Ultrasound Helps Diagnose Lung Congestion in Dialysis Patients

 

 

Asymptomatic lung congestion has been shown to increase dialysis patients’ risks of dying prematurely or experiencing myocardial infarctions or other cardiac events, according to recent research.

The findings also revealed that utilizing lung ultrasound to identify this congestion aids in diagnosing patients at risk. Italian investigators recently measured the degree of lung congestion in 392 dialysis patients by using a very simple and inexpensive technique – lung ultrasound.

Lung congestion due to fluid accumulation is very common among kidney failure patients on dialysis, but it frequently does not cause any symptoms. To see whether such asymptomatic congestion affects dialysis patients’ health, Carmine Zoccali, MD, from Ospedali Riuniti (Reggio Calabria, Italy; www.rc.ibim.cnr.it) and his colleagues published their study findings February 28, 2013, in the  Journal of the American Society of Nephrology (JASN).

Among the major findings (1) Lung ultrasound revealed very severe congestion in 14% of patients and moderate-to-severe lung congestion in 45% of patients. (2) Among those with moderate-to-severe lung congestion, 71% were asymptomatic. (3) Compared with those having slight or no congestion, those with very severe congestion had a 4.2-fold increased risk of dying and a 3.2-fold increased risk of experiencing heart attacks or other cardiac events over a two-year follow-up period. (4) Lastly, asymptomatic lung congestion identified by lung ultrasound was a better predictor of patients’ risk of dying prematurely or experiencing cardiac events than symptoms of heart failure.

By evaluating subclinical pulmonary edema can help better establish dialysis patients’ prognoses, according to the findings.The researchers will soon initiate a clinical trial that will integrate lung fluid measurements by ultrasound and will examine whether dialysis intensification in patients with asymptomatic lung congestion can reduce the risk of heart failure and cardiac events and prevent premature death.

From MII, June 2013

 Background

Advancement in dialysis technology and new drug therapies of uremic complications are major achievements of modern nephrology. As a result of progress in the care of ESRD, a continuous increase in survival of dialysis 4 patients has been documented over the last 13 years in the European Renal Association-European Dialysis Transplant Association (ERA-EDTA) registry (1). Adequate control of fluid balance is a primary goal of dialysis treatment and experience in centres applying strict volume control policies documented a remarkable reduction in mortality in comparison with average mortality rate in well matched cohorts in the USRDS and in the ERA-EDTA Registry (2). Even though specific recommendations in past and current guidelines emphasise the risk of volume overload, the problem still remains pervasive in the dialysis population (3). Unsatisfactory control of volume expansion depends on various reasons encompassing both medical and non-medical factors such as reimbursement of the cost of extra or longer dialyses and other organizational and logistic factors. As to the medical factors, it is widely agreed that the high prevalence of patients with LV dysfunction and heart failure and the lack of simple, non-expensive, bedside techniques that may serve to estimate and monitor parameters of central hemodynamics for guiding the prescription of ultrafiltration (UF) and drug treatment  is a factor of major clinical relevance.

Extra-vascular lung water (LW), a fundamental component of body fluids volume, represents the water content of the lung interstitium which is strictly dependent on the filling pressure of the left ventricle (4; 5). Chest ultrasound (US) has recently emerged as a reliable technique for detecting LW in intensive care patients (6) and in patients with heart failure (7). The basic principle of this technique is that in the presence of excessive LW, the ultrasound beam is efflected by subpleural thickened interlobular septa, a low impedance structure surrounded by air with a high acoustic mismatch. US reflection generates hyperechoic reverberation artefacts between thickened septa and the overlying pleura which are defined “lung comets” (8). These artefacts are easily detected with standard US probes and chest US has been formally validated as a reliable technique to estimate LW in patients with heart diseases (9). This method captures changes in LW which occur across dialysis and the feasibility and repeatability of chest US studies in hemodialysis patients has been recently described (10). However the clinical usefulness of this technique in the everyday care in ESRD patients is still untested and it remains unknown whether systematic application of chest US may translate into better clinical outcomes in these patients. With this background in mind the European Renal and Cardiovascular Medicine (EURECA-m) working group of the ERA-EDTA designed a randomised, multicenter, clinical trial investigating whether a treatment policy based on LW monitoring in haemodialysis patients by chest US is more effective than standard clinical monitoring for reducing death, decompensated heart failure and myocardial infarction and prevent the evolution of LVH and LV dysfunction in patients with myocardial ischemia or heart failure over a 2-year follow-up.

 

This trial will be the first which formally tests a biomarker as a guide the optimize volume control and drug treatment in high risk dialysis patients. Other promising indicators of fluid volume in dialysis patients - such as body impedance analysis (BIA) or cardiac natriuretic peptides - have never been tested into a clinical trial, which is a basic requirement for recommending systematic use of biomarkers in clinical practice.