Effect of Oxytocin Bolus Versus Slow Infusion on Haemodynamic Stability During Caesarean Section Under Spinal Anaesthesia

Effect of Oxytocin Administration Technique on Haemodynamic Stability During Caesarean Section Under Spinal Anaesthesia: A Randomised Controlled Trial

This study compares two standard ways of giving oxytocin (a medicine that helps the uterus contract) after the baby is born during a planned caesarean section performed under spinal anaesthesia. One group of women will receive oxytocin as a quick injection into the vein. The other group will receive the same dose of oxytocin as a slow infusion over 15 minutes. The researchers want to find out which method causes less drop in blood pressure and other heart-related changes, while still providing good contraction of the uterus and preventing excessive bleeding.

Postpartum haemorrhage remains a leading cause of maternal mortality worldwide. Oxytocin is the first-line uterotonic agent used after delivery of the baby during caesarean section. When given as a rapid intravenous bolus, oxytocin can cause significant hypotension, tachycardia and other haemodynamic changes, especially in women under spinal anaesthesia.

This prospective, randomised, controlled trial will compare the haemodynamic effects of oxytocin 5 IU administered as a rapid intravenous bolus versus the same dose given as a slow intravenous infusion over 15 minutes in women undergoing elective caesarean section under spinal anaesthesia.

Sixty women aged 18-40 years with singleton pregnancy at 37-42 weeks, ASA physical status I or II, will be randomly allocated to one of two groups:

Group A (Bolus): Oxytocin 5 IU given as an intravenous bolus over 15 seconds immediately after umbilical cord clamping.

Group B (Infusion): Oxytocin 5 IU diluted and infused over 15 minutes via syringe pump immediately after umbilical cord clamping.

The primary outcome is the change in systolic blood pressure from baseline at 2, 5 and 10 minutes after oxytocin administration. Secondary outcomes include changes in diastolic blood pressure and heart rate, incidence of hypotension and tachycardia, vasopressor requirements, uterine tone assessed by a 5-point scale, estimated blood loss, and side effects such as nausea, vomiting, flushing and chest discomfort.

The study will be conducted at Hayatabad Medical Complex, Peshawar. All participants will receive standard spinal anaesthesia and routine care. The results are expected to provide local evidence to support safer oxytocin administration practices during caesarean section under spinal anaesthesia.

Inclusion Criteria:

• Adult female patients aged 18 to 40 years
• American Society of Anesthesiologists (ASA) physical status class I or II
• Singleton pregnancy at 37 to 42 weeks gestational age
• Scheduled for elective caesarean section under spinal anaesthesia
• Written informed consent obtained

Exclusion Criteria:

• Patients with anticipated hemodynamic instability including severe preeclampsia/eclampsia, placenta previa with active bleeding, placental abruption, or hemorrhagic shock
• Pre-existing cardiovascular disease including ischemic heart disease, valvular heart disease, cardiomyopathy, or arrhythmias
• Baseline systolic blood pressure < 100 mmHg or heart rate > 100 bpm before spinal block
• Known hypersensitivity to oxytocin
• Failed spinal anaesthesia requiring conversion to general anaesthesia
• Patients receiving medications that may alter the hemodynamic response to oxytocin (beta-blockers, calcium channel blockers, ACE inhibitors, or angiotensin receptor blockers)
• Pre-existing anaemia (Hb < 8 g/dL)