Photo Credit: Hugo Grajales

Modern tools for fluid management in patients on dialysis, including lung ultrasound and echocardiography, can help achieve euvolemia and lower morbidity and mortality.

“Fluid overload contributes to hypertension, left ventricular hypertrophy, heart failure, and increased mortality [in patients with ESRD on dialysis],” researchers wrote in BMC Nephrology. “Conversely, excessive ultrafiltration can lead to intradialytic hypotension, myocardial stunning, and a decline in residual renal function. Accurate fluid status assessment and careful ultrafiltration management are crucial for optimal care of patients on dialysis.”

However, the tools used for this assessment—including blood pressure, body weight, dry weight, and X-rays—all have limitations. There is “a need for more objective ways to assess volume status,” Sharad Patel, MD, and colleagues wrote.

Modern Tools for Fluid Management

In their review, Dr. Patel and colleagues assessed five tools that offer clinicians more precise options for measuring fluid status in patients on dialysis, including lung ultrasound, echocardiography, venous excess ultrasound (VEXUS), bioimpedance analysis (BIA), and passive leg raise (PLR).

Lung Ultrasound

• Assess volume status by detecting extravascular lung water (EVLW) and pulmonary congestion.
• Focuses on detecting B-lines; the number and distribution of B-lines correlate with the degree of EVLW and can semi-quantitatively evaluate the severity of pulmonary congestion.
• Non-invasive, radiation-free, and can be done easily at the bedside.
• Can be used to monitor the response to interventions, such as ultrafiltration.

Echocardiography

• Provides information on cardiac structure and function, which enables analysis of volume-related abnormalities and monitoring response to interventions.
• Key parameter of echocardiographic assessment of fluid status is the diameter and collapsibility of the inferior vena cava.
• Inferior vena cava assessments must be contextualized within a patient’s clinical scenario, as factors such as cardiac function, intrathoracic pressure, and intra-abdominal pressure can impact measurements.

Venous Excess Ultrasound

• Evaluates venous congestion using hepatic, portal, and renal Doppler patterns in combination with examination of the inferior vena cava.
• Categorizes venous congestion into four groups based on the severity of abnormalities: inferior vena cava diameter, hepatic vein waveform, portal vein pulsatility index, and renal vein flow.
• By identifying venous congestion early, VEXUS may enable more targeted fluid management to stop or mitigate adverse effects.
• Experimental approach that shows promise for assessing venous congestion and its impact on renal function in patients on dialysis, but its utility in patients without residual renal function needs to be studied further.

Bioimpedance Analysis

• Non-invasive method for evaluating fluid status and body composition by measuring resistance and reactance of body tissue to a low-amplitude electrical current.
• Several parameters can be obtained from these measurements, including total body water (TBW), extracellular water (ECW), intracellular water (ICW), and overhydration (OH).
• Provides objective, quantitative evaluation of TBW and its distribution, which can guide ultrafiltration goals.
• Various factors, including body position, skin temperature, and the timing of measurements relative to dialysis, can influence the accuracy of BIA measurements.
• Cost and availability of BIA devices may limit use in some dialysis units.

Passive Leg Raise

• Simple, noninvasive bedside movement that transiently improves venous return to predict fluid responsiveness in critically ill patients.
• Requires an accurate method to measure pre-PLR and post-PLR cardiac output, which can be done using echocardiography, pulmonary artery catheter, or non-invasive methods such as bioimpedance.
• Traditionally used to assess volume responsiveness for patients in shock, but emerging evidence shows PLR may be valuable in guiding fluid removal during dialysis.
• Validation studies of PLR are primarily in critically ill patients on acute renal replacement therapy; applicability across different dialysis settings requires further investigation.

Incorporating Modern Tools in Clinical Settings

Dr. Patel and colleagues note that widespread use of these modern fluid assessment tools “requires consideration of both their economic impact and patient-centered outcomes.” While they acknowledge the initial costs involved, such as obtaining the necessary equipment and training staff, they also note that decreased healthcare utilization may offset these burdens.

“Incorporating these tools into clinical practice requires a thoughtful and individualized approach,” the researchers wrote. “By using these tools in conjunction with clinical judgment, the nephrology community can work towards achieving the goal of euvolemia and reducing the burden of cardiovascular morbidity and mortality in this high-risk population.”