Treating parvovirus on an outpatient basis | VETgirl Veterinary Continuing Education Podcasts
In this VETgirl online veterinary continuing education podcast, we review OPP: outpatient parvovirus treatment. Does it work?
Canine parvovirus (CPV) remains a devastating and potentially fatal disease among our canine population with mortality rates documented around 91% for untreated cases (1). Despite being almost 100% preventable with adequate preventative medicine (e.g., such as vaccines!), we still see parvovirus quite a bit throughout the United States. This is due to lack of pet owner education, lack of vaccination, lack of maternal antibody, etc. The treatment for parvovirus includes intravenous (IV) fluid therapy, anti-emetics, antibiotics, nutritional support, blood glucose and electrolyte monitoring, isolation, and symptomatic supportive care. The length of hospitalization typically needed to successfully treat the more severe cases can be days to over a week – all of this adds up quickly for the overall cost of treatment and hospitalization. In VETgirl’s clinical experience, most puppies are hospitalized for an average of 3-5 days. Often the cost of this level of care proves too great for owners and difficult decisions are then made on the best course of action when appropriate hospitalization cannot be pursued such as euthanasia due to suffering and poor prognosis without treatment.
So, Venn et al out of Colorado State University wanted to perform a modified “outpatient protocol” and compare it to traditional treatment. Does outpatient parvovirus (OPP) treatment work? In this prospective study, they evaluated 40 dogs that were not vaccinated for CPV and found to be positive for CPV in a study between June and August of 2012. The groups consisted of 20 puppies in the modified outpatient protocol group and 20 puppies in the inpatient protocol group. The age range for the inpatient dogs was 1.5 to 30 months, while for the outpatient group was 1.75 to 15 months. All dogs in this study were initially stabilized with IV fluid boluses for rehydration on admission to the hospital. The fluid boluses were provided at the discretion of the clinician, and dextrose boluses were also provided if indicated based on evidence of hypoglycemia on initial blood work. Once the puppies were stabilized, they were transitioned to their designated treatment protocol according to a randomized, computer-generated program, but the staff members were not blinded to their group designations. Preliminary blood work collected from the dogs in this study included baseline CBC, venous blood gas with electrolytes, packed cell volume and total plasma protein (TP). Fecal samples were also collected and 3 of the 29 dogs with reported fecal results were positive for concurrent GI parasitism. Daily monitoring for all dogs included a CBC, PCV/TP, venous blood gas with electrolytes, daily body weight, clinical severity score, appetite, parenteral fluid totals, if rescue treatment was required, visceral pain scores, temperature, pulse, respiratory rate, and hydration status.
All of the dogs remained hospitalized at CSU for the duration of their treatment to ensure treatments were carried out appropriately according to the protocols (hence, the term “modified outpatient” as they were still officially hospitalized for monitoring purposes). The inpatient group received IV Norsmol-R crystalloids at a base rate of 120ml/kg/day with added compensation for ongoing losses; an additional 20 mEq/L of KCl was added to the 1 liter bags. Additional potassium was supplemented according to the patient’s daily electrolyte monitoring, if needed. Puppies in the inpatient group received 22 mg/kg of cefoxitin IV q 8hr, maropitant 1 mg/kg IV q 24hr and additional treatments could be ordered at the discretion of the primary clinician. For nutrition, puppies in both groups were first offered 1 ml/kg of Science Diet a/d orally every 6 hours; if the patient refused to voluntarily eat, they were syringe fed 1-3mL at each designated feeding. If the patient was too reluctant for forced feedings or exhibited increased nausea with the feedings, the attempt at forced feeding was stopped and re-attempted again at 6 hour increments.Puppies in the outpatient group received 120 ml/kg/day of crystalloid fluids subcutaneously (SQ), but this was broken up into increments of 30 ml/kg administered subcutaneously every 6 hours. To compensate for dehydration, the