Association between preoperative shock index and hypotension after spinal anesthesia for non-elective cesarean section: a prospective cohort study.

Background: Shock index (SI) is calculated as heart rate divided by systolic blood pressure. In the obstetric population, SI of ≥ 0.9 is associated with maternal adverse outcomes. Our primary aim was to investigate the association between SI and post-spinal hypotension in non-elective cesarean section.

Methods: In this prospective, observational study, term parturient of ASA physical status II, and urgency categories 2 and 3, undergoing non-elective cesarean section with spinal anesthesia were enrolled. We performed univariable and multivariable logistic regression to explore the association between baseline SI (categorized as < 0.9 and ≥ 0.9) and hypotension after spinal anesthesia. The diagnostic ability of the baseline SI to predict post-spinal hypotension was assessed using ROC (receiver operating characteristics) curves.

Results: Three hundred forty-two parturient were recruited, and among them, 335 were analyzed. One hundred fifty-five (46.27%) parturients developed post-spinal hypotension, and 114 (34.03%) reported post-delivery hypotension. Preoperative SI (adjusted odds ratio [AOR], 2.77; 95% CI, 1.15-6.66; p = 0.023) and thoracic sensory block height > 4 (AOR, 2.33; 95%CI, 1.14-4.76; p = 0.020) were associated with post-spinal hypotension. Preoperative SI (AOR, 4.34; 95%CI, 1.72-10.94; p = 0.002) and anxiety (AOR,1.22; 95%CI, 1.06-1.40; p = 0.004) were associated with post-delivery hypotension. Area under the ROC curve for SI alone in predicting hypotension before and after delivery was 0.53 (95%CI 0.49-0.57) and 0.56 (95%CI 0.51-0.60) respectively. However, the model performance as reflected by ROC curve for the multivariable logistic regression analysis was 0.623 for post-spinal hypotension and 0.679 for post-delivery hypotension, respectively.

Conclusion: In parturients undergoing non-elective cesarean section, baseline SI ≥ 0.9 was associated with post-spinal and post-delivery hypotension. While the SI alone showed limited predictive power for post-spinal and post-delivery hypotension, integrating it with other risk factors improved the model's predictive ability.

Trial Registration: Registration number: NCT04692870. Date of registration: 05/01/2021. Website: https://clinicaltrials.gov .