Predicting a strongly positive fluid balance in critically ill patients with acute kidney injury: A multicentre, international study.

Background: In critically ill patients with acute kidney injury (AKI), a fluid balance (FB) > 2 L at 72 h after AKI diagnosis is associated with adverse outcomes. Identification of patients at high-risk for such fluid accumulation may help prevent it.

Methods: We used Australian electronic medical record (EMR)-based clinical data to develop the "AKI-FB risk score", validated it in a British cohort and used it to predict a positive FB >2 L at 72 h after AKI diagnosis.

Results: We developed the AKI-FB score in 32,030 patients with a median age of 63 years and a median APACHE 2 score of 16. We validated it in 4465 patients, with significant differences in admission diagnoses and interventions. The key score variables were admission after trauma, sepsis or septic shock, and, on the day of AKI diagnosis, highest creatinine, daily cumulative FB, mechanical ventilation, noradrenaline use, noradrenaline equivalent dose >0.07 μg/kg/min, lactate ≥2 mmol/L, transfusion, and nutritional support. A score threshold of 32 had a sensitivity of 75 % and a specificity of 72 % for predicting a > 2 L positive FB with an AUC-ROC of 0.805; 95 % CI 0.799 to 0.810. External validation demonstrated an AUC of 0.761 (95 % CI 0.746 to 0.775).

Conclusion: We developed and validated the "AKI-FB risk score" to predict patients who developed a positive FB >2 L within 72 h of AKI diagnosis. This prediction score was robust and facilitated the identification of high-risk AKI patients who could be the tarted for preventive measures and be included in future clinical trials of FB management.