Correlation of carotid corrected flow time and respirophasic variation in blood flow peak velocity with stroke volume variation in elderly patients under general anaesthesia

The predictive role of carotid artery flow time for anesthesia-induced hypotension in high-risk elderly patients

Hypotension induced by general anesthesia is associated with postoperative complications, increased mortality, and morbidity, particularly elderly patients. The aim of this study was to investigate the effectiveness of corrected carotid artery flow time (FTc) for predicting hypotension following anesthesia induction in patients over 65 years old. After faculty ethical committee approval and written informed consent, 138 patients (65 years and older, ASA physical status I-III) who scheduled for elective surgery were included in this study. In the pre-operative anesthesia unit, the carotid artery FTc value was measured by ultrasound and hemodynamic values were recorded. Following anesthesia induction with propofol, hemodynamic data were recorded at 1-minute intervals for 3 min. Measurements were terminated prior to endotracheal intubation, as direct laryngoscopy and endotracheal intubation could cause sympathetic stimulation and hemodynamic changes. Hypotension occurred in 52 patients (37.7%). The preoperative FTc value of the patients who developed hypotension was statistically lower (312.5 ms) than the patients who did not (345.0 ms) (p < 0.001). The area under the ROC curve for carotid artery FTc was 0.93 (95% CI for AUC:0.89-0.97; p < 0.001) with an optimal cut-off of value for predicting post-anesthesia hypotension 333 ms, a sensitivity of 90.4% and a specificity of 84.9%. As a result of the multiple logistic regression model, carotid artery FTc emerged as the sole independent risk factor for hypotension following anesthesia induction. Preoperative carotid artery FTc measurement is a simple, bedside, noninvasive, and reliable method for predicting anesthesia-induced hypotension in elderly patients.

Simultaneous Venous-Arterial Doppler Ultrasound During Early Fluid Resuscitation to Characterize a Novel Doppler Starling Curve: A Prospective Observational Pilot Study

Background: The likelihood of a patient being preload responsive-a state where the cardiac output or stroke volume (SV) increases significantly in response to preload-depends on both cardiac filling and function. This relationship is described by the canonical Frank-Starling curve. Research Question: We hypothesize that a novel method for phenotyping hypoperfused patients (ie, the "Doppler Starling curve") using synchronously measured jugular venous Doppler as a marker of central venous pressure (CVP) and corrected flow time of the carotid artery (ccFT) as a surrogate for SV will refine the pretest probability of preload responsiveness/unresponsiveness. Study Design and Methods: We retrospectively analyzed a prospectively collected convenience sample of hypoperfused adult emergency department (ED) patients. Doppler measurements were obtained before and during a preload challenge using a wireless, wearable Doppler ultrasound system. Based on internal jugular and carotid artery Doppler surrogates of CVP and SV, respectively, we placed hemodynamic assessments into quadrants (Qx) prior to preload augmentation: low CVP with normal SV (Q1), high CVP and normal SV (Q2), low CVP and low SV (Q3) and high CVP and low SV (Q4). The proportion of preload responsive and unresponsive assessments in each quadrant was calculated based on the maximal change in ccFT (ccFTΔ) during either a passive leg raise or rapid fluid challenge. Results: We analyzed 41 patients (68 hemodynamic assessments) between February and April 2021. The prevalence of each phenotype was: 15 (22%) in Q1, 8 (12%) in Q2, 39 (57%) in Q3, and 6 (9%) in Q4. Preload unresponsiveness rates were: Q1, 20%; Q2, 50%; Q3, 33%, and Q4, 67%. Interpretation: Even fluid naïve ED patients with sonographic estimates of low CVP have high rates of fluid unresponsiveness, making dynamic testing valuable to prevent ineffective IVF administration.

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

BACKGROUND

A noninvasive and accurate method of determining fluid responsiveness in ventilated patients would help to mitigate unnecessary fluid administration. Although carotid ultrasound has been previously studied for this purpose, several studies have recently been published. We performed an updated systematic review and meta-analysis to evaluate the accuracy of carotid ultrasound as a tool to predict fluid responsiveness in ventilated patients.

