General Anesthetics

Question 1

Most anesthetics have the effect of producing immobility in response to noxious stimuli. Where is this effect mediated?

Answer 1

spinal cord

• primary inhibitory NT in brainstem/spinal cord is GLYCINE

Question 2

Anesthetics have the effect of producing unconsciousness. How is this effect produced?

Answer 2

depressing thalamic neurons and blocking thalamo-cortical communication

Question 3

What are some potential presynaptic effects of anesthetics?

Answer 3

• inhibit glutamate release via AMPA, kainate, and NMDA receptors
• have been shown to both increase/decrease GABA release via GABAa receptors

CONCLUSION: different effects on different ion channels

Question 4

What kind of site of action do anesthetics likely bind?

Answer 4

• hydrophobic pockets on proteins

supported by firefly luciferase, unitary theory of anesthesia, and meyer-overton rule

Question 5

Which volatile anesthetic boils at room temp?

Answer 5

Desflurane (need a gas blender instead of a gas vaporizer to use)

Question 6

Sevoflurane’s MAC % is 1.8, and Isoflurane’s is 1.17. Which drug is more potent?

Answer 6

Isoflurane (lower MAC = more potent)

Question 7

What is unique about N2O’s MAC?

Answer 7

MAC % = 104, so ~100 x’s less potent than the volatile anesthetics

Question 8

What kind of factors in a patient will increase the MAC?

Answer 8

• hypermetabolic states (hyperthermia, red hair, increased catecholamines, cyclosporine use, hypernatremia)

Question 9

What kind of factors in a patient will decrease the MAC?

Answer 9

• hypometabolic states (hypothermia, increased age, decreased catecholamines, opioids, anxiolytics, a-2 agonist, lidocaine, hyponatremia, pregnancy)

Question 10

What is the main determinant of the uptake and distribution of an inhaled anesthetic?

Answer 10

partial pressure!

Question 11

Describe the 2nd gas effect

Answer 11

ability of high volume uptake of one gas (usually N2O) to accelerate the rate of increase in Palv of a second gas

Question 12

What two drugs can you use for mask induction in children?

Answer 12

N2O or sevoflurane

Question 13

What is a potential side effect in certain patients when using an anesthetic, due to deficiency of an enzyme of metabolism?

Answer 13

malignant hyperthermia

Question 14

What are the two barbituates used for IV induction of anesthesia, what is their effect, and how do they work?

Answer 14

Thiopental and Methohexital

• cause sedation/hypnosis via GABAa receptor but have no analgestic effect

Question 15

What are the actions of propofol?

Answer 15

• GABA agonist –> hypnosis
• a-2 receptor activity –> sedation
• NMDA-glutamate receptor inhibitor

Question 16

What are some benefits and drawbacks of using propofol?

Answer 16

Benefits: rapid on/off, does not trigger malignant hyperthermia, anti-emetic at low doses

Drawbacks: allergic reactions, pain at injection, propofol infusion syndrome (metabolic acidosis, myocardial failure, rhabdomyolysis, hyperkalemia, renal failure)

Question 17

You need to maintain anesthesia in a patient that has minimal cardiac reserve. What agent do you choose and what is its MOA?

Answer 17

etomidate, a GABAa agonist

Question 18

Your patient has been on long term narcotics. You acheive anesthesia, but he is moving around, his eyes are open, and his reflexes are intact. When he wakes up, he is panicked and keeps talking about his nightmares. What did you use for anesthesia, and what can you supplement with to reduce the unwanted side effects?

Answer 18

• used ketamine, an NMDA antagonist

- supplement with benzos

Question 19

You’re observing a craniotomy and the patient is awake enough to follow simple commands and respond to the surgeon’s questions. What drug is probably being used for anesthesia and how does it work?

Answer 19

• dexmedetomidine, an a2 adrenergic agonist that binds in locus coeruleus and spinal cord to produce sedation, sympatholysis, and analgesia

Question 20

The only depolarizing neuromuscular blocker we talked about, that is used for intubation and acts as a superagonist of the ACh receptor?

Answer 20

succinylcholine

Question 21

How do the -curonium/-curium agents work?

Answer 21

non-depolarizing, competitive blockage of ACh at receptor

- used as skeletal muscle relaxants

Question 22

What neuromuscular blockers can be used in patients with liver or renal dysfunction?

Answer 22

atracurium (causes histamine release in brief injections) or cis-atracurium

Question 23

What drugs can be used to reverse NMB?

Answer 23

AChEI’s (edrophonium, neostigmine, pyridostigmine) + antimuscarinic (glycopyrrolate)

Question 24

Tell me about sugammadex

Answer 24

complexes with rocuronium to act as a selective relaxant binding agent and immediately reverse rocuronium’s effects
- SE: hypotension, nausea/vomiting, dry mouth

Question 25

Patient comes into the OR after involvement in an MVA, and has lost significant blood. BP is 86/48… What agent do you use to induce anesthesia

Answer 25

ketamine