The Most Common Side Effect of Pancuronium
The most common side effect of pancuronium is tachycardia (a). This occurs due to pancuronium's prominent vagolytic actions, which result in mild and dose-dependent increases in heart rate 1.
Mechanism of Pancuronium's Cardiovascular Effects
Pancuronium is a long-acting, nondepolarizing neuromuscular blocking agent (NMBA) with significant vagolytic properties. According to clinical practice guidelines:
- Vagolytic actions are most prominent with pancuronium compared to other NMBAs 1
- More than 90% of ICU patients will experience an increase in heart rate of 10 beats/min after pancuronium administration 1
- This tachycardia occurs through pancuronium's inhibition of vagal activity 1
Clinical Significance of Pancuronium-Induced Tachycardia
The tachycardia associated with pancuronium has important clinical implications:
- Most clinicians avoid pancuronium in patients with coronary artery disease due to the risk of tachycardia-induced myocardial ischemia 1
- Pancuronium use can lead to ventricular ectopy and cardiovascular collapse in susceptible patients 1
- Studies have confirmed an increased incidence of myocardial ischemia during high-dose fentanyl-pancuronium anesthesia 2
Comparison with Other Neuromuscular Blocking Agents
Pancuronium's cardiovascular effects differ from those of other commonly used NMBAs:
- Rocuronium also has affinity for vagal receptors and can cause tachycardia in up to 30% of patients, but to a lesser degree than pancuronium 1
- Vecuronium has relatively little effect on the heart and is not vagolytic 1
- Cisatracurium may block M2 vagal receptors, but tachycardia does not appear to be clinically important 1
Other Potential Side Effects of Pancuronium
While tachycardia is the most common side effect, pancuronium can cause other adverse effects:
- Histamine release: Pancuronium causes minimal histamine release compared to agents like atracurium 1
- Ganglionic blockade: Pancuronium has weak ganglionic activity at recommended doses 1
- Prolonged neuromuscular blockade: In patients with renal failure or cirrhosis, pancuronium's effects are prolonged due to increased elimination half-life and decreased clearance of its active metabolite 1
- Hypotension: In specific contexts such as hemorrhagic shock, pancuronium has been associated with profound hypotension 3
Clinical Pearls and Pitfalls
- Avoid in cardiac patients: Pancuronium should be avoided in patients with coronary artery disease due to the risk of tachycardia-induced myocardial ischemia 1
- Beta-blockers interaction: Patients on beta-blockers may show a decrease rather than increase in heart rate when given pancuronium 4
- Dose adjustment: In patients with renal or hepatic dysfunction, dose adjustments may be necessary due to altered metabolism 1
- Reversal considerations: When reversing pancuronium-induced neuromuscular blockade, higher doses of neostigmine (60-80 μg/kg) combined with glycopyrronium may be needed for effective antagonism 5
Therefore, the correct answer is (a) tachycardia, as this represents the most common side effect of pancuronium administration.