Steven M. Brunelli

<b><i>Background:</i></b> Intradialytic hypotension (IDH) is common and is associated with increased morbidity and mortality in chronic hemodialysis patients. A higher dialysis ‘dose' may generate transient intradialytic osmotic gradients, predisposing to intracellular fluid shifts and resulting in hypotension. <b><i>Study Design:</i></b> We performed a post hoc analysis of the HEMO study, a multicenter trial that randomized chronic hemodialysis patients to high versus standard Kt/V and higher versus lower membrane flux. In order to achieve dose targets, per protocol, adjustments were made in membrane efficiency, blood flow or dialysate flow before changing session length. Detailed hemodynamic and urea kinetic modeling data were abstracted from 1,825 individuals. The primary outcome was the occurrence of hypotensive events necessitating clinical intervention (saline infusion, lowering of ultrafiltration rate or reduced blood flow). <b><i>Results:</i></b> Intradialytic hypotensive events occurred more frequently in the higher-Kt/V group (18.3 vs. 16.8%; p < 0.001). Participants randomized to higher-target Kt/V had a greater adjusted risk of IDH than those randomized to standard Kt/V [odds ratio (OR) 1.12; 95% confidence interval (CI) 1.01-1.25]. Higher vs. lower dialyzer mass transfer-area coefficient for urea and rate of urea removal were associated with greater adjusted odds of IDH (OR 1.15; 95% CI 1.04-1.27 and OR 1.05; 95% CI 1.04-1.06 per mg/dl/h, respectively). <b><i>Conclusions:</i></b> Higher dialysis dose, at relatively constrained treatment times, may associate with an increased risk of IDH. These findings support the possibility that rapidity of intradialytic reductions in plasma osmolality may play an important role in mediating hemodynamic instability during dialysis.

Intradialytic hypotension is a serious and frequent complication of hemodialysis; however, there is no evidence-based consensus definition of intradialytic hypotension. As a result, coherent evaluation of the effects of intradialytic hypotension is difficult. We analyzed data from 1409 patients in the HEMO Study and 10,392 patients from a single large dialysis organization to investigate the associations of commonly used intradialytic hypotension definitions and mortality. Intradialytic hypotension definitions were selected a priori on the basis of literature review. For each definition, patients were characterized as having intradialytic hypotension if they met the corresponding definition in at least 30% of baseline exposure period treatments or characterized as control otherwise. Overall and within subgroups of patients with predialysis systolic BP<120 or 120-159 mmHg, an absolute nadir systolic BP<90 mmHg was most potently associated with mortality. Within the subgroup of patients with predialysis BP≥160 mmHg, nadir BP<100 mmHg was most potently associated with mortality. Intradialytic hypotension definitions that considered symptoms, interventions, and decreases in BP during dialysis were not associated with outcome, and when added to nadir BP, symptom and intervention criteria did not accentuate associations with mortality. Our results suggest that nadir-based definitions best capture the association between intradialytic hypotension and mortality.

BACKGROUND AND OBJECTIVES: At least four definitions of AKI have recently been proposed. This study sought to characterize the epidemiology of AKI according to the most recent consensus definition proposed by the Kidney Disease Improving Global Outcomes (KDIGO) Work Group, and to compare it with three other definitions. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: This was a retrospective cohort study of 31,970 hospitalizations at an academic medical center in 2010. AKI was defined and staged according to KDIGO criteria, the Acute Dialysis Quality Initiative's RIFLE criteria, the Acute Kidney Injury Network (AKIN) criteria, and a definition based on a model of creatinine kinetics (CK). Outcomes of interest were incidence, in-hospital mortality, length of stay, costs, readmission rates, and posthospitalization disposition. RESULTS: AKI incidence was highest according to the KDIGO definition (18.3%) followed by the AKIN (16.6%), RIFLE (16.1%), and CK (7.0%) definitions. AKI incidence appeared markedly higher in those with low baseline serum creatinine according to the KDIGO, AKIN, and RIFLE definitions, in which AKI may be defined by a 50% increase over baseline. AKI according to all definitions was associated with a significantly higher risk of death and higher resource utilization. The adjusted odds ratios for in-hospital mortality in those with AKI were highest with the CK definition (5.2; 95% confidence interval [95% CI], 4.1 to 6.6), followed by the RIFLE (2.9; 95% CI, 2.2 to 3.6), KDIGO (2.8; 95% CI, 2.2 to 3.6), and AKIN (2.6; 95% CI, 2.0 to 3.3) definitions. Concordance in diagnosis and staging was high among the KDIGO, AKIN, and RIFLE definitions. CONCLUSIONS: The incidence of AKI in hospitalized individuals varies depending on the definition used. AKI according to all definitions is associated with higher in-hospital mortality and resource utilization. AKI may be inappropriately diagnosed in those with low baseline serum creatinine using definitions that incorporate percentage increases over baseline.

BACKGROUND AND OBJECTIVES: Patients undergoing hemodialysis have an elevated risk of cardiovascular disease-related morbidity and mortality compared with the general population. Intradialytic hypotension (IDH) is estimated to occur during 20%-30% of hemodialysis sessions. To date, no large studies have examined whether IDH is associated with cardiovascular outcomes. This study determined the prevalence of IDH according to interdialytic weight gain (IDWG) and studied the association between IDH and outcomes for cardiovascular events and mortality to better understand its role. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: This study retrospectively examined records of 39,497 hemodialysis patients during 2007 and 2008. US Renal Data System claims and dialysis provider data were used to determine outcomes. IDH was defined by current Kidney Disease Outcomes Quality Initiative guidelines (≥20 mmHg fall in systolic BP from predialysis to nadir intradialytic levels plus ≥2 responsive measures [dialysis stopped, saline administered, etc.]). IDWG was measured absolutely (in kilograms) and relatively (in percentages). RESULTS: IDH occurred in 31.1% of patients during the 90-day exposure assessment period. At baseline, the higher the IDWG (relative or absolute), the greater the frequency of IDH (P<0.001). For all-cause mortality, the median follow-up was 398 days (interquartile range, 231-602 days). Compared with patients without IDH, IDH was associated with all-cause mortality (7646 events; adjusted hazard ratio, 1.07 [95% confidence interval, 1.01 to 1.14]), myocardial infarction (2396 events; 1.20 [1.10 to 1.31]), hospitalization for heart failure/volume overload (8896 events; 1.13 [1.08 to 1.18]), composite hospitalization for heart failure/volume overload or cardiovascular mortality (10,805 events; 1.12 [1.08 to 1.17]), major adverse cardiac events (MACEs; myocardial infarction, stroke, cardiovascular mortality) (4994 events, 1.10 [1.03 to 1.17]), and MACEs+ (MACEs plus arrhythmia or hospitalization for heart failure/volume overload) (12,221 events; 1.14 [1.09 to 1.19]). CONCLUSIONS: IDH was potently associated with cardiovascular morbidity and mortality. Clinical trials to ascertain causality are needed and should consider reduction in IDWG as a potential means to reduce IDH.