Neuromuscular Blockers Flashcards
Depolarizing NMBD
Mimic ACh by binding to alpha subunit of NICOTINICnreceptor keeping channel open –> causes prolonged depolarization which manifests as diffuse contraction
- receptors can’t react to further ACh –> paralysis
- conditions with decreased ACh receptors (Myasthenia Gravis) require higher dose
Nerve stimulation: train of four ratio >70%
General mechanism
Work at postsynaptic NICOTINIC ACh receptor at NMJ –> stop conduction of nerve impulses –> paralysis
-improves incubating conditions
Pancuronium
Long acting aminosteroid- duration increased in renal and liver failure
Dose = 0.1 mg/kg
Onset = 3-4 min
-slow onset = limits usefulness
- vagolytic = causes dose dependent increase in HR, BP, CO
*no histamine release
Rocuronium
Dose = 0.6-1 mg/kg Onset = 1-2 min Short onset --> can be used for RSI Aminosteroid, intermediate duration No histamine release or CV effects
Vecuronium
Dose = 0.1 mg/kg Onset = 3.-4 min Intermediate acting, increased duration with liver disease No histamine release or CV effects Active metabolite makes longer duration Aminosteroid non-depolarizing
Non-depolarizing (NDMB)
Competitive ACh receptor antagonists -> bind without depolarizing
- can be overcome by increasing ACh (reversals)
Nerve Stimulation: train of four ratio
Atracurium
Benzylisoquinolines
Dose =0.5 mg/kg
Onset = 3-4 min
Metabolite causes CNS stimulation/seizure at high [ ]
Cleared by hydrolysis (independent of kidney/liver function)
Use is limited by histamine release –> hypotension, tachycardia, bronchi spasm
Cisatracurium
Dose = 0.15 mg/kg Onset = 2-3 min Degraded by Hofmann reaction No histamine release, minimal CV effects Useful as infusion in ICU/OR since recovery not related to infusion duration
Succinylcholine
Dose = 0.5-1 mg/kg
Onset = 0.5-1 min
Only depolarizing drug available (rapid onset and short duration)
Rapid hydrolysis I plasma by pseudocholinesterase, block duration determined by amount that reaches NMJ
Blockade prolonged by reduced pseudocholinesterase activity (liver disease, pregs, uremia, malnutrition)
Known for malignant hyperthermia
Increases intraocular and intracranial pressure, possible hyperkalemia
Adverse Effects of Succinylcholine
CV: sinus Brady, asystole due to stim of muscarinic receptors (more likely with 2’close together doses)
Hyperkalemia: transiently increases
Allergies: responsible for >50% anaphylaxis during anesthesia
Myalgia: fasciculations
GI: increased intraday trick pressure from lower esophageal sphincter, not an aspiration risk
Choline esterase inhibitors
Inhibit AChesterase, allows ACh to build up at NMJ and overcome competitive inhibition
- duration of action increased for all agents with renal failure
Can effect cardiac muscarinic receptors –> give anticholinergic (glycopyrolate - 10 mcg/kg)
Edrophonium
Anticholinesterase
Dose = 0.5-1 mg/kg
Peak = 1-3 min
Neostigmine
Anticholinesterase
Dose = 0.03-0.07 mg/kg
Peak = 7-10 min
May cross placenta
Pyridostigmine
Anticholinesterase
Dose = 0.1-0.4 mg/kg
Peak = 15-20 min
Physostigmine
Limited use as reversal agent due to penetration of BBB, may cause central cholinergicneffects
