Muscle relaxants are a class of anesthetic agents used to prevent movement and facilitate surgical exposure. Which of the following statement(s) is/are true concerning the use of muscle relaxants in surgical procedures

a. Succinylcholine produces rapid obvious muscle fasciculations

b. Pancuronium can be reversed by increasing the acetylcholine concentration using an anticholinesterase inhibitor (neostigmine)

c. Prolonged periods of muscle relaxation in patients requiring prolonged ventilation should be used in conjunction with analgesics and amnesic agents

Neuromuscular blocking agents can be classified as depolarizing or nondepolarizing inhibitors of the neurotransmitter, acetylcholine at the neuromuscular junction. The only noncompetitive inhibitor employed clinically is succinylcholine. This drug rapidly binds to the neuromuscular junction and produces depolarization, clinically obvious as fine muscle fasciculations occurring approximately 60 seconds after injection. All other clinically useful muscle relaxants are termed competitive inhibitors and do cause depolarization when they attach to the neuromuscular junction. Since these agents compete with acetylcholine, the block produced is in direct proportion to the concentration of the agent relative to the concentration of acetylcholine. If the concentration ratio is low enough, competitive relaxants can be “reversed” if the concentration of acetylcholine is artificially elevated. Increase of acetylcholine concentration can be achieved by giving a drug which blocks metabolism of anticholinesterase (neostigmine).

Nondepolarizing relaxants are frequently used in critically ill patients who are difficult to manage otherwise during prolonged periods of mechanical ventilation. It is imperative that these drugs be given in conjunction with analgesics and amnesic agents, since neuromuscular blocking agents have no analgesic or amnestic properties and only prevent motion of voluntary muscles. Patients may therefore be totally aware and in pain and unable to communicate. All muscles of the body do not have equal sensitivity in muscle relaxants. The diaphragm is both resistant to neuromuscular blockade while the neck and pharyngeal muscles that support the airway are most sensitive. It is possible for an intubated patient to spontaneously ventilate and even to produce a large negative inspiratory force and yet have complete airway obstruction when extubated due to effects of residual muscle relaxants on upper airway muscles. The definitive clinical test for complete reversal of neuromuscular blockade is the ability of the patient to sustain a head lift from the bed for five seconds.