Cold Injury

Frostbite is a relatively uncommon condition in healthy animals that have been properly acclimatized to cold temperatures. Animals that have recently moved from a warm climate to a cold one or those that are ill are more likely to succumb to frostbite. This may be due to prolonged exposure to freezing temperatures or contact with a frozen metal object. If an animal has a previous vascular condition or other abnormalities, external temperatures do not have to be very low to cause tissue necrosis (Maxie, 2016). Improper shelter, exposure to blowing wind, and wetness of the animal decrease the exposure time required for frostbite to develop (Maxie, 2016).

Frostbite usually affects the tips of the ears, scrotum, digits, mammary glands, skin folds in the flanks, and tip of the tail due to insufficient insulation by hair and blood vessels that are not as well protected in these locations (Merck & Miller, 2013; Maxie, 2016). When the skin is frozen it appears pale and is cool to the touch with decreased or impaired tactile senses (Merck & Miller, 2013; Maxie, 2016). There may be dark or bluish areas with diffuse subcutaneous edema and hemorrhage (Merck & Miller, 2013). After thawing, mild erythema, edema, scaling of margins, and eventual pain is observed. In mild cases, the hair in affected areas may turn white. The tips and pinnae of ears may curl. In severe cases the skin can become necrotic and slough. The lesions appear similar to burns (Maxie, 2016). Cell damage and death develop from ice crystal formation in the intracellular and extracellular spaces. Progression to ischemic necrosis may be observed followed by tissue sloughing. Full demarcation of the tissue damage may take 4-15 days (Munro & Munro, 2008).

Gross and Microscopic

Most macroscopic findings are nonspecific, and determination of hypothermia as a cause of death is based on the circumstances surrounding the death, exclusion of other causes, and physical examination findings (Merck & Miller, 2013). Microscopic findings can include intrapulmonary hemorrhage, acute hemorrhagic pancreatitis, focal pancreatitis with fat necrosis, and myocardial degenerative foci, and other complications such as frostbite may be observed. Histology of frostbite may illicit edema and hyperemia of the dermis with sporadic foci of inflammatory cell infiltrates (Merck & Miller, 2013).

Conclusion

This chapter explores multiple causes of environmental and situational injury or death encountered in companion animals. More research is required in many of the areas discussed. Consideration should always be given as to how such environmental and situation circumstances may affect companion animals to differentiate accidental versus nonaccidental etiologies.