Minimal Effective Weight-based Dosing of Ondansetron to Reduce Hypotension in Cesarean Section Under Spinal Anesthesia

A Randomized Controlled Superiority Trial

Maliwan Oofuvong; Thitikan Kunapaisal; Orarat Karnjanawanichkul; Nussara Dilokrattanaphijit; Jaranya Leeratiwong


BMC Anesthesiol. 2018;18(105) 

In This Article


Two hundred and twenty-eight women were enrolled in the study with details shown in the consort diagram in Figure 1. Data collection was completed in 215 patients for the intention-to-treat analysis. Patient characteristics and anesthetic data are presented in Table 1. No differences among the groups were observed in demographic data and anesthetic data. The overall incidence of maternal hypotension was 80%. There were no differences in the incidence of hypotension between the three groups either before or after delivery except episodes of hypotension before delivery were significantly higher in group O1 compared to NS (5 vs 2, P = 0.02) (Table 2). The arterial pressures (SBP, MAP, and DBP) are shown in Figure 2. MAP levels at 4 and 9 min after spinal anesthesia were significantly lower in group O1 compared to the NS group (P = 0.024 and P = 0.034, respectively). The overall heart rates throughout the operations were not different among the three groups (Figure 3). Ephedrine requirements were similar among the three groups: group NS (6 mg), group O1 (12 mg), and group O2 (6 mg) (P = 0.21). There were also no differences in blood loss among the three groups: group NS (447.9 ± 201.3 mL), group O1 (490.8 ± 241.2 mL), and group O2 (440.3 ± 198.2 mL) (P = 0.32). Table 3 shows the surgical and anesthetic parameters for the three groups. The metoclopramide requirement in the post-hoc analysis in group O2 was significantly lower than in group NS (P = 0.01). Table 4 compares the incidence of maternal and newborn adverse events between the three groups. No significant differences were found although tachypnea was slightly higher among newborns of women who received low dose ondansetron (7.0%, n = 5) compared to the control group (2.8%, n = 2) (P = 0.28). There were no reports of burning or QT prolongation in mothers and no reports of bradycardia or hypothermia in newborns in any group.

Figure 1.

Consort flow diagram. GA general anesthesia

Figure 2.

Changes in maternal systolic blood pressure (SBP), diastolic blood pressure (DBP) and mean arterial pressure (MAP) for the three groups. NS normal saline, O1 ondansetron 0.05 mg/kg, O2 ondansetron 0.1 mg/kg. Spinal anesthesia was performed between Time 0–1, Time 0 = baseline blood pressure, Time 1–60 = 1 to 60 min after spinal anesthesia, *P < 0.05 compared group O1 to NS at a certain time compared to Time 0

Figure 3.

Changes in heart rate for the three groups. NS normal saline, O1 ondansetron 0.05 mg/kg, O2 ondansetron 0.1 mg/kg. Time 0 = baseline heart rate, Time S = spinal anesthesia and 5 min after received intervention, Time 5–60 = 5 to 60 min after spinal anesthesia