The prevention of hypotension continues to be one of major challenges in spinal anesthesia (SA) for cesarean delivery. And prehydration is widely performed to prevent hypotension. However, some controversy exists over the types of fluid used for prehydration. Therefore, we investigated the effects of crystalloid versus colloid preload on the incidences of hypotension, and the notion that minimal local anesthetic used in combined spinal-epidural anesthesia (CSEA) could further decrease the incidence of hypotension after colloid preloading.

One hundred and fifty parturients were randomly allocated into three groups: CR (crystalloid)-SA, CO (colloid)-SA, and CO-CSEA according to the types of preload and anesthesia. In the CR-SA group, 1,000-1,500 ml of crystalloid was administered under spinal anesthesia. In the CO-SA and CO-CSEA groups, 500 ml of colloid followed by 500-1,000 ml of crystalloid under SA and CSEA was administered, respectively. Bupivacaine 9 mg with opioids was used for SA, and bupivacaine 6 mg with opioids and epidural top-up with 0.25% bupivacaine 10 ml for CSEA. Incidences of hypotension, nausea and vomiting were recorded until delivery.

Colloid preload reduced the incidence of hypotension (18% vs 44%, P = 0.005), and side effects (2% vs 20%, P = 0.005) compared to crystalloid in SA. However, lowering local anesthetic using CSEA (hypotension 20%, side effects 4%) did not further decrease the incidences of hypotension and side effects when using colloid.

Colloid is a better fluid for prehydration in cesarean section under spinal anesthesia. 18-20% is considered a minimum incidence of hypotension.