Triangle of death: Hypothermia, acidosis, and coagulopathy

Clinical studies have demonstrated a uniformly detrimental effect of hypothermia in trauma. Hypothermia occurs commonly in severely injured patients and is caused by a combination of accelerated heat loss and decreased heat production. Although current modalities for the treatment hypothermia may be inefficient, such as increasing the ambient temperature, these modalities do impart a limited amount of heat to the patient; more importantly, these measures decrease ongoing heat loss. Although recognized as a consequence of shock, acidosis is a potent vasodilator, decreasing vascular resistance to ischemic tissue beds and increasing oxygen delivery. Because of these adaptive benefits, treatment of acidosis should focus on correctig the source of shock rather than the acidosis. Administration of exogenous bicarbonate not only fails to treat the underlying cause of hypoperfusion but is also detrimental by creating an adverse shift of the oxyhemoglobin dissociation curve and may actually worsen intracellular acidosis. Exogenous bicarbonate therapy will also preclude the use of base deficit as a guide to resuscitation. The coagulopathy that accompanies hypothermia and acidosis completes the 'triangle of death.' While the cause of this coagulopathy is multifactorial, the most important determinants of developing and treating this coagulopathy are hypothermia and the degree and duration of shock. This coagulopathy is usually resistant to blood product transfusion until the hypothermia and hypoperfusion are corrected. Since the coagulopathy is determined more by the degree of shock and hypothermia, efforts should be directed to correcting the source of shock, improving perfusion, and rewarming. Prophylactic transfusion of fresh-frozen plasma and platelets is unwarranted. With the recognition of the triangle of death, abbreviated Emergency Department evaluations and operative procedures have been instituted. Blunt trauma patients with injury patterns, such as a temperature of <32°C and >20 units of blood transfusion, previously experienced a 100% mortality rate; now, these patients survive with a damage control approach and cognitive judgement.