individual patient’s estimated dehydration was assessed and this number was divided across the 4 subcutaneous fluid administrations within the first 24 hour period. To better mimic the at-home environment, no additives were added to the crystalloid fluids, and the administration site of subcutaneous fluids was between the scapula for ease of administration for clients. To improve fluid absorption, rectal temperatures were monitored and exogenous heat support provided as needed to maintain a body temperature >99°F. If a large portion of the prior SQ fluid administration remained in the subcutaneous space without being absorbed at the time of the next scheduled fluid dose, the amount to be administered was halved or skipped until the next scheduled fluid dose. Outpatient protocol dogs also received 8 mg/kg of cefovicin (Convenia) SQ once and 1 mg/kg of maropitant (Cerenia) SQ every 24 hours, but additional treatments could be prescribed at the clinician’s discretion. If any patient exhibited uncontrolled pain, as assessed by a modified VAS scale measurement of greater than or equal to 5, they could be administered buprenorphine at 0.02mg/kg IV for the inpatient protocol and SC for the outpatient protocol. For dogs that exhibited greater than or equal to 3 episodes of vomiting within any 6-hour period after maropitant had been initiated in the protocol, they were provided a one-time dose of ondansetron at 0.5mg/kg IV for the inpatient group and SC for the outpatient group. Hypoglycemic puppies (defined as a blood glucose < 80 mg/dL) were administered either intravenous dextrose as a bolus followed by 2.5-7.5% dextrose CRI for the inpatient group, or 1-5mL of high fructose corn syrup bucally every 4-6 hours for the outpatient group. Hypokalemic patients (defined as a potassium <3.4mEq/L) were administered either intravenous potassium supplementation within their crystalloid fluids for the inpatient group, or 2 mEq/L/4.5kg of oral potassium every 4-6 hours for the outpatient group. If an outpatient protocol canine exhibited a hyperlactatemia ≥ 4 mmol/L, a decline in mentation, a fever > 104°F, or progressive dehydration, they were deemed to have failed the outpatient protocol and were transitioned to the inpatient protocol.
To qualify for consideration for hospital discharge, puppies from either group had to exhibit the following: resolution of vomiting, voluntary appetite, and a CBC exhibiting the neutrophil count was rebounding from the nadir. Endpoints recorded at time of discharge for each patient included survival, length of hospitalization, days until clinical severity score was less than or equal to 2, days until appetite returned, total volume of resuscitation and maintenance fluids required, and body weight change since the time of hospital admission. Of the inpatient protocol group, 90% (18/20) survived to discharge on this protocol with 2 canines dying during hospitalization due to their disease. Of the outpatient protocol group, 80% (16/20) survived to discharge on this protocol with 2 dying within the hospital due to their disease, one being euthanized due to showing signs of imminent death, and 1 was transferred to the inpatient protocol group and ultimately survived. Overall, the median duration of hospitalization was not significantly different between the two groups and averaged around 4 days. The most interesting demographic noted in this CSU study was that all non-survivors were ≤4 months old and ≤4 kg. Overall, there were no statistically significant differences between the two protocol groups when comparing hydration after initial stabilization although the inpatient group had a lower plasma lactate concentration than the outpatient group which may or may not have been attributed to improved hydration or intravascular volume status. The inpatient group exhibited a greater increase in potassium level than the outpatient group, attributed to the intravenous administration of potassium compared to oral administration, but no adverse effects of oral supplementation compared to intravenous supplementation were observed.
This study showed that oral potassium supplementation can be successful in parvovirus patients, but interestingly, the authors also found that in the outpatient protocol canines that did not take their oral potassium supplementation, their potassium levels still increased without any noticed adverse effects.
So, what can we take away from this VETgirl podcast?
