Perfusion index-derived parameters as predictors of hypotension after induction of general anaesthesia: a prospective cohort study

Background: Induction of general anaesthesia is commonly associated with hypotension. This exposes patients to perioperative organ hypoperfusion and eventually damage. This study was designed to assess the ability of preoperative perfusion index (PI), plethysmographic variability index (PVI), and dicrotic plethysmography (Dic(pleth)) to predict hypotension after induction of general anaesthesia. Methods: In this cohort study, 95 ASA I and II adult patients who were scheduled for elective surgery under general anaesthesia were enrolled. The correlation between preoperative PI, PVI, Dic(pleth) and percentage decrease in mean arterial blood pressure after anaesthesia induction was investigated. Ability of PI, PVI, Dic(pleth) to detect post-induction hypotension was also analysed. Results: The percent decrease in MAP after anaesthesia correlated with baseline PI (r = -0.45, P < 0.001), PVI (r = 0.45, P = 0.001) and Dic(pleth) (r = 0.16, P = 0.12). The PI cut-off value was <= 3.03 for a patient at risk for post-induction hypotension with 77.8% sensitivity, 75% specificity, positive and negative predictive values of 74.5% and 78.3%, respectively. Similarly, the ROC analysis revealed that baseline PVI (AUC = 0.73, 95% CI = 0.622-0.812) was suitable for detecting post-induction hypotension. Moreover,baseline Dic(pleth) (AUC = 0.63) showed significant predictive ability. Conclusions: The pre-anaesthetic PI and PVI < 3.03 and > 17, respectively, have a good ability to predict those at risk of developing post-induction hypotension in adult patients undergoing elective surgery under general anaesthesia. Future studies are needed in order to investigate the usefulness of Dic(pleth) in different circumstances during anaesthesia.