Prediction Of Hypotension After Spinal Anesthesia For Elective Cesarean Section Based On Photoplethysmorgraphic Pulse Wave

Introduction:Spinal anesthesia is widely used for cesarean section. Hypotension after spinal anesthesia is common, which is the result of the decreased systemic vascular resistance due to sympathetic blockade and the decreased cardiac output due to blood pooling in blocked areas of the body. The increased sympathetic activity in pregnancy and the reduction in venous return caused by compression of the inferior vena cava by the gravid uterus are the reasons for the higher incidence of hypotension in parturients. Hypotension during spinal anesthesia may be harmful for mothers and fetus. Ages, BMI (body mass index), preoperative sympathetic activity, preoperative volume status and systemic vascular resistance are known to affect the degree of such hypotension.Photoplethysmorgraphy (PPG) is a simple and non-invasive optical technique that can be used to detect blood volume changes in the microvascular bed of tissue. It is generally accepted that they can provide valuable information about the cardiovascular system and autonomic function. Hence, we could speculate that the risk of hypotension after spinal anesthesia for cesarean section might be detected by parameters derived from PPG.Objective:To develop a model to predict the incidence of hypotension after spinal anesthesia for cesarean section based on parameters derived from PPG.Methods:69women with a healthy pregnancy, at term, scheduled to undergo elective cesarean section during spinal anesthesia were enrolled. PPG waveform was collected on-line and systolic blood pressure (SBP) was measured at the day before surgery (DBS), before pre-load of fluid on the day of surgery (DOS-BP), during the time between preload and spinal anesthesia (DOS-AP) and lmin after spinal anesthesia (SAB+1). Then we developed three models to predict hypotesion with multivariate logistic regression and chosed the best one to estimate sensitivity and specificity.Results:The model based on PPG waveform at the day before surgery can detect the risk of hypotension more efficiently(AUC0.8259,95%CI0.7285-0.9232). When the cut point is0.61, the sensitivity is72.50%and the specificity is72.41%.Conclusion:The model based on PPG waveform at the day before surgery can detect the risk of hypotension more efficiently.