Only some septicaemic patients develop hypernatremia in the burn intensive care unit: why?

From April 1993 to January 2000, 105 patients in the burn intensive care unit (BICU) that developed septicaemia in the course of their treatment were studied retrospectively to investigate as to why only 36 septicaemic patients (34%) developed hypernatremia (serum sodium >150mmol/l). Septicaemic burn patients who developed hypernatremia were found to have a higher incidence of inhalation injury and a larger burn area (TBSA) signifying greater free water losses in the face of increasing fluid requirements. Patients who developed hypernatremia showed a characteristic pattern of septicaemia: early onset, multiple episodes, polymicrobial, need for multiple antibiotics, longer duration and a higher mortality, indicating a more severe degree of sepsis. The level of incapacitation either from the burn itself, mechanical ventilation or from impaired mental status leading to an inadequate free water intake was more in septicaemic patients who developed hypernatremia. Increased urinary free water losses and solute diuresis from hyperglycemia were significant factors in the development of hypernatremia. Patients who were treated with early wound excisions were less prone to develop hypernatremia when compared to those who did not undergo early wound excision. The close association between the onset of hypernatremia and the onset of septicaemia noted in this study suggests the use of hypernatremia as a marker for septicaemia in burn patients. Hypernatremia in a septicaemic burn patient is multi-factorial and a thorough understanding of the underlying factors will help prevent the onset and progress of hypernatremia.