Three hours following a lengthy, complicated surgery secondary to extensive crush injuries, a 34-year-old man is found to have confusion, acute dyspnea, scattered petechial hemorrhages, and profuse bleeding from the surgical site. What is the most likely pathogenesis behind these clinical findings?
(A) acute idiopathic thrombocytopenic purpura
(B) disseminated intravascular coagulation
© hemolytic uremic syndrome
(D) hypovolemic shock
(B) The pathogenesis of this constellation of clinical findings is due to disseminated intravascular coagulation (DIC), most likely occurring secondary to the combination of this patient’s crush injuries and subsequent surgery. DIC occurs via two main mechanisms—as a result of diffuse endothelial damage, as in cases of infectious disease, such as gram-negative sepsis (e.g., meningococcemia; also, rickettsial, fungal infections), or by release of tissue factor (a procoagulant factor synthesized by the endothelium) or other thromboplastic substances, into the bloodstream (e.g., amniotic fluid embolism; fat embolism, snake venom; acute promyelocytic leukemia; mucinous carcinomas, etc.); burns can initiate DIC via either mechanism. In massive trauma, burns, or extensive surgery, traumatized tissue is believed to release tissue thromboplastins into the circulation which then trigger DIC. Release of thrombogenic stimuli into the circulation activates the coagulation cascade, via either the extrinsic or intrinsic pathway, resulting in the formation of small thrombi and emboli throughout the microcirculation. Widespread thrombotic diathesis results in the consumption of coagulation factors, fibrinogen, and platelets, which secondarily leads to hemorrhage. Activation of the fibrinolytic system generates fibrin degradation products, which also possess anticoagulant properties and thus help to exacerbate the bleeding tendency. Deposition of fibrin within the microvasculature may also lead to a microangiopathic hemolytic anemia, resulting from fragmentation of RBCs as they squeeze through the thrombi. Apatient with DIC may present with a range of signs and symptoms, from diffuse ischemia, thrombosis, and microinfarctions in the thrombotic phase, to skin, mucosal, and internal bleeding in the hemorrhagic phase. Clinical manifestations are numerous, but may include dyspnea, severe respiratory distress, neurological signs including convulsions and coma, cerebral hemorrhage, acute renal failure, and circulatory failure. None of the other choices offered fit this clinical scenario. Acute idiopathic thrombocytopenic purpura (choice A) is typically seen in young children following a history of a viral infection and is caused by immune complexes that bind to platelets and induce a transient thrombocytopenia; most patients recover in 4–6 weeks, and 90% recover within 6 months. Presenting symptoms are typically limited to purpura or petechiae. Hemolytic uremic syndrome (choice C) also occurs in children, and onset is again often associated with a preceding
viral illness; an immune-complex mediated cause has been proposed. In this disorder, thrombi deposition is localized to the kidney. Patients present with thrombocytopenia, microangiopathic hemolytic anemia, hypertension, and varying degrees of renal failure. While severe hypoxia may potentially be associated with hypovolemic shock (choice D) and therefore account for this patient’s confusion and acute dyspnea, it cannot explain his petechial hemorrhages or profuse bleeding. Likewise, rhabdomyolysis (choice E), the destruction of skeletal muscle with accompanying release of myoglobin into the circulation, may certainly have occurred in this case secondary to the patient’s crush injuries; however, it is associated with myoglobinuria and acute renal failure, and not with the constellation of signs and symptoms given here.