Which medication is most commonly associated with tachycardia: Fentanyl, Succinylcholine, Morphine, or Pancuronium?

Pancuronium Is Most Associated with Tachycardia

Pancuronium is the medication most commonly associated with tachycardia among the options listed. 1 Pancuronium is a long-acting, nondepolarizing neuromuscular blocking agent that has significant vagolytic effects, causing an increase in heart rate in more than 90% of ICU patients by at least 10 beats per minute.

Comparison of Cardiovascular Effects Among the Options

Pancuronium

• Primary cardiovascular effect: Tachycardia
• Mechanism: Vagolytic effect (blocks muscarinic receptors in the heart)
• Incidence: >90% of patients experience increased heart rate 1
• Clinical significance: Can limit its use in patients who cannot tolerate increased heart rate

Succinylcholine

• Primary cardiovascular effect: Bradycardia (especially in children and after repeated doses)
• Mechanism: Stimulates muscarinic receptors in the heart
• Clinical presentation: Different effects in children (bradycardia) versus adults (possible tachycardia after first dose, but bradycardia may still occur) 2, 3
• Other effects: Can cause arrhythmias due to potassium release, especially in patients with nerve damage 2

Fentanyl

• Not primarily associated with tachycardia
• When combined with pancuronium, the pancuronium-induced tachycardia may still occur 4
• More commonly associated with bradycardia, especially when combined with vecuronium 4

Morphine

• Not primarily associated with tachycardia
• Can cause histamine release leading to hypotension
• May cause bradycardia through vagal stimulation

Clinical Implications of Pancuronium-Induced Tachycardia

The tachycardia associated with pancuronium has important clinical implications:

1. Contraindications: Should be used with caution in patients with:

   • Coronary artery disease
   • Hypertension
   • Tachyarrhythmias
   • Heart failure

2. Increased myocardial oxygen demand: The increase in heart rate raises the rate-pressure product, potentially leading to myocardial ischemia in susceptible patients 5

3. Comparison with other neuromuscular blocking agents: Vecuronium, unlike pancuronium, does not cause tachycardia and may be preferred in patients with cardiovascular disease 2, 5

Common Pitfalls and Caveats

• Mistaken attribution: Don't confuse the bradycardic effects of succinylcholine with tachycardia
• Combination effects: When pancuronium is combined with other medications (like fentanyl), the tachycardic effect may still predominate 4
• Patient-specific factors: Preoperative beta-blocker therapy may modify the tachycardic response to pancuronium
• Dosing considerations: The vagolytic effects of pancuronium are dose-dependent

In summary, among the four medications listed (fentanyl, succinylcholine, morphine, and pancuronium), pancuronium is uniquely associated with a high incidence of tachycardia due to its vagolytic properties, making it the correct answer to this question.