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Use of anti-inflammatories on survival in dogs with pulmonary blastomycosis | VETgirl Veterinary CE Podcasts

In today’s VETgirl online veterinary continuing education podcast, we review the impact of anti-inflammatory medications on survival in dogs with pulmonary blastomycosis (secondary to Blastomyces spp). Blastomycosis is one of the major systemic fungal diseases we see in dogs, and for any of you that practice in endemic areas, you know what a devastating disease this can be. Studies have demonstrated that the remission rates for dogs with Blastomycosis can range from 68-75% (Arceneaux, McMillan, Mazepa). However those dogs with severe pulmonary disease tend to have a worse prognosis (Bromel, McMillan, Mazepa), and there is a pressing need to maximize our treatment strategies in these patients. Not only are the fungal organisms themselves destructive, but treatment of the disease can cause a marked and even dangerous inflammatory response. So, Walton et al at the University of Minnesota Veterinary Medical Center wanted to examine if anti-inflammatory medications, including nonsteroidal anti-inflammatory drugs (NSAIDs) and/or corticosteroids, affected outcome in dogs with pulmonary blastomycosis. They also wanted to determine if other factors such as itraconazole dose, patient characteristics, or the need for oxygen therapy impacted 30-day survival. The authors hypothesized that the use of anti-inflammatory medications would improve 30-day survival.

In this retrospective study, the authors evaluated dogs with pulmonary blastomycosis that presented to the University of Minnesota Veterinary Medical Center from May 2002 to October 2012. In order to be included, cytology of sputum or fine needle aspirate of the lung were required. If these diagnostics were not available, a necropsy diagnosis or appropriate clinical signs with thoracic radiographs consistent with blastomycosis in addition to a positive urine blastomycosis antigen test were sufficient to be included. If a dog had non-pulmonary blastomycosis, they were excluded from this study. The investigators also recorded signalment, initial pulse oximetry (SpO2) readings, arterial blood gas results when available, respiratory rate at presentation, and the need for oxygen supplementation. Thirty-day survival after initial presentation was the outcome of interest.

So, what did the authors find? Overall, 139 dogs met the inclusion criteria, with Golden Retrievers and Labrador Retrievers being the most common breeds represented (These 2 breeds are very popular in Minnesota!). Ages ranged from 0.4 to 11 years of age, with a median age of 4.3 years. Thirty-eight percent of dogs required oxygen supplementation at admission, and 88% of all dogs received itraconazole, with a median dosage of 5.5 mg/kg/day. One dog received ketoconazole and 1 received fluconazole. There were 10% of dogs that did not receive antifungal treatment, but unfortunately all dogs without antifungal treatment died or were euthanized within the 30-day time period. So what about anti-inflammatories? In the dogs that received antifungal treatment, 50% were also treated with an NSAID, and 18% with a corticosteroid. 3% of dogs received both an NSAID and a corticosteroid at some point during treatment, leaving 29% that did not receive any anti-inflammatory medication.

As we said earlier, the question that Walton et al set out to answer was whether the use of such anti-inflammatory medications impacted the outcome in these dogs. Overall, 61% of the dogs survived 30 days, but the use of an anti-inflammatory medication was NOT significantly associated with survival in this population. Additionally, there was no association between the use of these medications and the need for oxygen supplementation, though not surprisingly, dogs requiring oxygen supplementation had a significantly lower 30-day survival. Interestingly, intact female dogs had a significantly lower 30-day survival compared to neutered and intact males, though there was only a small subpopulation of intact females included. Other limitations that the authors discuss include the fact that this was a retrospective study, and therefore the timing and clinician’s reasoning for using an anti-inflammatory was unclear. For instance, clinicians may have used anti-inflammatory medications more readily in patients with severe disease. Also there were only a small number of patients that died rather than being euthanized, as well as a small number of cases treated with an NSAID and corticosteroid, making these parameters difficult to assess. Lastly, many of the patients that received oxygen did not have a documented SpO2, which makes an objective assessment of the reason for and severity of their need for oxygen supplementation difficult to assess.

So, what can we take away from this VETgirl podcast? Even though this study did not demonstrate a convincing benefit of the use of anti-inflammatory medications for Blastomycosis, it is important to remember that there were several limitations given its retrospective nature. In fact, this VETgirl will often still treat severe cases of pulmonary blastomycosis with anti-inflammatory therapies (No animal should die without the benefit of steroids, right?). The study did not demonstrate any negative effects from the use of these therapies either, but ultimately we will need prospective studies to gain a better understanding of how these drugs may impact outcome on canine pulmonary blastomycosis.

References:
1. Arceneaux KA, Taboada J, Hosgood G. Blastomycosis in dogs: 115 cases: 1980–1995. J Am Vet Med Assoc 1998; 213(5):658–664.
2. Bromel C, Sykes JE. Epidemiology, diagnosis, and treatment of blastomycosis in dogs and cats. Clin Tech Small Anim Pract 2005; 20(4):233–239.
3. Mazepa ASW, Trepanier LA, Foy DS. Retrospective comparison of the efficacy of fluconazole or itraconazole for the treatment of systemic blastomycosis in dogs. J Vet Intern Med 2011; 25:440–445.
4. McMillan CJ, Taylor SM. Transtracheal aspiration in the diagnosis of pulmonary blastomycosis 17 cases: 2000–2005. Can Vet J 2008; 49(1):53–55.
5. Walton RAL, Wey A, Hall KE. A retrospective study of anti-inflammatory use in dogs with pulmonary blastomycosis: 139 cases (2002-2012). J Vet Emerg Crit Care 2017; 27(4):439-443.

Abbreviations:
NSAID: Non steroidal anti-inflammatory drug

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