Routine Antiemetic Prophylaxis for Nonfasted Parturients Undergoing Cesarean Sections Under Spinal Anesthesia

This prospective, randomized, double-blind clinical trial is designed to evaluate the comparative effectiveness of routine antiemetic prophylaxis for preventing intraoperative nausea and vomiting in non-fasted parturients undergoing emergency cesarean section under spinal anesthesia.

Eligible participants will be pregnant women with American Society of Anesthesiologists (ASA) physical status I-II who undergo emergency cesarean delivery under spinal anesthesia. Only non-fasted (full-stomach) parturients will be included.

Exclusion criteria

include ASA physical status III or higher, preoperative anemia, massive intraoperative hemorrhage, requirement for additional intraoperative hypnotic agents, known gastrointestinal disease, psychiatric disorders or psychotropic medication use, and administration of antiemetic medication within 24 hours before surgery.

Participants will be randomized using a sealed-envelope allocation method before arrival in the operating room. Before transfer to the operating room, patients will receive the assigned study medication according to the randomization protocol. Both patients and the attending anesthesiologist responsible for outcome assessment will remain blinded to group allocation.

Participants will receive one of the following prophylactic antiemetic regimens:

Group O: 5-HT3 receptor antagonist (e.g., ondansetron or equivalent agent) Group M: Dopamine receptor antagonist (e.g., metoclopramide)

Standard monitoring will include electrocardiography, non-invasive blood pressure measurement, and peripheral oxygen saturation (SpO₂). Following intravenous cannulation, Ringer's lactate infusion will be initiated.

Spinal anesthesia will be performed at the L4-L5 interspace using 10 mg hyperbaric bupivacaine. After block placement, patients will be positioned supine with left uterine displacement to minimize aortocaval compression. Supplemental oxygen will be administered via nasal cannula at 2 L/min.

All participants will receive prophylactic intravenous ephedrine 5 mg. Additional 5 mg boluses will be administered if systolic blood pressure decreases below 100 mmHg or more than 20% from baseline values. Intravenous atropine 0.5 mg will be administered in cases of bradycardia (heart rate below 50-60 beats/min).

Following delivery of the fetal shoulders, oxytocin 20 IU will be administered intravenously as an infusion.

Demographic and perioperative data including age, body mass index, fasting duration since last solid food intake, smoking status, and operative duration will be recorded.

Hemodynamic variables (blood pressure and heart rate) will be recorded every 2 minutes until delivery and every 5 minutes thereafter until completion of surgery.

Intraoperative nausea and vomiting will be assessed during three predefined periods:

From 5 minutes after spinal anesthesia until delivery During and immediately after delivery From delivery until skin closure

Severity of nausea and vomiting will be evaluated using the Bellville scoring system:

0 = No nausea

• = Nausea
• = Retching (gagging)
• = Vomiting

Primary Outcome

Incidence of intraoperative nausea and vomiting occurring during and immediately after delivery.

Secondary Outcomes

Incidence and severity of intraoperative nausea and vomiting during the other predefined assessment periods.

Postoperative complications associated with antiemetic therapy

Inclusion criteria

• Pregnant women scheduled for emergency cesarean delivery under spinal anesthesia
• Non-fasted (full-stomach) parturients
• American Society of Anesthesiologists (ASA) physical status I-II
• Age ≥ 18 years
• Singleton pregnancy
• Ability to provide written informed consent

Exclusion criteria

• ASA physical status III or higher
• Refusal to participate
• Elective cesarean delivery (non-emergency cases)
• Preoperative antiemetic use within 24 hours before surgery
• Known allergy or contraindication to study drugs (ondansetron or metoclopramide)
• Pre-existing gastrointestinal disorders (e.g., severe GERD, gastroparesis, bowel obstruction)
• Psychiatric illness or current use of psychotropic medications
• Preoperative anemia (as defined by institutional threshold, e.g., Hb < 10 g/dL)
• Intraoperative conversion to general anesthesia
• Massive intraoperative hemorrhage (>1000-1500 mL or requiring transfusion, depending on your protocol definition)
• Intraoperative administration of additional sedative or antiemetic agents outside study protocol
• Multiple gestation pregnancies