Aortocaval compression is a major cause of maternal hypotension. A randomized controlled trial was designed to determine the effectiveness of a mechanical intervention using a right lumbar-pelvic wedge in preventing hypotension after spinal anesthesia for cesarean delivery.
Eighty healthy women undergoing elective cesarean section were randomly allocated immediately after spinal blockade to either a lumbar-pelvic wedge positioned under the right posterior-superior iliac crest (Wedge group, n=40) or the complete supine position (Supine group, n=40). Hemodynamic values, vasopressor consumption and adverse effects were collected during the surgical procedure. Hypotension was defined as a reduction in systolic blood pressure of 25% from baseline. Patient allocation, management and data collection were performed by a single unblinded anesthetist.
There was no difference in the incidence of hypotension between the two groups (42.5% vs. 50%, P=0.51). During the first 5 min, blood pressure decreased less in the Wedge group. There were significant differences in median [interquartile range] vasopressor requirements between the Wedge group and the Supine group (1 [0-2] vs. 3 [1-4] mg, P<0.01) and in nausea during the procedure (6 vs. 22 patients, P<0.01).
In our study population the use of right lumbar-pelvic wedge was not effective in reducing the incidence of hypotension during spinal anesthesia for cesarean section. Patients in whom the wedge was used had higher systolic blood pressure values during the first 5 min of anesthesia and fewer episodes of nausea. The risk of hypotension remains substantial.