Hypophosphatemia in critically ill patients with acute kidney injury treated with hemodialysis is associated with adverse events

Background. Hypophosphatemia in critically ill patients may be exacerbated by renal replacement therapy (RRT). We aimed to identify risk factors and adverse outcomes associated with hypophosphatemia in intensive care patients treated with RRT for acute kidney injury (AKI). Methods. This was a secondary analysis of data from a single-center prospective cohort study of medical and surgical intensive care patients with RRT for AKI between 18 December 2010 and 3 April 2013. Demographic, comorbidity, laboratory and RRT data were retrieved from patient case notes and electronic medical records. Outcomes assessed were hypophosphatemia (serum phosphate <0.94 mmol/L) during RRT, intensive care unit (ICU) mortality, and duration of mechanical ventilation and vasopressor support. Results. Among 96 patients who received acute RRT, 25 (26.0%) developed hypophosphatemia. On multivariate logistic regression, serum phosphate at RRT initiation [adjusted odds ratio (OR) 0.29, 95% confidence interval (CI) (0.09, 0.91), P = 0.03] was independently associated with hypophosphatemia during acute RRT. Patients with hypophosphatemia during RRT required longer ventilatory support [median 12 (interquartile range: 8, 17) days versus 5 (3, 9) days, P < 0.001] and vasopressor support [5 (4, 15) days versus 2 (2, 6) days, P = 0.003] compared with those without hypophosphatemia but there was no significant difference in ICU mortality [5 patients (20.0%) versus 24 patients (33.8%), P = 0.20]. Hypophosphatemia during RRT was independently associated with prolonged mechanical ventilation (≥7 days) [adjusted OR 14.0, 95% CI (1.37, 143.90), P = 0.03]. Conclusion. Hypophosphatemia is common during acute RRT for critically ill patients and was associated with adverse clinical outcomes.