This prospective observational study aims to evaluate the role of pleth variability index (PVI) and perfusion index (PI) monitoring in intraoperative hemodynamic control among pediatric patients undergoing craniosynostosis surgery. Patients aged 0-6 years will be monitored intraoperatively using standard anesthesia monitoring together with PVI and PI measurements. Hemodynamic parameters, including systolic, diastolic and mean arterial pressure, heart rate, central venous pressure, oxygen saturation, body temperature, urine output, blood loss, fluid replacement, blood product requirement, serum lactate level, blood gas parameters and intraoperative complications will be recorded. The study will assess the association between PVI/PI changes and intraoperative hemodynamic status, bleeding and transfusion requirements.

Craniosynostosis surgery in pediatric patients is associated with a high risk of intraoperative blood loss and hemodynamic instability. Because children have a relatively low circulating blood volume, early detection of intravascular volume changes is essential for maintaining adequate perfusion and preventing hypotension. Goal-directed fluid management may improve oxygen delivery and overall hemodynamic stability during major surgical procedures.

Pleth variability index (PVI) is a noninvasive dynamic parameter derived from pulse oximetry waveform analysis and reflects respiratory variations in the perfusion index (PI). PI and PVI may provide useful information regarding peripheral perfusion, volume status and fluid responsiveness during mechanical ventilation. However, data regarding the utility of these parameters in pediatric craniosynostosis surgery are limited.

In this prospective observational study, pediatric patients aged 0-6 years undergoing craniosynostosis surgery will be followed intraoperatively. PVI and PI values will be recorded at predefined time points during surgery together with standard hemodynamic and perioperative parameters. Systolic, diastolic and mean arterial pressure, heart rate, central venous pressure, oxygen saturation, body temperature, urine output, estimated blood loss, amount of fluid replacement, blood product requirement, serum lactate level, blood gas parameters and intraoperative complications will be documented. The relationship between PVI/PI measurements and intraoperative hemodynamic changes, bleeding, fluid administration and transfusion requirements will be analyzed.

Inclusion Criteria:

• Pediatric patients aged 0 to 6 years
• Patients scheduled to undergo craniosynostosis surgery
• American Society of Anesthesiologists physical status I, II or III
• Written informed consent obtained from the parent or legal guardian

Exclusion Criteria:

• Patients older than 6 years
• American Society of Anesthesiologists physical status IV
• Inappropriate preoperative fasting status
• History of significant cardiac, pulmonary or renal disease
• Patients operated at another institution and subsequently transferred to the study center
• Patients with peripheral circulatory impairment
• Withdrawal of consent by the parent or legal guardian

Pediatric patients aged 0-6 years who are scheduled to undergo craniosynostosis surgery at Başakşehir Çam and Sakura City Hospital will constitute the study population.

Individual participant data will not be shared due to the pediatric study population, the small sample size and the potential risk of participant re-identification despite de-identification. Aggregate study results may be shared in scientific publications or presentations.