Evaluation of Carotid Flow Time to Assess Fluid Responsiveness in the Emergency Department

Background:

Assessing fluid responsiveness in critically ill patients is challenging. Objective, noninvasive tests that are easy to perform are needed. Doppler measurements of dynamic carotid artery parameters such as carotid blood flow (CBF) and carotid flow time (CFT) are being studied as the potential indicators of volume responsiveness, but the data supporting its use are sparse.

Methods:

This prospective, observational study was conducted in the adult emergency department from June to September 2018. Patients who were prescribed a bolus of 500 ml of crystalloid for any indication were enrolled. Carotid Doppler was performed before and after a fluid bolus to measure the change in CBF and CFT. The aim of our study was to determine if CFT can be used as a marker of fluid responsiveness.

Results:

During the 4-month study period, 209 patients were recruited through convenient sampling after obtaining informed written consent. 29.6% of patients presented with a mean arterial pressure (MAP) <65, among whom 58.1% had septic shock. The baseline CBF was 643.0 ± 212.7 ml/min, and it was 583.9 ± 207.1 ml/min and 668 ± 210.8 ml/min in hypotensive and normotensive patients, respectively. Considering a >10% increase in CBF as fluid response, there were 59% responders and 41% nonresponders. The MAP increased by 9.5% in the responders, while there was no significant change in CFT after the fluid bolus. There was no difference in CFT among the responders as compared to the nonresponders. There was no correlation between the change of CBF and CFT (r^[207] = 0.013, P = 0.061) after the fluid bolus.

Conclusion:

Though easy to perform, CFT is probably not a good indicator of fluid responsiveness.

Carotid doppler indices do not predict fluid responsiveness in mechanically ventilated patients undergoing coronary artery bypass grafting surgery

BACKGROUND AND AIM OF THE STUDY

This study aimed to determine the predictive value of carotid artery blood flow (CABF), corrected carotid flow time (CFT), and respiratory variation in carotid peak systolic velocity (DVPeakCA) for fluid responsiveness in mechanically ventilated patients undergoing coronary artery bypass grafting (CABG) surgery. It also aimed to correlate each of these indices with changes in stroke volume index (SVI) after a fluid bolus.

METHODS

This prospective, interventional, before-after study recruited 45 adult patients undergoing CABG. Following induction of anesthesia, a fluid challenge of 6 ml/kg of a crystalloid solution was delivered over 10 min. Mean arterial pressure (MAP), heart rate (HR), central venous pressure (CVP), CABF, CFT, and DVPeakCA were recorded before and following the intervention. Patients with an increase in SVI of >15% from baseline were considered responders.

RESULTS

We had 22 responders and 23 nonresponders. Areas under the receiver operating characteristic (AUROC) curves for the studied indices (CABF, 0.516, CFT, 0.502, and DVPeakCA, 0.671) did not suggest any strong predictive value to detect fluid responsiveness. Similarly, the r values for correlation of these carotid doppler-derived indices, both baseline and as % change from baseline with the % alteration of SVI were all <0.2, which demonstrates a very weak correlation between these variables.

CONCLUSIONS

Carotid doppler indices are unreliable to assess fluid responsiveness, and cannot replace invasive methods of analyzing preload optimization. There was no significant correlation between carotid doppler-derived indices and alterations in SVI before and after the fluid bolus.

An Assessment of Carotid Flow Time Using a Portable Handheld Ultrasound Device: The Ideal Tool for Guiding Intraoperative Fluid Management?

Volume resuscitation is a cornerstone of modern anesthesia care. Finding the right balance to avoid inadequate or excess volume administration is often difficult to clinically discern and can lead to negative consequences. Pulse pressure variation is often intraoperatively used to guide volume resuscitation; however, this requires an invasive arterial line and is generally only applicable to patients who are mechanically ventilated. Unfortunately, without a pulmonary artery catheter or another costly noninvasive device, performing serial measurements of cardiac output is challenging, time-consuming, and often impractical. Furthermore, noninvasive measures such as LVOT VTI require significant technical expertise as well as access to the chest, which may not be practical during and after surgery. Other noninvasive techniques such as bioreactance and esophageal Doppler require the use of costly single-use sensors. Here, we present a case report on the use of corrected carotid flow time (ccFT) from a portable, handheld ultrasound device as a practical, noninvasive, and technically straightforward method to assess fluid responsiveness in the perioperative period, as well as the inpatient and outpatient settings.

Correlation between corrected carotid flow time and left ventricular outflow tract velocity-time integral using a novel technique

BACKGROUND

Transthoracic echocardiography (TTE) is widely used for assessing patients in the intensive care unit, with cardiac output measurement being crucial for hemodynamic monitoring. This is achieved by measuring the velocity-time integral (VTI) of the left ventricular outflow tract (LVOT), which serves as a surrogate of stroke volume. However, conducting TTE in the critical care setting presents several challenges. Our primary objective was to investigate the relationship between carotid corrected flow time (cCFT) and LVOT VTI. Additionally, we aimed to determine the threshold cCFT value that reliably predicts a normal LVOT VTI.

MATERIALS AND METHODS

This proof-of-concept study involves a post-hoc analysis from a diagnostic accuracy investigation conducted in a medical-surgical intensive care unit. We included patients admitted to the ICU from December 2021 to January 2022. We used a phased array transducer to measure the cCFT at the left supraclavicular fossa and the LVOT VTI in an apical 5-chamber view.

RESULTS

We included 22 patients. The Spearman coefficient between LVOT VTI and cCFT was 0.82 (p < 0.0001). The area under the ROC curve for cCFT to predict LVOT VTI equal to or greater than 17 cm was 0.871 (95% CI 0.660-0.974). A cCFT exceeding 283 ms predicted LVOT VTI equal to or greater than 17 cm with a sensitivity of 93.3% (95% CI 68.1% to 99.8%) and specificity of 85.7% (95% CI 42.1% to 99.6%).

CONCLUSION

The cCFT, measured using a novel technique with a phased array transducer, shows a strong correlation with LVOT VTI. Additionally, cCFT predicts a normal LVOT VTI with good sensitivity and specificity in critically ill patients. Larger studies are warranted to validate these findings.