General Anesthetics Flashcards
Nitrous Oxide
Class: Inorganic gas
Mech: NMDA receptor antagonist
Thera: Mask induction in children; adjuvant to volatile anesthetics, opioids
Tox: Post-operative nausea and vomiting; inactivates vitamin B (leading to abnormal embryonic development, abortion); accumulates in closed, air-containing spaces (bowel, middle ear, pneumothoraces, air emboli) because N2O insoluble in blood
Misc: No muscle relaxation
Isoflurane
Class: Volatile anesthetic
Mech: Most potent
Thera: Gold standard for maintenance of anesthesia
Tox: Pungent; 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; increase in HR; malignant hyperthermia
Desflurane
Class: Volatile anethetic
Mech: Least soluble, least potent (allows for rapid emergence from anesthesia)
Thera: Maintenance of anesthesia
Tox: Most pungent (airway irritation symptoms); 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; increase in HR; malignant hyperthermia
Sevoflurane
Class: Volatile anesthetic
Mech: Less soluble, less potent (but not irritating)
Thera: Mask induction in children and adults; maintenance of anesthesia
Tox: Can form CO if not combined with CO2 correctly; 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
Methohexital
Class: Barbiturates
Mech: GABAa receptor agonist, antagonist of NMDA-glutamate receptor; produce hypnosis & sedation, but is anti-analgesic
Thera: Induce general anesthesia
Tox: Hypotension due to vasodilation, respiratory depression, negative inotropes.
Misc: Redistribute from brain to muscle and fat, metabolized by liver; dosed based on lean body mass
Propofol
Class: Alkylphenol (a fatty acid)
Mech: GABAa receptor agonist, antagonist of NMDA-glutamate receptor; some a2 receptor activity; rapid onset and offset
Thera: Anti-emetic at low doses; induction and maintenance of general anesthesia; sedation in ICU, procedural sedation
Tox: Propofol infusion syndrome: being given for several days leads to metabolic acidosis, rhabdomyolysis, heart & renal failure, lowering of BP, bradycardia, and death (likely due to fatty acid oxidation)
Painful injection site; supports bacterial growth
Misc: Administered IV in a lipid emulsion (cause of pain); be aware of allergies (egg and soy in emulsion); no malignant hyperthermia
Etomidate
Class: Carboxylated imidazole
Mech: GABAa receptor agonist (only D-isomer)
Thera: Hypnosis; no analgesic activity
Tox: Pain on administration (due to solvent, propylene glycol); involuntary myoclonic movements due to subcortical disinhibition (not a seizure); post-operative nausea and vomiting; single dose inhibits cortisol synthesis
Misc: Minimal cardiorespiratory depression (good agent in patients with minimal cardiac reserve)
Ketamine
Class: Phenycyclidine
Mech: NMDA receptor antagonist, kappa opiate agonist; leads to dose-dependent unconsciousness, amnesia, analgesia
Thera: Sedative/anesthetic for pediatric/developmentally delayed patients; induction in patients with reactive airway disease, hypovolemia (trauma patients), cardiac disease; with propofol for IV procedural sedation; adjuvant during and after surgery to reduce opiod use; part of multimodal pain therapy regimen; depression treatment
Tox: Stimulates sympathetic nervous system outflow; increases cerebral blood flow, ICP; emergence delerium; nystagmus, lacrimation, salivation, and dissociative anesthesia
Misc: Racemic mixture (S more potent); metabolized by P450 (norketamine, a third to a fifth as effective); great bronchodilator; contraindicated in CAD patients and those with with intracranial lesions
Dexmedetomidine
Class: a2 adrenergic agonist
Mech: Binds a2a and a2b in locus coeruleus and spinal cord (produces sedation, sympatholysis, and analgesia)
Thera: Awake intubations, awake craniotomies; adjunct to general anesthesia in patients susceptible to narcotic-induced post-op respiratory depression; withdrawal/detoxification
Tox: Limited respiratory depression (wide safety margin)
Misc: Since GABA not hit, sedation is easier to wake from and is similar to non-REM sleep; FDA approved only for ventilation of ICU patients for under 24 hours
Succinylcholine
Class: Depolarizing NMB
Mech: Divalent ACh molecule; attaches to all ACh receptors, overstimulating them (first seen as disorganized muscular contractions (fasiculations), then paralysis)
Thera: Skeletal muscle relaxant (intubation)
Tox: Malignant hyperthermia; cardiac dysrhythmias, hyperkalemia, increased intraocular pressure, increased intracranial pressure, increased intragastric pressure, myalgias, masseter spasm
Misc: Hydrolyzed by pseudocholinesterase (in plasma); blockade cannot be reversed; only NMB with rapid onset and ultra-short duration of action
Pancuronium
Class: Amino steroid non-depolarizing NMB
Mech: Competitive blockade of ACh (no depolarization); vagolytic
Thera: Skeletal muscle relaxant; avoid in patients with renal insufficiency
Tox: Increase in HR
Misc: Only long acting non-depolarizing agent; supplied as liquid; 80% excreted unchanged in liver (low metabolism in liver); reverse with AChEI
Vecuronium
Class: Amino steroid non-depolarizing NMB
Mech: Competitive blockade of ACh (no depolarization)
Thera: Skeletal muscle relaxant
Tox: No cardiovascular effects
Misc: Intermediate acting; supplied as a powder (reconstitute); hepatic metabolism, hepatic and renal excretion; reverse with AChEI
Rocuronium
Class: Amino steroid non-depolarizing NMB
Mech: Competitive blockade of ACh (no depolarization)
Thera: Skeletal muscle relaxant (can substitute succinylcholine in rapid sequence intubation)
Tox: No cardiovascular effects
Misc: Intermediate acting; supplied as a liquid; hepatic metabolism, hepatic and renal excretion; can speed onset with higher dose; reverse with AChEI
Sugammadex
Class: Selective relaxant binding agent
Mech: Complexes with rocuronium, rendering it inactive; no effect on AChesterase
Thera: Immediate reversal of rocuronium
Tox: Decrease in blood pressure, nausea and vomiting, dry mouth
Misc: Not yet FDA approved
Atracurium
Class: Isoquinoline non-depolarizing NMB
Mech: Competitive blockade of ACh (no depolarization)
Thera: Skeletal muscle relaxant; use in patients with liver or renal dysfunction
Tox: Histamine release (especially if given as rapid IV bolus), with resultant hypotension and tachycardia
Misc: Undergoes spontaneous, non-enzymatic degradation (Hofman elimination); intermediate acting; reverse with AChEI
