Effect of preoperative oxytocin infusion on haemodynamics among women undergoing elective caesarean section under spinal anaesthesia: A randomised controlled study.

Background and aims: Various strategies to improve haemodynamics to avoid hypotension following spinal anaesthesia for caesarean section are reported. Uterine contractions induced with oxytocin lead to autotransfusion that may aid in maintaining blood pressure by increasing preload. This study aimed to compare the haemodynamic effects of initiating prophylactic oxytocin infusion preoperatively versus starting it after foetal delivery among women undergoing elective caesarean section under spinal anaesthesia.

Methods: In this randomised controlled study, women undergoing elective caesarean section under spinal anaesthesia were assigned following simple randomisation to receive either oxytocin infusion at the rate of 6 milli-IU/min (Group O) or only normal saline alone (Group C), started before spinal anaesthesia, along with both receiving preloading with normal saline infusion. Hypotension was treated with a bolus dose of intravenous phenylephrine. Changes in the haemodynamic parameters, heart rate, systolic blood pressure (SBP), mean arterial pressure and non-invasive cardiac output (CO) indices (CO and stroke volume) assessed using a non-invasive CO monitor were compared between groups.

Results: Hypotension occurred in 19 women in Group C (59.4%) compared to three in Group O (8.6%). A significant fall in SBP and CO was observed in Group C compared to Group O (P < 0.001). Phenylephrine requirement was significantly higher in Group C [21.9 (21.4, 95% confidence interval {CI} 13.6, 28.2)] compared to Group O [1.7 (5.7, 95% CI: 0.2, 3.7)] (P < 0.001). The total dose of oxytocin was significantly higher in Group C (median 10 IU, range: 8-13) versus Group O (median 5 IU, range: 0-5) (P < 0.001).

Conclusion: Preoperative prophylactic oxytocin infusion provides better haemodynamic stability in women undergoing elective caesarean section under spinal anaesthesia and reduces the incidence of hypotension and the requirement for phenylephrine.