Damage control resuscitation (DCR) is a systematic approach to the massively hemorrhaging trauma patient that prioritizes hemostasis and prevention of the lethal triad of trauma: hypothermia, acidosis, and coagulopathy. These three derangements form a self-perpetuating cycle that, if uncorrected, leads to irreversible physiological collapse. Massive hemorrhage triggers a cascade of pathophysiological events. Blood loss reduces circulating volume and oxygen delivery, causing tissue hypoperfusion. Cells shift to anaerobic metabolism, producing lactic acid and hydrogen ions that drive metabolic acidosis (pH < 7.2). Acidosis impairs clotting factor enzyme function — coagulation factors are serine proteases that require optimal pH to catalyze thrombin generation. At pH 7.0, thrombin generation is reduced by approximately 70%. Hypothermia (core temperature < 35°C) develops from exposure during resuscitation, infusion of cold fluids, and loss of metabolic heat production. Hypothermia further inhibits the coagulation cascade — platelet adhesion and aggregation decrease significantly below 35°C, and clotting factor activity drops by approximately 10% for each 1°C decrease. The combination of acidosis, hypothermia, and coagulopathy creates a vicious cycle: coagulopathy worsens hemorrhage, which worsens hypoperfusion and acidosis, which further impairs...