13 animal emergencies that should receive immediate veterinary consultation and/or care

1. Severe bleeding or bleeding that doesn't stop within 5 minutes
2. Choking, difficulty breathing or nonstop coughing and gagging
3. Bleeding from nose, mouth, rectum, coughing up blood, or blood in urine
4. Inability to urinate or pass feces (stool), or obvious pain associated with urinating or passing stool
5. Injuries to your pet's eye(s)
6. You suspect or know your pet has eaten something poisonous (such as antifreeze, xylitol, chocolate, rodent poison, etc.)
7. Seizures and/or staggering
8. Fractured bones, severe lameness or inability to move leg(s)
9. Obvious signs of pain or extreme anxiety
10. Heat stress or heatstroke
11. Severe vomiting or diarrhea - more than 2 episodes in a 24-hour period, or either of these combined with obvious illness or any of the other problems listed here
12. Refusal to drink for 24 hours or more
13. Unconsciousness

The bottom line is that ANY concern about your pet's health warrants, at minimum, a call to your veterinarian.

Courtesy of the American Veterinary Medical Association  

Here are several great places to contact in case of an emergency.