Abstract
Fluid overload (FO) with coincident acute kidney injury has been associated with increased mortality. However, it is unclear whether FO is an independent determinant of mortality for disease severity. We aimed to explore whether the development of fluid balance (FB) during the first 72 h of continuous renal replacement therapy (CRRT) is independently associated with hospital mortality. All patients admitted to a single centre ICU requiring CRRT for at least 24 h between years 2010–2019 were included. Extracted data included patient demographics and clinical parameters including daily cumulative fluid balance (FBcum), lactate, SOFA score and vasoactive requirement at the initiation and during the first 72 h of CRRT. 399 patients were included in the analysis. Hospital survivors had a significantly lower FBcum at CRRT initiation compared to non-survivors (median 1382 versus 3265 ml; p = 0.003). Hourly fluid balance per bodyweight (FBnet) was lower in survivors at 0–24, 24–48 and 48–72 h after initiation of CRRT (p < 0.008 for all comparisons). In the survival analysis (analyzed with counting process model) significant time-dependent explanatory variables for hospital mortality were FBnet (per ml/kg/h: HR: 1.319, 95% CI 1.038–1.677, p = 0.02), lactate (HR: 1.086, 95% CI 1.030–1.145, p = 0.002) and SOFA score (per ml/kg/h: HR: 1.084, 95% CI 1.025–1.146, p = 0.005) during the first 72 h of CRRT. Even after careful adjustment for repeated measures of disease severity, FBnet during the first 72 h of CRRT remains independently associated with hospital mortality, in critically ill patients with AKI.
Highlights
Ill patients often require fluid resuscitation in the early phase of treatment, which can lead to fluid overload and a later need for fluid removal
Several observational studies have shown that fluid overload with coincident acute kidney injury (AKI) is associated with worsening organ dysfunction and increased mortality in critically ill patients1–3 and extracorporeal removal of excess fluid using renal replacement therapy (RRT) techniques is associated with reduced m ortality1, 4
The median FBcum from intensive care unit (ICU) admission to initiation of continuous renal replacement therapy (CRRT) was 1767 (193–5114) ml. FBcum at CRRT initiation was associated with the time to CRRT initiation from ICU admission (r = 0.67, p < 0.0001) (Supplemental Fig. S2)
Summary
Ill patients often require fluid resuscitation in the early phase of treatment, which can lead to fluid overload and a later need for fluid removal. Several observational studies have shown that fluid overload with coincident acute kidney injury (AKI) is associated with worsening organ dysfunction and increased mortality in critically ill patients and extracorporeal removal of excess fluid using renal replacement therapy (RRT) techniques is associated with reduced m ortality . Severity of illness and need for organ support may be more important determinants of mortality, whereas, fluid balance may serve as a mere surrogate marker In line with this assumption, a recent survey of net ultrafiltration (nUF) prescription in Europe showed that in the occurrence of hemodynamic instability, defined as onset or worsening of tachycardia, hypotension or need to start or increase the dose of vasopressors, 70% of practitioners decreased the rate of fluid removal or even administered fluid boluses. Previous studies have not included multivariable models with repeated measures of disease severity markers such as SOFA score, lactate level or vasopressor requirement during the first days following CRRT initiation as the models have only been adjusted with disease severity at the time of CRRT initiation
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