Granisetron Use, Blood Pressure, and Nausea and Vomiting During Cesarean Delivery Under Spinal Anesthesia

This single-center prospective observational cohort study will be conducted in the Department of Anesthesiology and Reanimation at Kayseri City Hospital. The planned sample comprises 80 consenting pregnant adults with singleton pregnancies and American Society of Anesthesiologists physical status II undergoing cesarean delivery under spinal anesthesia, with a target of 40 participants in each exposure group.

Anesthetic technique, antiemetic prophylaxis, fluid management, and treatment of hypotension remain at the discretion of the treating anesthesiologist as part of routine clinical care. No drug or treatment is assigned by the research protocol. The granisetron-exposed group comprises patients receiving prophylactic intravenous granisetron within the interval from 5 minutes before to 5 minutes after spinal anesthesia. The comparison group comprises patients receiving no prophylactic antiemetic. Rescue antiemetic treatment is recorded separately from prophylaxis. Granisetron dose and timing and other medications are recorded. Apfel scores are not collected.

Systolic, diastolic, and mean arterial pressure, heart rate, and oxygen saturation are recorded at baseline; 0, 2, 5, 10, 15, 20, 25, 30, 45, and 60 minutes after spinal anesthesia while surgery is ongoing; at delivery of the baby; and at the end of surgery. Hypotension is evaluated as the number of recorded intraoperative measurement points with mean arterial pressure below 65 mmHg and, separately, systolic arterial pressure below 90 mmHg. These measures are counts of low-pressure measurement points, not estimates of time spent hypotensive.

The primary outcome is the cumulative intraoperative ephedrine dose in milligrams. Other recorded data include intraoperative nausea and vomiting, rescue antiemetic use, bradycardia, other vasopressors, spinal anesthetic and opioid doses, sensory block level, demographic and obstetric characteristics, surgical times, fluid administration, and estimated blood loss. Observation is limited to the intraoperative period.

The sample size calculation described in the protocol is based on a published between-group difference in total ephedrine consumption, with an effect size of approximately 0.91, two-sided alpha of 0.05, and 95% power. The target was increased from 66 to 80 participants to allow for missing data. Continuous variables will be compared using a t-test or Mann-Whitney U test as appropriate, and categorical variables using a chi-square or Fisher exact test. Potential confounding may be assessed using multivariable regression.

• Granisetron (Drug): Prophylactic intravenous granisetron administered during routine clinical care within 5 minutes before or 5 minutes after spinal anesthesia for cesarean delivery. The decision to use granisetron and the dose are determined by the treating anesthesiologist independently of this observational study. Actual dose and administration timing are recorded; no study-mandated dosing is imposed.

Primary outcomes

• Total Intraoperative Ephedrine Dose [Throughout the intraoperative period, from spinal anesthesia administration to the end of surgery.]: Cumulative dose of ephedrine administered to each participant during the intraoperative period, expressed in milligrams. All intraoperative ephedrine administrations are summed. Participants who receive no ephedrine have a total dose of 0 mg.

Secondary outcomes

• Number of Intraoperative Measurement Points With Mean Arterial Pressure Below 65 mmHg [Scheduled intraoperative assessments from spinal anesthesia administration to the end of surgery.]: For each participant, the number of scheduled intraoperative blood pressure measurement points at which mean arterial pressure is below 65 mmHg. Measurements are recorded at 0, 2, 5, 10, 15, 20, 25, 30, 45, and 60 minutes after spinal anesthesia while surgery is ongoing, at delivery of the baby, and at the end of surgery. This outcome is a count of low-pressure measurement points and is not a duration in minutes.
• Number of Intraoperative Measurement Points With Systolic Arterial Pressure Below 90 mmHg [Throughout the intraoperative period, from spinal anesthesia administration to the end of surgery.]: For each participant, the number of scheduled intraoperative blood pressure measurement points at which systolic arterial pressure is below 90 mmHg. Measurements are recorded at 0, 2, 5, 10, 15, 20, 25, 30, 45, and 60 minutes after spinal anesthesia while surgery is ongoing, at delivery of the baby, and at the end of surgery. This outcome is a count of low-pressure measurement points and is not a duration in minutes.
• Incidence of Intraoperative Nausea [Throughout the intraoperative period, from spinal anesthesia administration to the end of surgery.]: Percentage of participants with at least one episode of nausea during the intraoperative period, based on the intraoperative case report form.
• Incidence of Intraoperative Vomiting [Throughout the intraoperative period, from spinal anesthesia administration to the end of surgery.]: Percentage of participants with at least one episode of vomiting during the intraoperative period, based on the intraoperative case report form.

Sex: Female, ages: 18 Years to any

Inclusion Criteria:

* Pregnant women aged 18 years or older with a singleton pregnancy.
* American Society of Anesthesiologists (ASA) physical status II.
* Elective or emergency cesarean delivery under spinal anesthesia at Kayseri City Hospital.
* Written informed consent to participate.
* Routine intraoperative monitoring and a prophylactic antiemetic decision made independently by the treating anesthesiologist.

Exclusion Criteria:

* Age below 18 years.
* Cesarean delivery performed under general or epidural anesthesia, or intraoperative conversion from spinal to general anesthesia.
* Multiple pregnancy.
* Serious cardiovascular disease, severe arrhythmia, or advanced heart failure.
* Severe preeclampsia, eclampsia, or HELLP syndrome.
* Known allergy to 5-HT3 receptor antagonists.
* Massive intraoperative bleeding or blood transfusion.
* Refusal to participate or absence of written informed consent.
* Missing intraoperative hemodynamic measurements or other required study data.

• Salih Gale, MD, Principal investigator, Kayseri City Hospital