#201 Bedside lung ultrasound and bioimpedance spectroscopy for assessment of volume status in chronic kidney disease patients on hemodialysis
Authors: Malhotra Asheesh 
Published: May 2024

Abstract

Background and Aims
Fluid balance is important in patients with chronic kidney disease undergoing hemodialysis (HD). Majority of HD treatment incorporate a prescription for fluid removal targeted to patient's dry weight. Overestimation of dry weight causes hypertension, left ventricular hypertrophy and heart failure, while underestimation is responsible for chronic dehydration leading to the risk of hypotension. Both complications have a significant impact on the overall morbidity and mortality. Dry weight of the patient is usually assessed by using clinical parameters (edema, BP, JVP etc.), Biochemical parameters (BNP, ANP), Bioimpedance Spectroscopy (BIS) or IVC diameter and collapsibility on ultrasound (VCI index). The use of chest ultrasound to detect lung water has recently received growing attention in clinical research. Ultrasonographic lung comets (counting B-lines artifact) evaluate extravascular lung water and hence is considered as a useful tool to evaluate the hydration status of hemodialysis patients. This study aims to compare the efficacy of body fluid volume status and lung water assessment by clinical methods, Ultrasound chest and Bioimpedance Spectroscopy in chronic kidney disease patients on hemodialysis.

Method
A cross-sectional study was conducted over a period of 6 months. Dry weight of the patient was assessed by the attending nephrologist based on clinical criteria such as: weight, blood pressure, presence of edema or vascular congestion. A Longitudinal Ultrasound scan of the chest was performed using MicroMaxx Ultrasound System with patient in supine position from second to fourth intercostal space of left hemi-thorax and second to fifth intercostal space of right hemi-thorax along parasternal, midclavicular, anterior axillary and midaxillary lines of each side in a total of 28 sectors. B-lines were defined as hyperechogenic linear artifact emerging from the pleural line, up to the bottom of the screen. Pre and Post dialysis comet score was determined by calculating the total B-lines in each sector. Bioimpedance spectroscopy using Bodystat QuadScan 4000 was performed. Pre and post dialysis total body water (TBW), intracellular water (ICW), extracellular water (ECW) and residual fluid overload (ECW pre HD- ECW post HD) were recorded.

Results
We conducted 100 assessments on 34 patients presenting to the hospital for maintenance hemodialysis. The mean age of the study population was 54.3 + 11 years with a sex ratio (M/F) of 6:1. Mean systolic blood pressure was 141.1 + 19 mmHg and diastolic blood pressure was 83 + 9.3 mmHg with 3 episodes of intradialytic hypotension. The mean dry weight was 59.8 + 10 Kg and weight gain by clinical assessment was 2.1 + 1.5 Kg. Comet score assessed by ultrasound chest had a mean of 4.54 + 2.53 before dialysis and 1.73 ± 1.36 after dialysis. Residual fluid overload on Bio impedance spectroscopy was 1.11 ± 0.85 litre. The residual fluid overload on Bio impedance spectroscopy and lung ultrasound comet score after dialysis had a significant correlation (p value &lt;0.0001). Of the 100 assessments, 40% had fluid overload after dialysis on Bio impedance and 35% had lung congestion on ultrasound chest even after achieving euvolemia according to the dry weight assessed clinically.

Conclusion
Lung comets on ultrasound chest and residual volume on bio impedance spectroscopy may precede the development of clinical sign and symptoms in a patient. Therefore, these methods are superior to clinical volume status assessment in chronic kidney disease patients on hemodialysis.