Three days after operation , the change of hemoglobin was ( 46.00 13.29 ) g/L and total blood loss was ( 1,304.72 421.75 ) ml ; while in low negative pressure drainage group , the changes of hemoglobin was ( 43.87 11.39 ) g/L and total blood loss was ( 1,196.78 344.20 ) ml ; there were no statistically significant differences between two groups .