#5006 relationship between extracellular water percentage and mortality in patients undergoing chronic hemodialysis

Abstract Background and Aims Chronic hemodialysis (HD) patients have a high cardiovascular and mortality risk. This is secondary to numerous risk factors specific to the HD population. Relevant on cardiovascular disease and mortality in HD, is the sodium intake and the extent of the sodium pool of patients. An increase in the total sodium pool may have a negative action on cardio vascular system directly and mediated by the increase in total body water associated with an increase in the sodium pool. However, the assessment of the sodium pool in patients is clinically complex. Some evidence has suggested that the assessment of the extracellular water percentage (ECW%) in the HD patient may be a marker of the sodium pool. In fact, the increase in extracellular sodium is followed by a shift of water from the intracellular compartment to the extracellular compartment. The assessment of ECW% could therefore identify patients with greater ECW increase secondary to the greater sodium pool and therefore with high clinical risk. Primary aim: to evaluate the relationship between extracellular water percentage and mortality in patients on chronic hemodialysis. Method This is an observational prospective cohort study. The inclusion criteria were chronic HD for at least three months, minimum follow-up of six months, age greater than 18 years. In all of the included patients we performed the bioimpedance examination with a dedicated instrument after hemodialysis session, after the long interdialytic interval, for the evaluation of ECW (L), ECW (%), TBW (L / m), ICW (L). The protocol involved dividing the population into two groups based on normal or pathological ECW%, according to values calculated by gender and age and then evaluating the incidence of death in a 36-month follow-up. Results We enrolled 101 patients with an average age of 71± 14 years in HD for 51 ±15 months. During the average follow-up of 19 months we observed 31 deaths (30% of the population) with an annual mortality of 15%. ECW % correlated positively with age (R: 0.498 P:0.01) and differential post-dialysis pressure (R: 0.260; P:0.01). 41 patients (aged 64 ± 13 years) had a normal ECW % (ECW-N) and 60 patients (75±13 years) had pathological ECW% (ECW-P). ECW-P patients had an increased mortality respect to ECW-N patients (60% vs 20% p: 0.01). The survival curve confirmed higher mortality in the ECW-P group (log-rank test P 0.02). These results were confirmed in a sub-analysis of two age-matched ECW-N (n. 20 age 64±10 years) vs ECW-P (n. 20 age 65±12 years) subgroups (log-rank test P:0.05). Conclusion Our data showed that ECW% identifies HD patients at increased mortality risk in 36- month follow-up. These data are also confirmed in age-related subgroups, suggesting the ECW % assessment can be a simple and useful parameter to evaluate for targeted treatment choices in patients with chronic HD.