Thursday, October 2, 2008
Leeches, Hirudin and Life Saving Dialysis
Approximately 1 in 10,000 people in Western industrialized countries relies on dialysis to replace impaired kidney function or kidney failure. The more than 300,000 Americans, and 30,000 Canadians, who have their blood cleaned of toxins and metabolic waste, can thank leeches for the invention of this life-saving treatment. Georg Haas pioneered experimental dialysis treatments on animals at the University Hospital of Internal Medicine in Geising Germany. Preventing blood from clotting in the dialysis tubes was (and still is) critical to the success of the procedure. All of Haas' early experimental work was accomplished using crude leech extracts to prevent clotting. Unfortunately, the unpurified extracts proved toxic and leeches were hard to come by in light of over-exploitation during the latter half of the 19th century. Haas suspended his experiments during WWI until he learned, from the Father of American Pharmacology, John J. Abel at Johns Hopkins in Baltimore, of the availability of purified hirudin (the anti-thrombin from Hirudo medicinalis seen at right here). Haas performed the first human dialysis treatment in 1924 using this newly available purified hirudin. Expensive, hirudin would be supplanted by the wide availability of heparin in the next 3 years. Heparin is still used in dialysis treatments. Recently, at least 80 people were killed as a result of world heparin supplies being intentionally contaminated with cheaper chondroitin sulfate. It was another 20 years after Haas' bold move before Willem Kolff invented the first dialysis machine and 20 more before Belding Scribner opened the world’s first outpatient dialysis facility at the University of Washington Medical School.