Ability of Carotid Corrected Flow Time to Predict Fluid Responsiveness in Patients Mechanically Ventilated Using Low Tidal Volume after Surgery

Abstract

Predicting fluid responsiveness in patients under mechanical ventilation with low tidal volume (VT) is challenging. This study evaluated the ability of carotid corrected flow time (FTc) assessed by ultrasound for predicting the fluid responsiveness during low VT ventilation. Patients under postoperative mechanical ventilation and clinically diagnosed with hypovolemia were enrolled. Carotid FTc and pulse pressure variation (PPV) were measured at VT of 6 and 10 mL/kg predicted body weight (PBW). FTc was calculated using both Bazett’s (FTcB) and Wodey’s (FTcW) formulas. Fluid responsiveness was defined as a ≥15% increase in the stroke volume index assessed by FloTrac/Vigileo monitor after administration of 8 mL/kg of balanced crystalloid. Among 36 patients, 16 (44.4%) were fluid responders. The areas under the receiver operating characteristic curves (AUROCs) for the FTcB at VT of 6 and 10 mL/kg PBW were 0.897 (95% confidence interval [95% CI]: 0.750–0.973) and 0.895 (95% CI: 0.748–0.972), respectively. The AUROCs for the FTcW at VT of 6 and 10 mL/kg PBW were 0.875 (95% CI: 0.722–0.961) and 0.891 (95% CI: 0.744–0.970), respectively. However, PPV at VT of 6 mL/kg PBW (AUROC: 0.714, 95% CI: 0.539–0.852) showed significantly lower accuracy than that of PPV at VT of 10 mL/kg PBW (AUROC: 0.867, 95% CI: 0.712–0.957; p = 0.034). Carotid FTc can predict fluid responsiveness better than PPV during low VT ventilation. However, further studies using automated continuous monitoring system are needed before its clinical use.

Carotid artery ultrasound for assessing fluid responsiveness in patients undergoing mechanical ventilation with low tidal volume and preserved spontaneous breathing

“…In our study, the AUROC of the ΔFTc bolus was 0.935, and the cutoff value was 0.725 with a sensitivity of 97.1% and specificity of 84%. The AUROC was higher than that was reported by Jung et al (46).…”

“…However, there is a relative lack of research on predicting fluid responsiveness in mechanically ventilated patients with a tidal volume < 8 mL/kg PBW while preserving spontaneous breathing, particularly regarding FTc and Δ V peak. Jung et al (46) indicated that in postoperative patients, carotid artery FTc at VT = 6 mL/kg PBW (0.897, P < 0.0001, 95% CI: 0.750–0.973) performed better in predicting fluid responsiveness than PPV at VT = 10 mL/kg PBW (0.867, P < 0.0001, 95% CI: 0.712–0.957). The study used the absolute value of carotid artery FTc.…”

Role of carotid corrected flow time and peak velocity variation in predicting fluid responsiveness: a systematic review and meta-analysis

“…So, in recent times there has been considerable interest in using carotid ultrasound for predicting fluid responsiveness [7, 10-15, 17,18, 20-22]. These papers studied carotid corrected flow time [7, 10,14,15,17,18,22] changes in peak velocity [11-13, 17, 18, 20, 21] or carotid blood flow [22] to predict fluid responsiveness. Since most of the available studies used carotid corrected flow time or changes in peak velocity, we decided to use those two parameters for our systematic review and meta-analysis.…”

“…All rights reserved. Studies using carotid corrected flow time have used either Bazett's [10,18] or Wodey's [10,[14][15]17] formulas for assessing FTc. Bazett's formula is calculated by dividing the flow time with square root of cycle time while Wodey's formula gives FTc as measured flow time + [1.25 (heart rate -60].…”

Predicting Fluid Responsiveness Using Carotid Ultrasound in Mechanically Ventilated Patients: A Systematic Review and Meta-Analysis of Diagnostic Test Accuracy Studies

“…[34][35][36][37] The single systematic review and meta-analysis investigating solely mechanically ventilated adult patients is itself limited by a low number of included studies. 39 Since the 2018 publication of this review, 8 more relevant studies [40][41][42][43][44][45][46][47] have been performed.…”