Hypophosphatemia in critically ill patients with acute kidney injury on renal replacement therapies

Hypophosphatemia is a common but often underestimated electrolyte derangement among intensive care unit (ICU) patients. Low phosphate levels can lead to cellular dysfunction with potentially relevant clinical manifestations (e.g., muscle weakness, respiratory failure, lethargy, confusion, arrhythmias). In critically ill patients with severe acute kidney injury (AKI) renal replacement therapies (RRTs) represent a well-known risk factor for hypophosphatemia, especially if the most intensive and prolonged modalities of RRT, such as continuous RRT or prolonged intermittent RRT, are used. Currently, no evidence-based specific guidelines are available for the treatment of hypophosphatemia in the critically ill; however, considering the potentially negative impact of hypophosphatemia on morbidity and mortality, strategies aimed at reducing its incidence and severity should be timely implemented in the ICUs. In the clinical setting of critically ill patients on RRT, the most appropriate strategy could be to anticipate the onset of RRT-related hypophosphatemia by implementing the use of phosphate-containing solutions for RRT through specifically designed protocols. The present review is aimed at summarizing the most relevant evidence concerning epidemiology, prognostic impact, prevention and treatment of hypophosphatemia in critically ill patients with AKI on RRT, with a specific focus on RRT-induced hypophosphatemia.