Spinal anesthesia for elective cesarean section is frequently associated with hemodynamic instability and postoperative complications such as postoperative nausea and vomiting (PONV) and delayed gastrointestinal recovery. Although intraoperative fluid administration is routinely used to prevent spinal-induced hypotension, the optimal fluid strategy remains unclear. Both restrictive and liberal fluid approaches may influence maternal hemodynamics and postoperative outcomes through different physiological mechanisms.

This prospective, single-center, randomized controlled trial aims to compare restrictive (≤3 mL/kg/h) and liberal (>3 mL/kg/h) intraoperative crystalloid fluid strategies in patients undergoing elective cesarean section under spinal anesthesia. The primary outcome is the incidence of PONV within the first 24 hours postoperatively. Secondary outcomes include postdural puncture headache (PDPH), time to first flatus, hypotension frequency, and vasopressor requirements.

Spinal anesthesia is the preferred anesthetic technique for elective cesarean section; however, it is frequently associated with sympathetic blockade-induced hypotension. Intraoperative crystalloid administration is commonly used to mitigate hemodynamic instability, yet the optimal fluid strategy remains controversial. Liberal fluid administration may reduce the incidence or severity of hypotension but can contribute to tissue edema, including gastrointestinal wall edema, potentially delaying the recovery of bowel function. Conversely, restrictive fluid strategies may limit fluid overload but could increase vasopressor requirements and compromise splanchnic perfusion. The balance between these approaches and their influence on postoperative maternal outcomes has not been clearly established.

Postoperative nausea and vomiting (PONV) remains one of the most common and distressing complications following cesarean section. Hemodynamic fluctuations, vasopressor use, and visceral perfusion changes may all contribute to its development. In addition, delayed gastrointestinal recovery and postdural puncture headache (PDPH) are relevant postoperative outcomes that may be influenced by intraoperative fluid management.

This prospective, single-center, parallel-group randomized controlled trial is designed to compare two intraoperative crystalloid fluid strategies in patients undergoing elective cesarean section under spinal anesthesia. Patients will be randomized in a 1:1 ratio to receive either a restrictive (≤3 mL/kg/h) or a liberal (>3 mL/kg/h) intraoperative fluid approach. All other anesthetic procedures, spinal technique, and perioperative management will be standardized according to institutional protocol.

The primary outcome of the study is the incidence of PONV within the first 24 postoperative hours. Secondary outcomes include the incidence and severity of PDPH, time to first flatus as a marker of gastrointestinal recovery, frequency of hypotension, and vasopressor requirements. Intraoperative hemodynamic parameters and fluid administration data will be recorded prospectively.

The study aims to clarify whether intraoperative fluid volume influences postoperative maternal recovery and to contribute evidence toward optimizing perioperative fluid management in elective cesarean section.

Inclusion Criteria:

• Female patients aged 18-45 years
• ASA physical status II
• Scheduled for elective cesarean section under spinal anesthesia
• Provision of written informed consent

Exclusion Criteria:

• Emergency cesarean section
• Preeclampsia or eclampsia
• Known cardiac failure
• Known renal failure
• Known hepatic failure
• Coagulopathy
• Contraindication to spinal anesthesia
• Conversion to general anesthesia
• Major technical complications during spinal anesthesia
• Refusal to participate

Individual participant data (IPD) will not be publicly shared due to institutional policies and ethical considerations related to patient confidentiality. De-identified data may be made available upon reasonable request to the corresponding investigator, subject to approval by the institutional ethics committee and data protection regulations.

Participants will be blinded to group allocation. The anesthesia team will not be blinded due to the nature of the intervention (intraoperative fluid strategy). Postoperative outcomes will be collected by a blinded assessor who is not involved in intraoperative care and has no access to allocation information. Group allocation will be recorded in a separate study log and concealed from participants and outcome assessors until completion of follow-up.