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Sam is a 5 year old domestic medium haired cat who presented to us last week with a history of having been attacked by neighborhood dogs. On presentation, Sam was depressed and shocky. He had poor perfusion to his gums and was having difficulty walking. His fur was wet with dog saliva and on close inspection, we found that he had multiple superficial bite marks, but fortunately, no deep puncture wounds. His breathing was rapid and slightly labored. We took radiographs (x-rays) of the chest and belly to look for internal injury. On the chest films, we found 2 ribs had been broken but the lungs were not injured. There was no evidence of other fractures noted.
We took blood to look for evidence of internal organ damage and found no gross abnormalities. We initiated treatment for shock (fluid therapy, steroids, pain medication and antibiotics) placed Sam in an incubator and notified the owner that we would have to re-evaluate Sam's condition the next morning.
The next day, Sam was depressed and not very responsive. He could barely use his back legs indicating that some damage must have occurred to the spinal cord when the dog was shaking him. His gums were pale so we checked his blood count and his packed cell volume (pcv = the percent of blood made up of red blood cells) had dropped from a normal value of 38% on admission to 22%! Since Sam had been in the dog fight we assumed that he must be bleeding internally to lose that much blood overnight. We performed ultrasound of the abdomen and could find no evidence of internal bleeding. Repeated chest radiographs did not show any bleeding in the lungs or chest cavity. We checked the stool and there was no evidence of gastro intestinal bleeding either.
Since we had no evidence of active bleeding, we had to assume that the body was destroying the red cells in a process known as Auto Immune Hemolytic Anemia. In this syndrome, the immune system begins to recognize the blood cells as "foreign" to the body and then destroys them as if they were invaders. In order to successfully treat this syndrome, we must depress the immune system with immunosuppressive drugs. If we stop the destruction of red cells, then the body will usually make new cells within days. We started Sam on prednisone (a corticosteroid) and cyclosporine to hopefully depress the immune system. Since he had not eaten in days, we sedated him and placed an esophagostomy tube (flexible tube placed through the skin in the neck, into the esophagus) to allow us to feed him and administer medications easily.
Unlike on TV medical shows, the response to drugs does not happen in minutes, but can take days. The following day, Sam's blood count dropped to 15%. This is a point at which we were contemplating a blood transfusion. However, if the immune system is still destroying the red cells, a transfusion with foreign blood cells (even if cross matched) can worsen the condition. Sam appeared weak, but stable, so we held off on the transfusion for 24 hours at which point, his PCV rose to 17%. Another 24 hours of supportive care and immunosuppression brought the PCV up to 20%. Sam started feeling better and started eating on his own so we discharged him to his happy owners. At the one week recheck, Sam's PCV was up to 28% and he was feeling great.
Sam will stay on the immunosuppressive drugs for about 6 months and we will try to slowly withdraw one drug at a time and check to see that the blood destruction does not start again. If we are lucky, he will get off the drugs and live a long and happy life. We know that certain drugs and vaccines can stimulate recurrence of the anemia, so we will avoid these things for the rest of his life.
We don't know what all the stimuli are, which can cause AUTO IMMUNE HEMOLYTIC ANEMIA. In this case, the stress of the traumatic dog fight must have been the inciting event. More often, the cause is related to immunizations, certain drugs, chronic infection and cancer.