Which statement best describes the incidence of brady-dysrhythmias with succinylcholine given intramuscularly in neonates?

Which statement best describes the incidence of brady-dysrhythmias with succinylcholine given intramuscularly in neonates?

• A. They are increased
• B. They are decreased
• C. They are unchanged
• D. They are unpredictable

Answer: (B)

The main idea here is how the route of administration affects the heart’s response to succinylcholine in newborns. Succinylcholine can cause bradycardia and other dysrhythmias because it increases acetylcholine activity at muscarinic receptors in the heart. In neonates, the heart is particularly sensitive to this vagal stimulation, so rapid, high peak levels of the drug—such as with an intravenous dose or repeated dosing—raise the risk of bradycardia. Giving succinylcholine intramuscularly slows absorption, producing a lower and more gradual peak in the blood. That gentler rise means less acute muscarinic stimulation of the heart, so brady-dysrhythmias are less likely. Of course, bradycardia can still occur in some cases, especially with larger or repeated doses, which is why atropine is sometimes used prophylactically.

The main idea here is how the route of administration affects the heart’s response to succinylcholine in newborns. Succinylcholine can cause bradycardia and other dysrhythmias because it increases acetylcholine activity at muscarinic receptors in the heart. In neonates, the heart is particularly sensitive to this vagal stimulation, so rapid, high peak levels of the drug—such as with an intravenous dose or repeated dosing—raise the risk of bradycardia.

Giving succinylcholine intramuscularly slows absorption, producing a lower and more gradual peak in the blood. That gentler rise means less acute muscarinic stimulation of the heart, so brady-dysrhythmias are less likely. Of course, bradycardia can still occur in some cases, especially with larger or repeated doses, which is why atropine is sometimes used prophylactically.