Correlation between carotid Doppler ultrasound-derived parameters and cardiac output measurements: a systematic review and meta-analysis.

Background: The utility of carotid Doppler ultrasound (CDU) as a noninvasive tool for cardiac output (CO) monitoring has been a subject of considerable debate. This meta-analysis was conducted to synthesize the available evidence and quantitatively assess the correlation between CDU-derived parameters and standard CO measurements. Methods: We searched the databases of PubMed, EMBASE, Science Direct/Elsevier, MEDLINE, Web of Science, Cochrane Library, China National Knowledge Infrastructure, and China Biology Medicine from the date of inception up to August 2024. Data were analyzed by extracting Pearson's or Spearman's correlation coefficients from each study and converting them to Fisher's Z. The pooled r value was calculated using Fisher's Z and standard error. STATA (Version 15.0) software was used to facilitate data synthesis. Results: After screening titles and abstracts, 476 studies required full-text evaluation. Based on the inclusion and exclusion criteria, 17 observational studies were selected for meta-analysis. The results indicated a positive correlation between CDU-derived parameters and CO measurements [0.53, 95% confidence interval (CI): 0.39-0.64], with parameter change values being more relevant than absolute values (0.76, 95% CI: 0.49-0.90) versus (0.43, 95% CI: 0.27-0.57). Furthermore, the carotid velocity-time integral (CVTI) exhibited a stronger correlation (0.81, 95% CI: 0.62-0.91) than the other three parameters (carotid-corrected flow time 0.59, 95% CI: 0.31-0.77), carotid peak systolic velocity (0.40, 95% CI: 0.21-0.57), and carotid blood flow (0.33, 95% CI: 0.12-0.52) in the subgroup analysis. Egger regression analysis and the trim-and-fill method indicated no publication bias (P>0.05). Conclusions: CDU-derived parameters demonstrated positive correlations with CO measurements, providing evidence for the use of CDU-derived parameters as surrogate CO monitors.