Transcutaneous carbon dioxide levels and oxygen saturation following caesarean section performed under spinal anaesthesia with intrathecal opioids

BackgroundIntrathecal opioids can be associated with respiratory depression which may have serious consequences. We describe the use of a non-invasive monitor (TOSCA) to measure transcutaneous carbon dioxide levels and percentage of haemoglobin oxygen saturation in post-caesarean section patients in two hospitals which used different intrathecal opioids.MethodsEighty-nine women undergoing caesarean section were monitored postoperatively until 08.00 h on the first postoperative day. In addition to hyperbaric bupivacaine, patients from Hospital 1 received intrathecal diamorphine 300 μg: those from Hospital 2 received intrathecal fentanyl 15 μg and postoperative intramuscular morphine 10 mg and were given morphine patient-controlled analgesia. Data from TOSCA were analysed the following day. Respiratory depression was defined as oxygen saturations <90% or transcutaneous carbon dioxide levels >7 kPa for >2 min or the need for medical intervention for clinical respiratory depression.ResultsSustained hypercapnia was recorded in 8/45 (17.8%) patients from Hospital 1 and 3/44 (6.8%) from Hospital 2. Sustained oxygen saturations <90% were recorded in one patient from Hospital 2 and none from Hospital 1. The overall incidence of respiratory depression was 17.8% in Hospital 1 and 9.1% in Hospital 2. The median duration of hypercapnia was 9 min [IQR 5.8–12.4] in Hospital 1 and 11.5 min [IQR 7–32.8] in Hospital 2. No patient required medical intervention.ConclusionsThe incidence of opioid-induced respiratory depression detected by TOSCA is higher than previously reported by other monitoring methods. TOSCA may have a role in detecting subclinical respiratory depression in the obstetric population. Further studies with a control population are needed.