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

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·min, a PCA bolus of 0.25 μg·kg 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·min as required; the bolus was kept constant at 0.25 μg·kg. In Group B, the bolus was increased from 0.25 to 0.5, 0.75 and 1 μg·kg as necessary; the infusion was kept constant at 0.025 μg·kg·min. 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, with a lockout interval of two minutes and continuous infusion of 0.025-0.1 μg·kg·min. The potential for respiratory depression mandates close respiratory monitoring. Large-scale trials to evaluate safety issues are warranted.