Parvovirus is unfortunately a rather costly virus to effectively treat despite it being preventable with a relatively inexpensive vaccine. When confronted with the anticipated costs of hospitalization and treatment, owners may not be able to financially invest in the appropriate medical plan and are left facing less favorable options such as possible euthanasia. This study has demonstrated that a standardized outpatient protocol can provide similar duration of treatment and clinical recovery as those canines treated with an inpatient protocol provided patients are stabilized initially first! This outpatient protocol may be a viable option for owners that cannot invest in hospitalization costs. This study suggests that the outpatient protocol can be considered for patients >4kg and >4 months of age, owing to the finding that all non survivors were ≤4kg in body weight and ≤4 months of age. Maintaining hydration is a large concern for patients with parvovirus. This study concluded that as long as animals are first stabilized with intravenous fluids and then are provided exogenous heat to maintain normothermia throughout treatment that they are able to effectively absorb subcutaneously administered fluids to maintain hydration. The authors of this study focused on providing early enteral nutrition as it is known to improve gut permeability and demonstrate earlier clinical recovery (2). They accomplished this by way of forced feedings in puppies not voluntarily eating to mimic the conditions owners would have at home in managing their ill dog. However, even the inpatient groups did not use NG feeding tubes in this study, which is common practice to place in animals that are not voluntarily eating to minimize risk of aspiration pneumonia. It would have been interesting to see if there would be any difference between the study groups when comparing forced feedings to NG tube feedings. As for antiemetic therapy, maropitant has gained widespread use through the small animal veterinary community in recent years, and its use in young patients has been a hot topic among many ER clinicians dealing with vomiting puppies and kittens. Although maropitant is only labeled for animals older than 8 weeks of age due to bone marrow hypoplasia seen at higher than recommended doses in this age group, the authors of this study felt that the benefits of controlling nausea outweighed the risks of dehydration from vomiting, and so they administered 1 mg/kg of maropitant daily to both groups in animals less than 8 weeks of age without any witnessed adverse effects. Lastly, money. Although the authors did not focus on the cost savings of an outpatient versus an inpatient protocol, they estimated that their outpatient protocol would be roughly one-third the cost of the inpatient protocol at their hospital over the duration of 4-5 days. The cost savings would obviously vary greatly with each hospital’s fee structures and should be considered before presenting this option to clients over inpatient hospitalization for management of CPV.
The authors bring up the concern that the inpatient group required more potassium supplementation, more rescue antiemetics due to increased vomiting, and less of an increase in lymphocyte and monocyte counts during treatment which may all indicate that the inpatient group were more severely affected than the outpatient group of puppies. This could bias the results of the study in that the outpatient group may have had misleadingly good results attributed to the possibility that they were less affected by the CPV than the inpatient group. Keep in mind that the staff were not blinded to the treatments groups, but the study design involved rotating staff between groups so each group experienced various staff members. One important consideration in this study? There is a valid concern that since the outpatient protocol puppies were managed by hospital staff, that they may have received better attention and adherence to protocol than what clients would be able to provide for these patients at home. Further studies on the use of this outpatient protocol by clients at home would be helpful in determining how effective it is when placed in the hands of non-medical persons to manage.
In conclusion, this study outlines an outpatient parvovirus protocol may prove to be a cost-effective alternative to our traditional therapy. Ideally, in-hospital therapy with aggressive IV fluid therapy and supportive care is ideal, but the outpatient protocol can be considered in dogs that are ideally older than 4 months of age and larger than 4 kg in body weight. When finances prevent a pet owner from being able to hospitalize their parvovirus positive dog, an outpatient protocol may be an effective alternative and warrants consideration on a case-by-case basis. That said, pet owners should be educated that 1 out of every 5 dogs still dies of parvovirus despite treatment, and humane euthanasia may be indicated if secondary complications (such as aspiration pneumonia, hypercoaguability, sepsis, etc.) develop.
References:
1. Kariuki NM, Nyaga PN, Buoro IBJ, et al. Effectiveness of fluids and antibiotics as supportive therapy of canineparvovirus-2 enteritis in puppies. Bull Anim Health Prod Afr 1990; 38:379–389.
2. Mohr AJ, Leisewitz AL, Jacobson LS, et al. Effect of early enteral nutrition on intestinal permeability, intestinal protein loss, and outcome in dogs with severe parvoviral enteritis. J Vet Intel Med 2003;17(6):791–798.
3. Venn EC, Preisner K, Boscan PL, et al. Evaluation of an outpatient protocol in the treatment of canine parvoviral enteritis. J Vet Emerg Crit Care 2017;27(1):52–65
Abbreviations:
CPV = canine parvovirus
NG = nasogastric
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