PERFUSION INDEX AS AN INDICATOR OF SPINAL ANAESTHESIA INDUCED HYPOTENSION AND EFFECT

Abstract

Identifying patients at higher risk of developing hypotension before the onset of anaesthesia could allow preventive strategies and improved patient safety. The perfusion index (PI), a simple non-invasive parameter derived from pulse oximetry, reflects the ratio of pulsatile to non-pulsatile blood flow and has shown promise as an indicator of peripheral perfusion and sympathetic tone. Its role in predicting spinal anaesthesia-induced hypotension has been of growing clinical interest. Aim: The present study aims to evaluate the role of baseline perfusion index as an indicator of spinal anaesthesia-induced hypotension and to assess its effect on the magnitude of blood pressure drop, vasopressor requirement, and early haemodynamic outcomes among patients undergoing spinal anaesthesia. Methods: This prospective observational study was conducted on 100 adult patients of either sex, aged 20 to 60 years, belonging to ASA physical status I and II, scheduled for elective lower abdominal and lower limb surgeries under spinal anaesthesia. Baseline perfusion index was measured using a pulse oximeter before anaesthesia. Standard spinal anaesthesia was administered using 3 ml of 0.5% hyperbaric bupivacaine at the L3–L4 interspace. Haemodynamic parameters such as systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), and heart rate (HR) were recorded at baseline, and at 2, 5, 10, 15, 20, and 30 minutes after spinal anaesthesia. Hypotension was defined as a decrease of 20% or more in SBP from baseline and was managed with intravenous fluids and incremental doses of mephentermine. Patients were divided into two groups: Group A (PI ≤ 3.5) and Group B (PI > 3.5). The incidence of hypotension, vasopressor requirement, and time to haemodynamic stabilization were compared between groups. Results: Out of 100 patients, 54 were males and 46 were females, with a mean age of 38.6 ± 10.4 years. The mean baseline perfusion index in Group A was 2.9 ± 0.4 and in Group B was 4.7 ± 0.6. The incidence of hypotension was 22% in Group A and 68% in Group B (p < 0.001). The mean fall in systolic blood pressure was 18.5 ± 6.2 mmHg in Group A and 34.2 ± 8.1 mmHg in Group B. The mean total dose of mephentermine required was 3.5 ± 1.2 mg in Group A and 7.9 ± 2.5 mg in Group B. The average time to haemodynamic stabilization was 8.6 ± 2.3 minutes in Group A and 15.2 ± 3.8 minutes in Group B. The mean duration of sensory block regression to T12 was 112 ± 14 minutes in Group A and 118 ± 16 minutes in Group B. Conclusion: The study demonstrated that a higher baseline perfusion index is significantly associated with an increased risk of spinal anaesthesia-induced hypotension. Patients with a baseline PI greater than 3.5 experienced a higher incidence and severity of hypotension and required greater vasopressor support compared to those with lower PI values. Hence, baseline perfusion index measurement can serve as a reliable, simple, and non-invasive tool for predicting hypotension following spinal anaesthesia, allowing timely preventive measures and improved haemodynamic stability during surgery.