Understanding Anesthesiology - The Global Regional Anesthesia ...

and cis-atracurium. Table 15 presents the relevant pharmacology
and includes an older NDMR, pancuronium
which is a long-acting agent that is still in use. Atracurium,
another short-acting NDMR, is included in Chapter
6 (Drug Finder) although it is no longer available in
many jurisdictions.
Figure 20 Neuromuscular junction
Many factors may exaggerate or prolong the effects of
NDMR. These include:
• factors which increase the susceptibility of the neuromuscular
junction to NDMR: muscular dystrophies,
myasthenia gravis, hypocalcemia, hypermagnesemia,
acid-base abnormalities and many drugs (aminoglycosides,
lithium, diuretics, volatile anesthetics)
• factors which delay metabolism or excretion: hypothermia,
renal insufficiency and liver disease
The reader is referred to Chapter 6 for a more complete
discussion of the pharmacology of the nondepolarizing
muscle relaxants.
During maintenance of anesthesia, the degree of muscular
paralysis is best monitored using a peripheral nerve
stimulator. The anesthesiologist observes the magnitude
and number of twitches in response to a series of
four electrical stimuli (2 per second) applied over the
ulnar nerve. The importance of carefully titrating
NDMR is two-fold:
• to ensure sufficient muscle relaxation during the procedure
1. nerve terminal 2. sarcolemma 3. acetylcholine vesicles
4. acetylcholine receptors 5. mitchondrion.
• to ensure the ability to adequately reverse muscle relaxation
at the end of the procedure
Image from Wikimedia Commons, used under GNU Free
Documentation License, version 1.2. Drawn by user
Dake.
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