Spinal anesthesia is widely preferred for elective cesarean delivery due to its favorable safety profile and superior postoperative analgesia. However, post-spinal hypotension (PSH) remains a common complication, with reported incidence rates ranging from 40% to 70%, potentially compromising maternal hemodynamic stability and uteroplacental perfusion. Early identification of patients at high risk for PSH is therefore of critical clinical importance.

This prospective observational study aims to evaluate the predictive performance of preoperative internal jugular vein collapsibility index (IJV-CI), assessed by ultrasonography, and baseline perfusion index (PI), obtained via pulse oximetry, for the development of PSH in patients undergoing elective cesarean section under spinal anesthesia. While IJV-CI reflects intravascular volume status and preload, PI represents peripheral vascular tone; thus, their combined use may improve predictive accuracy.

Study Design This is a single-center, prospective observational study conducted in patients scheduled for elective cesarean delivery under spinal anesthesia. No additional intervention will be applied, and all anesthetic management will follow standard clinical practice.

Objectives

Primary Objective:

To assess the ability of preoperative IJV collapsibility index (IJV-CI) and baseline perfusion index (PI) to predict post-spinal hypotension.

Secondary Objectives:

To evaluate the relationship between IJV-CI and PI with:

Duration and number of hypotensive episodes Minimum systolic and mean arterial pressure Total vasopressor requirement Incidence of intraoperative nausea and vomiting Pregnant women aged 18-45 years, ASA II, with singleton pregnancies scheduled for elective cesarean section under spinal anesthesia.

Inclusion Criteria Age 18-45 years Elective cesarean section Planned spinal anesthesia ASA physical status II Singleton pregnancy Exclusion Criteria Hypertensive disorders of pregnancy (e.g., preeclampsia, HELLP) Significant cardiac or pulmonary disease Chronic kidney disease Multiple pregnancy Emergency cesarean delivery Conversion to general anesthesia

Conditions preventing IJV ultrasonographic assessmentBaseline PI will be recorded preoperatively using standard pulse oximetry. IJV diameters will be measured via ultrasound, and the collapsibility index will be calculated as:

IJVI: (Dmax-Dmin/Dmax)X100 Hemodynamic parameters will be recorded at 3-minute intervals from spinal anesthesia administration until delivery. Statistical analysis will include ROC curve analysis, correlation analysis, and logistic regression to evaluate predictive performance.

Inclusion Criteria:

Age 18-45 years Singleton pregnancy Scheduled for elective cesarean section Planned spinal anesthesia ASA physical status II

Exclusion Criteria:

Hypertensive disorders of pregnancy (e.g., preeclampsia, HELLP syndrome) Known significant cardiac disease or pulmonary hypertension Chronic kidney disease Hemoglobinopathies Multiple pregnancy Emergency cesarean section Conversion to general anesthesia Anatomical or pathological conditions preventing IJV ultrasound assessment -

Female

Pregnant women undergoing elective cesarean section under spinal anesthesia at a tertiary care hospital.