Carotid Ultrasound for Predicting Fluid Responsiveness in Mechanically Ventilated Patients

Accurate evaluation of fluid status in intubated, critically ill patients is crucial for effective patient management. Both hypovolemia and fluid overload can lead to adverse outcomes. Assessing fluid responsiveness—identifying patients who will benefit from volume administration—is essential in these settings. Carotid ultrasound has emerged as a novel, noninvasive method for predicting fluid responsiveness. This systematic review aims to update the literature on carotid ultrasound’s accuracy in predicting fluid responsiveness in mechanically ventilated patients.

Carotid ultrasound, also known as carotid duplex ultrasound, is a noninvasive imaging technique used primarily to evaluate the structure and function of the carotid arteries. These arteries, located on either side of the neck, are vital as they supply blood to the brain,neck, and face. Carotid ultrasound combines traditional ultrasound with Doppler ultrasound to visualize the carotid arteries and assess blood flow.

In recent years, carotid ultrasound has emerged as a novel tool for assessing fluid responsiveness in critically ill patients. Fluid responsiveness refers to the ability of a patient’s cardiovascular system to respond to fluid administration with a significant increase in stroke volume. This is particularly important in the management of patients in intensive care units (ICUs) or undergoing major surgery.

Mechanism

• Carotid Doppler Peak Velocity (CDPV): Measures the peak velocity of blood flow through the carotid artery. Changes in CDPV can indicate changes in cardiac output and stroke volume in response to fluid administration.
• Corrected Flow Time (FTc): Assesses the time taken for blood to flow through the carotid artery, corrected for heart rate. FTc can provide insights into the filling status of the heart and fluid responsiveness.

META-ANALYSIS OF CURRENT LITERATURE

Carotid Ultrasound Parameters and Outcomes

• Common Parameters:
  • Corrected Flow Time (FTc)
  • Change in Carotid Doppler Peak Velocity (∆CDPV)
  • Change in Carotid Artery Velocity-Time Integral (∆CAVTI)
• Common Cardiac Output Measures:
  • Transthoracic Echocardiography (TTE)
  • PiCCO
  • Pulmonary Artery Catheter (PAC)
  • FloTrac
  • LiDCO

Meta-Analysis Results

• ∆CDPV:
  • Sensitivity: 0.79 (95% CI, 0.74–0.84)
  • Specificity: 0.85 (95% CI, 0.76–0.90)
• FTc:
  • Sensitivity: 0.82 (95% CI, 0.74–0.87)
  • Specificity: 0.82 (95% CI, 0.75–0.87)

The use of carotid ultrasound, specifically ∆CDPV and FTc, shows promise in predicting fluid responsiveness in mechanically ventilated patients. However, study heterogeneity and bias limit the generalizability of these findings. Future high-quality studies with standardized methodologies are needed to validate these parameters.

For further detailed information, please refer to the systematic review published in Anesthesia & Analgesia.
Lipszyc AC, Walker SCD, Beech AP, Wilding H, Akhlaghi H. Predicting Fluid Responsiveness Using Carotid Ultrasound in Mechanically Ventilated Patients: A Systematic Review and Meta-Analysis of Diagnostic Test Accuracy Studies. Anesthesia & Analgesia. 2024;138(6)

To learn more about assessing fluid status using point-of-care ultrasound, download NYSORA’s POCUS App!