J Burn Care Res. 2022 Apr 11:irac047. doi: 10.1093/jbcr/irac047. Online ahead of print.
Patients with severe thermal injuries have increased metabolic demands necessitating frequent phosphate supplementation. Patients with acute renal failure may have less requirements, due to reduced elimination. However, patients being supported with renal replacement therapy have varying degree of requirements. Little published evidence depicts the incidence of hypophosphatemia and repletion requirements in patients with severe thermal injuries treated with high-volume hemofiltration (HVHF) and a high-flux membrane. The objective of this retrospective chart review was to determine the incidence of hypophosphatemia and characterize repletion requirements and response in this population. Enrolled patients had at least 20% total body surface area (TBSA) thermal injuries and required continuous hemofiltration with prefilter replacement fluid doses ≥ 35 mL/kg IBW/hr. A randomly selected cohort without acute kidney injury (AKI) and matched based on age and extent of TBSA was used to compare phosphorus requirements over an initial 14-day period. Demographics, diet, and variables affecting phosphorus concentrations were collected. Sixteen patients were included in the retrospective HVHF group and sixteen patients in a case-control cohort to better depict the impact of HVHF. The average age was 60.2 ± 15.1 years and median TBSA was 30% (23.4, 56.3) in the HVHF group, compared to 53.3 ± 16.4 years (p = 0.22) and TBSA 29% (26.4, 33.9; p = 0.73). All patients in the HVHF group were started on HVHF with a 1.6 m2 polyethersulfone (PES) membrane for AKI. As expected, the HVHF group exhibited statistically higher than normal baseline potassium and phosphorous laboratory values. The HVHF group experienced more days with hypophosphatemia (49.6 ± 12.4 % vs 29.3 ± 16.3 %, p = 0.012), despite 0.75 mmol/kg/day phosphorous supplementation (compared to 0.66 mmol/kg/day for the control group, p = 0.45). Patients with longer durations of HVHF therapy experienced increasing risk of hypophosphatemia, reaching 100% by the end of the study period. This study demonstrates severe thermally injured patients receiving HVHF for AKI are at increased risk for hypophosphatemia, and require high phosphate supplementation.