Your grandmother’s doctor probably took her off the prescribed blood thinner (warfarin) so that she would not excessively bleed during and after surgery. This is standard practice. If she were to start taking an herbal blood thinner, she may excessively bleed during surgery and the doctor may not be able to stop the bleeding. Follow her doctor’s advice and keep your grandmother off her prescribed blood thinner and don’t substitute anything else to thin her blood unless her doctor recommends it. Make sure your grandmother informs her surgeon of all her medications (prescribed and over the counter) including vitamin, mineral and herbal supplements. Make sure that your grandmother’s tumor surgeon is conferring with her heart surgeon as they may work in different hospitals or clinics.
Vitamin K promotes blood clotting. Ask your grandmother’s doctor if there is any need to limit vitamin K foods pre or post surgery.