in pts with minimal cardiac reserve

Question 9

What are the side effects of Etomidate?

Answer 9

Pain on administration; involuntary myoclonus (due to subcortical disinhibition, not a seizure); PONV; inhibits cortisol synthesis

Question 10

What is Ketamine’s mechanism and use?

Answer 10

NMDA antagonist- dose dependent unconsciousness, amnesia, analgesia
Adjuvant during (w/Propofol) and after surgery
Pain therapy; depression

Question 11

What are the side effects of Ketamine?

Answer 11

• sympathetic stimulation: useful in hypovolemic, cardiac myopathy; contraindicated in CAD
• increases cerebral blood flow and intracranial pressure (contraindicated if mass lesion)
• bronchodilator

Question 12

What is the mechanism and side effects of nitrous oxide?

Answer 12

• NMDA receptor antagonist
• post-op nausea/vomit, inactivated vit B, insoluble in blood and accumulates in spaces
• NO muscle relaxation

Question 13

What is the mechanism and therapeutic use of Dexmedetomidine?

Answer 13

• a2 adrenergic agonist in spinal cord (produces sedation, sympatholysis, and analgesia)
• FDA approved for ventilation of ICU pts <24 hrs
• used for awake intubations, awake craniotomies; adjunct to general anesthesia in patients susceptible to narcotic-induced post-op respiratory depression; withdrawal/detoxification

Question 14

What is the only depolarizing NMB agent used today? Use?

Answer 14

Succinylcholine

-facilitates endotracheal intubation (short duration of action: 9-12 min)

Question 15

What are the side effects of Succinylcholine?

Answer 15

Malignant hyperthermia; cardiac dysrhythmias, hyperkalemia, increased intraocular pressure, increased intracranial pressure

Question 16

What are 3 drugs used to reverse non-depolarizing NMB drugs? Which is most common?

Answer 16

AChesterase inhibitors: Edophonium (shortest), Pyridostigmine, Neostigmine (most common)

Question 17

What are the 3 non-depolarizing amino steriod NMBs? The 2 Isoquinolinium agents?

Answer 17

amino steriod- Pancuronium, Vecuronium, Rocuronium

isoquinolinium- Atracurium, cisatracurium

Question 18

Which non-depolarizing NMB subclass is used for pts with liver or renal dysfunction?

Answer 18

Isoquinolinium (atracurium and cisatracurium)