Overhydration, Cardiac Function and Survival in Hemodialysis Patients

<div><p>Background and objectives</p><p>Chronic subclinical volume overload occurs very frequently and may be ubiquitous in hemodialysis (HD) patients receiving the standard thrice-weekly treatment. It is directly associated with hypertension, increased arterial stiffness, left ventricular hipertrophy, heart failure, and eventually, higher mortality and morbidity. We aimed to assess for the first time if the relationship between bioimpedance assessed overhydration and survival is maintained when adjustments for echocardiographic parameters are considered.</p><p>Design, setting, participants and measurements</p><p>A prospective cohort trial was conducted to investigate the impact of overhydration on all cause mortality and cardiovascular events (CVE), by using a previously reported cut-off value for overhydration and also investigating a new cut-off value derived from our analysis of this specific cohort. The body composition of 221 HD patients from a single center was assessed at baseline using bioimpedance. In 157 patients supplemental echocardiography was performed (echocardiography subgroup). Comparative survival analysis was performed using two cut-off points for relative fluid overload (RFO): 15% and 17.4% (a value determined by statistical analysis to have the best predictive value for mortality in our cohort).</p><p>Results</p><p>In the entire study population, patients considered overhydrated (using both cut-offs) had a significant increased risk for all-cause mortality in both univariate (HR = 2.12, 95%CI = 1.30–3.47 for RFO>15% and HR = 2.86, 95%CI = 1.72–4.78 for RFO>17.4%, respectively) and multivariate (HR = 1.87, 95%CI = 1.12–3.13 for RFO>15% and HR = 2.72, 95%CI = 1.60–4.63 for RFO>17.4%, respectively) Cox survival analysis. In the echocardiography subgroup, only the 17.4% cut-off remained associated with the outcome after adjustment for different echocardiographic parameters in the multivariate survival analysis. The number of CVE was significantly higher in overhydrated patients in both univariate (HR = 2.46, 95%CI = 1.56–3.87 for RFO >15% and HR = 3.67, 95%CI = 2.29–5.89 for RFO >17.4%) and multivariate (HR = 2.31, 95%CI = 1.42–3.77 for RFO >15% and HR = 4.17, 95%CI = 2.48–7.02 for RFO >17.4%) Cox regression analysis.</p><p>Conclusions</p><p>The study shows that the hydration status is associated with the mortality risk in a HD population, independently of cardiac morphology and function. We also describe and propose a new cut-off for RFO, in order to better define the relationship between overhydration and mortality risk. Further studies are needed to properly validate this new cut-off in other HD populations.</p></div

Demographic characteristics, bioimpedance and echocardiography assessment of the echocardiographic subgroup and of the overhydrated and normohydrated patients (using the RFO = 17.4% cut-off).

<p>Data are expressed as mean ± SD, median with IR, or total number with percentages, as appropriate. Bold values are statistically significant. AFO–absolute fluid overload; BMI–body mass index; CAD–coronary artery disease; CV–cardiovascular; DBP–diastolic blood pressure; ECW–extracellular water; FTI–fat tissue index; ICW–intracellular water; LTI–lean tissue index; LVEF–left ventricular ejection fraction; LVMI–left ventricular mass index; LVPWT–left ventricular posterior wall thickness; PVD–peripheral vascular disease; RFO–relative fluid overload; SBP–systolic blood pressure; TBW–total body water.</p><p>*—comparison between the entire and the echocardiographic cohort</p><p>^#—comparison between groups.</p><p>Demographic characteristics, bioimpedance and echocardiography assessment of the echocardiographic subgroup and of the overhydrated and normohydrated patients (using the RFO = 17.4% cut-off).</p

Demographic characteristics and bioimpedance assessment of the entire study population and of the overhydrated and normohydrated patients (using the RFO = 15% cut-off).

<p>Data are expressed as mean ± SD, median with IR, or total number with percentages, as appropriate. Bold values are statistically significant. AFO–absolute fluid overload; BMI–body mass index; CAD–coronary artery disease; CV–cardiovascular; CVE–cardiovascular events; DBP–diastolic blood pressure; ECW–extracellular water; FTI–fat tissue index; ICW–intracellular water; LTI–lean tissue index; PVD–peripheral vascular disease; RFO–relative fluid overload; SBP–systolic blood pressure; TBW–total body water.</p><p>^#—comparison between groups.</p><p>Demographic characteristics and bioimpedance assessment of the entire study population and of the overhydrated and normohydrated patients (using the RFO = 15% cut-off).</p

Time to first cardiovascular event analysis for a RFO > 15% cut-off point (Log rank p < 0.001).

<p>Time to first cardiovascular event analysis for a RFO > 15% cut-off point (Log rank p < 0.001).</p

Kaplan Meier survival analysis for a RFO > 15% cut-off point (Log rank p = 0.002).

<p>Kaplan Meier survival analysis for a RFO > 15% cut-off point (Log rank p = 0.002).</p