Study Objective: To determine the effects of respiratory acidosis and alkalosis by mechanical ventilation on the onset, duration, and recovery times of vecuronium. Design: Randomized, prospective study. Setting: Operating rooms in the Sapporo Medical University Hospital and Kitami Red Cross Hospital. Patients: 90 ASA physical status I and II patients undergoing lower abdominal surgery. Interventions: Patients were randomly allocated to one of three groups by arterial carbon dioxide tension level (PaCO 2; mmHg) after induction: hyperventilation group (PaCO 2 = 25-35), normoventilation group (PaCO 2 = 35-45), and hypoventilation group (PaCO 2 = 45-55). Anesthesia was maintained by spinal block with inhalation of 50% to 66% nitrous oxide in oxygen and intermittent intravenous administration of fentanyl and midazolam with tracheal intubation. Measurements and Main Results: After vecuronium 0.08 mg/kg was given, onset, duration, and recovery time were measured by mechanomyography (Biometer Myograph 2,000, Odense, Denmark). There were significant differences in the duration and recovery time of vecuronium among the normoventilation group (12.7 ± 3.3 min and 11.8 ± 2.8 min, respectively), the hyperventilation group (10.6 ± 3.5 min and 9.2 ± 2.7 min, respectively; p < 0.01), and the hypoventilation group (14.4 ± 3.1 min and 15.0 ± 3.7 min, respectively; p < 0.01) (mean SD). The closest significant correlation in this study was observed between recovery time and arterial blood pH (r = 0.57; p < 0.05). Conclusion: In humans, duration and recovery times of vecuronium are prolonged in respiratory acidosis and shortened in respiratory alkalosis.
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