A small amount can make a difference: a prospective human study of the paradoxical coagulation characteristics of hemothorax.

BACKGROUND: The evacuated hemothorax has been poorly described because it varies with time, it has been found to be incoagulable, and its potential effect on the coagulation cascade during autotrans- fusion is largely unknown. METHODS: This is a prospective descriptive study of adult patients with traumatic chest injury ne-cessitating tube thoracostomy. Pleural and venous samples were analyzed for coagulation, hematology, and electrolytes at 1 to 4 hours after drainage. Pleural samples were also analyzed for their effect on the coagulation cascade via mixing studies. RESULTS: Thirty-four subjects were enrolled with a traumatic hemothorax. The following measured coagulation factors were significantly depleted compared with venous blood: international normalized ra-tio (>9 vs 1.1) (P < .001) and activated partial thromboplastin time (aPTT) (>180 vs 24.5 seconds) (P < .001). Mixing studies showed a dose-dependent increase in coagulation dilutions through 1:8 (P < .05). CONCLUSIONS: An evacuated hemothorax does not vary in composition significantly with time and is incoagulable alone. Mixing studies with hemothorax plasma increased coagulation, raising safety concerns. [ABSTRACT FROM AUTHOR]