Perfusion index as a predictor of hypotension following propofol induction - A prospective observational study

Hypotension during propofol induction is a common problem. Perfusion index (PI), an indicator of systemic vascular resistance, is said to be predictive of hypotension following subarachnoid block. We hypothesised that PI can predict hypotension following propofol induction and a cut-off value beyond which hypotension is more common can be determined.

Fifty adults belonging to the American Society of Anesthesiologists' physical status I/II undergoing elective surgery under general anaesthesia were enrolled for this prospective, observational study. PI, heart rate, blood pressure (BP) and oxygen saturation were recorded every minute from baseline to 10 min following induction of anaesthesia with a titrated dose of propofol, and after endotracheal intubation. Hypotension was defined as fall in systolic BP (SBP) by >30% of baseline or mean arterial pressure (MAP) to <60 mm Hg. Severe hypotension (MAP of <55 mm Hg) was treated.

Within first 5-min after induction, the incidence of hypotension with SBP and MAP criteria was 30% and 42%, respectively, and that of severe hypotension, 22%. Baseline PI <1.05 predicted incidence of hypotension at 5 min with sensitivity 93%, specificity 71%, positive predictive value (PPV) 68% and negative predictive value (NPV) 98%. The area under the ROC curve (AUC) was 0.816, 95% confidence interval (0.699-0.933), P < 0.001.

Perfusion index could predict hypotension following propofol induction, especially before endotracheal intubation, and had a very high negative predictive value.