I know that blood letting has been around 2000 years,

Blood Letting : From the Roman Empire a "barber-surgeon" performed tooth extraction, cupping, leeching, bloodletting, enemas, amputations, etc. The red and white stripes of the barber pole symbolising blood and bandages. The pole itself represents the staff that the patient gripped during the procedure to encourage blood flow, and the twined pole motif is likely related to the Caduceus, the staff of the Greek god of speed and commerce Hermes.

Under Pope Innocent II in 1139, science and religion were seperated (medical practice from ecclesiastics). At the Council of Tours in 1163, the Roman Catholic clergy was banned from the practice of surgery.

Bloodletting as based on an ancient system of medicine in which blood and other bodily fluids were regarded as "humours" that had to remain in proper balance to maintain health. "Humoral balance" was the basis of illness or health, the four humours being blood, phlegm, black bile, and yellow bile. Bloodletting was the most common medical practice performed by surgeons for 2,000 years (from antiquity until the late 19th century ~ 1870). In order to balance the humours, a physician would either remove "excess" blood (plethora being a large or excessive amount of something) from the patient or give them an emetic to induce vomiting, or a diuretic to induce urination. Today's barber poles represent a barbershop that cuts hair and shaves.

https://www.printernational.co.uk/timmann/plasmapheresis.htm