Brachial artery Doppler as a novel predictor of post-induction hypotension: a prospective observational study

Post-induction hypotension (PIH) is a frequent complication of general anesthesia, especially with propofol, and may result from systemic vasodilation, reduced cardiac output, and decreased myocardial contractility. Given the superficial location and ease of access of the brachial artery, we hypothesized that Doppler-derived indices of the brachial artery could serve as early predictors of PIH.

In this prospective observational study, 90 ASA I adult patients (aged 20-60 years) undergoing abdominal or pelvic surgery were evaluated. Doppler ultrasound of the right brachial artery was performed before and after the induction of anesthesia. The pulsatility index (PI) and resistive index (RI) were analyzed using the autotrace function. Simultaneously, the waveform was evaluated for the change in shape from a triphasic pattern to a monophasic wave (ΔM). PIH was defined as a >20% decrease in the mean arterial pressure within 10 min of induction.

PIH occurred in 39% of the patients. Both PI and RI decreased following induction, with significantly greater reductions in hypotensive patients. Baseline PI demonstrated good predictive ability for PIH, with an area under the curve (AUC) of 0.86 and an optimal cutoff value of >5.22. Dynamic changes in Doppler indices, namely, ΔPI, ΔRI, and ΔM, showed strong predictive accuracy, with AUCs of 0.93, 0.83, and 0.92, respectively. The optimal thresholds were 13.6% for ΔPI and 12% for ΔRI, respectively. Notably, the presence of waveform morphological changes from a triphasic to a monophasic pattern predicted PIH with 100% sensitivity and 84% specificity.

Among adult patients undergoing abdominal or pelvic surgery, dynamic changes in brachial artery Doppler indices, specifically a ΔPI greater than 21% and a ΔRI >12%, demonstrated a strong predictive value for PIH. Additionally, the baseline PI was a reliable predictor of PIH, with a cutoff value of >5.22. Notably, the transition in waveform morphology from a triphasic to monophasic pattern confirmed the occurrence of PIH with 100% sensitivity and 84% specificity.