Acute kidney injury in polytrauma and rhabdomyolysis

Abstract

The term ‘polytrauma’ refers to blunt (or crush) trauma that involves multiple body regions or cavities, and compromises physiology to potentially cause dysfunction of uninjured organs. Polytrauma frequently affects muscles resulting in rhabdomyolysis. In daily life, it mostly occurs after motor vehicle accidents, influencing a limited number of patients; after mass disasters, however, thousands of polytrauma victims may present at once with only surgical features or with additional medical complications (crush syndrome). Among the medical complications, acute kidney injury (AKI) deserves special mention, since it is frequent and has a substantial impact on the ultimate outcome.Several factors play a role in the pathogenesis of polytrauma (or crush)-induced AKI: (1) hypoperfusion of the kidneys, (2) myoglobin-induced direct nephrotoxicity, and intratubular obstruction, and also (3) several other mechanisms (i.e. iron and free radical-induced damage, disseminated intravascular coagulation, and ischaemia reperfusion injury). Crush-related AKI is prerenal at the beginning; however, acute tubular necrosis may develop eventually. In patients with crush syndrome, apart from findings of trauma, clinical features may include (but are not limited to) hypotension, oliguria, brownish discoloration of urine, and other symptoms and findings, such as sepsis, acute respiratory distress syndrome, disseminated intravascular coagulation, bleeding, cardiac failure, arrhythmias, electrolyte disturbances, and also psychological trauma.In the biochemical evaluation, life-threatening hyperkalaemia, retention of uraemic toxins, high anion gap metabolic acidosis, elevated serum levels of myoglobin, and muscle enzymes are noted; creatine phosphokinase is very useful for diagnosing rhabdomyolysis.Early fluid administration is vital to prevent crush-related AKI; the rate of initial fluid volume should be 1000 mL/hour. Overall, 3–6 L are administered within a 6-hour period considering environmental, demographic and clinical features, and urinary response to fluids. In disaster circumstances, the preferred fluid formulation is isotonic saline because of its ready availability. Alkaline (bicarbonate-added) hypotonic saline may be more useful, especially in isolated cases not related to disaster, as it may prevent intratubular myoglobin, and uric acid plugs, metabolic acidosis, and also life-threatening hyperkalaemia.In the case of established acute tubular necrosis, dialysis support is life-saving. Although all types of dialysis techniques may be used, intermittent haemodialysis is the preferred modality because of medical and logistic advantages. Close follow-up and appropriate treatment improve mortality rates, which may be as low as 15–20% even in disaster circumstances. Polytrauma victims after mass disasters deserve special mention, because crush syndrome is the second most frequent cause of death after trauma. Chaos, overwhelming number of patients, and logistical drawbacks often result in delayed, and sometimes incorrect treatment. Medical and logistical disaster preparedness is useful to improve the ultimate outcome of disaster victims.