Hyperkalemia in Combat Casualties: Implications for Delayed Evacuation.

Objective: Fixed facilities and rapid global evacuation ensured that delayed complications of trauma, such as hyperkalemia, occurred late in the evacuation chain where renal replacement therapies were available. However, future conflicts or humanitarian disasters may involve prolonged evacuation times. We sought to quantify one potential risk of delayed evacuation by assessing hyperkalemia in combat casualties.

Methods: Retrospective study of military members admitted to intensive care units in Iraq and Afghanistan from February 1, 2002, to February 1, 2011. This study was approved by the U.S. Army Medical Research and Materiel Command Institutional Review Board. Demographics, injury severity score, burn injury, mechanism of injury, vital signs, creatinine, and potassium were collected. Logistic regression models were used to identify incidence and risk factors for hyperkalemia.

Results: Of 6,011 patient records, 1,472 had sufficient data to be included for analysis. Hyperkalemia occurred in 5.8% of patients. Those with hyperkalemia had higher injury severity scores, higher shock index, were more likely to have acute kidney injury, and were more likely to die. On multivariate analysis, acute kidney injury and shock index were significantly associated with the development of hyperkalemia. In a subgroup of patients with data on creatine kinase, rhabdomyolysis was associated with hyperkalemia in the univariate model, but was not significant after adjustment.

Conclusion: Hyperkalemia occurred in 5.8% of patients in our cohort of critically injured combat casualties. The development of hyperkalemia was independently associated with acute kidney injury and shock index. In future conflicts, with prolonged evacuation times, mitigation strategies should be developed to treat hyperkalemia in casualties before arrival at definitive care.