/// QUARTERLY BEAT / DECEMBER 2022
QUARTERLY BEAT / DECEMBER 2022 ///
organ systems. Severe hypokalemia (< 2.5 mEq/L) results in neuromuscular weakness, ataxia, diaphragmatic and respiratory muscle fatigue, gastrointestinal stasis, and cardiac arrhythmias. For patients with severe hypokalemia or with clinical signs due to hypokalemia, potassium chloride (KCl) can be administered at a rate of 0.5 mEq/kg/hr for 1-2 hours. This is commonly referred to ‘Kmax’, the maximum rate at which potassium can be safely administered. Serum potassium should be monitored every 2-4 hours when administering high doses of potassium (KCl). Magnesium is an important cofactor in potassium homeostasis, and supplementation may help restore normal serum potassium levels. The recommended dose for magnesium supplementation is 0.75-1 mEq/kg/day as a CRI, which can be added to the base fluids. There are several published charts with recommendations for potassium supplementation based on the patient’s serum potassium. The author prefers to base potassium supplementation on potassium requirements. Normal potassium requirements are 0.05-0.1 mEq/kg/hr. This rate of supplementation can be considered in animals with a normal potassium. Most dogs with CPV will be at risk for hypokalemia, so supplementation with 0.1-0.25 mEq/kg/hr may be required. As a reminder, 0.5 mEq/kg/hr is considered the maximum rate at which potassium can be administered. KCl or any source of potassium should never be administered as a bolus. GASTROINTESTINAL SUPPORT Vomiting and nausea should be addressed immediately to improve patient comfort and limit ongoing losses. A multimodal approach should be considered to control vomiting. Commonly used anti-emetics are listed below with recommended doses: • Maropitant: 1 mg/kg IV q24hr Maropitant is an effective antiemetic in dogs for a wide range of etiologies, including CPV. In a previous study, maropitant and ondansetron appeared to be equally effective in controlling vomiting and nausea in dogs with CPV (Sullivan 2019). A multimodal approach should be considered to control vomiting/nausea in patients with CPV. Maropitant, ondansetron, and metoclopramide work via different receptors, so a combination of these three drugs may be considered. • Ondansetron: 0.5-1 mg/kg IV q8hr • Metoclopramide: 1-2 mg/kg/day CRI • Dolasetron: 0.6-1 mg/kg IV q24hr ANALGESICS Dogs with CPV may demonstrate moderate to severe visceral pain. Several classes of analgesics may be considered, and a multi-modal approach is recommended. Given the
A combination of fluids, such as an isotonic crystalloids and colloids, can be used and commonly provides benefits of both fluid choices without having to use large volumes/ doses of either. Fluid resuscitation should be stopped when hemodynamic monitoring parameters have normalized. Transition to the maintenance phase should be started at this point. Calculating a maintenance fluid rate includes the following components: 1. Correction of dehydration a. Liters to replace = % dehydration X body weight (kg) b. This volume should be replaced over a period of 12-24 hours 2. Sensible losses (maintenance calculation) a. mL to administer over 24 hours = BW 0.75 x 70 b. Accounts for normal urinary, fecal, and respiratory losses 3. Ongoing losses a. Due to vomiting, diarrhea, PU/PD, third spacing, etc. b. Estimated and replaced every 4-6 hours The sum of the three values obtained above is the final fluid rate. Balanced, isotonic crystalloids may be used as part of the maintenance fluid plan, although iatrogenic hypernatremia can develop in patients not receiving free water. Colloidal support can be considered in cases of refractory hypotension, progressive hypoalbuminemia, and/or in patients with signs of interstitial edema. Fresh frozen plasma doesn’t distribute into the interstitial space like crystalloids, so it treats hypovolemia more efficiently and maintains intravascular volume. In addition, FFP supports COP (albumin), replenishes clotting factors and other important molecules, and protects the endothelial glycocalyx. For more information on colloid and transfusion medicine, please review an appropriate emergency-critical care resource.
Please note the opinions of this article are the expressed opinion of the author and not directly endorsed by VETgirl.
