Pulmonary congestion in hemodialysis: an old chestnut worth screening for?

It is well documented that pulmonary congestion is common among patients undergoing treatment with hemodialysis, and recent evidence suggests a strong association with mortality (1–4). The cyclical, and very predictable, nature of each hemodialysis session carries several major risks that may compromise cardiorespiratory function and threaten the patient’s well-being (5). Onemajor consequence is the accumulation offluid during the interdialytic period, which has a propensity to collect in the lungs and lead to progressive pulmonary congestion, particularly among patients with compromised left ventricular function (1). Although the pathogenesis of this process is generally well understood and the inevitable consequences are obvious, our ability to effectively diagnose and treat this common condition has been less than satisfactory, exposing patients to unnecessary and potentially lethal clinical consequences (6). Pulmonary congestion that becomes clinically apparent from symptoms of shortness of breath prompts the clinical team to conduct a rapid set of clinical investigations and follow through with a personalized treatment strategy. Changes in the dialysis treatment prescription such as increased ultrafiltration, provision of extra dialysis treatments, re-evaluation of a patient’s dry weight, and a cardiac assessment are some of the recognized treatment practices that may be required. Pulmonary congestion that is not clinically apparent to the team or indeed the patient presents an even more challenging scenario (7,8). This “silent” pulmonary congestion by its very nature is difficult to detect, develops insidiously, and poses a serious threat to patient welfare. In this issue of CJASN, Enia and colleagues (9) provide a novel and unique perspective into the association of pulmonary congestion with physical functioning in hemodialysis. Using data from a multicenter study of 270 Italian hemodialysis patients, they describe for the first time an independent and inverse association of pulmonary congestion with impaired physical functioning measured before hemodialysis treatments. The primary exposure, pulmonary congestion, was assessed by chest ultrasonography, which measures the amount of extravascular water that accumulates in the lung from the thickness of the interlobular septa (1). The extent of water accumulation in the lungs was calculated by a cumulative score that indicated the thickness of the interlobular septa. Physical performance assessment was based on self-report using the physical functioning scale of the Kidney Disease Quality of Life Short Form (KDQOL-SF). There are three major findings that merit discussion in this editorial. First, 58% of hemodialysis patients in this survey had evidence of moderate to severe lung congestion before each hemodialysis session, whereas almost 40% of these patients had apparently no pulmonary symptoms. As a practicing clinical nephrologist, onemustbe alarmedat theobservation that almost two thirds of patients have moderate to severe pulmonary congestion before a hemodialysis treatment at a time when classic thrice-weekly hemodialysis remains the “gold” standard prescription for most hemodialysis programs. Assuming good external validity, one might also infer that most patients in standard hemodialysis programs are in a perpetual state of central volume overload that possibly begins soon after a hemodialysis treatment and progressively worsens before the next treatment. There is an increasing body of evidence that supports the finding of excessive fluid gains with elevated mortality (1–4,10). Indeed, Zoccali and colleagues recently demonstrated the independent prognostic effect of severe pulmonary congestion on all-cause and cardiovascular mortality in amulticenter prospective cohort study (10). The risk of all-cause death increased.4-fold, whereas that of fatal and nonfatal cardiovascular events increased .3-fold. These data highlight the detrimental effect of pulmonary congestion on clinical outcomes amongmaintenance hemodialysis patients and our inability to effectively manage them as we continue with conventional hemodialysis treatment practices. A second, and equally noteworthy finding, was the strong correlation of pulmonary congestion with poorer physical functioning before hemodialysis treatment. Regardless of age, coexisting cardiovascular comorbidity, and several nutritional markers, the greater the degree of pulmonary congestion before hemodialysis, the higher the probability of poor physical functioning. For many readers, it may not be surprising to learn that overt pulmonary congestion was linked with poor patient physical performance and indeed, one might have expected to see the graded effect of increasing pulmonary congestionwith reducedphysical functioning. What was surprising was the complete lack of association of commonly measured nutritional and Departments of Medicine and Nephrology, University Hospital Limerick, Limerick, Ireland; and Graduate Entry Medical School, University of Limerick, Limerick, Ireland