Carotid corrected flow time and Doppler shock index for prediction of post-induction hypotension in patients undergoing elective abdominal surgery: a prospective observational study.

Background: Abdominal surgical patients who have deficient blood volume are at an elevated risk of post-induction hypotension (PIH). New strategies have been adopted, i.e., carotid ultrasound, to evaluate volume status. The study aimed to investigate and compare the predictive value of various carotid ultrasound parameters for PIH.

Methods: Adult patients scheduled for abdominal surgery were enrolled. Carotid ultrasound was performed before induction to evaluate the carotid flow time (FT), carotid artery velocity time integral (VTI), and Doppler shock index (the DSI_FTc and DSI_VTI). Both Wodey's (W) and Bazett's (B) formulae determined the corrected flow time (FTc). The predictive ability of these parameters was analyzed via receiver operating characteristic (ROC) curve analysis.

Results: Finally, 94 patients were analyzed, and of those, 40 (42.6%) developed PIH. The areas under the curve for FT, FTc(W), 1/DSI_FTc, and FTc(B) were 0.790 (95% CI 0.697-0.883) (P < 0.05), 0.788 (95% CI 0.695-0.881) (P < 0.001), 0.729 (95% CI 0.626-0.832) (P < 0.001), and 0.689 (95% CI 0.582-0.796) (P < 0.05), respectively. The optimal cut-off for FTc(W) was 334.15 ms (sensitivity 82.5%, specificity 70.4%), while for FT, it was 313.33 ms (sensitivity 72.5%, specificity 79.6%), indicating FTc(W) as the best predictor among these various parameters. The 1/DSI_FTc was an inferior predictor of PIH, with an optimal cutoff value of 4.58. The sensitivity (80.0%) and specificity (61.1%) values were obtained.

Conclusion: Carotid flow time corrected by Wodey's formula was a reliable indicator of PIH in patients undergoing elective abdominal surgery, superior to FT, DSI_FTc, and FTc(B).