EMS Canine Evaluation and Treatment of Dehydration

Etiology

EMS workers will most likely encounter canine dehydration associated with fluid loss due to thermoregulation problems. Considering that working dogs may also suffer from gastroenteritis or diarrheal illness, just like their human counterparts, is essential. Recognition of dehydration through history taking and a physical exam is essential. 

Canine thermoregulation involves autonomic processes with heat conservation and dissipation similar to human physiology. As with human physiology, the processes of thermoregulation and thirst regulation in canines are primarily controlled by the hypothalamus, which promotes physiologic changes and behaviors in response to homeostatic needs that are influenced by environmental conditions and physical activity.[7][9] Core body temperature is often decreased through convection and evaporation of water in both humans and canines, but the fur coat found on canines is a major insulator that reduces the efficiency of radiation of heat to the environment.[7] Canines with heavier coats or coats with longer hair will experience hyperthermia faster than canines with shorter or lighter coats.[3]

Evaporation of water is the most effective method for heat dissipation from the body.[10] The canine fur coat and the limited production of sweat leave evaporation of water from the mucous membranes as the primary method of heat loss from the canine body. As the canine engages in prolonged or increasing exertion of activity, the resulting state of hyperthermia causes an increase in fluid loss from the evaporation of water from mucous membranes lining the nasal turbinates and the oral cavity.[11] Without the consumption of water, the net fluid loss will cause a state of dehydration. 

Epidemiology

Epidemiological data regarding canine dehydration can vary based on geographic location, climate, breed prevalence, and socioeconomic factors. Some general trends and characteristics include:

Climate and Season: Dogs are more prone to dehydration during hot and humid weather. Regions with higher temperatures or prolonged heatwaves can see an increase in cases of dehydration due to the increased fluid loss from panting.[12]

Breed Predisposition: Brachycephalic breeds (short-nosed breeds) such as bulldogs, pugs, and boxers might be more susceptible to heat-related issues due to their compromised ability to regulate body temperature.[13] Additionally, certain breeds may be more prone to conditions that lead to dehydration, such as kidney disease.

Activity Level: Dogs that engage in vigorous exercise, especially in warm weather, are at a higher risk of dehydration. This includes working dogs, sporting breeds, and dogs participating in agility and flyball activities.[14]

Age: Puppies and senior dogs might be more vulnerable to dehydration. Puppies have higher water requirements per unit of body weight, while older dogs may have underlying health conditions contributing to dehydration.[12]

Underlying Medical Conditions: Dogs with conditions like kidney disease, diabetes, or gastrointestinal disorders are more likely to experience chronic dehydration. These conditions can lead to increased water loss or reduced water intake.[12]

Access to Clean Water: Dogs with limited access to clean and fresh water are at a higher risk of dehydration. This can be due to confinement, neglect, or insufficient water sources.

Nutrition: Diet plays a role in hydration. Dogs consuming dry kibble need more water than wet or raw diets.

Awareness and Education: Increased awareness among pet owners about the importance of hydration and prevention strategies can impact the incidence of canine dehydration. Proper education can help prevent dehydration-related issues.[12]

Pathophysiology

Progressive worsening of dehydration leads to hypovolemic shock or decreased perfusion of tissues. Compensation for early canine hypovolemia stages presents signs of tachycardia, tachypnea, and elevated core body temperature.[6] As fluid loss progresses, the compensatory effects of increased heart rate and vasoconstriction can no longer sustain adequate blood pressure. They will ultimately lead to hypotension, electrolyte abnormalities, cardiac dysrhythmias, acute kidney injury, circulatory collapse, and cardiac arrest.[6][11] If the canine remains in an environment with elevated temperature or continues to engage in physical exertion, the canine may experience heatstroke, a potentially fatal condition caused by ineffective thermoregulation.[11]

History and Physical

The working canine’s handler may report that the canine was engaged in an activity requiring physical exertion. The handler may include environmental descriptors that were not able to be observed by the EMS worker, including the heat and humidity of the working environment. The handler may also describe that the canine had limited access to water during physical exertion.[6] The history may include descriptions of a hypersalivation period that dissipated with the canine becoming less energetic, consistent with decreased mental status.[11]

Physical assessment of a canine may be difficult for an emergency medical technician or paramedic to complete in the field, given their limited experience and limited access to laboratory testing that can confirm dehydration.[6][7][8] Although salivation or mucosal surface changes are unreliable indicators of hydration, the canine’s vitals, skin turgor, and capillary refill should be evaluated.[15] 

In addition to tachycardia and tachypnea in the early phases of dehydration, increased skin tent time and delayed capillary refill time are field assessments indicative of canine dehydration.[6] The process of assessing for skin tent time and delayed capillary refill is similar to that for a human patient, but the EMS worker needs to assess in different locations on a canine than on a human patient. The “skin lying parallel to the sagittal crest” should be pinched between the thumb and index finger for approximately 2 seconds, counting aloud or using a stopwatch after releasing the skin to determine the tent time.[6] Applying pressure on the maxillary gingiva with a finger can assess the capillary refill of the oral mucosa.[6] 

