Better AKI Patient Survival Linked to Negative Fluid Balance
The mortality rate among patients with negative fluid balance was just 7.4%, compared with 43.5% for patients with a positive fluid balance.
Optimal fluid management of critically ill patients with or at risk for acute kidney injury (AKI) is still uncertain. Now a new prospective study from India confirms that patients with negative fluid balance live longer.
Anup P. Chaudhari, MD, of Lilavati Hospital and Research Centre in Mumbai, and colleagues examined fluid balance and other clinical and laboratory data for 130 adult patients with or at risk for AKI from the intensive care unit (ICU) through discharge, 60 days after admission, or death within 60 days of hospital discharge, whichever occurred first. Most had injury or failure by RIFLE criteria. The investigators calculated daily fluid balance as the difference between fluids given (i.e., intravenous, blood, enteral, and renal replacement fluids) and fluids lost through ultrafiltrate from renal replacement therapy (RRT), urine, and drainage.
According to results published in the Iranian Journal of Kidney Diseases, 48.2% of patients had a positive mean daily fluid balance and 52.8% had a negative balance. On average, positive daily fluid balance was 533 mL and negative, -223.8 mL.
Patients with a positive fluid balance fared worse: They had a longer ICU stay and more often required mechanical ventilation and inotrope, and for longer periods. Most importantly, mortality was significantly higher: 43.5% vs 7.4%. The investigators similarly determined that negative fluid balance was independently associated with reduced mortality, ICU stay, and need for ventilator and RRT.
Accumulating research has questioned aggressive fluid administration. Dr Chaudhari and the team cited studies associating positive fluid balance with poor outcomes in general populations, lung patients (Am Rev Respir Dis. 1992;145:990-998 and Intensive Care Med. 2005;31:1643-1647), and those with septic shock (Chest 2000;117:1749-54 and Crit Care Resusc. 2004;6:12-16). A 2015 Chinese study by Na Wang and colleagues, which was not cited by the investigators, similarly found that fluid overload was associated with both AKI and mortality (Crit Care. 2015; 19:443).
“The consistent association between a positive FB and unfavorable outcome suggests the need to exert prudence with fluid administration in patients with AKI,” Dr Chaudhari and colleagues stated.
The researchers also noticed that RRT started early after ICU admission was associated with better outcomes, in agreement with recent research.
The current study was limited by the small number of participants and lack of a control group without AKI.