A prospective observational study of maternal oxygenation during remifentanil patient-controlled analgesia use in labour

Numerous studies of remifentanil patient-controlled analgesia during labour have shown high levels of maternal satisfaction, but concerns remain, especially over the side-effects of sedation and respiratory depression. We conducted a prospective observational study of maternal oxygen desaturation during remifentanil patient-controlled analgesia. Pulse oximetry values were recorded every eight s and later downloaded for analysis. A desaturation episode was defined as oxygen saturation < 90%. We collected 148 h of data in 61 women, during which we observed 176 desaturation episodes. These episodes occurred in 43 (70%) women. The median (IQR [range]) of the lowest saturation during each episode was 87 (85-89 [68-89])% with duration 16 (8-24 [8-104]) s. Supplementary oxygen reduced the time per hour spent with saturation < 90%, but not the depth or duration of individual episodes. Desaturation episodes were twice as common during the second stage of labour as compared with the first stage. Prior opioid administration, bolus size and use of nitrous oxide during patient-controlled analgesia use were not found to influence frequency, depth or duration of desaturation episodes. Although these findings suggest desaturation occurs more frequently during remifentanil patient-controlled analgesia than previously reported, the results are comparable with earlier oximetry studies of women who received nitrous oxide and pethidine during labour.