Neuromuscular Blocking Agents Flashcards
Structure of NMB
Quaternary Ammoniums
Structurally related to Ach
Synthetic Alkaloids
except Tubocuraine
Structure of Succinylcholine
Two ACh molecules linked by acetate methyl groups
Dose of Succinylcholine
1.0mg/kg
How long does Succinylcholine take to work?
60 seconds
How long does it take to recover 90% muscle strength?
9-13 minutes
Metabolism of Succinylcholine
short action due to rapid hydrolysis
Enzyme that breaks down Succinylcholine
butrylcholinesterase
Metabolites of Succinylcholine
Succinylmonocholine and choline
Succinylmonocholine is a
weak NMB; succinic acid and choline
Where does recovery from succinylcholine motor blockade occur?
as it drifts away from NMJ down a concentration gradient
Where is butyrylcholinesterase metabolized?
liver and found in plasma
What is butyrylcholinesterase responsible for the metabolism of?
succinylcholine, mivacurium, procaine, chloroprocaine, tetracaine, cocaine and heroin
Factors that decrease butyrylcholinesterase activity?
advance liver disease age malnutrition pregnancy burns oral contraceptives MAO inhibitors echothiophate cytotoxic drugs neoplastic disease anticholinersterase drugs
Beta Blockers will
cause a mild prolongation of Succinylcholine
Genetic variations with the administration of succinylcholine
will significantly prolongation
Dibucaine
local anesthetic that inhibts typical PchE
Reflects the typical PChE not quantity
dibucaine number
Heterogenous for atypical gene
dibucaine number 40-60
Prolongs block 1.5-2times longer
Homogenous for atypical gene
dibucaine number less then 30
prolonged for 4-8 hours
Cardiac Side Effects of Succinylcholine
bradycardia, tachycardia junctional rhythm sinus arrest due to muscarinic receptors on cardiac cells
Cardiac effects due to succinylochine are more likely to occur
second dose within 5 minutes of first dose
pediatric patients
Stimulation of autonomic ganglia may cause
ventricular dysrhythmias
tachycardia
increased BP
Hyperkalemia
0.5-1mEq/L increase in plasma concentration
More severe in: burns, abdominal infectinos, metabolic acidosis, closed head injury and conditions with upregulation of nAChR (paraplegia, muscular dystrophy, Gullian-Barre)
Myoglobinuria
damage to skeletal muscle especially pediatric patients
Most found to have muscular dystrophy or by malignant hyperthermia susceptible
Increased intraocular pressure
peaks 2-4 minutes; pressure returns to normal by 6 minutes
not widely accepted in open eye injury
Increased intragastric and lower esophageal pressures
related to intensity of fasciculations of abdominal muscles
Prevented by prior administration of ND-NMB
does not increase risk of regulation
Increased intracranial pressure
can be attenuated with pre-treatment of ND-NMB
Masseter Spasm
trigger for MH