Peripheral Perfusion Index: A Predictor of Post-Spinal Hypotension in Caesarean Section

Background Early prediction of hypotension helps to decide appropriate prophylactic measures and, hence, safe anaesthesia for mothers and improved neonatal outcomes. Perfusion index (PI) measured from a standard pulse oximeter has shown positive results in the prediction of hypotension. This study aims to determine if PI can equally predict hypotension in parturients after administration of spinal anaesthesia at different time points. Methods Parturients posted for elective caesarean section belonging to the American Society of Anesthesiology II (ASA II) were divided into two groups based on baseline PI as group A <3.5 and group B ≥3.5. Fifty-six parturients were enrolled in the study. PI and blood pressure were monitored at baseline, every two minutes for 12 minutes and every five minutes until the end of the surgery, after administration of spinal anaesthesia with hyperbaric bupivacaine 10 mg. Incidence of hypotension was compared between groups at all time points of observation. Spearman's rank correlation coefficient was determined to check the correlation between baseline PI and the number of episodes of hypotension. Receiver operating characteristic (ROC) curve was plotted to determine the ideal cut-off at different time points. Results Baseline PI significantly correlated with the number of episodes of hypotension (r-0.525). The overall incidence of hypotension was significantly higher in parturients with baseline PI ≥3.5 (79.16%) as compared to those with PI <3.5 (33.33%). The incidence of hypotension at sixth, 10th and 37th minutes post-spinal anaesthesia administration was significantly higher in the group with PI ≥3.5. The sensitivity and specificity for the 3.5 cut-off of PI were 85.7% and 60%, respectively, at the 6th and 10th minute after spinal administration. A higher cut-off of 3.9 increases the specificity to 69% without much change in the sensitivity. Conclusion  Parturients with PI >3.9 at baseline have a higher risk of hypotension in the initial 10-12 minutes following spinal anaesthesia during caesarean delivery.