Comparison of the carotid corrected flow time and tidal volume challenge for assessing fluid responsiveness in robot-assisted laparoscopic surgery

Purpose: We aimed to evaluate the ability of carotid corrected flow time assessed by ultrasound to predict fluid responsiveness in patients undergoing robot-assisted laparoscopic gynecological surgery in the modified head-down lithotomy position.  Methods: This prospective single-center study conducted at the Chongqing University Cancer Hospital included patients undergoing robot-assisted laparoscopic surgery in the modified head-down lithotomy position. Carotid doppler parameters and hemodynamic data, including corrected flow time, pulse pressure variation (PPV), stroke volume variation, and stroke volume index at a tidal volume of 6 mL/kg predicted body weight and after increasing the tidal volume to 8 mL/kg predicted body weight (tidal volume challenge), respectively, were measured. Fluid responsiveness was defined as a stroke volume index >=10% increase after volume expansion. Results: Among the 52 patients included, 26 were classified as fluid responders and 26 as non-responders based on the stroke volume index. The area under the receiver operating characteristic curve values measured to predict the fluid responsiveness to corrected flow time and changes in PPV (ΔPPV6–8) after tidal volume challenge were 0.82 [95% confidence interval (CI): 0.705–0.937; P < 0.0001] and 0.85 (95% CI: 0.740–0.956; P < 0.0001), respectively. Both values were higher than those for PPV at a tidal volume of 8 mL/kg (0.79, 95% CI: 0.674–0.911; P = 0003). The optimal cut-off values for corrected flow time and ΔPPV6–8 were 356.5 ms and >1%, respectively. Conclusion: The change in PPV after tidal volume challenge and corrected flow time reliably predicted fluid responsiveness in patients undergoing robot-assisted laparoscopic gynecological surgery in the modified head-down lithotomy position. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement The author(s) received no specific funding for this work ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Not Applicable The details of the IRB/oversight body that provided approval or exemption for the research described are given below: This study was approved by the Institutional Review Board of Chongqing University Cancer Hospital (approval number: CZLS2021041-A) and registered before patient enrollment on the Chinese Clinical Trial Register (CHiCTR2200060573) I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Not Applicable I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Not Applicable I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Not Applicable All relevant data are within the manuscript and its Supporting Information files.