Vol.:(0123456789) 1 3 Journal of Nephrology https://doi.org/10.1007/s40620-019-00648-5 REVIEW Hypophosphatemia in critically ill patients with acute kidney injury on renal replacement therapies Valentina Pistolesi 1  · Laura Zeppilli 1,2,3  · Enrico Fiaccadori 4  · Giuseppe Regolisti 4  · Luigi Tritapepe 5  · Santo Morabito 1 Received: 11 July 2019 / Accepted: 6 September 2019 © Italian Society of Nephrology 2019 Abstract 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 specifc 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 appro- priate strategy could be to anticipate the onset of RRT-related hypophosphatemia by implementing the use of phosphate- containing solutions for RRT through specifcally 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 specifc focus on RRT-induced hypophosphatemia. Keywords Acute kidney injury · Critically ill patients · CRRT  · Hypophosphatemia · Phosphate-containing solutions · RRT Introduction Hypophosphatemia is a common electrolyte disorder among critically ill patients, but it is frequently underestimated in the intensive care units (ICUs) [1, 2]. Critical illness exposes patients to an increased risk of developing hypophosphatemia [3, 4] throughout several mechanisms involved in serum phosphate level regulation; indeed, many causal factors are involved, such as volume expansion, drugs, acid–base derangements, refeeding syndrome, sepsis [3, 5]. In patients with severe acute kidney injury (AKI) renal replacement therapies (RRTs) may represent a further risk factor for hypophosphatemia, especially if the most intensive and pro- longed modalities of RRT are used [6–13]. Hypophosphatemia may have a negative impact on patient’ outcomes, with an increase in morbidity and mor- tality [10, 13–16]. Indeed, low phosphate levels can lead to cellular dysfunction with possibly relevant clinical mani- festations involving diferent organs and/or systems (e.g., muscle weakness, respiratory failure, lethargy, confusion, arrhythmias) [3, 16]. Therefore, strategies aimed at reduc- ing the incidence and the severity of hypophosphatemia should be timely implemented in the ICUs. However, no evidence-based specifc guidelines are currently available for the management of hypophosphatemia in this clinical setting [17]. In any case, many protocols for phosphate supplemen- tation by means of intravenous administration of phosphate * Valentina Pistolesi valentina.pistolesi@uniroma1.it 1 UO Dialisi, Azienda Ospedaliero-Universitaria Policlinico Umberto I, “Sapienza” Università di Roma, Viale del Policlinico, 155, 00161 Rome, Italy 2 UOC Nefrologia, Fondazione Policlinico Universitario A. Gemelli IRCCS, Rome, Italy 3 Università Cattolica del Sacro Cuore, Rome, Italy 4 UO Nefrologia, Azienda Ospedaliero-Universitaria Parma, Dipartimento di Medicina e Chirurgia, Università di Parma, Parma, Italy 5 UO Anestesia e Terapia Intensiva in Cardiochirurgia, Azienda Ospedaliero-Universitaria Policlinico Umberto I, “Sapienza” Università di Roma, Rome, Italy