Cryotherapy is the therapeutic use of cold and is frequently used for the treatment of pain, inflammation, swelling, and edema associated with soft tissue trauma. Direct application of a cold object (eg, a compress) to the skin will decrease the temperature of both superficial and deeper tissues.1–4 Lowering tissue temperature decreases tissue metabolism, edema formation, muscle spasm, and signs of pain and minimizes the inflammatory processes associated with soft tissue injury.5–8 Lowering the metabolic rate helps protect local and surrounding tissue from enzymatic reactions associated with the injury and subsequent inflammation.9,10 Cold reduces blood flow by increasing viscosity and vasoconstriction and reducing metabolic activity, which reduces edema formation at the site of injury.11,12 Analgesia results from alteration in cellular metabolism and slowing of nerve conduction velocity in local sensory neurons.13–16
Cryotherapy is performed during the postoperative healing period in many small animal surgical patients. The use of a cold compress is widespread and frequently justified because of the perceived beneficial results, low cost, and convenient use; however, there is area for improvement in cryotherapy recommendations.17–19 There is no definition of an optimal frequency and duration of treatment in the scientific literature.20,21 From clinical and research studies20,21 performed to evaluate the effectiveness of cryotherapy, the general consensus is that repeated applications of a cold compress for 10 to 30 minutes are effective at improving clinical outcome in humans. There is debate on the appropriate recommended method of application and duration of use as well the actual effectiveness of cold compress treatment in human patients.20 There is limited scientific information on this topic in dogs. One study22 found that cold treatment with intermittent pneumatic compression improved signs of pain, swelling, lameness, and range of motion during the first 24 hours following tibial plateau leveling osteotomy.
One area of uncertainty is the optimal temperature to which tissue should be cooled to limit secondary injury associated with soft tissue trauma. The supporting literature on this issue is limited. It is frequently assumed that greater cooling results in increased metabolic suppression and is therefore more efficacious.2,8,10 Cryotherapy studies3,8–10,23 in humans have detected a wide range of temperature changes at various tissue depths, none of which have proven an optimal target temperature. Not all reported studies are controlled for method of sedation, area of cold application, method of cold application, subcutaneous tissue depth, artifactual cold influence, or method of measuring depth and temperature.21 More clinical studies with standardized methods of controlling for variables would aid in improving cryotherapy recommendations.
Currently, application of cryotherapy in dogs is largely empirical, with minimal evidence-based research, and has been extrapolated from human recommendations. The purpose of the study reported here was to accurately establish the effect of a commonly used method of cold compress treatment on tissue temperature at various depths in healthy dogs and to establish recommendations on appropriate duration of application. We hypothesized that decreases in tissue temperature would be directly proportional to duration of cold compress application and that increasing tissue depth would result in a lower magnitude of temperature change.
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