An experimental model of hemothorax autotransfusion: impact on coagulation.

BACKGROUND Traumatic hemothorax (HTX) has been demonstrated to predictably contain low fibrinogen, low hematocrit, and low platelet counts. When analyzed on its own, shed HTX demonstrates coagulopathy. However, when mixed with normal pooled plasma (NPP) at physiologically relevant dilutions, HTX demonstrates accelerated coagulation. We hypothesize that when HTX is mixed with a patient's own plasma, the mixture will demonstrate hypercoagulability. The accelerated coagulation of this mixture would have important implications for the autotransfusion of HTX as a method of resuscitating a trauma patient. METHODS Adult trauma patients from whom greater than 140 mL of HTX was evacuated within 1 hour of tube thoracostomy were included. HTX was sampled at 1 hour after evacuation, and a portion of the sample was centrifuged and stored as frozen plasma for later analysis. The remainder of the sample was analyzed (coagulation, hematology, electrolytes), and values were compared with concurrent venous values extracted via chart review. A citrate tube containing the patient's venous blood was additionally spun down and frozen for subsequent mixing study analysis. Coagulation was further evaluated by mixing serial dilutions of the previously frozen HTX with NPP. Additionally, the previously frozen HTX was mixed in serial dilutions with the previously frozen sample of patient plasma (PTP). RESULTS Subjects (10) were enrolled based on inclusion criteria and collection of a discarded venous sample. In HTX samples analyzed alone, no thrombus was formed in any coagulation test (activated partial thromboplastin time [aPTT] > 180). The median aPTT value of PTP alone was 25.5. In 1-hour specimens mixed at a clinically relevant dilution of 1:4, HTX mixed with NPP had a mediana PTT value of 26.0, whereas HTX mixed with PTP had a median aPTT value of 21.7. Thus, the mixture of HTX + PTP demonstrated a statistically significantly lower aPTT than the mixture of HTX + NPP (P = 0.01). Additionally, the mixture of HTX and PTP shows a statistically significantly lower aPTT value than PTP alone (P = 0.03), indicating a hypercoagulable state. CONCLUSIONS HTX demonstrates coagulopathy when analyzed independently, but is hypercoagulable when mixed with NPP or PTP. Furthermore, mixing studies show a statistically significantly lower aPTT when HTX is mixed with PTP versus HTX mixed with NPP. Thus, autotransfusion of HTX would likely produce a hypercoagulable state in vivo, and should not be used in place of other blood products to resuscitate a trauma patient. The autotransfusion of HTX may, however, be of use in a resource-limited environment where other blood products are not available.