Regarding neuromuscular blockers which of the following is true: March 2009
Ans. C: Pancuronium should be avoided in renal disease Neuromuscular Blockers Used to aid in intubation or airway management Used to facilitate surgery (large abdominal surgery, eye surgery) Can help break laryngospasm Competitive/Non-depolarizing: Quaternary ammonium compounds; Rocuronium Vecuronium, Pancuronium Cisatracurium Atracurium Reversible competition between drug and ACh binding site No fasciculations Nerve stimulation exhibits a fade in train-of-four or tetany Best clinical marker of strength is sustained head-lift Long-acting: Pancurounium Intermediate-acting: Vecuronium, Rocuronium, Cisatracurium Sho-acting: Mivacurium Rocuronium, vecuronium metabolized by the liver Pancuronium excreted primarily by the kidneys, So should be avoided in renal diseases Cisatracurium is degraded by a Hoffman degradation (spontaneous) and does not rely on kidneys or liver None of the neuromuscular blockers cross the blood-brain barrier Effects can be potentiated by: inhalational anesthetics, aminoglycoside antibiotics, tetracycline, underlying weakness, hypermagnesemia and other electrolyte abnormalities, hypothermia In a patient with hypercarbia or poor respiratory effo, always expect residual neuromuscular blockade Fine muscles affected first such as eyes and fingers, then limbs, neck, trunk, intercostal muscles, and finally, the diaphragm Recovery is in the reverse order Effect reversed by cholinesterase inhibitor like neostigmine II. Depolarizing: Mimics action of neurotransmitter ACh; a. Succinylcholine Causes brief twitches or fasciculations, followed by flaccid paralysis Paralysis is due to depolarization of the nerve terminal and the nerve being in a refractory state because the membrane is depolarized Onset of succinylcholine is approximately 20-30 seconds Effects last around 3- 5 minutes Dose 1 mg/kg Eliminated by pseudocholinesterase Myalgias/muscle soreness is a common problem in postoperative period. Increase in serum K (0.5-1mEq/dL); exaggerated in patients with burns, motor neuron disease, muscle disease Increase in intraocular pressure, intragastriac pressure, intracerebral pressure Cardiac arrhythmias, bradycardia Prolonged block due to pseudocholinesterase deficiency
Neostigmine reverses the effect of succinylcholine
Atracurium is a depolarizing agent
Pancuronium should be avoided in renal disease
Depolarizing blocking drugs shows no fasciculations