Pleural Diseases in Horses PDF

Andy Durham BSc.BVSc.CertEP.DEIM.DipECEIM.MRCVS ◦ Review the anatomy of the pleura and mediastinum ◦ Understand the functional effects of expansion of the pleural space ◦ Know the commonest causes of pleural space expansion in horses (pleuropneumonia, wounds, neoplasia, haemothorax, pneumothorax)...

Andy Durham BSc.BVSc.CertEP.DEIM.DipECEIM.MRCVS ◦ Review the anatomy of the pleura and mediastinum ◦ Understand the functional effects of expansion of the pleural space ◦ Know the commonest causes of pleural space expansion in horses (pleuropneumonia, wounds, neoplasia, haemothorax, pneumothorax) ◦ Understand risk factors for pleuropneumonia in horses ◦ Know the diagnostic methods for investigation and differentiation of pleural diseases (incl. ultrasonography, radiography, pleurocentesis) ◦ Understand the treatment options for pleural diseases  Pleural ◦ Pleura = a thin membrane of connective tissue plus a layer of cavity mesothelial cells ◦ Parietal pleura = lining of the thoracic cavity ◦ Visceral pleura = covers outer surface of lungs and other thoracic structures ◦ Pleural cavity = the space between the parietal and the lung skin visceral pleura (right and left). Normally just a potential space with a small volume of pleural fluid lubricating the surfaces ◦ Mediastinum = central thoracic area between the two lungs and the two pleural cavities ◦ Pleural diseases are typified by expansion of the pleural cavity visceral parietal which restricts lung capacity pleura pleura  trachea Lung Parietal pleura Pleural cavity diaphragm Visceral pleura mediastinum  trachea Lung Parietal pleura Pleural cavity diaphragm Visceral pleura mediastinum Pleural space may fill with:  Fluid effusion o transudate = hydrothorax o modified transudate o exudate (pus) = pyothorax blood = haemothorax chyle = chylothorax  Air = pneumothorax Pleural space may fill with:  Fluid effusion o transudate = hydrothorax o modified transudate o exudate (pus) = pyothorax blood = haemothorax chyle = chylothorax  Air = pneumothorax  Extremely rare in horses Transudate – increased volume of normal fluid (low cells, low protein) Might theoretically arise due to: increased venous pressure congestive heart failure decreased plasma colloidal pressure hypoproteinaemia  Extremely rare in horses Generally following blunt trauma (fall) Possibly following neoplasia  69 horses with pleural effusion 26 (38%) caused by neoplasia (modified transudate) 43 (62%) caused by infection (exudate) neoplastic infection International transport 0% 33% mean age 13 y 8y Mean fluid volume 32 L 10 L Temperature 38.2°C 38.6°C Plasma fibrinogen 5.3 g/L 7.8 g/L Serum amyloid A 59 mg/L 230 mg/L Pleural cell count 9 x 109/L 64 x 109/L Pleural protein 36 g/L 58 g/L 2nd commonest cause of pleural effusion modified transudate mild increase in cells (5-20x109/L, mixed cell types, 50x109/L),  %neutrophils (>95%),  total protein (>50 g/L),  lactate (>3 mmol/L),  glucose (95% neutrophils (+bacteria?)  Usually simply shows white-creamy-yellow exudate >95% neutrophils (+bacteria?) Sometimes shows orange exudate or frank bleeding  Usually simply shows white-creamy-yellow exudate >95% neutrophils Sometimes shows orange exudate or frank bleeding Culture from trachea is more successful than culture from the pleural fluid Often mixed oropharyngeal bacteria Streptococci Enterobacteriacea Anaerobes Klebsiella sp. especially destructive and persistent  Normal lung simply reflects ultrasound (a gliding white line)  Normal lung simply reflects ultrasound (a gliding white line) Progression: points of ultrasound penetration (“comet tails”) reflecting pleural roughening and inflammation  Normal lung simply reflects ultrasound (a gliding white line) Progression: points of ultrasound penetration (“comet tails”) reflecting pleural roughening and inflammation larger areas of lung consolidation (pneumonia)  Normal lung simply reflects ultrasound (a gliding white line) Progression: points of ultrasound penetration (“comet tails”) reflecting pleural roughening and inflammation larger areas of lung consolidation (pneumonia) pleural effusion  Normal lung simply reflects ultrasound (a gliding white line) Progression: points of ultrasound penetration (“comet tails”) reflecting pleural roughening and inflammation larger areas of lung consolidation (pneumonia) pleural effusion pleural fibrin  Collection of a small sample is important for diagnosis cell count, neutrophil% and protein, glucose, lactate; culture Teat cannula or needle + 3-way tap 1. All open 2. Chest closed 3. Chest open straight 4. Chest open side port  Collection of a small sample is important for diagnosis cell count, neutrophil% and protein, glucose, lactate; culture teat cannula or needle + 3 way tap Drainage of large effusions as part of treatment Thoracic trocar May leave in-dwelling  Collection of a small sample is important for diagnosis cell count, neutrophil% and protein, glucose, lactate ; culture teat cannula or needle + 3 way tap Drainage of large effusions as part of treatment Thoracic trocar May leave in-dwelling Heimlich valve (or condom) to stop air ingress  Collection of a small sample is important for diagnosis cell count, neutrophil% and protein, glucose, lactate ; culture teat cannula or needle + 3 way tap Drainage of large effusions as part of treatment Thoracic trocar May leave in-dwelling Heimlich valve (or condom) to stop air ingress Can flush pleural cavity via the trocar saline +/- fibrinolytics  Antimicrobials ideally based on culture results (tracheal wash/pleural fluid) Broad spectrum including anaerobes procaine penicillin (20,000 iu/kg IM q 12h) + gentamicin (7 mg/kg IV q 24h) + metronidazole (25 mg/kg PO q 12h) oxytetracycline (5.0-7.5 mg/kg IV q 12h) (ceftiofur, cefquinome) – should be conserved! NSAIDs Pain, pyrexia Flunixin meglumine (1.1 mg/kg IV or PO q 24h (or q 12h?)) Anti-fibrinogenesis Heparin systemically or as a flush? – might potentiate pleural bleeding Fibrinolytics Tissue plasminogen activator (tPA) (“Alteplase”, “Tenecteplase”) 12 mg intrapleural  Penetrating trauma usually following a stake wound  Penetrating trauma usually following a stake wound aspiration of food following oesophageal obstruction (“choke”) (surprisingly rare)  Penetrating trauma usually following a stake wound Aspiration following oesophageal obstruction (“choke”) (surprisingly rare) Oesophageal rupture Spontaneous (Friesians?) Iatrogenic?  Generally following blunt trauma (fall) (Possibly following neoplasia) Swirling “smoke” Generally resolves as blood returns to circulation (via lymphatics?) Don’t drain unless compromises breathing  Generally following penetrating trauma (stake wound) Possibly following neoplasia Possibly following pleuropneumonia Lung sinks to ventral thorax Diagnosis Radiography – dorsal lung borders visible  Generally following penetrating trauma (stake wound)  ventral - dorsal  Possibly following neoplasia Possibly following pleuropneumonia Lung sinks to ventral thorax Diagnosis Radiography – dorsal lung borders visible Ultrasonography – “still” air reflection (not gliding) in dorsal thorax  Treatment May self-resolve if mild Aspirate from dorsal thorax if compromising breathing X