http://www.ivis.org/proceedings/navc/2005/SAE/063.pdf?LA=1
RATTLESNAKE ENVENOMATION: PATHOGENESIS AND TREATMENT
Kate Hopper BVSc DACVECC
University of California
Davis, CA
...SUPPORTIVE CARE
Antihistamines are commonly used in the management of
snake bite. They can provide some sedation in a distressed
animal and are often chosen in an attempt to prevent
anaphylaxis to the antivenom. One study found that dogs
given phenergen and antivenom died sooner than those
animals treated with antivenom alone. This may have been
due to the hypotension produced by the antihistamine.
Currently antihistamines are only recommended in human
snake bite victims if there are signs of reaction to the
antivenom. The antivenom is stopped and histamine 1 and
histamine 2 blockers are given (+/- epinephrine) and the
patients are observed closely. If the patient improves the
antivenom infusion is continued at a slow rate.
Corticosteroids are the most controversial topic in snake
bite therapy. In the literature there is no evidence
demonstrating that corticosteroids provide benefit to humans
or animals with crotalid bites. Several of these studies have
found that patients treated with corticosteroids and antivenom
have a higher morbidity and mortality than those treated with
antivenom alone.
Pain is a major clinical sign following envenomation.
In human medicine, a reduction in the degree of pain
association with a snake bite is seen as an indication of
adequate antivenom administration. In veterinary medicine
pain can make patients very difficult to handle and treat.
Analgesia is often an important therapeutic consideration.
Opioids such as hydromorphone, butorphanol or
buprenorphine are recommended as they can provide
analgesia with minimal cardiovascular effects.
Broad spectrum antibiotics are advised as snake mouths
are known to contain numerous pathogenic bacterial,
predominantly gram negative bacteria. As a snake bite lesion
progresses and there is tissue death present, secondary
infection of the area is a risk.
In the past crotalid bites have sometimes been treated with
surgical debridement. This has been found to substantially
increase morbidity and mortality compared to antivenom
therapy alone and is not advised. Fasciotomy to relieve
pressure in swollen tissue (compartment syndrome) has also
been found to contribute to morbidity and can often result in
greater tissue trauma than the necrosis and damage due to
the venom alone. Progressive tissue swelling is most
effectively treated with further antivenom administration. Tissue
edema and swelling will resolve in 7-10 days if sufficient
supportive care is provided.
