In high negative pressure drainage group , the change of hemoglobin was ( 41.74 15.69 ) g/L , total blood loss was ( 1,217.73 459.50 ) ml and the drainage volume was ( 312.94 103.44 ) ml ; while in low negative pressure drainage group , the results were ( 34.90 12.90 ) g/L , ( 904.01 381.58 ) ml and ( 129.25 44.25 ) ml separately .