Comparison of cisatracurium-induced neuromuscular blockade between immediate postpartum and nonpregnant patients

Abstract

Study Objective: To evaluate and compare cisatracurium-induced neuromuscular blockade and intubating conditions between immediate postpartum (PP) and nonpregnant (NP) patients. Design: Prospective control study Settings: University Hospital Center Patients: 44 ASA physical status I and II patients: 22 immediate postpartum (PP) patients (<48 hours after delivery) scheduled for elective postpartum tubal ligation and 22 nonpregnant (NP) patients (>40 weeks from prior pregnancy) scheduled for elective gynecological procedures. Interventions: General anesthesia was induced intravenously (IV) with thiopental sodium 5 mg/kg, fentanyl 2.0 to 3.0 ug/kg, midazolam 0.015 to 0.025 mg/kg, and cisatracurium 0.2 mg/kg. Evoked electromyographic responses of the adductor pollicis muscle were obtained by supra-maximal train-of-four stimulation of the ulnar nerve every ten seconds via surface electrodes at the wrist. Intubation was attempted at 90 s after completion of cisatracurium administration and again at 120 seconds if the first attempt was unsuccessful. The intubating anesthesiologist assessed the intubating conditions with four variables: jaw relaxation, vocal cord immobility and exposure, patient/diaphragmatic movement, and overall intubating impression. Intraoperative anesthetic was maintained with 30% oxygen, 70% nitrous oxide, and 1% end-tidal isoflurane, as tolerated. Patient temperature was maintained at 35.5° to 37.5° Celsius (C), and end-tidal carbon dioxide at 30 to 36 mmHg. Measurements and Main Results: The mean onset times to 50%, 90%, and maximal T 1 depression and mean time to 25% T 1 recovery in the PP group (68 ± 19 sec, 110 ± 26 sec, 147 ± 32 sec, 60 ± 6 min) were significantly less than those in the NP group (80 ± 17 sec, 131 ± 28 sec, 181 ± 44 sec, 69 ± 12 min), respectively (p < 0.05). All patients were successfully intubated on the first attempt at 90 seconds. 91% of the NP group and 81% of the PP group had excellent overall intubating conditions. Conclusions: This is the first published control study to compare the effects of cisatracurium between NP and PP patients. The results suggest that the mean onset time and clinical duration of cisatracurium are significantly shorter in immediate postpartum patients than those in nonpregnant female patients.