Speed of onset of regional analgesia in labour: a comparison of the epidural and spinal routes

This study compares the speed of onset of effective analgesia in two randomly assigned groups of patients requesting analgesia in labour. Patients in the combined spinal-epidural group (n = 69) were given a subarachnoid injection of 1.5 ml containing bupivacaine 2.5 mg and fentanyl 25 mu g for initiation of analgesia. Patients in the epidural group (n = 73) were given an epidural injection of 10 ml containing bupivacaine 12.5 mg and fentanyl 50 mu g. Mean (SD) onset times to the first pain-free contraction were 10.0 (5.7) min in the combined spinal-epidural group and 12.1 (6.5) min in the epidural group (p = 0.054). Patients in the combined spinal-epidural group suffered a higher incidence of motor weakness and proprioceptive deficit than those in the epidural group (p = 0.01). The incidence of technique failure and side-effects was similar in the two groups. It is our contention that the statistically nonsignificant difference in onset times does not justify the additional potential for side-effects and the extra cost of the equipment involved in the combined spinal-epidural technique.