Disseminated intravascular coagulation (DIC) is a disease process in which the entire coagulation pathway undergoes activation. All critically ill patients undergo some degree of coagulation activation due to inflammation and hemodynamic changes. In some cases, the balance of anticoagulations and procoagulants is tipped in favor of procoagulants, leading to DIC. No single laboratory test defines DIC, and there is no gold standard for diagnosis. Laboratory assays allow practitioners to define the state of the disease and assess the risk of bleeding and thrombosis. Table 98-1 lists laboratory values that assist in the diagnosis and management of DIC.
TABLE 98-1Laboratory Test in the Diagnosis and Management of DIC ||Download (.pdf) TABLE 98-1 Laboratory Test in the Diagnosis and Management of DIC
|Laboratory Test ||System Tested ||Acute DIC ||Chronic DIC ||Confounding Physiologic State |
|Activated partial thromboplastin time (aPTT) ||Coagulation (intrinsic pathway) ||Increased ||Normal ||Liver disease, anticoagulant therapy |
|Prothrombin time ||Coagulation (extrinsic pathway) ||Increased ||Normal ||Liver disease, anticoagulant therapy |
|Specific coagulation factors ||Coagulation (intrinsic/extrinsic pathway) ||Decreased ||Normal ||Hemophilia |
|Platelet count ||platelet number (not function) ||Decreased ||Increased/decreased ||Splenomegaly, sepsis |
|Fibrin split products ||Fibrin Degradation ||Increased ||Increased ||Pulmonary embolism |
|D-dimer ||Fibrin Degradation ||Increased ||Increased ||Pulmonary embolism |
|Antithrombin III ||Intrinsic anticoagulation ||Decreased ||Increased/decreased || |
|Protein C ||Intrinsic anticoagulation ||Decreased ||Increased/decreased || |
The International Society of Thrombosis and Haemostasis has devised a diagnostic algorithm for DIC (Figure 98-1). A score of 5 or more carries a 93% sensitivity and 98% specificity for development of acute DIC. The scoring system also correlates with severity and can predict mortality in patients with sepsis. It is important to recognize, diagnose, trend, and treat DIC because clinical studies suggest an increased risk of morbidity and mortality associated with its diagnosis—this is how DIC has earned the alias “Death is Coming.”
Algorithm for the diagnosis of DIC. (Reproduced with permission from Taylor FB Jr, Toh CH, Hoots WK, et al. Towards definition, clinical and laboratory criteria, and a scoring system for disseminated intravascular coagulation. Thromb Haemost. 2001 Nov;86(5):1327-1330.)
DIC is a microangiopathic hemolytic anemia, so one may also find the classic schistocytes on peripheral smear. Thromboelastogram (TEG) analysis is a useful tool for assessing the progress of acute DIC. There are two classic TEG results for a patient with DIC. “Early” DIC will yield a shortened reaction plus clotting time (R + K time) and shortened lysis time (L time) due to the hypercoaguable state. “Late” DIC occurs after consumption of coagulation factors and yields a long R + K time and decreased maximum amplitude (mA) due to a decrease in platelets (Figure 98-2). Trending laboratory values (e.g., every 2 hours) allows the practitioner to estimate the trajectory of the disease and predict impending complications. In acute DIC, repeated measures ...