Skin that does not readily return to the normal position for the canine or a delayed capillary refill can identify body water loss of as low as 1.8%.[6] Skin tent time is the preferred assessment option, as capillary refill time does not significantly decrease in the early stages of dehydration.[6] The literature lacks a baseline value for skin tent time or capillary refill specific to the maxillary oral mucosa. Additionally, the handler should assess the canine before undertaking physical exertion.[6]

Evaluation

Prehospital evaluation of canines using laboratory testing is limited to glucometer or point-of-care lab testing. Point-of-care glucometers are accurate when used on canines, with similar expected values.[16] Some prehospital services carry an excess postexercise oxygen consumption or i-STAT blood analyzer veterinarians use.[17] However, the utility of such information in the prehospital setting is questionable.

Treatment / Management

Like human medicine, the approach to treating canine dehydration is fluid replacement through the least invasive route possible, given the canine’s clinical presentation.[15][18] If the canine can access potable water and maintain oral intake without vomiting or having airway compromise, giving the canine ad libitum access to tap water is the least invasive method of fluid replacement. (Providing water ad libitum means providing the canine water in a bowl or other appropriate source until they stop drinking water.)[8] Zanghi and Gardner identified that canines provided nutrient-enriched water have an increased total liquid intake, though this may not be available in the field.[8](B3)

If the canine cannot consume water, parenteral administration of crystalloid fluids is appropriate in the field setting to manage canine dehydration.[4] Parenteral routes typically used in the veterinary setting include intravenous (IV) and subcutaneous fluid administration. Intraosseous (IO) administration of bolus fluids is performed when volume resuscitation is indicated. However, venous vascular access is not readily obtainable.[4] Given the training required to achieve IO access in canines, there are other feasible routes for EMS workers. The process of attaining peripheral IV access, often in the cephalic vein, is similar to the procedure used to obtain IV access in human patients. Such placement may be hindered by decreased visibility or palpability of canine veins and lack of familiarity with canine vascular anatomy. Parenteral fluid administration may cause the canine to respond to painful stimuli. The EMS worker providing care must be prepared for the animal to react in a manner that could cause injury, such as biting.  

Subcutaneous (SC) access is the most feasible way and requires the least procedural familiarity. The EMS worker should identify a suitable location for SC fluid administration, typically in loose skin tissue on the dorsal surface at the level of the shoulder blades. After cleansing the site, an open region of skin is gently pinched, and a sterile needle is inserted, directed cranially, until it is in the SC space. Crystalloid fluids are then typically administered IV or IO to human patients and include 0.9% sodium chloride solution via drip set to the needle and allowed to flow by gravity. When administered subcutaneously, fluid volumes should be limited to 200 mL to allow for effective fluid absorption and decrease the risk of tissue injury.

Dehydrated canines may be hypovolemic, and rapid fluid resuscitation may be indicated. Rapid IV access cannot be obtained in such cases, and SC fluid administration may not be sufficient. An additional route of fluid administration for canines includes cannulation of the corpus cavernosum, which is easily located on male canines and requires no specialized equipment.[19] The corpus cavernosum (the spongy tissue located along the lateral aspects of the penis that engorges with blood to sustain an erection) provides a site for highly vascularized tissue that permits fluid volume resuscitation.[19] (B3)

After locating the appropriate site, the location should be cleansed with alcohol or chlorohexidine preps, and a large bore needle or angiocatheter (18- or 19-gauge) should be inserted obliquely into the corpus cavernosum caudally.[19] After placing the needle or catheter, confirm placement by the positive aspiration or blood.[19] Once verified, vascular access via the corpus cavernosum can be used like EMS workers traditionally use IO access in human patients. A significant advantage of vascular access via the corpus cavernosum is the ability to administer blood products, epinephrine, and atropine.[19] If parenteral fluid administration is necessary, the overall goal is for the canine to begin consuming water orally to maintain hydration.[18] (B3)

Differential Diagnosis

Canine dehydration can result from various underlying causes. When diagnosing dehydration in a dog, considering a range of potential differential diagnoses to identify the underlying cause is essential. Common differential diagnoses for canine dehydration include:

