Perfusion index as a predictor of hypotension following spinal anaesthesia – A prospective observational study

Background & Aims: Perfusion index (PI) is a non – invasive parameter that can be assessed using a pulse oximeter, which works by directing light of different wavelengths into vascular tissue. It can be used to monitor hypothermia, assess adequate circulation in newborns, determine depth of anaesthesia, to evaluate pain. Spinal anaesthesia is widely regarded as the gold standard anaesthetic technique for lower abdominal surgeries, with hypotension being a frequent complication. This observational study aims to explore baseline PI as a predictor of hypotension following spinal anaesthesia.Materials and Methods: 62 patients aged 18 years and above, with ASA physical status I and II, who were scheduled for elective surgery under spinal anaesthesia were enrolled for this prospective study. Baseline vital signs, including heart rate (HR), blood pressure (BP), oxygen saturation (SpO2), PI, and the volume of intravenous (IV) fluids administered before spinal anaesthesia, were recorded. Hypotension was defined as a systolic blood pressure (SBP) < 90 mmHg or a mean arterial pressure (MAP) < 65 mmHg or a reduction of 30% from baseline. Any complications, including hypotension, were treated accordingly.Results: The Receiver operating characteristic (ROC) curve indicated that baseline PI could serve as a valuable parameter for identifying patients at risk of developing hypotension, with a cut-off value of 0.7. The area under the curve (AUC) was 0.605. At this cut-off, the sensitivity was 59.3%, specificity was 51.4%, positive predictive value (PPV) was 54.5%, and negative predictive value (NPV) was 49.3%.Conclusion: Baseline Perfusion Index (PI) less than 0.7 is associated with higher risk of hypotension following spinal anaesthesia, making it a useful, non-invasive tool for early identification of at-risk patients and guiding preemptive interventions.