Pleuropneumonia – advances in treatment and prognosis

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Abstract

Pleuropneumonia – advances in treatment and prognosis
Kristopher Hughes BVSc (Hons) FANZCVS DipECEIM
School of Animal and Veterinary Sciences, Charles Sturt University, Wagga Wagga, New South Wales, 2678 Australia
krhughes@csu.edu.au
Introduction
Bacterial pleuropneumonia is a common condition of horses that is an important cause of morbidity and mortality. For horses with pleuropneumonia, outcome have varied considerably between studies, with survival rates of 44-96% reported. Conventional strategies for treatment of pleuropneumonia include systemic administration of antimicrobial and non-steroidal anti-inflammatory drugs, fluid and nutritional support and drainage of pleural effusions. While antimicrobial drug regimens may be empirical, selection is best directed by cytological examination and bacterial culture of tracheal aspirate and pleural fluid samples. Pleural drainage is important when septic parapneumonic effusion is suspected or confirmed, based on cytology/bacteriology findings, gross appearance, biochemical examination and/or ultrasonographic findings. Despite these approaches, poor responses to treatment, progression of parenchymal and/or pleural effusion and development of complications can occur. In these ‘complicated’ pleuropneumonia cases, additional treatment options may be warranted in an effort to improve outcomes and careful case assessment is required to best determine prognosis.
Prognosis
While the clinical course of horses with pleuropneumonia can be unpredictable, certain factors have been associated with prognosis. Negative prognostic indicators include markers of systemic and/or pulmonary dysfunction (e.g. increased blood concentrations of creatinine, systemic inflammatory response syndrome, necrotising pneumonia, foul odour to breath, pulmonary haemorrhage), bacterial isolates (e.g. Klebsiella spp., anaerobes, Actinobacillus spp.), increased volume of pleural effusion and accumulation of fibrin, sharp thoracic radiographic demarcation between marked alveolar infiltration and normal lung and development of complications (e.g. laminitis, thrombophlebitis, colitis, bronchopleural fistula) [1-3].
Pleural drainage – advances in management
Horses with pleuropneumonia frequently require drainage of pleural effusions via intermittent or indwelling chest drains. However, fibrinous effusions are associated with decreased efficacy of drainage. In one study, fibrinous parapneumonic effusions developed in 85% of horses with pleuropneumonia and the fibrin accumulation was associated with a greater number of drains required for treatment and decreased survival [3]. Given the propensity for accumulation of fibrin within the pleural cavities and development of loculated effusions, there is increasing interest in the use of local fibrinolytic treatment to facilitate more effective pleural drainage and clinical outcomes. There are several reports of the successful use of recombinant tissue plasminogen activators (rTPA) for local fibrinolytic therapy in horses with pleuropneumonia [4,5]. Uncertainty remains regarding dose, frequency and timing of rTPA treatment; however, in one study, earlier onset of treatment was associated with increased odds of survival [4]. Newer generation rTPA drugs (e.g. tenectoplase) have a longer half-life, greater fibrin specificity and are more resistant to the inhibitory effects of plasminogen activator inhibitor-1 than earlier recombinant and natural plasminogen activators. The concurrent use of alphadornase (recombinant DNase) with rTPA may be superior to rTPA alone in improving pleural drainage by liquefying empyaemic pleural material [5].
Lateral thoracotomy
Thoracotomy has often been considered a salvage procedure in horses with refractory pleuropneumonia and fibrinous parapneumonic effusions that don’t respond to conventional management. However, standing lateral thoracotomy may be used earlier in the treatment of pleuropneumonia to facilitate pleural drainage, management of pleural abscesses and resection of necrotic lung. Lateral thoracotomy can be performed by rib resection, although intercostal muscle myectomy or myotomy may provide adequate surgical visualisation and lower morbidity and shorter healing times [6]. The often chronic nature of disease and the use of ultrasonographic examination to identify diseased tissue margins in relation to the thoracic wall prior to surgery reduces the likelihood of bilateral pneumothorax [6]. Pre-surgical placement of a chest drain adjacent to the intended thoracotomy site for equilibration with atmospheric pressure can also be used to assess for a perforate mediastinum. Standing lateral thoracotomy is well tolerated by most horses with minimal short-term complications and is associated with good clinical outcomes [6] and increased odds of survival in horses with pleuropneumonia [1].
References
[1] Arroyo, M.G., Slovis, N.M., Moore, G.E. and Taylor, S.D. (2017) Factors associated with survival in 97 horses with septic pleuropneumonia. J. Vet. Intern. Med. 31, 894-900.
[2] Estell, K.E., Young, A., Kozikowski, T., Swain, E.A., Byrne, B.A., Reilly, C.M., Kass, P.H. and Aleman, M. (2016) Pneumonia caused by Klebsiella spp. in 46 horses. J. Vet. Intern. Med. 30, 314-321.
[3] Tomlinson, J.E., Reef, V.B., Boston, R.C. and Johnson, A.L. (2015) The association of fibrinous pleural effusion with survival and complications in horses with pleuropneumonia (2002-2012): 74 cases. J. Vet. Intern. Med. 29, 1410-1417.
[4] Tomlinson, J.E., Byrne, E., Pusterla, N., Magdesian, K.G., Hilton, H.G., McGorum, B., Davis, E., Schoster, A., Arroyo, L., Dunkel., B., Carlslake, H., Boston, R.C. and Johnson, A.L. (2015) The use of recombinant tissue plasminogen activator (rTPA) in the treatment of fibrinous pleuropneumonia in horses: 25 cases (2007-2012). J. Vet. Intern. Med. 29, 1403-1409.
[5] Rendle, D.I., Armstrong, S.K. and Hughes, K.J. (2012) Combination fibrinolytic therapy in the treatment of chronic septic pleuropneumonia in a Thoroughbred gelding. Aust. Vet. J. 90, 358-362.
[6] Hilton, H., Aleman, M., Madigan, J. and Neito, J. (2010) Standing lateral thoracotomy in horses: indications, complications, and outcomes. Vet. Surg. 39, 847-855
Original languageEnglish
Pages189-189
Number of pages1
Publication statusPublished - 2018
EventBritish Equine Veterinary Association Congress - ICC, Birmingham, United Kingdom
Duration: 12 Sep 201815 Sep 2018
https://www.beva.org.uk/Education/CPD/Event-Details/eventDateId/268
https://researchoutput.csu.edu.au/admin/files/44428874/2018_BEVA_FINAL_PROGRAMME.pdf (Conference program)
https://researchoutput.csu.edu.au/admin/files/44428876/BEVA_Congress_2018_Handbook.pdf (Conference proceedings)

Conference

ConferenceBritish Equine Veterinary Association Congress
CountryUnited Kingdom
CityBirmingham
Period12/09/1815/09/18
OtherEurope's largest equine veterinary congress, BEVA Congress offers delegates world-class science in a lively commercial environment.
Internet address

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    Hughes, K. (2018). Pleuropneumonia – advances in treatment and prognosis. 189-189. Abstract from British Equine Veterinary Association Congress , Birmingham, United Kingdom.