A study of the lethal effects of intravenous injection of thrombin in rabbits

Thrombin can stop bleeding during ophthalmic surgery by directly converting fibrinogen to fibrin. Little attention has been given to the potential risk of inadvertent intravenous administration of thrombin causing massive intravascular coagulation. We injected rabbits with a dose of thrombin, adjusted for body weight, equivalent to the amount used in ocular surgery. We also studied the effects of treating the rabbits with heparin. The rabbit injected with thrombin alone died within 30 seconds due to total intravascular coagulation. Three additional rabbits injected with thrombin but treated with heparin (intraperitoneally 40 minutes before thrombin, intravenously 30 minutes before thrombin, and intravenously immediately after thrombin injection) survived without any ill effects noted over the next month. For extraocular cases we recommend color coding the thrombin with some methylene blue. Using an eye dropper, rather than a syringe, reduces the chance of intravascular injection.