METHODS

Studies eligible for review investigated the accuracy of carotid ultrasound parameters in predicting fluid responsiveness in ventilated patients, using sensitivity and specificity as markers of diagnostic accuracy (International Prospective Register of Systematic Reviews [PROSPERO] CRD42022380284). All included studies had to use an independent method of determining cardiac output and exclude spontaneously ventilated patients. Six bibliographic databases and 2 trial registries were searched. Medline, Embase, Emcare, APA PsycInfo, CINAHL, and the Cochrane Library were searched on November 4, 2022. Clinicaltrials.gov and Australian New Zealand Clinical Trials Registry were searched on February 24, 2023. Results were pooled, meta-analysis was conducted where possible, and hierarchical summary receiver operating characteristic models were used to compare carotid ultrasound parameters. Bias and evidence quality were assessed using the Quality Assessment of Diagnostic Accuracy Studies (QUADAS) tool and the Grading of Recommendations, Assessment, Development, and Evaluations (GRADE) guidelines.

RESULTS

Thirteen prospective clinical studies were included (n = 648 patients), representing 677 deliveries of volume expansion, with 378 episodes of fluid responsiveness (58.3%). A meta-analysis of change in carotid Doppler peak velocity (∆CDPV) yielded a sensitivity of 0.79 (95% confidence interval [CI], 0.74-0.84) and a specificity of 0.85 (95% CI, 0.76-0.90). Risk of bias relating to recruitment methodology, the independence of index testing to reference standards and exclusionary clinical criteria were evaluated. Overall quality of evidence was low. Study design heterogeneity, including a lack of clear parameter cutoffs, limited the generalizability of our results.

CONCLUSIONS

In this meta-analysis, we found that existing literature supports the ability of carotid ultrasound to predict fluid responsiveness in mechanically ventilated adults. ∆CDPV may be an accurate carotid parameter in certain contexts. Further high-quality studies with more homogenous designs are needed to further validate this technology.

The impact of pre-rehydration guided by carotid corrected flow time on hypotension prevention following general anesthesia induction in patients undergoing gastrointestinal surgery: a prospective randomized controlled trial

Background

Patients undergoing gastrointestinal surgery often experience hypotension following general anesthesia induction due to insufficient volume. This study aimed to assess whether pre-rehydration guided by carotid corrected flow time (FTc) could mitigate post-induction hypotension induced by general anesthesia.

Methods

Patients undergoing resection of gastrointestinal tumors were assigned to either the conventional treatment group (Group C) or the fluid treatment group based on FTc (Group F). Within Group F, patients were further divided into Group A (carotid FTc <340.7 ms) and Group B (carotid FTc ≥340.7 ms) based on pre-rehydration carotid FTc values. Group A patients received pre-rehydration with 250 mL of colloids (hydroxyethyl starch-HES) administered within 15 min until carotid FTc reached ≥340.7 ms to counteract hypovolemia prior to induction. Patients in Group B and Group C received a continuous HES infusion at a rate of 6 mL/kg/h 30 min before induction to compensate for physiological fluid loss. All patients received a perioperative background infusion of 3 mL/kg/h compound sodium chloride, with infusion rates optimized based on mean arterial pressure (MAP) and heart rate (HR). The incidence of post-induction hypotension was compared between Group C and Group F, as well as between Group A and Group B.

Results

The incidence of hypotension after induction was significantly lower in Group F compared to Group C (26.4% vs. 46.7%, respectively; p < 0.001). Patients in Group A received significantly more pre-rehydration, leading to a greater increase in carotid FTc values compared to Group B (336.5 ± 64.5 vs. 174.3 ± 34.1 ms, p = 0.002). However, no significant difference in carotid FTc values after pre-rehydration was observed between the groups. There was no significant difference in the incidence of hypotension after general anesthesia induction between Group A and Group B (22.9% vs. 28.8%, p = 0.535).

