Although it frequently looks like a lot of blood, the volume of blood lost during epistaxis usually is not life threatening. Rather, the epistaxis serves as an important marker of an underlying clinical condition that warrants further evaluation. Limit stress and decrease excitability (sedation may be required for this purpose).
Often a blood clot will form and the bleeding will stop on its own. Your veterinarian still should evaluate your pet, but an emergency visit probably is not required. Except when caused by trauma, epistaxis in cats usually is a significant finding that often will recur if a definitive diagnosis is not obtained. Meanwhile, do the following:
Apply cold compresses and direct pressure to help decrease the bleeding.
If the bleeding does not stop, gets worse or if bleeding is observed at other sites, consider it an emergency and call your veterinarian immediately.