Pupillary Light Reflex to Predict Post-Spinal Hypotension in Elective Cesarean Delivery

Spinal anesthesia is the standard technique for elective cesarean delivery, yet it is frequently associated with maternal hypotension due to sympathetic blockade. According to the study protocol, spinal anesthesia-induced hypotension (SAIH) occurs in 50-90% of cases, and currently available predictors-including baseline blood pressure, BMI, and block height-demonstrate limited accuracy (AUC <0.65). The pupillary light reflex (PLR) is a sensitive indicator of autonomic nervous system balance, and pupillary reaction latency may reflect parasympathetic conduction efficiency. As noted in the protocol, no published studies have evaluated PLR as a predictor of hypotension after spinal anesthesia in obstetric patients.

This prospective observational cohort study aims to determine whether pre-anesthetic PLR parameters, particularly pupillary reaction latency, can predict the occurrence and severity of hypotension following spinal anesthesia for elective cesarean section. Additional pupillometry parameters-including baseline diameter, constriction velocity, and minimum diameter-will also be assessed. Measurements are obtained using a handheld pupillometer after 5 minutes of dark adaptation, with three readings taken at 60-second intervals.

Following spinal anesthesia with hyperbaric bupivacaine and fentanyl, maternal blood pressure is monitored every 5 minutes for the first 20 minutes. The primary outcome is hypotension, defined as a >20% decrease in systolic blood pressure. Secondary outcomes include severe hypotension, vasopressor requirements, maternal symptoms, and neonatal Apgar scores and umbilical artery pH.

Statistical analysis includes ROC curve evaluation, Youden's index for cutoff determination, and multivariate logistic regression. The study involves no interventions beyond routine care, and pupillometry is non-invasive and safe. Findings may support the development of a novel, objective, and clinically useful predictor for SAIH in obstetric anesthesia.

Inclusion criteria

ASA II Term pregnancy ≥37 weeks Singleton pregnancy Elective cesarean section Age 18-45 years Written informed consent

Exclusion criteria

Emergency cesarean section Hypertensive disorders Diabetes mellitus Cardiovascular disease Neurological or autonomic disorders Ophthalmic disease Medications affecting autonomic function BMI >40 kg/m² Failed spinal anesthesia