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0, no change; +, increased; ++, more increased; +++, most increased; -, decreased; —, more decreased;---, most decreased.

0, no change; +, increased; ++, more increased; +++, most increased; -, decreased; —, more decreased;---, most decreased.

4.7. Nondepolarizing Muscle Relaxants

The majority of nondepolarizing muscle relaxants have minimal effects on cardiovascular and hemodynamic stability. When induced, nondepolarizing muscle relaxants are believed to elicit their cardiovascular effects by stimulating the release of histamine and affecting muscarinic and nicotinic receptors (Table 7). For example, pancuronium may cause vagal blockade (antimuscarinic effect) at the sinoatrial node, resulting in elevation of heart rate. The administration of pancuronium is also associated with activation of the sympathetic nervous system (51,52). Likewise, large doses of atracurium and mivacurium are associated with histamine release, which may result in tachycardia and hypotension; such patients may display facial flushing as a result of histamine release. Interestingly, cisatracurium (a stereoisomer of atracurium) is not associated with histamine release. Finally, vecuronium and rocuronium are agents that are considered totally devoid of significant cardiovascular effects.

4.8. Depolarizing Muscle Relaxant

Succinylcholine is a depolarizing muscle relaxant; it has a structure similar to acetylcholine and mimics it by binding to nicotinic cholinergic receptors. The duration of action of succi-nylcholine is short (minutes) and is broken down by the abundant pseudocholinesterase enzyme. Importantly, the administration of succinylcholine may be associated with cardiac dysrhythmias (i.e., junctional rhythm and sinus bradycardia) by its muscarinic activity at the sinoatrial node. Administration of succinylcholine may also be associated with hyperkalemia in susceptible patients, such as those with malignant hyperther-mia, muscular dystrophy, spinal cord injury, and burn injury. More specifically, in boys with Duchenne muscular dystrophy, the administration of succinylcholine has been linked to episodes of sudden cardiac death.

Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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