Effect of timing of fluid bolus on reduction of spinal-induced hypotension in patients undergoing elective cesarean delivery

Spinal-induced hypotension remains the most common complication associated with spinal anesthesia for cesarean delivery. Recent evidence indicates that a 20-mL/kg bolus via pressurized infusion system administered at the time of subarachnoid block (SAB) (coload) may provide better prophylaxis than the traditional administration of a 20-mL/kg crystalloid infusion (preload) approximately 20 minutes before SAB; however, this method raises some concerns. We hypothesized that administering half of the fluid bolus (10 mL/kg) before and half immediately following injection of the SAB would provide benefit. Variables included demographics, spinal anesthetic dermatome level obtained, additional intravenous (IV) fluid bolus and vasopressor requirements, and maternal vital signs. We enrolled 87 subjects in this prospective, randomized investigation, 43 preload (control) and 44 preload/coload (experimental). There were no demographic differences between groups. The increased supplemental vasopressors required to treat maternal hypotension in the preload group were not statistically significant. Total IV fluids and supplemental IV bolus requirements were significantly higher in the preload group. No differences in neonatal outcomes were noted between groups. Maternal vital signs were not significantly different between groups; hypotension was treated as it occurred. We recommend replacing standardized prophylactic crystalloid fluid administration with the preload/coload method described herein.