ASA I

Minimal Risk

Normal healthy animal, no underlying disease

ASA II

Slight risk, minor disease present

Animal with slight to mild systemic disturbance, animal able to compensate

Neonate or geriatric animals, obese

ASA III

Moderate risk, obvious disease present

Animal with moderate systemic disease or disturbances, mild clinical signs

Anemia, moderate dehydration, fever, low-grade heart murmur or cardiac disease

ASA IV

High risk, significantly compromised by disease

Animals with preexisting systemic disease or disturbances of a severe nature

Severe dehydration, shock, uremia, or toxemia,  high fever, uncompensated heart disease, uncompensated diabetes, pulmonary disease, emaciation

ASA V

Extreme risk, moribund

Surgery often performed in desperation on animal with life threatening systemic disease

Advanced cases of heart, kidney, liver or endocrine disease, profound shock, severe trauma, pulmonary embolus, terminal malignancy

"E" denotes emergency