Nmba Flashcards
What is the structure of succinylcholine?
2 joined Ach molecules
What is the dosage of succinylcholine ?
1-1.5 mg/kg
What is the intubating dose of suc if you use a defasciculating dose of roc?
1.5-2 mg/kg
What is the defasciculating dose of roc?
0.03mg/kg
How is succinylcholine metabolized?
By pseudocholinesterases
How long can paralysis last in someone homozygous for pseudocholinesterase deficiency?
3-8 hours
How can you tell if they have pseudocholinesterase deficiency?
Dibucaine inhibits normal pseudocholinesterase by 80% but only 20% in abnormal
What drug prolongs neuromuscular blockade?
Cyclosporine (has solvent polyethoxylated castor oil) Aminoglycosides Tetracyclines Polymixin Clindamycin
What drug prolongs the action of succinylcholine?
Echothiophate
How does Echothiophate prolong succinylcholine ?
By inhibiting pseudocholinesterase
Can cause 95% decrease in plasma butyrylcholinesterase for 4-6 weeks after stopping the drug
What is Echothiophate?
A topical eye medication for glaucoma- an acetylcholinesterase inhibitor
How do all neuromuscular blocking agents work?
They are quaternary ammonium compounds with a positively charged nitrogen that has an affinity for the nicotinic receptors
What is a phase I block?
When a depolarizing muscle blocker is bound to Ach receptors the perijunctional voltage gated Na channels close after a certain amount of time so you get the initial excitation (propagation of signal via the sodium channels and then release of calcium from the sarcoplasmic reticulum) and then the sodium channel closes again. The endplate cannot repolarize while the muscle blocker is bound to the Ach receptors
How do nondepolarizing muscle relaxants work?
Competitive antagonism
They do not produce a conformational change for ion channel opening
What are the two subunits on the neuromuscular Ach receptors that bind acetylcholine?
Two identical alpha subunits
How many binding sites have to be occupied by acetylcholine to elicit a conformational change?
The 2 alpha subunits
What is the difference in the fetal form of Ach receptor?
It has a gamma unit instead of epsilon
Low channel conductance
What happens in conditions of chronically decreased acetylcholine release?
More expression of the extrajudicial all Ach receptor.
Why do states with more extrajunctional receptors have prolonged blockade with depolarizing muscle relaxants?
Because there are more receptors being depolarized
What is the sensitivity of neuromuscular blockade in myasthenia gravis.
A resistance to depolarizing relaxants (because there are fewer receptors)
Increased sensitivity to nondepolarizing relaxants (only takes one subunit to bind to cause muscle relaxation)
What are other ways of causing neuromuscular blockade?
Channel blockade
What drugs may cause channel blockade?
Neostigmine
Antibiotics
Cocaine
Quinidine
What is sugammadex
A cyclodextrin that binds tightly in a 1:1 ratio with steroidal nondepolarizing agents (roc, vec)
How much current should a peripheral nerve monitor be able to create for muscle contraction?
50 mA across 1000 ohm load