We present a patient with pseudothrombocytopenia undergoing abdominal aortic aneurysm repair under cardiopulmonary bypass, for whom TEG6s was used to assess intraoperative coagulation and hemostatic function. Platelet aggregation was found in preoperative sampling tubes containing ACD, which was also expected to occur in ACD containing tubes to examine TEG6s. However, the intraoperative results of TEG6s were compatible with results in patients who have normal platelet function, and therefore, transfusion of platelet was avoided. TEG6s may have a role for assessing coagulation and hemostatic function during cardiovascular surgery. Successful use of TEG5000 during coronary bypass surgery for a patient with citrate associated pseudothrombocytopenia was reported , but non-citrated blood samples were used in this case. To the best of our knowledge, this is the first case report using TEG6s in a patient with pseudothrombocytopenia.
The incidence of pseudothrombocytopenia in adults is 0.9% to 2%. Pseudothrombocytopenia may be related to malignancy, myeloma, autoimmune disease, liver disease, cardiovascular disease, sepsis, and the use of certain medications . Although the mechanism is not fully understood, the presence of anticoagulant-dependent anti-platelet autoantibodies may induce platelet clumping , which is frequently observed in EDTA containing blood samples. Other anticoagulants (citrate, heparin, and oxalate) have also been implicated in the disease, while in 52% of the cases, no apparent causes are identified . To determine the actual platelet count, examination of a peripheral blood smear is required. For intraoperative assessment of the platelet count, using non-agglutinating blood collection tubes is recommended . In this patient, platelet aggregation developed in all blood sample tubes for preoperative evaluation, and platelet aggregation had been expected with citrated blood samples for intraoperative TEG6s.
Four different assays can run simultaneously on the TEG6s within 10 min. RapidTEG, one of the four assays, is an accelerated assay with tissue factor and kaolin for activation of both extrinsic and intrinsic coagulation pathways. In these assays, the maximum amplitude is the point at which the clotting intensity is maximized, reflecting eventual maximal platelet-fibrin interaction via the GPIIb/IIIa receptor. The blood is pipetted into TEG6s cartridges, which accept either citrated or heparinized blood samples. In this patient, citrate-related antibodies against platelet membranes might have been present in the blood samples used for TEG6s, and the results of maximum amplitude might have been affected. However, the results were compatible with results in people with normal platelet function, while the platelet count was simultaneously low when measured by a standard laboratory analyzer.
For patients with pseudothrombocytopenia, in vitro platelet agglutination may progress over time . In this patient, the preoperative platelet count measured by the rapid test was higher than by the standard EDTA or ACD tests (Table 1), suggesting time-dependent platelet aggregation. We performed the TEG6s test expeditiously after blood collection, and therefore, the effect of platelet aggregation on the results of TEG6s was minimized.
Among four different assays of the TEG6s, the citrated functional fibrinogen assay, a method to quantify fibrin polymerization, may not be reliable since the effects of anticoagulant-dependent anti-platelet autoantibodies on GIIb/IIIa inhibitor or GPIIb/IIIa receptors are unclear. In this patient, the maximum amplitude of the citrated functional fibrinogen and serum fibrinogen levels after protamine administration showed adequate coagulation status (Table 1). Adequate hemostasis was also obtained at the operating field. These results suggest that significant platelet agglutination was avoided by expeditious TEG analysis or that no significant interaction was present between the autoantibodies and GIIb/IIIa inhibitors/receptors.
By performing TEG6s analysis, surgical repair of an abdominal aortic aneurysm under cardiopulmonary bypass was successfully performed for a patient with pseudothrombocytopenia. During the surgery, coagulation and hemostatic function evaluated by TEG6s was consistent with clinical findings, not with the platelet count by standard laboratory testing. As a point-of-care test, prompt TEG analysis may have avoided significant citrate-associated platelet aggregation. The reliability and usefulness of TEG6s for patients with pseudothrombocytopenia needs further evaluation with a larger sample of patients undergoing surgery with an associated elevated bleeding risk.