NMB Flashcards
What are they
Non depolarizing
Tubocurarine ( protype)
It is clinically rarely used due to excessive histamine release
Semisynthetic derivatives:
Mevacurium
Atracurium and cisatracurium
Vecuronium
Depolarising
Succinylcholine ( suxamethonium)
Absorption and distribution of them
They are quaternary ( polar) so they cant be absorbed orally and must be taken parenterally
They cant cross BBB and placental barrier
Duration of non depolarising
Mevacurium 10-20 m
Atracurium 20-30 m
Vecuronium. 30-40 m
Duration of depolarising
Few minutes ( 5-15m )
Mechanism of non depolarising
Competitive blocker of Nm receptor => paralysis
It can be reversed by increasing ACH (ACHE inhibitors)
Mechanism of depolarising
Depolarising block => parylsis through 2 phases
Phase 1 intial depolarisation => transient contraction of sk ms followed by paralysis due to maintend depolarisation ( depolarising block)
Phase 2 the ms become repolarised again but insensitive to ACH ( needs excessive ACH to stimulate ) causing desensitization block
Reversal of block of non depolarising
Neostigmine can reverse paralysis as it increases ACH and displace these compititve blockers
Reversal of block of depolarising
Neostigmine increases paralysis in phase 1 as it increases depolarisation but can reverse it in phase 2 as the receptor is insensitive needing excessive ACH to stimulate
Fresh blood transfusion
Therapeutic uses of non depolarising
-Surgeries
-To control convulsions in electroconvlusive therapy (ECT)
Therapeutic uses of depolarising
Short surgeries eg endotracheal intubation
Adverse effects of non depolarising
Histamine release => bronchspasm , hypotension
Respiratory paralysis in large dose
Adverse effects of depolarising
6
1- sudden increase IOP due to contraction of extraocular ms
2- postoperative ms pain
3- acute hyperkalemia that is dangerous and life theartening due to excessive k efflux during repolarization
4- bradycardia due to effects of m receptors
5-prolonged respiratory paralysis (apnea) may result from PSCHAE enzyme deficiency ( treated by artificial respiration and blood transfusion)
6- malignant hyperthermia ( in gene defect patients)
Contraindications in non depolarising
1- BA
2- epilepsy
3- with amino glycosides and quindine ( aggravates the effect )
4- myasthenia gravis
Contraindications in depolarising
1- PSCHA enzyme deficiency
2- peptic ulcer
3- glaucoma and recent eye surgery
Metabolism on non depolarising
Mevacurium by PSCHE enzyme
Atracurium cause spontaneous plasma hydrolysis and breakdown products can cause seizures ( hofmann elimination)
Vecruonium in liver
