General Anesthetics Flashcards
Most anesthetics have the effect of producing immobility in response to noxious stimuli. Where is this effect mediated?
spinal cord
- primary inhibitory NT in brainstem/spinal cord is GLYCINE
Anesthetics have the effect of producing unconsciousness. How is this effect produced?
depressing thalamic neurons and blocking thalamo-cortical communication
What are some potential presynaptic effects of anesthetics?
- 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
What kind of site of action do anesthetics likely bind?
- hydrophobic pockets on proteins
supported by firefly luciferase, unitary theory of anesthesia, and meyer-overton rule
Which volatile anesthetic boils at room temp?
Desflurane (need a gas blender instead of a gas vaporizer to use)
Sevoflurane’s MAC % is 1.8, and Isoflurane’s is 1.17. Which drug is more potent?
Isoflurane (lower MAC = more potent)
What is unique about N2O’s MAC?
MAC % = 104, so ~100 x’s less potent than the volatile anesthetics
What kind of factors in a patient will increase the MAC?
- hypermetabolic states (hyperthermia, red hair, increased catecholamines, cyclosporine use, hypernatremia)
What kind of factors in a patient will decrease the MAC?
- hypometabolic states (hypothermia, increased age, decreased catecholamines, opioids, anxiolytics, a-2 agonist, lidocaine, hyponatremia, pregnancy)
What is the main determinant of the uptake and distribution of an inhaled anesthetic?
partial pressure!
Describe the 2nd gas effect
ability of high volume uptake of one gas (usually N2O) to accelerate the rate of increase in Palv of a second gas
What two drugs can you use for mask induction in children?
N2O or sevoflurane
What is a potential side effect in certain patients when using an anesthetic, due to deficiency of an enzyme of metabolism?
malignant hyperthermia
What are the two barbituates used for IV induction of anesthesia, what is their effect, and how do they work?
Thiopental and Methohexital
- cause sedation/hypnosis via GABAa receptor but have no analgestic effect
What are the actions of propofol?
- GABA agonist –> hypnosis
- a-2 receptor activity –> sedation
- NMDA-glutamate receptor inhibitor
What are some benefits and drawbacks of using propofol?
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)
You need to maintain anesthesia in a patient that has minimal cardiac reserve. What agent do you choose and what is its MOA?
etomidate, a GABAa agonist
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?
- used ketamine, an NMDA antagonist
- supplement with benzos
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?
- dexmedetomidine, an a2 adrenergic agonist that binds in locus coeruleus and spinal cord to produce sedation, sympatholysis, and analgesia
The only depolarizing neuromuscular blocker we talked about, that is used for intubation and acts as a superagonist of the ACh receptor?
succinylcholine
How do the -curonium/-curium agents work?
non-depolarizing, competitive blockage of ACh at receptor
- used as skeletal muscle relaxants
What neuromuscular blockers can be used in patients with liver or renal dysfunction?
atracurium (causes histamine release in brief injections) or cis-atracurium
What drugs can be used to reverse NMB?
AChEI’s (edrophonium, neostigmine, pyridostigmine) + antimuscarinic (glycopyrrolate)
Tell me about sugammadex
complexes with rocuronium to act as a selective relaxant binding agent and immediately reverse rocuronium’s effects
- SE: hypotension, nausea/vomiting, dry mouth
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
ketamine
