Tackling Spinal Anaesthesia-Induced Hypotension in Caesarean Deliveries: Study Evaluating Interventions and the Role of Vasopressors

Spinal anaesthesia (SA) is frequently associated with hypotension during caesarean sections (CS), with reported occurrences between 30% to 83%. To mitigate this complication, various preventive measures have been explored, including uterine tilting, crystalloid or colloid preloading, and the use of vasopressors. Recent meta-analyses suggest the effectiveness of vasopressors such as mephentermine and phenylephrine, albeit with ephedrine exhibiting less efficacy. This study investigates the impact of preoperative oxytocin infusion on haemodynamics in women undergoing elective CS under SA, specifically comparing the effects of administering oxytocin preoperatively versus post-delivery.

Study Design and Participants

The study was approved by the Ethics Committee and adhered to the Declaration of Helsinki. It involved women aged 18 or older with singleton pregnancies who were at least 37 weeks along. Exclusion criteria included hypertensive disorders, pre-labour rupture of membranes, and various risk factors complicating CS outcomes. Participants were randomized into two groups: Group C received preloading with a saline infusion, and Group O received preoperative oxytocin at 6 milli-IU/min.

Pre-operative Evaluations and Monitoring

All pre-operative participants underwent baseline evaluations for haemodynamic parameters, including blood pressure, heart rate, and cardiac output, using a sophisticated monitoring system. Upon shifting to the surgical environment, a standard protocol was followed for administering SA. The timing of measurements was critical, with haemodynamics assessed every minute until delivery and subsequently at regular intervals until the end of surgery.

Outcome Measures and Statistical Analysis

The primary outcome measure was the change in systolic blood pressure (SBP) following SA. Secondary outcomes included heart rate, mean arterial pressure, cardiac output, and any need for additional doses of vasopressors or oxytocin. Statistical analyses used t-tests and Mann-Whitney U tests for comparison between groups, with significance set at a p-value below 0.05.

Results and Comparison of Groups

From the 70 recruited patients, three were excluded, leaving 67 for analysis. The results indicate that Group O exhibited a significantly higher SBP at the 1-minute mark following SA when compared to Group C (107 mmHg vs. 89 mmHg respectively, p < 0.05). Moreover, Group O maintained a higher SBP for a longer duration after delivery, with significant differences observed for up to 15 minutes (p < 0.001). Participants in Group C required significantly more doses of both phenylephrine and oxytocin compared to those in Group O, showcasing improved haemodynamic stability in the preoperative oxytocin group.

Neonatal Outcomes

APGAR scores at both 1 and 5 minutes post-delivery were comparable between groups, suggesting that the preoperative administration of oxytocin did not negatively impact neonatal outcomes.

Conclusions and Future Directions

Considering these findings, the study concludes that preoperative oxytocin administration during elective CS under SA promotes better haemodynamic stability by preserving SBP and cardiac output. This approach also decreases the requirement for vasopressors, providing a potentially safer anaesthetic practice in this population. However, the research acknowledges limitations including a restricted sample size and the exclusive focus on elective pre-labour CS, which may not fully represent the broader population of women undergoing intrapartum procedures. Further studies are suggested to enhance understanding of the efficacy and safety of prophylactic oxytocin administration in varied clinical scenarios.

Key Points

- Spinal anaesthesia (SA) during caesarean sections (CS) is commonly linked to hypotension, with incidences reported between 30% and 83%. The study evaluates the effects of preoperative oxytocin infusion on haemodynamics in women undergoing elective CS under SA, comparing the outcomes of administering oxytocin either preoperatively or post-delivery.

- A randomized controlled trial was conducted involving women with singleton pregnancies, aged 18 or older, at least 37 weeks gestation, excluding those with hypertensive disorders or other risks affecting CS outcomes. Participants were divided into two groups: Group C received saline preloading, while Group O received oxytocin at a dosage of 6 milli-IU/min preoperatively.

- Participants underwent thorough baseline evaluations of haemodynamic parameters such as blood pressure and heart rate. Blood pressure was monitored every minute after SA, with further assessments until the end of surgery to track changes in the patient's condition.

- The primary outcome measure was the change in systolic blood pressure (SBP) post-SA, while secondary outcomes included heart rate, mean arterial pressure, cardiac output, and the requirements for additional vasopressors. Statistical analysis demonstrated significant differences, notably a higher SBP in Group O at the 1-minute mark post-SA (107 mmHg) compared to Group C (89 mmHg), with continued superiority for 15 minutes (p < 0.001).

- Group C also required more doses of phenylephrine and oxytocin than Group O, indicating that preoperative oxytocin administration significantly improved haemodynamic stability during elective CS under SA.

- Neonatal outcomes, measured by APGAR scores at 1 and 5 minutes post-delivery, were found to be similar between both groups, suggesting that the preoperative oxytocin administration did not adversely affect neonatal health. Future research is recommended to explore the broader applicability of these findings in varied clinical contexts.

Reference –

Ram Jeevan et al. (2025). Effect Of Preoperative Oxytocin Infusion On Haemodynamics Among Women Undergoing Elective Caesarean Section Under Spinal Anaesthesia: A Randomised Controlled Study. *Indian Journal Of Anaesthesia*. https://doi.org/10.4103/ija.ija_1062_24.