Ultrafiltration Tolerance: A Phenotype That We Need to Recognize

BACKGROUND: The evaluation and management of fluid balance are key challenges in critical care patients who require renal replacement therapies because cumulative fluid balance is an independent factor that increases morbidity and mortality in different clinical scenarios. SUMMARY: One of the strategies when fluid overload is refractory to diuretics is extracorporeal fluid removal (i.e., net ultrafiltration [UFNET] during kidney replacement therapy). However, problems with UFNET without individualized assessment are cardiovascular events and intradialytic hypotension, events that contribute to decreasing organ perfusion and sympathetic stress. Therefore, we must consider and try to predict the best timing for the start of ultrafiltration and find the point where the patient is most tolerant to ultrafiltration, making a simile to the concept of fluid tolerance. KEY MESSAGES: UFNET is a continuous and dynamic process, going through moments of tolerance and intolerance to ultrafiltration; as nephrologists, we must take the necessary measures to move through this period.