Conclusion

Pre-rehydration based on FTc can effectively reduce the occurrence of post-induction hypotension in patients undergoing gastrointestinal surgery who present with insufficient volume.

Clinical trial registration

https://www.chictr.org.cn/showprojEN.html?proj=201481.

The Reliability of Carotid Artery Doppler Ultrasonography Indices in Predicting Fluid Responsiveness during Surgery for Geriatric Patients: A Prospective, Observational Study

BACKGROUND

The reliability of determining fluid responsiveness during surgery in geriatric patients is challenging. Our primary outcome was to determine the reliability of Corrected Flow Time (FTc) in predicting fluid responsiveness.

METHODS

Elderly patients undergoing major surgery under general anesthesia were included. Measurements of common carotid artery diameter, velocity time integral, and systolic flow time (FT) were performed before and after a fluid challenge. FTc and carotid blood flow (CBF) were subsequently calculated.

RESULTS

The median change in carotid diameter was significantly higher in the fluid-responder (R) compared to the non-responder (NR) (6.51% vs. 0.65%, p = 0.049). The median change in CBF was notably higher in R compared to NR (30.04% vs. 9.72%, p = 0.024). Prior to the fluid challenge, systolic FT was significantly shorter in R than NR (285 ms vs. 315 ms, p = 0.027), but after the fluid challenge, these measurements became comparable among the groups. The change in systolic FT was higher in R (15.38% vs. 7.49%, p = 0.027). FTc and the change in FTc exhibited similarities among the groups at all study time points. Receiver operating characteristic analysis demonstrated an area under the curve of 0.682 (95% CI: 0.509-0.855, p = 0.039) for carotid diameter, 0.710 (95% CI: 0.547-0.872, p = 0.011) for CBF, 0.706 (95% CI: 0.540-0.872, p = 0.015) for systolic FT, and 0.580 (95% CI = 0.389-0.770, p = 0.413) for FTc.

CONCLUSIONS

In geriatric patients, potential endothelial changes in the carotid artery may influence the dynamic markers of fluid responsiveness. Despite the demonstrated effectiveness of FTc in predicting fluid responsiveness in the general population, this study underscores the limited reliability of carotid Doppler ultrasonography indices for prediction in a geriatric patient population.

Effect of carotid corrected flow time combined with perioperative fluid therapy on preventing hypotension after general anesthesia induction in elderly patients: a prospective cohort study

BACKGROUND

Hypotension often occurs following the induction of general anesthesia in elderly patients undergoing surgery and can lead to severe complications. This study assessed the effect of carotid corrected flow time (FTc) combined with perioperative fluid therapy on preventing hypotension after general anesthesia induction in elderly patients.

MATERIALS AND METHODS

The prospective cohort study was divided into two parts. The first part (Part I) consisted of 112 elderly patients. Carotid FTc was measured using Color Doppler Ultrasound 5 min before anesthesia induction. Hypotension was defined as a decrease of greater than 30% in systolic blood pressure (SBP) or a decrease of greater than 20% in mean arterial pressure (MAP) from baseline, or an absolute SBP below 90 mmHg and MAP below 60 mmHg within 3 min after induction of general anesthesia. The predictive value of carotid FTc was determined using receiver operating characteristic (ROC) curve. The second part (Part II) consisted of 65 elderly patients. Based on the results in Part I, elderly patients with carotid FTc below the optimal cut-off value received perioperative fluid therapy at a volume of 8 ml/kg of balanced crystalloids (lactated Ringer's solution) in 30 min before induction. The effect of carotid FTc combined with perioperative fluid therapy was assessed by comparing observed incidence of hypotension after induction.

RESULTS

The area under the ROC for carotid FTc to predict hypotension after induction was 0.876 [95% confidence interval (CI) 0.800-0.952, P <0.001]. The optimal cut-off value was 334.95 ms (sensitivity of 87.20%; specificity of 82.20%). The logistic regression analysis revealed that carotid FTc is an independent predictor for post-induction hypotension in elderly patients. The incidence of post-induction hypotension was significantly lower ( P <0.001) in patients with carotid FTc less than 334.95 ms who received perioperative fluid therapy (35.71%) compared to those who did not (92.31%).

