Early net ultrafiltration rate and mortality in critically ill patients receiving continuous renal replacement therapy

Abstract

Background In patients treated with continuous renal replacement therapy (CRRT), early net ultrafiltration (NUF) rates may be associated with differential outcomes. We tested whether higher early NUF rates are associated with increased mortality in CRRT patients. Methods We performed a retrospective, observational study of all patients treated with CRRT within 14 days of intensive care unit admission. We defined the early (first 48 h) NUF rate as the volume of fluid removed per hour adjusted for patient body weight and analysed as a categorical variable (>1.75, 1.01–1.75 and <1.01 mL/kg/h). The primary outcome was 28-day mortality. To deal with competing risk, we also compared different time epochs. Results We studied 347 patients {median age 64 [interquartile range (IQR) 53–71] years and Acute Physiology and Chronic Health Evaluation III score 73 [IQR 54–90]}. Compared with NUF rates <1.01 mL/kg/h, NUF rates >1.75 mL/kg/h were associated with greater mortality rates in each epoch: Days 0–5, adjusted hazard ratio (aHR) 1.27 [95% confidence interval (CI) 1.21–1.33]; Days 6–10, aHR 1.62 (95% CI 1.55–1.68); Days 11–15, aHR 1.87 (95% CI 1.79–1.94); Days 16–26, aHR 1.92 (95% CI 1.84–2.01) and Days 27–28, aHR 4.18 (95% CI 3.98–4.40). For every 0.5 mL/kg/h NUF rate increase, mortality similarly increased during these epochs. Conclusion Compared with early NUF rates <1.01 mL/kg/h, NUF rates >1.75 mL/kg/h are associated with increased mortality. These observations provide the rationale for clinical trials to confirm or refute these findings.

Net ultrafiltration prescription survey in Europe

“…Similarly, a recent study supported that a UF NET rate > 1.75 mL/kg/hr. in the first 48 h was associated with increased mortality, lower potassium, higher hypophosphatemia, a longer duration of CRRT, and longer stay in ICU [28]. Observational studies in chronic hemodialysis patients showed similar results: high rates of fluid removal were associated with increased cardiovascular mortality, possibly due to impaired plasma refilling rate and myocardial stunning [29,30].…”

How To Prescribe And Troubleshoot Continuous Renal Replacement Therapy: A Case-Based Review

“…However, data on the rate of fluid removal are mostly observational and likely confounded by indication. [21][22][23] Given the lack of clinical trials addressing this important aspect of the CRRT prescription, as well as the lack of fully validated methods of predicting and assessing fluid removal tolerance and need, significant heterogeneity in practice exists. 24 Although the prescription of net ultrafiltration (net UF or UF net ) is highly dynamic and commonly individualized, it is recommended not to exceed 1.5-2.0 ml/kg/hr of net UF as a general rule.…”

Heterogeneity of Effect of Net Ultrafiltration Rate among Critically Ill Adults Receiving Continuous Renal Replacement Therapy

“…The rate for the duration of study treatment was calculated as follows [9,10,15]: NUF rate (mL/kg/h) = cumulative NUF volume (mL)/(weight at enrollment [kg] * actual treatment duration [hours])…”

“…Based on previous data [9,10] and according to the distribution of the data in the RENAL trial, the NUF rate was stratified into tertiles: (1) low (<1.01 mL/kg/h), (2) middle (1.01-1.75 mL/kg/h), or (3) high (>1.75 mL/kg/h).…”

“…A fast NUF rate may cause hemodynamic instability, but a slow NUF rate may lead to a positive fluid balance and persistent organ edema [7,8]. Recently, a secondary analysis of the "Randomized Evaluation of Normal Versus Augmented Level of Renal Replacement Therapy" (RENAL) trial reported that NUF rates >1.75 mL/kg/h (upper tertile) compared with NUF rates <1.01 mL/kg/h (lowest tertile) were independently associated with a higher 90day mortality [9], a finding now confirmed in an independent CRRT cohort [10].…”