Venous Excess and Lung Ultrasound During Continuous Kidney Replacement Therapy in Critically Ill Patients

Lung and cardiac ultrasonography can augment the definite diagnosis of volume overload. Thoracic ultrasound demonstrating B-lines which suggest thickened interstitial or fluid filled alveoli or increased vena cava diameter by ultrasound can also be used to assess volume status.

Recently, the venous excess ultrasound grading system (VExUS) has been introduced to be used in conjunction with POCUS to assess significant congestion. This technique used to classify the level of venous congestion by assessing the abdominal blood flow, including hepatic veins (HVs), portal veins (PVs) and intrarenal veins (IRVs). Abnormal patterns of flow in these organs can enhance the clinical evaluation of venous congestion in addition to Inferior vena cava (IVC) ultrasound since organ dysfunction occurring with venous congestion can also be from the transmission of pressure from right atrium (right atrial pressure, RAP) to the peripheral organ. Venous congestion is classified into four grades , ranging from grade 0 (no congestion) to the most severe form, grade 3 (severe congestion) or VExUS "A" through "E".

In the Modified VExUS score, the VExUS grade 0 by IVC cut-off by ≤ 2 cm is replaced with the IVC distensibility index < 18% or the IVC collapsibility index < 50%, depending on patient passive or active ventilation, respectively.

Lung ultrasound and AKI Volume overload is associated with interstitial edema which increases the diffusion distance for oxygen and induces an increase in interstitial fluid pressure, impairing capillary blood flow and exacerbating organ dysfunction . A prospective pilot observational study with 45 adult patients with AKI at any time during ICU stay employed the FALLS (Fluid Administration Limited by Lung Ultrasound) protocol in which they use the LUS for assessing volume status. A new onset of the B-lines was considered as the endpoint of fluid administration. The study demonstrated a linear correlation between baseline B-line scores and PaO2/FiO2 ratio in ICU patients VExUS and lung ultrasound during CKRT

Previous studies have shown that VExUS and lung ultrasound may play a role in predicting AKI severity and may aid fluid de-escalation in critically ill patients. However, no studies have evaluated the role of both VExUS, modified VExUS and lung ultrasound in guiding fluid management during CKRT. Our research aims to evaluate the prevalence of venous congestion by VExUS, mVExUS and lung ultrasound during CKRT and its association with clinical outcomes.

Inclusion criteria

• Adults (≥ 18 years of age)
• Admitted to ICU
• Plan to initiate CKRT by clinician's judgement

Exclusion criteria

• Refuse to participate
• Previous diagnosis of end-stage kidney disease (ESKD) currently on kidney replacement therapy
• Kidney tran splant recipient
• Receive KRT before ICU admission
• Structural kidney diseases which will interfere with intrarenal doppler ultrasound e.g. renal artery stenosis, autosomal dominant polycystic kidney disease etc.
• Patients with previously known conditions that interfere with portal doppler assessment, namely liver cirrhosis, severe tricuspid regurgitation with structural heart disease or massive ascites.
• Underlying disease process with a life expectancy less than 90 days
• Pregnancy
• Concomitant severe respiratory distress syndrome
• Expected life expectancy <48 hours
• Receiving extracorporeal membrane oxygenation (ECMO)