CONCLUSIONS

Carotid FTc combined with the perioperative fluid therapy could significantly reduce the incidence of hypotension after the induction of general anesthesia in elderly patients.

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

We aimed to compare the ability of carotid corrected flow time assessed by ultrasound and the changes in dynamic preload indices induced by tidal volume challenge predicting fluid responsiveness in patients undergoing robot-assisted laparoscopic gynecological surgery in the modified head-down lithotomy position. This prospective single-center study 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, 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. 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 measured to predict the fluid responsiveness to corrected flow time and changes in pulse pressure variation (ΔPPV6-8) after tidal volume challenge were 0.82 [95% confidence interval (CI) 0.71-0.94; P < 0.0001] and 0.85 (95% CI 0.74-0.96; P < 0.0001), respectively. The value for pulse pressure variation at a tidal volume of 8 mL/kg was 0.79 (95% CI 0.67-0.91; P = 0.0003). The optimal cut-off values for corrected flow time and ΔPPV6-8 were 357 ms and > 1%, respectively. Both the corrected flow time and Changes in pulse pressure variation after tidal volume challenge reliably predicted fluid responsiveness in patients undergoing robot-assisted laparoscopic gynecological surgery in the modified head-down lithotomy position. And pulse pressure variation at a tidal volume of 8 mL/kg maybe also a useful predictor.Trial registration: Chinese Clinical Trial Register (CHiCTR2200060573, Principal investigator: Hongliang Liu, Date of registration: 05/06/2022).

Diagnostic Efficacy of Carotid Ultrasound for Predicting the Risk of Perioperative Hypotension or Fluid Responsiveness: A Meta-Analysis

Despite the acceptance of carotid ultrasound for predicting patients' fluid responsiveness in critical care and anesthesia, its efficacy for predicting hypotension and fluid responsiveness remains unclear in the perioperative setting. Electronic databases were searched from inception to May 2023 to identify observational studies focusing on the use of corrected blood flow time (FTc) and respirophasic variation in carotid artery blood flow peak velocity (ΔVpeak) for assessing the risks of hypotension and fluid responsiveness. Using FTc as a predictive tool (four studies), the analysis yielded a pooled sensitivity of 0.82 (95% confidence interval (CI): 0.72 to 0.89) and specificity of 0.94 (95% CI: 0.88 to 0.97) for the risk of hypotension (area under curve (AUC): 0.95). For fluid responsiveness, the sensitivity and specificity of FTc were 0.79 (95% CI: 0.72 to 0.84) and 0.81 (95% CI: 0.75 to 0.86), respectively (AUC: 0.87). In contrast, the use of ΔVpeak to predict the risk of fluid responsiveness showed a pooled sensitivity of 0.76 (95% CI: 0.63 to 0.85) and specificity of 0.74 (95% CI: 0.66 to 0.8) (AUC: 0.79). The current meta-analysis provides robust evidence supporting the high diagnostic accuracy of FTc in predicting perioperative hypotension and fluid responsiveness, which requires further studies for verification.

Correlation of carotid Doppler flowmetry with fluid responsiveness in mechanically ventilated patients undergoing coronary artery bypass grafting-A popular gray zone

The authors conducted a prospective, observational study to evaluate the correlation of fluid responsiveness with commonly used carotid Doppler-derived indices like carotid artery blood flow, carotid corrected flow time, respirophasic variation in carotid artery blood flow peak velocity in patients undergoing coronary artery bypass grafting. They claimed that altough only ΔVpeak demonstrated some predictive power with areas under receiver operating characteristic of 0.671, carotid Doppler ultrasound indices were found to be not dependable as a substitute for invasive methods to assess fluid responsiveness. The presence of studies advocating quite different sentiments in the literature regarding feasibility and reliability show that there is a long way gone and a long way to go.