The debate about how much blood to remove from a patient is not of recent origin. Galen proposed that for the safety of patients, the first bloodletting be kept to a minimum. He indicated that the most blood to be taken should be limited to one and one-half pounds. Avicenna, who lived from 980 to 1037 CE, believed that the total amount of blood in a man was 25 pounds and that one could still live even after a loss of 20 pounds. In the 18th and 19th centuries, the standard advice to bloodletters was to “bleed to syncope.” In today’s understanding of the term, it would mean to bleed the patient until the patient nearly goes into shock.
