Comparison of neuromuscular, cardiovascular, and histamine-releasing properties of doxacurium and pipecuronium.

Study Objectives: To determine the neuromuscular, cardiovascular, and histamine releasing properties of doxacurium and pipecuronium at three times effective ED95 doses (3XFD95).

Design: Prospective, randomized clinical trial of adult patients.

Setting: University teaching hospital.

Patients: 20 ASA status I and II adult patients.

Interventions: Subjects were anesthetized with thiopental sodium, fentanyl, and nitrous oxide and oxygen (N2O:O2). Plasma samples were taken preoperatively, after thiopental, and 2 and 5 minutes after doxacurium 75 micrograms/kg or pipecuronium 123 micrograms/kg were given for the determination of histamine levels. The ulnar nerve was stimulated via surface electrodes using train-of-four stimulation at 0.1 Hz. The force of contraction of adductor pollicis was recorded using a mechanomyograph. Recovery of the twitch response was followed and, if necessary, neuromuscular block was antagonized with neostigmine and glycopyrrolate.

Measurements And Main Results: Three patients in the doxacurrium group and one patient in the pipecuronium group exhibited a marked increase in plasma histamine levels. In both groups statistically significant changes were seen in heart rate (HR) measurements (p < 0.02). Doxacurium had a slower onset than pipecuronium [3.1 +/- 0.2 min vs. 1.8 +/- 0.1 min (p < 0.0003)] and a more rapid recovery [72 +/- 8 min vs. 123 +/- 9 min (p < 0.01)].

Conclusion: Neither drug caused a clinically significant change in HR or histamine release. In the doses chosen for this study, the rate of onset of block is slower with doxacurium while recovery is more rapid. Histamine release in three patients was caused by thiopental, while in a fourth patient it may have been due to doxacurium.