Inferior vena cava collapsibility index for predicting hypotension after spinal anesthesia in patients undergoing total knee arthroplasty.

Objective: This study aimed to identify risk factors associated with hypotension in patients undergoing total knee arthroplasty (TKA) under spinal anesthesia.

Method: A total of 200 patients (50-75 years of age) who underwent elective TKA under spinal anesthesia between October 2023 and January 2024 were enrolled. Patients were divided into two groups (hypotensive and nonhypotensive) depending on the occurrence of postspinal anesthesia hypotension (PSAH). Patient characteristics (age, sex, body mass index, and medical history), blood pressure, heart rate, and ultrasound data before anesthesia were documented. Multivariate logistic regression models were used to determine risk factors for hypotension after spinal anesthesia. Furthermore, a nomogram was constructed according to independent predictive factors. The area under the curve (AUC) and calibration curves were employed to assess the performance of the nomogram.

Results: In total, 175 patients were analyzed and 79 (45.1%) developed PSAH. Logistic regression analysis revealed that variability of the inferior vena cava (odds ratio, OR, 1.147; 95% confidence interval, CI: 1.090-1.207; p < 0.001) and systolic arterial blood pressure (SABP, OR 1.078; 95% CI: 1.043-1.115; p < 0.001) were independent risk factors for PSAH. Receiver operating characteristic (ROC) curve analysis showed that the AUC of the inferior vena cava collapsibility index (IVCCI) and SABP alone were 0.806 and 0.701, respectively, while the AUC of both combined was 0.841. Specifically, an IVCCI of > 37.5% and systolic arterial blood pressure of > 157 mm Hg were considered threshold values. Furthermore, we found that the combination had a better predictive value with higher AUC value, sensitivity, and specificity than the index alone. The nomogram model and calibration curves demonstrated the satisfactory predictive performance of the model.

Conclusion: Elevated preoperative systolic arterial blood pressure and a higher IVCCI were identified as independent risk factors for hypotension in patients receiving spinal anesthesia, which may help guide personalized treatment.