This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Surgery
[{'content': 'Blood loss during major surgery is best estimated by - \nSelect and explain. \nA. Visual assessment, B. Suction bottles, C. Transesophageal USG Doppler, D. Cardiac output by thermodilution', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Blood\xa0loss during operation is measured by -\nWeighing the swabs after use and subtracting the dry weight +\xa0Volume of blood collected in suction or drainage\nThis is\xa0k/a Gravimetric method of estimation\xa0of blood\xa0loss', 'role': 'assistant'}]