One winter’s day in 1933, a young farmer named Ed Carlson drove 200 miles in a blizzard, to the biochemistry building at the University of Wisconsin with a dead cow, a bucket of un-clotted blood and a truckload of old sweet clover. He carried the bucket of blood into the only office that was open, and pleaded with the researcher, one Karl Link, to help him with his dying cattle.
So begins a wonderful story of scientific discovery, Vitamin K, newborn haemorrhagic disease, and of course rat poison (years later, Link was recuperating from tuberculosis in a facility with a rat problem and he got to thinking…) with the eventual development of a drug that has saved countless lives from stroke and DVT over the last 60 years.
I once by chance sat next to a professor of medical history from Wisconsin in a restaurant in New York. He didn’t know any of this. I gave him a short tutorial …
More clinically, although many consider warfarin’s days to be numbered, there are a lot of patients out there who will be on it for years to come, and there’s a fair chance that in the middle of the night, if the anaesthetist does not know how to correctly manage a patient on warfarin, then nobody else in theatre will be able to either.
T/F 3mg intravenous Vitamin K will bring the INR down to 1.4 in 90% of patients within 12 hours
T/F Macrolide administration to a patient on warfarin will invariably make the INR increase to dangerously high levels
T/F Acute increases in the dose of warfarin can cause catastrophic skin necrosis
T/F Reversal of warfarin with Prothrombinex works in 5 minutes but costs 500 times as much as Vitamin K
Peck & Hill has the basic facts on warfarin & reversal.
Australian reversal protocols here: An update of consensus guidelines for warfarin reversal. The Medical Journal of Australia, 198(4), 198–199.2013, Tran, H. A., et al
For those of you with oodles of time, you can read more of the history online here, or here, or in Wardrop & Keeling (2008) – The story of the discovery of heparin and warfarin. British Journal of Haematology, 141(6), 757–763.