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Remifentanil patient-controlled analgesia for labour: optimizing drug delivery regimens

[L’analgésie au rémifentanil contrôlée par le patient pour le travail obstétrical : l’optimisation des régimes d’administration des médicaments]

Mrinalini Balki, MBBS MD^*, Shilpa Kasodekar, MBBS MD^*, Sudhir Dhumne, MBBS MD^*, Paul Bernstein, MD FRCSC and Jose C.A. Carvalho, MD PhD FANZCA fRCPC^*,

^* From the Department of Anesthesia and Pain Management, and the
Department of Obstetrics & Gynecology, University of Toronto, Mount Sinai Hospital, Toronto, Ontario, Canada.

Address correspondence to: Dr. Mrinalini Balki, Department of Anesthesia and Pain Management, Mount Sinai Hospital, 600 University Avenue, Room 781, Toronto, Ontario M5G 1X5, Canada. Phone: 416-586-5270; Fax: 416-586-8664; E-mail: mrinalini.balki{at}uhn.on.ca

Purpose: A pilot study was undertaken to compare the efficacy of two regimens of intravenous patient-controlled analgesia (PCA) with remifentanil for labour analgesia.

Methods: Twenty term parturients requesting labour analgesia were randomized to receive one of two regimens of intravenous remifentanil. The initial settings in both groups consisted of an infusion of 0.025 µg·kg^–1·min^–1, a PCA bolus of 0.25 µg·kg^–1 and a lockout interval of two minutes. In Group A, the infusion was increased in a stepwise manner from 0.025 to 0.05, 0.075 and 0.1 µg·kg^–1·min^–1 as required; the bolus was kept constant at 0.25 µg·kg^–1. In Group B, the bolus was increased from 0.25 to 0.5, 0.75 and 1 µg·kg^–1 as necessary; the infusion was kept constant at 0.025 µg·kg^–1·min^–1. Maternal pain, satisfaction and sedation scores, remifentanil requirement, and side effects were recorded.

Results: Mean pain and patient satisfaction scores, and cumulative doses of remifentanil were similar in the two groups. The overall incidence of side effects was greater in Group B (P = 0.0007), with drowsiness observed in 100% of patients, as compared to 30% in Group A (P = 0.003). The minimum oxygen saturation levels were 94.3% ± 2.6% and 92.2% ± 3.8% in Groups A and B respectively (P = 0.19).

Conclusions: Although pain and satisfaction scores were similar in both groups, the regimen used in Group A was associated with fewer side effects compared to the Group B dosing regimen. This pilot study suggests that remifentanil intravenous PCA is efficacious for labour analgesia as a bolus of 0.25 µg·kg^–1, with a lockout interval of two minutes and continuous infusion of 0.025–0.1 µg·kg^–1·min^–1. The potential for respiratory depression mandates close respiratory monitoring. Large-scale trials to evaluate safety issues are warranted.