Perfusion Index as a Reliable Tool for Prediction of Hypotension during Subarachnoid Block in Caeserean Section: A Prospective Observational Study

Introduction: Hypotension after subarachnoid block is a common occurrence due to sympathetic blockade leading to vasodilation, which causes a decrease in cardiac preload and results in a decrease in cardiac output. Early detection of hypotension and prompt treatment during caesarean delivery under subarachnoid block is the primary responsibility of the anaesthesiologist. Aim: To evaluate and validate the Perfusion Index (PI) as a predictor of hypotension following Subarachnoid Block (SAB) in patients undergoing Lower Segment Caesarean Section (LSCS) and to assess the usefulness of perioperative pulse oximetry-derived PI as a monitoring tool. Materials and Methods: This was a prospective hospital-based observational study was conducted in the Department of Anaesthesiology at BJMC Ahmedabad, Gujarat, India over a period from March 2020 to February 2021, that included 60 American Society of Anaesthesiolgy (ASA) II pregnant patients, divided into two groups (A and B) based on PI, who were planned for elective caesarean delivery under regional anaesthesia. Variables recorded included heart rate, blood pressure, SpO2, and PI at different time intervals. The quantitative data were presented as mean and standard deviation and compared using the Student's t-test. Results: Demographic parameters of both groups A and B, such as mean age (26.93 +/- 3,24 years, 28.33 +/- 4.02 years), mean height (155.56 +/- 4.29 cm, 155.17 +/- 4.31 cm), mean weight (62.70 +/- 5.87 kg, 60.36 +/- 5 kg), Body Mass Index {BMI (25.92 +/- 2.42, 25.01 +/- 2.14 kg/m2)}, and gestational age (36.03 +/- 0.32, 36.53 +/- 0.32 weeks) respectively, were comparable between the two groups. There was a statistically significant drop in Mean Arterial Pressure (MAP) in both Group A and Group B after induction, from one minute to 70 minutes (p<0.05) from the baseline. The difference in the proportion of PI between the hypotension groups was statistically significant (p-value=0.002). The number of episodes of hypotension and the total dose of Mephenteramine were significantly higher in Group B (Chi-square=52.500 with 2 degrees of freedom; p<0.001) than in Group A. Conclusion: Parturients with a baseline PI>3.5 were at a higher risk of developing hypotension following a subarachnoid block compared to those with a baseline PI<3.5. Therefore, appropriate preventive measures can be instituted preoperatively to prevent hypotension and improve outcomes in such patients.