Accuracy of Inferior Vena Cava (IVC) and Lung Point-of-Care Ultrasonography (POCUS) as an Adjunct in the Evaluation of Hypervolemia among Patients on Maintenance Hemodialysis

Background: Fluid overload is a burdensome problem among maintenance hemodialysis patients that is associated with morbidity and mortality.1 There is no gold standard to predict or estimate dry weight.2 It is traditionally determined clinically but can be complex, varied, and confounded by several factors. Incorporating a simple, quick, and more objective method using point-of-care ultrasound (POCUS) gives a more accurate evaluation of fluid volume status.3 Methods: This is an observational, cross-sectional study involving 45 examinations among 29 adults on maintenance hemodialysis. A primary investigator performed IVC and lung POCUS before and after dialysis using a handheld ultrasound device. Results were recorded and validated by a nephrologist trained in POCUS. Another fellow who is blinded to the POCUS findings performed the clinical volume status assessment. Results: Using the cut-off scores for lung B-lines, IVC diameter, and IVC-CI examinations, there were 37.78%, 33.33%, and 68.89%, respectively, which had hypervolemia at pre-dialysis, and 24.44%, 15.56%, and 71.11%, respectively which had hypervolemia at post-dialysis. The sensitivity of lung B-lines, IVC diameter, and IVC-CI were 61.5%, 53.8%, and 61.5%, respectively, and specificity of 65.6%, 75%, and 28.1%, respectively. The AUC-ROC of all three parameters, 0.636, 0.644, and 0.448, did not reach AUC > 0.7. Post-hemodialysis, there were 27.27% by lung B-lines, 15.91% by IVC diameter, and 70.45% by IVC collapsibility index who already had negative hypervolemia by clinical assessment. This finding is consistent with the fact that physical examination (crackles and peripheral edema) is helpful when signs of congestion are present, but their absence does not exclude congestion. The interrater reliability and agreement of lung and IVC POCUS were also similar to that of the nephrology fellow and the nephrologist trained in POCUS. Conclusion: This study cannot strongly conclude IVC and lung POCUS as a single method to accurately identify hypervolemia among adult hemodialysis patients but the real-time changes can help assess a patient’s physiologic response to fluid volume changes. Integrating insonation into clinical assessment can be used as an adjunct in objectively estimating fluid status and guiding clinicians in their day-to-day practice.