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Background: Accurate risk stratification may help reduce the burden of excessive blood loss after cardiac surgery. We measured the incremental value of thrombelastography to an existing risk prediction model for excessive blood loss in cardiac surgery., Methods: This observational study included 434 patients who underwent cardiac surgery with cardiopulmonary bypass (CPB) and had thrombelastographic measures before and during CPB, their risk of excessive blood loss could be calculated with an existing risk prediction model and they had not received clopidogrel or warfarin within 5 days of surgery. Excessive blood loss was defined as transfusion of > or = 5 U of red blood cells from termination of CPB to 1 day after surgery. Logistic regression models including an existing risk prediction model without and with thrombelastographic measures were constructed. Improvement in risk prediction was measured by the area under the curve and net reclassification improvement., Results: Excessive blood loss occurred in 59 of 434 patients (13.6%). The only thrombelastographic measure that improved risk stratification was maximum amplitude during CPB, which reflects maximum clot strength. Although the addition of this variable to the existing prediction model did not have a material effect on the area under the curve (increased from 0.780 to 0.784; P = 0.8), it did improve the net reclassification improvement by 12% (P = 0.05), primarily by improving the detection of high-risk cases., Conclusions: Risk stratification for excessive blood loss after cardiac surgery is improved when on-CPB thrombelastography is added to an existing risk prediction model that incorporates readily available patient- and surgery-related variables, but large, multicenter trials are needed to verify this finding and create a new risk prediction model.

Objective: Recombinant activated factor VII (rFVIIa) is being increasingly used in cardiac surgical patients with refractory hemorrhage. In this study, the authors assessed the ability of thromboelastography (TEG) in guiding rFVIIa therapy in this setting., Design: Retrospective study., Setting: Tertiary care university hospital., Participants: Thirty-eight consecutive patients who received rFVIIa for refractory hemorrhage after cardiac surgery and had a complete coagulation profile including TEG within 30 minutes before and after rFVIIa., Interventions: Standard coagulation (prothrombin time, partial thromboplastin time, platelet number, and fibrinogen) and TEG measurements (r time, k time, alpha angle, and maximum amplitude) before and after rFVIIa therapy were compared between responders and nonresponders (determined retrospectively based on clinical records)., Measurements and Results: Twenty-eight patients (74%) were classified as responders. There were no consistent changes in standard coagulation and TEG measurements before and after rFVIIa therapy. The number of abnormalities in pretreatment coagulation tests was related to response rates; odds of response were 11-fold (95% confidence interval [CI]) and 33-fold (95% CI) greater among patients with 0 or 1 abnormality in standard coagulation tests and TEG measures, respectively, than those with 2 or more abnormalities., Conclusions: TEG may be a useful tool for predicting response to rFVIIa in the setting of refractory hemorrhage after cardiac surgery.

Purpose: Thromboelastography (TEG) evaluates the visco-elastic properties of whole blood to assess clot formation and hemostasis. When blood cannot be analyzed immediately, it is stored in citrated tubes to be analyzed after recalcification. In this study, we evaluated the results of TEG analysis performed on citrated blood and compared these results to values obtained from activated (kaolin and tissue factor) and non activated, fresh blood samples, obtained at various time intervals (one, two, and three hours)., Methods: Four blood samples were collected from each of ten healthy volunteers. The following TEG analyses were performed on each sample: reaction time (r), k time (k), alpha angle (alpha), and maximum amplitude (MA). Studies were done using fresh, non citrated blood, obtained within five minutes of collection, and using citrated blood, one, two, and three hours after collection. Samples were analyzed, with and without activation, using kaolin and tissue factor., Results: Tissue factor activated and non activated, citrated samples had shorter r and k times (P=0.03, P=0.008, P<0.0001, and P<0.0001, respectively) and higher alpha angle and MA values (P<0.0001, P<0.0001, P=0.79, and P=0.03, respectively) compared to fresh, non citrated samples. These findings were consistent with a hypercoagulable state. Conversely, citrated samples, activated with kaolin, yielded results similar to those obtained from fresh, non citrated samples. The TEG measurements were similar among citrated samples stored from one to three hours., Conclusions: Our results demonstrate that TEG measures, performed on citrated blood samples, yield results that are consistent with a hyperocoagulable state. Using kaolin to activate citrated samples, on the other hand, yields results similar to those obtained from non citrated, fresh blood samples.

Use of cardiopulmonary bypass in cardiac surgery strongly influences haemostatic system, activating fibrinolysis as well. The widespread use of antiplatelet and fibrinolytic drugs creates haemostatic disturbances in the perioperative period. Thromboelastography seems to be a useful tool in the assessment of this complex process, particularly in the early postoperative period.