2．血胸

Hemothorax

血胸とは胸膜腔への血液貯留であり，胸腔内貯留液のHt値が末梢血の50％を超える場合をいう1）．胸腔内への出血量とその速度によって症状と重症度が異なる．大量血胸では胸腔内圧の上昇と胸腔内臓器の圧迫をきたし，低心拍出量（循環不全）と低酸素血症（呼吸不全）が同時に進行するため，心停止のおそれがある切迫した状況となる．

Hemothorax is defined as blood accumulation in the pleural cavity with a hematocrit value of the effusion exceeding 50％. Symptoms and severity vary, ranging from asymptomatic to an imminent state of threatened cardiac arrest. This paper presents the etiology, initial work-up, and treatment of hemothorax, with an emphasis on massive hemothorax requiring an emergent thoracotomy for hemostasis. The etiology of hemothorax can be traumatic, iatrogenic, and non-traumatic/non-iatrogenic. Regardless of the etiology, the initial medical examination should be performed as in the initial trauma examination to evaluate the urgency, the amount of bleeding in the chest cavity, and the coexistence of pneumothorax. If massive hemothorax or tension pneumothorax is present, thoracic tube drainage should be started immediately. Contrast-enhanced computed tomography （CT） should be performed to identify the source of bleeding. Treatment includes fluid and blood transfusions to stabilize the circulation. Anticoagulants and antiplatelet agents should be neutralized, reduced, or withdrawn. Emergent thoracotomy for hemostasis is indicated for massive hemothorax with unstable circulation. Anterior-parasternal thoracotomy performed in the supine position has the advantage of rapid thoracotomy and good visualization. Endovascular therapy is effective when contrast-enhanced CT identifies the source of bleeding.