SPONSORED ARTICLE
Treatment of Canine Parvovirus
KRISTIN ZERSEN , DVM, DACVECC Colorado State University Veterinary Teaching Hospital
In this VETgirl feature article sponsored* by Elanco, Dr. Kristin Zersen, DACVECC reviews “Treatment of Canine Parvovirus.” Missed the webinar? Check it out HERE !
capillary refill time, weak femoral pulses, cold extremities, and altered mentation. Most CPV patients display moderate to severe abdominal pain, which is most likely due to diffuse enteritis. However, intestinal intussusception should remain a differential diagnosis and abdominal ultrasound should be considered in cases of severe pain. Mentation changes and generalized weakness may be due to a combination of hypoperfusion, hypoglycemia, and/or hypokalemia. Myocardial disease has been reported with neonatal infection and often results in peracute death. Other organs affected by CPV may include the respiratory system, liver, and kidneys. TREATMENT Fluid Therapy Treatment for hypovolemic shock should be initiated immediately with rapid IV resuscitation. The ideal fluid type is a balanced, isotonic crystalloid without additives, like LRS, Normosol-R, or Plasmalyte-A. A fraction of the dog’s blood volume (BV = 90 mL/kg) can be administered as a bolus over 10-20 minutes. Most clinicians start with ¼ of a patient’s blood volume, also called a ¼ shock bolus. The response to this bolus should be assessed using perfusion parameters, lactate, and blood pressure. Additional isotonic crystalloid boluses may be administered if the patient is fluid responsive, meaning the patient’s monitored parameter improved following the administration of the bolus. After one hour, approximately 20% of an administered crystalloid volume is retained within the intravascular space. The vast majority (80%) is either excreted through the urinary system or redistributed to the interstitial space. This movement of fluid into the interstitial space may be desired in dehydrated patients. However, a substantial amount of data indicate that it is detrimental in patients without an interstitial fluid deficit.
BACKGROUND Canine parvovirus (CPV) is a small, non-enveloped DNA virus that replicates in rapidly dividing cells, including the intestinal crypt cells, bone marrow, and myocardiocytes. The two CPVs that have been described are CPV-1 and CPV-2. Dogs infected with CPV-1 are usually asymptomatic. The more virulent strain, CPV-2, has undergone many genetic alterations over the years, which has allowed CPV to be a continuing problem in at-risk populations. The three strains of CPV-2 that have been identified are CPV-2a, CPV-2b, and CPV-2c. CPV-2b and CPV-2c predominate with naturally occurring disease in the United States. Clinical research suggests that disease severity and outcome do not differ between CPV-2b and CPV-2c infection. CPV often infects unvaccinated puppies between 6 weeks and 6 months of age. Breed, genetic background, and the innate immune system are factors that play a role in the individual response to infection. Disease is rarely seen in neonatal puppies because they are protected by maternally derived antibodies for the first 10 days of life. After this, they are at risk for infection. Lack of vaccination poses the greatest threat to puppies exposed to CPV. Other factors known to predispose dogs to CPV include overcrowded and unsanitary conditions, stressful environments, and intestinal parasites. In addition, Rottweilers, Doberman Pinschers, American Pit Bull Terriers, and Labrador Retrievers have been shown to be at increased risk for infection, although the reason for this susceptibility is not known. CLINICAL SIGNS Severe vomiting and hemorrhagic diarrhea may lead to dehydration, hypovolemia, and cardiovascular collapse. Dogs often present with evidence of hypovolemic shock, including tachycardia, pale mucous membranes, prolonged
Electrolytes: Hypoglycemia and Hypokalemia Hypoglycemia can be a severe and life-threatening
complication resulting in altered mentation, weakness, ataxia, and vision loss. If the blood glucose of a symptomatic puppy with CPV is < 60 mg/dl, an IV dextrose bolus should be administered. The recommended dose of 50% dextrose is 0.5 to 1 mL/kg diluted 1:2 with an isotonic crystalloid. Additional dextrose boluses can be administered if necessary. Dextrose should also be added to the base fluids as a CRI during the maintenance fluid stage. Usually, a solution of 2.5-5.0% dextrose is sufficient. If 7.5% or higher is required, a central line should be placed.
Hypokalemia is a common electrolyte disturbance seen in dogs with CPV and can have adverse effects on multiple
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