The use of muscle relaxants in surgical procedures : rapid review

•  Introduction.
•  Muscle relaxants.
•  Non-depolarizing muscle relaxants.
•  D-tubocurarin.
•  Pancuronium.
•  Depolaring muscle muscle relaxants.

• Acetylcholine is a major neurotransmitter in the autonomic nervous system. In the peripheral nervous system, acetylcholine activates muscles .
• The enzyme acetylcholinesterase converts acetylcholine into the inactive metabolites choline and acetate .
• Acetylcholinestrase enzyme is abundant in the synaptic cleft, and its role in rapidly clearing free acetylcholine from the synapse is essential for proper muscle function .
• Acetylcholine receptor agonists and antagonists can either have an effect diretly on the receptors or exert their effects indirectly, e.g., by affecting the enzyme acetylcholinesterase, which degrades the receptor ligand. Agonists increase the level of receptor activation. antagonists reduce it.
• Certain neurotoxins work by inhibiting acetylcholinesterase, thus leading to excess acetylcholine at the neuromuscular junction, thus causing paralysis of the muscles needed for breathing and stopping the beating of the heart.

• Muscle relaxants Used as adjuncts to general anesthesia, to ensure that surgical procedures aren't distributed by muscle contraction of the patient.
• Two types of those muscle relaxants used with anesthesia :

• Its effect start within 4 minutes & continues for 30 minutes
• The duration of action of d-tubocurarin can be shortened by administrating its antidote neostigmine (ACH esterase inhibitor) so inhibit ACH breakdown .
• Unwanted side effects result from non immune mediated release of histamine from mast cell leading to hypotension ,urticaria & bronchospasm .

• It's 5 fold more potent than d-tubocurarin & with somewhat longer duration & not likely to cause histamine release .
• Side effects : increase heart rate & blood pressure due to M2 cholinoceptor blockade &this effect not shared by newer congeners like vecuronium & pibecuronium .

• This class contain only succinylcholines (succinyldicholine & suxamethonium) .
• Its structure has double ACH molecule. it is not hydrolyzed by acetylcholinestrase but by butyrylcholinesterase, (a plasma cholinesterase). This hydrolysis by butyrylcholinesterase is much slower than that of acetylcholine by acetylcholinesterase.
• Its effect start within seconds & continues for 10 minutes so used at the start of the anesthesia to facilitate intubation.
• Side effects :
  • histamine release (scoline apnea).
  • hyperkalemia which may lead to cardiac arrhythmia .
  • bradycardia .
• Care must be taken during eye surgery ,as increasing in intraocular pressure may occur.

Posted by Unknown on 7/14/2010. Filed under featured, muscloskeletal, pharmacology, rapid reviews . You can subscribe to the site updates through the RSS 2.0 or by Email