The Transverse Diameter of Right Common Femoral Vein by Ultrasound in the Supine Position for Predicting Post-spinal Hypotension During Cesarean Delivery

Background: Post-spinal anesthesia hypotension during cesarean delivery is caused by decreased systemic vascular resistance due to the blockage of autonomic nerves, which is further worsened by aortocaval compression by the gravid uterus. The aim of this study was to assess whether peak velocities and diameters of the abdominal aorta (AA) and inferior vena cava (IVC) below the xiphoid or the right common femoral artery (RCFA) and right common femoral vein (RCFV) in the inguinal region, as measured on ultrasound, could reflect the degree of aortocaval compression and further identify parturients at risk of post-spinal hypotension.Methods: After ultrasound measurement of peak velocities and anteroposterior diameters of the AA, and IVC and peak velocities and transverse diameters of the RCFA and RCFV before anesthesia, 56 parturients undergoing elective cesarean section with spinal anesthesia were enrolled in this study. Multinomial logistic regression analysis was used to identify the risk factors for post-spinal hypotension during cesarean delivery. Receiver operating characteristic curves were used to test the abilities of the identified parameters to predict post-spinal hypotension, and the areas under the curve and the optimum cut-off values for the predictive parameters were calculated. Results: The transverse diameter of the RCFV was a risk factor for post-spinal hypotension (odds ratio = 2.022, 95% confidence interval [CI] 1.261–3.243). The area under the receiver operating characteristics curve for the prediction of post-spinal hypotension was 0.759 (0.628–0.890; P = 0.001). A transverse diameter of the RCFV longer than 12.2 mm could predict post-spinal hypotension during cesarean delivery. Conclusions: We demonstrated a higher transverse RCFV diameter was associated with hypotension and it could effectively predict parturients at risk of hypotension before anesthesia. Trial Registration: This study was registered at http://www.chictr.org.cn on 16, May, 2018. No. ChiCTR1800016163