Muscle relaxants and monitoring Flashcards
The ACh receptor is contained within the motor cell membrane and consists of five glycoprotein subunits
2 - a
1 - B
1 - S
1 - E
Which subunit does acetylcholine bind to?
a
ACh receptors are found in several areas: (3)
Postjunctional (most Ach receptors found)
Prejunctional
Extrajunctional
Which junction influence the release of Ach?
Prejunctional
How much receptor channels are open and a threshold potential is reached, a muscle action potential (MAP) is generated.
5 to 20%
Half life of mature Ach receptors
2 weeks
Half life of immature receptors
24 hours
The immature receptors depolarize more easily in the presence of ACh or SCH and thus are more prone to release potassium.
Where is pseudocholinesterase produced?
Liver and circulates in the plasma
When added to the serum under study, this inhibits normal plasma cholinesterase by 80%, whereas the atypical plasma cholinesterase is inhibited by only 20%.
Dibucaine
Normal dibucaine number
80
2 Muscle relaxants with biliary excretion
Vecuronium and rocuronium
Like SCH, is metabolized by pseudocholinesterase.
Mivacurium
This non-depolarizing muscle blocker does not seem to cause significant histamine release.
Cisatracurium
Tachycardia is usually a side effect of this non-depolarizing muscle blocker because of ganglionic stimulation and vagolysis.
Pancuronium
What antibiotic appears to have negative prejunctional and postjunctional effects.
Aminoglycoside
Discuss important characteristics of a nerve stimulator.
A nerve stimulator should be capable of delivering single-twitch stimulation at 0.1 Hz (1 stimulus every 10 seconds), train of four (TOF) at 2 Hz (2 per second), and tetanic stimulation at 50 Hz (50 per second).
Nerve stimulator electrodes (depolarizes or hyperpolarizes)
Black?
Red?
Black - depolarize
Red - Hyperpolarize
Which stimulation mode is most commonly used to assess degree of blockade? How is it done?
TOF
Four stimuli are delivered at a frequency of 2 Hz (2 per second), and the ratio of the amplitude of the fourth to the first response in a train (T4:T1) ratio estimates the degree of block.
Study
Twitch disapears when 4th twitch : 75% to 80% occupancy 3rd twitch : 85% occupancy 2nd twitch : 85% to 90% occupancy 1st twitch : 90% to 95% occupancy
Consists of repetitive, high-frequency stimulation at frequencies of 50 Hz or greater.
Tetanic stimulation
Loss of contraction during tetanic stimulation
Tetanic fade
Mode of stimulation which involves the application of an initial burst of three 0.2-ms impulses at 50 Hz followed by an identical stimulation in 750 ms.
Double burst
Which nerves can be chosen for stimulation?
Adductor pollicis muscle of the thumb
What is adequate muscular relaxation?
Adequate relaxation is generally present when one to two twitches of the TOF response are present, correlating with 80% depression of single-twitch height.
