Position-Induced Change in Carotid Corrected Flow Time Predicts Spinal Hypotension in Cesarean Delivery

Background: Spinal anesthesia-induced hypotension (SAIH) complicates 50– 70% of cesarean deliveries, posing maternal-fetal risks. This prospective, single-center observational study (ClinicalTrials.gov: ChiCTR2300077480) evaluated whether pre-induction positional change in carotid corrected flow time (δcFT) predicts SAIH in term parturients. Methods: In this single-center prospective observational study, 54 healthy term parturients (≥ 37 weeks, ASA I–II), high-resolution carotid Doppler measured corrected flow time (cFT) and respiratory variation in peak velocity (δVpeak) in supine and left-lateral positions immediately before neuraxial block. The primary outcome was SAIH incidence within 15 minutes post-induction. Results: Of 54 participants analyzed, 34 developed SAIH (63%). The SAIH group exhibited significantly shorter supine cFT (330.30± 18.44 vs 351.14± 19.57 ms, P < 0.001) and greater positional cFT increase (δcFT: 22.55± 14.29 vs 0.23± 13.30 ms, P < 0.001). δcFT demonstrated superior discriminatory accuracy (AUC 0.872, 95% CI 0.772– 0.972, P < 0.001) compared with supine cFT (AUC 0.769) and δVpeak (AUC 0.50– 0.52). Optimal δcFT threshold was 6.49 ms (sensitivity 94.1%, specificity 75.0%). Exploratory multivariable logistic regression analysis suggested that δcFT was associated with SAIH after adjustment for prespecified covariates (OR 1.125 per 1-ms increase, 95% CI 1.049– 1.206, P =0.001), whereas higher supine cFT was associated with a lower risk (OR 0.934, P =0.002). δcFT correlated significantly with the magnitude of blood pressure decrease (r=0.437, P =0.001). Interobserver reliability was excellent (ICC 0.969). Conclusion: Pre-induction δcFT could be a promising noninvasive predictor of SAIH. Bedside assessment of positional changes in cFT might identify high-risk parturients and guide targeted prophylactic strategies. δVpeak lacked predictive utility in spontaneously breathing patients. Further external validation studies are warranted.