Cumulative Fluid Balance assessed by Venous Excess Ultrasound (VExUS) scan and its impact on clinical outcomes in Critically Ill Adults: A Prospective Observational Study

After obtaining approval from the Department Postgraduate Research monitoring committee, Institute ethics committee and completing CTRI registration, patients satisfying eligibility criteria will be enrolled in the study. After obtaining informed written consent from the legally acceptable representative (LAR) the patient will be enrolled. The detailed history and demographic details (age, sex, height, weight, BMI and comorbidities) along with baseline vitals, baseline investigations (Urea, Creatinine, total protein, albumin, bilirubin, Hb, platelet count, TLC), echocardiography(velocity time integral, TAPSE, Ejection fraction), sequential organ failure assessment (SOFA) score and clinical diagnosis will be noted. Cumulative fluid balance will be recorded for 7 days after ICU admission. Fluid balance consists of fluid input including both enteral, parenteral intake and fluid output includes urine output, drainage fluid will be calculated daily from day zero of ICU admission to 7 days. At time of ICU admission, at 72 hours and at 7 days of admission venous excess ultrasonography (VExUS) scan will be performed for IVC and abnormal ultrasonography of hepatic vein (HV), portal vein (PV) and intrarenal veins (RV). An intensivist who has performed at least 25 VExUS scans and graded the intra-abdominal venous congestion that has been counterchecked by a radiologist will scan the participants in this study to obtain the VExUS scores.Ultrasonographic Assessment of HV, PV and RV:

Ultrasound assessment will be performed at the bedside using a phased array probe of 2-5 MHz.. The transducer will be placed at the level of xiphisternum in the craniocaudal direction. The maximum diameter of the IVC is found and measured at the hepatic vein exit. IVC size of >2 cm will be considered as having venous congestion and size of <2 cm will be considered as normal.

Acquisition of Hepatic Vein (HV) window: The transducer is placed in the mid axillary line and the liver is located trying to insonate the hepatic veins in its drainage towards the inferior vena cava. The hepatic veins will be acquired and color flow doppler (BLUE color) will be placed over the hepatic veins as they enter the IVC. The pulse wave doppler cursor will be activated on a hepatic vein prior to it entering the IVC and pulse wave doppler will be initiated. Interrogation by pulsed wave doppler identification and analysis of A, S, and D waves:

1)      S > D = Normal pattern

2)      S < D with antegrade S = Mild abnormality pattern

3)      S flat or inverted or biphasic trace = Severe abnormality pattern

 Acquisition of Portal Vein (PV) window: A 2-D image of the Portal Vein will be acquired, and color flow Doppler RED flow (towards the probe) will be placed. The pulse wave Doppler will be performed on the Portal Vein.

Interpretation of PV Doppler study: Pulsatility index is calculated as (Vmax  - Vmin)/Vmax♦        Continuous monophasic waveform without pulsatility = Normal pattern

♦        <0.3 pulsatility index with s and d waves above baseline = Mild abnormal pattern

♦       >0.3 pulsatility index with to and froaround the baseline= Severe abnormal pattern

Intrarenal Vein (RV): Kidney will be scanned at the posterior axillary line and color Doppler will be placed to look for the interlobar vessels. The pulse wave Doppler cursor will be placed at the best color Doppler signal and flow will be obtained.

♦        Continuous monophasic waveform below baseline = Normal pattern

♦        Biphasic S and D waves below baseline = Mild abnormal pattern

♦        Monophasic D wave below baseline = Severe abnormal pattern

Venous doppler ultrasound grading (VExUS)

The IVC diameter is measured then the portal, hepatic and intrarenal veins are scanned. Corresponding to a level of venous congestion, Doppler USG yields a specific pattern: normal, mild, or severe. According to the results, the VExUS score will be obtained as follows:

VExUS 0: IVC < 20mm;

VExUS 1: IVC  diameter  with normal patterns or mild abnormalities;

VExUS 2: IVC diameter and severe abnormality in at least one pattern

VExUS 3: IVC  diameter and severe abnormalities in multiple patterns

 The VExUS score will be correlated with cumulative fluid balance. The patient will be followed for development of new onset Acute Kidney Injury using  AKIN criteria, need for renal replacement therapy, number of mechanical ventilation free days, ICU length of stay will be recorded.

Withdrawal criteria: If there is difficulty in obtaining the window for performing the Doppler Study, then that patient will be withdrawn from this study

Ethical considerations: Performing USG of the abdomen is routine clinical practice