A Comparative Study between Perfusion index derived from pulse oximeter versus ultrasound measurement of caval aorta diameter index in predicting hypotension during spinal anesthesia for elective caesarean section

Background: Sympathetic blockade and reduced cardiac output are the main causes of hypotension after spinal anaesthesia. The impact is more pronounced in pregnant women because their bodies are more sensitive to local anaesthetics, less responsive to vasopressors, and their mean arterial pressure (MAP) is naturally lower at term. Aim and objectives: Pregnant women undergoing spinal anaesthesia for elective caesarean sections (CSs) will have their caval aorta diameter index (perfusion index), which is defined as the ratio of the largest diameters of the IVC and the aorta, evaluated for its ability to predict hypotension. Materials and methods: This prospective study was carried out on 100 patients scheduled for elective full-term CS admitted to Al-Hussein Hospital, Al-Azhar University, Cairo, Egypt, from February 2023 to October 2024. Results: With a cut-off of 0.7, the IVC/AO index has a considerably high predictive value for hypotension incidence (P<0.001 and AUC=0.970), a specificity of 82.54%, a PPV of 75.6%, and an NPV of 94.5%. At a cut-off value of 3.5, the perfusion index has a sensitivity of 83.78%, specificity of 82.54%, PPV of 73.8%, and NPV of 89.7% in predicting the occurrence of hypotension (P<0.001 and AUC=0.9). Conclusion: The IVC/AO index can significantly predict the incidence of hypotension at a cut-off of ≤0.7 with 91.89% sensitivity and 82.54% specificity, and the perfusion index can significantly predict the incidence of hypotension at a cut-off of>3.5 with 83.78% sensitivity and 82.54% specificity in patients undergoing elective CS under spinal anesthesia.