A REEVALUATION OF THE ROLE OF CRYSTALLOID PRELOAD IN THE PREVENTION OF HYPOTENSION ASSOCIATED WITH SPINAL-ANESTHESIA FOR ELECTIVE CESAREAN-SECTION

Background. Hypotension after spinal anesthesia for cesarean section r emains a common and serious complication despite the use of uterine di splacement and volume preloading. The current study revaluated the rol e of crystalloid volume preloading in this context. Methods. In a two- stage open sequential design, patients presenting for elective repeat cesarean section were allocated to receive either no preload or 20 ml/ kg crystalloid administered over 15-20 min before spinal anesthesia. H ypotension was defined as a decrease in systolic pressure to less than 100 mmHg and to less than 80% of baseline value, and the study was de signed to detect a 20% difference in the incidence of hypotension betw een the groups, with statistical significance at the 10% (alpha = 0.1) level, one-tailed. Results: One hundred forty patients were studied. Hypotension occurred in 43 (55%, 95% CI 43.4-66.4) preloaded and 44 (7 1%, 95% CI 58-81.8) unpreloaded subjects, a difference in incidence of 16% (95% CI 0.04-31.6), which was statistically significant. There we re no significant differences in the severity, timing, or duration of hypotension; the dose requirement for ephedrine; or the clinical and b iochemical status of neonates between the groups. The only difference seen was a lower mean base excess (-3.4, SD 2.81 mm-1) in the neonates of hypotensive mothers compared to neonates of nonhypotensive mothers (-2.4, SD 1.99 mM-1). Conclusions. The study confirms that hypotensio n associated with spinal anesthesia for cesarean section cannot be eli minated by volume preloading in the supine wedged patient. The relativ ely small reduction in incidence of hypotension challenges our percept ion of the value of crystalloid preload. Though volume preload in the elective cesarean section is advocated, the requirement for a mandator y administration of a fixed volume before spinal anesthesia for urgent cases has been abandoned.