Working dogs, such as search-and-rescue dogs, need to remain hydrated to safely and effectively perform lifesaving tasks in a variety of environmental conditions. Working dogs and some pet dogs are highly motivated to perform the tasks for which they have been trained. As a result, they may not respond to physiologic signals that drive thirst. Thus, canine handlers need to be responsible for monitoring the health of the dogs and to schedule rest and rehydration. One of the most common conditions affecting dogs responding to disasters is dehydration.1–3 Working dogs may work for extended periods in adverse environments. Similarly, pet dogs may be motivated to endlessly chase a ball or accompany an owner on a run. The handler or owner must know when to allow the dog to rest to optimize safety and performance. One strategy that can be readily performed in a field setting is monitoring the hydration status of a dog. Veterinarians can teach handlers to recognize life-threatening illnesses and injuries and to evaluate vital signs (including heart rate, respiratory rate, body temperature, CRT, and skin turgor) of dogs. The ability of handlers to recognize important signs of illness and perform basic and advanced first aid may make the difference in the ability of a dog to survive or return to work.4
A common sign of dehydration in humans and other animals is an increase in SkTT associated with a decrease in skin turgor. Dehydrated critically ill small animal patients can become hypovolemic as a lower interstitial hydrostatic pressure drives fluid shifts from the intravascular space into the interstitial space.5 Changes in skin pliability (ie, turgor) can be used as an index of body fluid balance because the skin will lose pliability when water balance is negative.6 A sign of dehydration is an increase in the time required for the skin to return to its normal contour. Skin turgor is a common component of hydration assessment in clinical patients. Results of experiments with dogs suggest that clinical signs of dehydration can only be detected after a loss of > 5% BW.7 The location at which skin turgor is monitored may influence sensitivity of the assessment of hydration.
The optimal location for monitoring skin turgor has been evaluated in horses8–10 but is rarely specified in dogs.11 The skin parallel to the sagittal crest (ie, the forehead) of a dog is less likely to be influenced by the degree of subcutaneous fat or body position and represents an area at which there is rapid loss of transepidermal fluid.12 Evaluation of skin turgor on the forehead of a dog is a simple noninvasive method at an easy-to-access anatomic location that may be useful for monitoring a dog's hydration status in clinic or field settings.
Dehydration can also lead to changes in peripheral perfusion variables and a prolonged CRT. When used in conjunction with pulse quality, respiratory effort, heart rate, and mucous membrane color, the CRT can be of use in assessing an animal's blood volume and peripheral perfusion.13 Fluid shifts out of the intravascular space during substantial interstitial dehydration, and intravascular hypovolemia can ensue. Although CRT is not a direct clinical sign of dehydration, a prolonged CRT in combination with increased skin turgor suggests substantial dehydration has resulted in hypovolemia. In a meta-analysis14 of children brought to emergency departments because of vomiting and diarrhea, a prolonged CRT had high specificity (88% to 94%) for identifying children with moderate dehydration (≥ 5%). To the authors’ knowledge, no studies have been conducted on the correlation between CRT and short-term exercise in animals.
The purpose of the study reported here was to evaluate the effect of 15 minutes of exercise on SkTT (as a clinical measure of dehydration) and CRT (as a measure of poor perfusion) in working dogs. Both SkTT and poor perfusion may accompany dehydration with intravascular volume depletion. There is little information for use in identifying clinical signs of dehydration after a 15-minute exercise period in working dogs, a period during which a dog is likely to lose < 5% BW as water. We hypothesized that clinical markers traditionally considered to be predictors of dehydration (eg, skin turgor as measured by SkTT or altered perfusion as measured by CRT) may be useful for predicting mild dehydration after a 15-minute exercise period in working dogs.
Supported by Nestlé Purina Research.
The authors thank Patricia Kaynaroglu and Vicki Berkowitz for technical assistance.
Capillary refill time
Penn Vet Working Dog Center
Skin tent time
Purina Pro Plan Sport All Life Stages Performance 30/20 Formula, Nestlé Purina PetCare Co, St Louis, Mo.
Purina Pro Plan Focus Sensitive Skin and Stomach Formula, Nestlé Purina PetCare Co, St Louis, Mo.
Purina Pro Plan Overweight Management Formula, Nestlé Purina PetCare Co, St Louis, Mo.
Nutro Wholesome Essential Lamb & Rice, Mars Inc, McLean, Va.
CorTemp indigestible core body temperature sensor and data recorder, HQInc, Palmetto, Fla.
HD Handycam, Sony, New York, NY.
Exmor R CMOS sensor, Sony, New York, NY.
Movavi video editor, version 4, Movavi Software Ltd, St Louis, Mo.
Jorgensen Laboratories Inc, Loveland, Colo.
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