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Point of care venous Doppler ultrasound: Exploring the missing piece of bedside haemodynamic assessment
Point of care venous Doppler ultrasound: Exploring the missing piece of bedside haemodynamic assessment
REVIEWED BY Matt Adams, AFASA | ASA SIG: Vascular
REFERENCE | Authors: Galindo P, Gasca C, Argaiz E, and Koratala A
WHY THE STUDY WAS PERFORMED
This educational review was created due to the clinical significance of accurate haemodynamic assessment in the critically ill patient. Point-of-care tests such as passive leg raising with noninvasive cardiac output monitoring and measuring capillary refill time have stood the test of time in the intensive care unit (ICU) but the accuracy of these tests suffers in states of hypervolemia. Fluid overload in very poorly patients is not uncommon and significantly affects venous volume and compliance, which, in turn, influences venous Doppler waveforms. This study explains how these waveforms can be reliably assessed with point-of-care ultrasound (POCUS) to provide complementary information on venous congestion and where it is having a significant impact.
HOW THE STUDY WAS PERFORMED
No information on how evidence for this literature review was provided. This study is a summary of the rationale for integrating this technology into routine care for patients with volume-related disorders.
WHAT THE STUDY FOUND
Increased right atrial pressure (RAP) has a significant effect on the venous system and its spectral Doppler waveforms. This article explains the difference between normal and abnormal venous Doppler waveforms and why they are an important part of the diagnostic workup. The following points summarise different locations in which POCUS can be performed and what to expect in pathological states.
Increased RAP causes hepatic vein S wave amplitude reduction below that of its D wave (S < D pattern). The S wave can even become obliterated/retrograde if RAP worsens.
Progressive increase in portal vein pulsatility in the setting of increased RAP. This can be quantified into a pulsatility fraction using the below formula where anything > 50% is considered severe (PSV max–PSV min/PSV max) x 100.
Normal intrarenal vein flow is continuous but can become biphasic as RAP increases with the creation of distinct S and D waves. Studies have shown that adverse intrarenal venous waveform patterns not only reflect increasing RAP but also strongly predict adverse clinical outcomes in patients with heart failure, pulmonary hypertension and those undergoing cardiac surgery.
The common femoral veins (CFV) are directly linked to the IVC, making their waveforms very sensitive to an increase in proximal pressure. Normal CFV flow undulates with respiration at rest but becomes pulsatile in instances of increased RAP with very distinct antegrade and retrograde components.
Doppler of abdominal veins provides useful insights into a patient’s hemodynamics when interpreted in conjunction with other sonographic parameters such as the cardiac pump function, lung ultrasound and conventional clinical assessment.
RELEVANCE TO CLINICAL PRACTICE
Venous Doppler waveform assessment at the bedside is a tool that can provide complementary information to the global haemodynamic assessment of the critically ill patient. This physiological parameter should definitely be considered as part of the standard workup for the ICU patient, but its implementation should be approached with caution. It is well known that ultrasound is operator-dependent, especially when it comes to the interpretation of Doppler waveform nuances. Healthcare professionals who intend to perform this assessment need to learn via accredited programs that include extensive clinical experience. If done properly, however, this application of POCUS could be very beneficial as part of routine investigations and lends itself very well to the impending portable ultrasound revolution.
