Neuromuscular and cardiovascular effects of pipecuronium. A comparative study between different doses.

Background And Objectives: Pipecuronium is a non-depolarizing neuromuscular blocker with similar properties to pancuronium, but without cardiovascular effects. Neuromuscular effects, conditions of tracheal intubation, and hemodynamic repercussions of two different doses of pipecuronium were evaluated.

Method: Patients were divided into two groups according to the dose of pipecuronium: Group I (0.04 mg x kg(-1)) and Group II (0.05 mg x kg(-1)). Intramuscular midazolam (0.1 mg x kg(-1)) was administered 30 minutes before the surgery. Propofol (2.5 mg x kg(-1)), preceded by fentanyl (5 microg x kg(-1)) and pipecuronium (0.04 and 0.05 mg x kg(-1) for Groups I and II, respectively), was administered for anesthetic induction. Patients were ventilated with 100% oxygen via a face mask until a 75% reduction in the amplitude of the response to an isolated stimulus (1 Hz) is achieved, at which time laryngoscopy and intubation were carried out. Anesthetic maintenance was achieved with isoflurane (0.5 to 1%) with a mixture of 50% O2 and N2O. Mechanical ventilation was used to maintain P(ET)CO2 between 32 and 36 mmHg. The pharmacodynamics of pipecuronium was evaluated by acceleromyography.

Results: Mean times and standard deviation for the onset of action, clinical duration (T1(25%)), and recovery index (T1(25-75%)) were: Group I (122.10 +/- 4.18 sec, 49.63 +/- 9.54 min, and 48.21 +/- 6.72 min), and Group II (95.78 +/- 8.91 sec, 64.84 +/- 13.13 min, and 48.52 +/- 4.95 min). Onset of action, clinical duration, and conditions of tracheal intubation were significantly different for both groups.

Conclusions: Pipecuronium at a dose of 0.05 mg x kg(-1) can be used in prolonged procedures in which cardiovascular changes should be avoided.