• Heatstroke: This condition occurs when a dog’s body temperature rises to a dangerous level due to excessive heat exposure. Heatstroke can lead to severe dehydration and other life-threatening complications.[13]
• Gastrointestinal issues: Conditions like gastroenteritis (inflammation of the stomach and intestines), viral or bacterial infections, parasites, and dietary indiscretion can lead to vomiting and diarrhea, resulting in fluid loss and dehydration.[15]
• Diabetes: This can cause excessive thirst and urination, leading to dehydration if not properly managed.[20]
• Kidney disease: Chronic kidney disease can lead to a reduced ability to concentrate urine and excessive water loss, resulting in dehydration.
• Pancreatitis: Inflammation of the pancreas can cause vomiting, diarrhea, and decreased appetite, leading to fluid loss and dehydration.[15]
• Addison disease: This involves insufficient production of adrenal hormones, leading to electrolyte imbalances and dehydration.[15]
• Cushing disease: Excessive production of cortisol can lead to increased thirst and urination, potentially resulting in dehydration.[21][15][21]
• Infectious diseases: Certain infections, such as parvovirus or leptospirosis, can cause vomiting, diarrhea, and fluid loss, leading to dehydration.[15]
• Malnutrition: Inadequate food and water intake can result in dehydration over time.
• Diarrheal diseases: Conditions like inflammatory bowel disease or dietary intolerances can cause chronic diarrhea and dehydration.[15]
• Medication adverse effects: Certain medications, particularly diuretics, can increase urine production and dehydration.[15]
• Excessive exercise: Intense physical activity without access to adequate water can cause dehydration, especially in warm weather.[22]
• Toxicities: Ingesting certain toxins, such as antifreeze, can lead to vomiting, diarrhea, and dehydration.[15]
• Parasitic infections: Heavy infestations of internal parasites, such as hookworms or roundworms, can cause gastrointestinal symptoms and fluid loss.[15]
• Urinary tract issues: Conditions like urinary tract infections, bladder stones, or urinary obstruction can lead to changes in urination and potential dehydration.
• Neurological disorders: These disorders can affect a dog’s ability to drink water or regulate body temperature, leading to dehydration.
• Endocrine disorders: Other endocrine disorders, such as hyperthyroidism or hypothyroidism, can disrupt a dog’s metabolic balance and contribute to dehydration.[15]

This list is not exhaustive, and the specific differential diagnoses considered will depend on the dog’s history, clinical signs, physical examination, and any relevant diagnostic tests. 

Prognosis

The prognosis for canine dehydration depends on several factors, including the underlying cause of dehydration, the severity of dehydration, the overall health of the dog, and how quickly the condition is diagnosed and treated. In many cases, with prompt and appropriate treatment, the prognosis for resolving dehydration is generally good. However, the outlook can vary based on specific circumstances.

Here are some scenarios that can affect the prognosis for canine dehydration:

• Mild dehydration with prompt treatment: The prognosis is usually excellent if dehydration is caught early and treated with fluid replacement therapy (either orally or intravenously).[23] Most dogs respond well to rehydration and recover fully.
• Severe dehydration: In cases where dehydration is severe and the dog’s condition has deteriorated, the prognosis can be more guarded.[23] Severe dehydration can lead to organ dysfunction, electrolyte imbalances, and other complications.
• Underlying medical conditions: If dehydration is a symptom of an underlying medical condition (such as kidney disease or diabetes), the prognosis will depend on successfully managing the primary condition. Treating the underlying cause can improve the dog’s overall health and reduce the risk of recurrent dehydration.
• Age and health status: Puppies, senior dogs, and those with compromised immune systems or other health issues may have a worse prognosis, as their bodies may not cope with dehydration and the associated stress.
• Timely veterinary care: Seeking veterinary attention once dehydration is suspected can significantly improve the prognosis. Delayed treatment can lead to more severe complications and a less favorable outcome.[13]
• Complications: If dehydration leads to complications like electrolyte imbalances, organ failure, or shock, the prognosis may become more severe and require more intensive and specialized treatment.
• Heatstroke: If dehydration results from heatstroke, the prognosis can vary depending on how quickly the dog is cooled down and rehydrated. Heatstroke can cause irreversible damage if not treated promptly.[12]
• Response to treatment: How well the dog responds to rehydration therapy and any necessary medical interventions will influence the prognosis.[24] Some dogs may require ongoing monitoring and treatment.

Remember that dehydration is often a sign of an underlying issue, and addressing the root cause is crucial for long-term health. If canine dehydration is suspected, early care is recommended as guided by the tactical EMS agency’s protocols or veterinarian guidance.  

Ultimately, the prognosis for canine dehydration depends on early intervention, the effectiveness of treatment, and addressing any contributing factors. A veterinarian can provide a more accurate prognosis.

Complications

Unrecognized or inadequately treated dehydration in canines can be further complicated by manifestations of hypovolemic shock, renal injury, hyponatremia, hypokalemia, and cardiac dysrhythmias, resulting in death.[11] Dehydration in working canines is often coupled with hyperthermia.[11] Without sufficient body water due to evaporative heat loss, dehydration will increase the risk of heat-related injury, including heat stroke.[11] The invasive nature of parenteral fluid administration is associated with an increased risk of localized and subsequent systemic infection.[19] IO access complications include fat embolism, osteomyelitis, and tissue necrosis.[19]