Influence of traumatic brain injury on potassium and phosphorus homeostasis in critically ill multiple trauma patients

Abstract

Objective The intent of this study was to ascertain whether multiple trauma patients with traumatic brain injury (TBI) had lower serum concentrations of potassium and phosphorus and required more aggressive supplementation than multiple trauma patients without TBI. Methods Ventilator-dependent adult patients without renal impairment who were admitted to the trauma intensive care unit or neurosurgical intensive care unit and who received enteral nutrition were evaluated for the first 14 d after hospital admission. Patients were grouped according to the presence or absence of TBI. Target serum concentrations for potassium and phosphorus were 4 mEq/L and 4 mg/dL, respectively. Electrolyte repletion therapy was given according to the nutritional support service guidelines. Results Fifty trauma patients (25 with and without TBI) were studied. Daily serum potassium concentrations were consistently lower for those with TBI ( P ≤ 0.001), whereas the mean net potassium intake was greater (1.3 ± 0.5 versus 0.7 ± 0.3 mEq · kg −1 · d −1, respectively, P ≤ 0.001). Serial serum phosphorus concentrations were similar between groups ( P = NS) except for a significantly lower serum phosphorus concentration for trauma patients with TBI on day 3 after hospital admission (2.5 ± 0.5 versus 2.9 ± 0.7 mg/dL, respectively, P ≤ 0.05). However, the mean net phosphorus intake was significantly greater for trauma patients with TBI (0.65 ± 0.25 versus 0.45 ± 0.17 mmol · kg −1 · d −1, P ≤ 0.001). Conclusion Potassium and phosphorus requirements are greater for multiple trauma patients with TBI compared with those without TBI.