BACKGROUND: The optimal strategy of fluid administration during spinal anesthesia for cesarean delivery is still unclear. Ultrasonography of the inferior vena cava (IVC) has been recently used to assess the volume status and predict fluid responsiveness. In this double-blind, randomized controlled study, we compared maternal hemodynamics using a combination of 500-mL colloid preload and 500-mL crystalloid coload versus 1000-mL crystalloid coload. We assessed the IVC at baseline and at subsequent time points after spinal anesthesia.
METHODS: Two hundred American Society of Anesthesiologists physical status II parturients with full-term singleton pregnancies scheduled for elective cesarean delivery under spinal anesthesia were randomly allocated to receive either 500-mL colloid preload followed by 500-mL crystalloid coload (combination group) or 1000-mL crystalloid coload (crystalloid coload group) administered using a pressurizer. Ephedrine 3, 5, and 10 mg boluses were administered when the systolic blood pressure decreased below 90%, 80% (hypotension), and 70% (severe hypotension) of the baseline value, respectively. The IVC was assessed using the subcostal long-axis view at baseline, at 1 and 5 minutes after intrathecal injection, and immediately after delivery; the maximum and minimum IVC diameters were measured, and the IVC collapsibility index (CI) was calculated using the formula: IVC-CI = (maximum IVC diameter – minimum IVC diameter)/maximum IVC diameter. The primary outcome was the total ephedrine dose.
RESULTS: Data from 198 patients (99 patients in each group) were analyzed. The median (range) of the total ephedrine dose was 11 (0–60) mg in the combination group and 13 (0–61) mg in the crystalloid coload group; the median of the difference (95% nonparametric confidence interval) was −2 (−5 to 0.00005) mg, P = .22. There were no significant differences between the 2 groups in the number of patients requiring ephedrine, the incidence of hypotension and severe hypotension, the time to the first ephedrine dose, and neonatal Apgar scores at 1 and 5 minutes. The maximum and minimum IVC diameters in each group increased after spinal anesthesia and after delivery, and they were larger in the combination group. The IVC-CI after delivery was higher in the crystalloid coload group.
CONCLUSIONS: The combination of 500-mL colloid preload and 500-mL crystalloid coload did not reduce the total ephedrine dose or improve other maternal outcomes compared with 1000-mL crystalloid coload. The IVC was reliably viewed before and during cesarean delivery, and its diameters significantly changed over time and differed between the 2 groups.