Comparison of Effect of Two Different Doses of Intravenous Oxytocin on Patients Undergoing Elective Cesarean Section

Cesarean section is one of the most commonly performed obstetric surgical procedures worldwide. Uterine atony and postpartum hemorrhage are important causes of maternal morbidity and mortality following cesarean delivery. Oxytocin is routinely administered to stimulate uterine contractions and prevent postpartum uterine atony. It promotes myometrial contraction, facilitates uterine retraction, and helps achieve effective hemostasis following delivery.

Although oxytocin is widely used during cesarean section, the appropriate dose remains an important consideration. Administration of higher doses, particularly as a rapid intravenous bolus, may produce cardiovascular effects, including vasodilatation, hypotension, reflex tachycardia, and increased cardiac output. These effects may increase myocardial oxygen demand. Therefore, selecting an appropriate dose is important to achieve adequate uterine contractions while minimizing blood loss and potential adverse effects.

Previous studies comparing low-dose and high-dose oxytocin have reported inconsistent findings. Maqbool et al. reported no statistically significant difference in adequate uterine contractions or blood loss between the two dosage groups. Similarly, Somjit et al. reported comparable uterine contraction rates and no significant difference in blood loss exceeding 500 ml. However, Bhardwaj et al. reported significantly lower rates of adequate uterine contractions in the low-dose group compared with the high-dose group. These conflicting findings indicate that further investigation is required to establish the comparative effectiveness of different oxytocin doses during cesarean delivery.

The primary objective of this study is to compare the effects of two different doses of intravenous oxytocin (5 IU and 10 IU) in patients undergoing elective cesarean section in terms of adequate uterine contractions and blood loss.

This study will be conducted as a randomized controlled trial in the Department of Obstetrics and Gynecology, Shalamar Hospital, Lahore. The study duration will be six months after approval of the synopsis. A total of 120 pregnant women scheduled for elective cesarean section will be enrolled, with 60 participants allocated to each study group. The sample size has been calculated using the WHO sample size calculator, with 80% power of the test and a 5% level of significance, considering the expected frequency of adequate uterine contractions of 43.3% and 70.0% in the low-dose and high-dose oxytocin groups, respectively. Non-probability consecutive sampling will be used for participant recruitment.

Pregnant women aged 18-35 years, with a gestational age of 37-42 weeks, ASA physical status I or II, uncomplicated pregnancies, and scheduled for elective cesarean section under spinal anesthesia will be eligible for inclusion.

Women with active labour, multiple pregnancy, premature rupture of membranes, pregnancy-induced hypertension or preeclampsia will be excluded. Patients at risk of blood loss greater than 800 ml, those with inherited or acquired coagulation abnormalities or thrombocytopenia, and women with hypersensitivity to oxytocin will also be excluded.

After obtaining approval from the Hospital Ethical Review Board, eligible participants will be enrolled following informed written consent. Participants will be randomly allocated into two groups using the lottery method.

Group A (Low-Dose Oxytocin): Participants will receive 5 IU of intravenous oxytocin diluted in 1,000 ml of normal saline or Ringer's lactate solution.

Group B (High-Dose Oxytocin): Participants will receive 10 IU of intravenous oxytocin diluted in 1,000 ml of normal saline or Ringer's lactate solution.

The assigned intervention will be administered at the time of umbilical cord clamping during elective cesarean section. Administration will follow the protocol specified in the approved study synopsis. Cesarean sections will be performed according to the standard procedure of the hospital. All procedures will be performed by the same team to minimize procedural variation and potential bias. Study findings will be assessed and recorded by a senior consultant.

The primary outcome measures will be adequate uterine contractions and blood loss following administration of the assigned oxytocin dose. Adequate uterine contractions will be defined as at least one uterine contraction at three minutes after oxytocin administration, lasting 40-60 seconds, with sufficient intensity to make the uterus feel firm upon palpation, indicating effective uterine contraction and hemostasis. Blood loss will be measured by combining the volume of blood collected in a kidney tray, subsequently measured using a graduated cylinder, and blood retained on soaked gauze. Blood retained on gauze will be estimated by subtracting the weight of unused gauze from the weight of soaked gauze, using the study protocol's conversion of 1 mg to 1 ml. Additional observations will include the occurrence of complications such as nausea, vomiting, hypotension, and headache. Demographic and clinical variables, including maternal age, gestational age, and body mass index, will also be recorded.

All collected data will be entered and analyzed using Statistical Package for the Social Sciences (SPSS), version 26. Numerical variables, including age, gestational age, body mass index, and blood loss, will be presented as mean and standard deviation. Categorical variables, including adequate uterine contractions and complications, will be presented as frequencies and percentages.

The frequency of adequate uterine contractions will be compared between the two groups using the chi-square test. Stratification will be performed according to age, gestational age, and body mass index to address potential effect modifiers. Post-stratification comparisons will also be performed using the chi-square test. A p-value of ≤0.05 will be considered statistically significant. This study will provide comparative evidence regarding the effects of 5 IU and 10 IU intravenous oxytocin in women undergoing elective cesarean section. By evaluating adequate uterine contractions, blood loss, and associated complications, the study will help clarify the effectiveness of the two dosage regimens and may contribute to selecting an appropriate oxytocin dose in future obstetric practice.