The timing of intravenous crystalloid administration and incidence of cardiovascular side effects during spinal anesthesia:: The results from a randomized controlled trial

We conducted a randomized clinical trial to evaluate the efficacy of crystalloids in preventing spinal-induced hypotension (SIH) and cardiovascular side effects (CVSE) in a group of surgical patients. Participants were assigned to receive lactated Ringer's solution at 1-2 mL/min (Placebo group, n = 1,42); lactated Ringer's at 20 mL/kg starting 20 min before spinal block (n = 130); or lactated Ringer's at 20 mL/kg starting at the time of spinal block (n = 132). SIH was defined as a decrease of greater than or equal to30% in baseline systolic blood pressure, and CVSE as SIH plus nausea, vomiting, or faintness requiring treatment. The incidence of SIH was similar in all treatment groups. Compared to placebo, crystalloid administration at die time of spinal block resulted in a significant reduction in the proportion of patients developing CVSE from 9.9% to 23%. The corresponding relative proportion was 0.23 (95% confidence interval, 0.07-0.78; P = 0.019), and one additional case of CVSE was avoided for each 13 loids at the time of,,pinal block instead of placebo. Administration of crystalloids at the time of spinal block seems to be effective because it provides additional intravascular fluids during the period of highest risk of CVSE after spinal anesthesia.