Equine bacterial pleuropneumonia (Proceedings)

Definitions

• Bacterial pneumonia = inflammation of the lung caused by bacterial colonization and multiplication

• Lung Abscess – localized, encapsulated regions of pulmonary necrosis, debris & exudate

Pleuropneumonia

• Microbial colonization of lung

• Development of pneumonia ± lung abscesses

• Extension to visceral pleura & pleural space

• Development of "parapneumonic effusion"

Economic Importance

o Not studied analytically

o Medical care

o Loss of potential income

o Extensive recuperation period

o Diminished performance

o Mortality

Pathophysiology

Bacterial pneumonia

• Occurs when pulmonary defense mechanisms are:

• Compromised

• Overwhelmed

Pulmonary Defense Mechanisms

• Non-immunologic

• Aerodynamic filtration

• Mucociliary transport apparatus

• Clears particulate debris from lungs at 17 mm/min

• Cough reflex

• Immunologic

• Alveolar macrophages – distal airways & alveoli

o Microbial phagocytosis & killing

• Neutrophils – more proximal airways

• Cellular immunity

• Humoral immunity

o IgA - upper airways

o IgG - lower airways & alveoli

Pulmonary Defenses

Pathophysiology

Overwhelmed PDM

• Aspiration of oropharyngeal bacteria

• Pharyngeal / laryngeal dysfunction

• Esophageal dysfunction / choke

• Aspirated foreign bodies

• General anesthesia

• Thromboembolic disease

• Severe bacteremia

Suppression of pulmonary defense mechanisms

• Transportation

• Exercise

• Viral infections

• Stress

• Inhaled toxins (ie. ammonia)

• Poor ventilation / overcrowding

• Immunosuppressive drugs

• Immunologic diseases

• Endotoxemia / systemic diseases

Effects of Transport

Transport is well-accepted as a predisposing factor for respiratory infection

• Increased production of cortisol

• Decreased quantity & bactericidal function of AM

• Decreased mucociliary clearance (dehydration)

• Increased concentration of airborne particulates in airways

• Road & hay dust

• Bacteria & fungi

• Racklyeft, et al, Aust Vet J, 1990

• Restraining the head during transport prevents postural drainage and enhances bacterial colonization of the LRT

• Raidal, et al, Aust Vet J, 1995, 1997

• Confinement with head elevated results in inflammation and increased numbers of bacteria in TBA of horses within 6-12 hours

o Antimicrobial therapy did not alleviate

o Intermittent release of head did not alleviate

Effects of Exercise

• Racehorses

• Aspiration of track debris

• Aspiration of oropharyngeal secretions

• Exercise-induced pulmonary hemorrhage

• Ideal environment in lung for bacterial growth

• Exercise results in increased bacterial contamination of lower respiratory tract

• Raidal et al, Aust Vet J, 1997

• Compared quantitative cultures from TBA before & after strenuous exercise:

o 10-fold increase in aerobic bacteria

o 100-fold increse in anaerobic bacteria

Effects of Exercise on PDM

• Cortisol

• Increased serum cortisol

• Increased cortisol in BAL-F

• Alveolar macrophages

• Decreased concentration in BAL-F

• Decreased phagocytosis

• Decreased bacterial killing cap

• Neutrophils

• Increased concentration in blood & BAL-F

• Decreased chemotaxis & bacterial killing cap

• Lymphocytes

• Increased concentration in blood

• Decrease in CD4+ : CD8+ ratio

• Increased susceptibility to experimentally-induced influenza

• Increased severity & duration of clinical signs

Effects of Viral Infection on PDM

• Influenza / Herpes virus

• Damage tracheobronchial epithelial cells

o Enhance bacterial attachment and colonization

o Suppress mucociliary clearance

• Decreased surfactant levels

• Destruction of alveolar type II cells

o Collapse of distal airways

• Impaired alveolar macrophage function

• Increased pulmonary secretions associated with pulmonary inflammation

Pathophysiology

Bacterial pneumonia

• Bacterial contamination, colonization & proliferation

• Local tissue damage

• Influx of inflammatory cells & mediators => tissue damage

• Accumulation of cellular debris, serum & fibrin

• Dissemination of inflammatory response

• Ventilation / perfusion mismatch => impaired gas exchange

• Systemic hypoxemia & toxemia

Anaerobic pneumonia

• Opportunistic / facultative anaerobes

• Normal flora of URT

• Anaerobes require:

• Low oxygen tension

• Low oxidation - reduction potential

• Normal lung protected from anaerobes

• Altered lung (pneumonia, trauma, ischemia, shock) => environment for colonization & multiplication of anaerobes

• Anaerobes release exotoxins & enzymes

• Heparinases, collagenases

• Pulmonary destruction => abscess & necrosis

• Microbial synergy b/w aerobes & anaerobes

• Mutually amplify multiplication & pathogenicity

Epidemiology

Limited analytical data

• Any age, breed, sex, occupation

• Suggested risk factors

• Long-distance transport

• Strenuous exercise

• Viral respiratory infections

• Poorly ventilated stalls

• Occupation - racing

o EIPH?

o Inhalation of dirt?

• General anesthesia?

• Aspiration - laryngeal / pharyngeal dysfunction

• Immunosuppression

Raphel & Beech, JAVMA 1982;181:808

• 90 affected horses

• Most prevalent in TB & STB racehorses (n=68)

• Predisposing stresses (n=34)

• Long-distance transport (n=22)

• Post surgical patients (n=11)

o URT surgery (n=5)

• Recumbent horse (n=1)

Epidemiology

• Collins et al, JAVMA, 1994

• 36 horses with acute pleuropneumonia

o Racehorses (n=22)

o TB (89%) vs hospital population (35%)

o Recent long distance transport (n=11)

o Recent episode of EIPH (n=4)

o Recent viral resp infection (n=4)

• Byars and Becht, VCNA (Equine) 1991

• 153 affected horses

o Recent van transport (n=60; 39%)

Causes of Pleural Effusion in Horses

• Bacterial pleuropneumonia

• Neoplasia

• Penetrating chest wound

• Hemothorax

• Esophageal perforation

• Concurrent peritonitis

• Diaphragmatic hernia

• Coccidioidomycosis

• Pulmonary granuloma

• Mycotic pneumonia

• Viral pneumonia

• Post-thoracotomy

• Fibrosing pneumonia

• Hypoalbuminemia

• Cryptococcosis

• Pericarditis

• XS fluid therapy

• Uroperitoneum

• Septicemia

• EIA

• Aberrant metacestodes

• Idiopathic pleuritis

• Liver failure

• Congestive heart failure

• Mycoplasma felis

• Chylothorax

• Pulm embolism

• Pulm hydatidosis

Pathophysiology of Pleural Effusion

Mechanisms

• ↑ microvascular hydrostatic pressure

• ↓ hydrostatic pressure in pleural space

• ↓ microvascular oncotic pressure

• ↑ oncotic pressure in pleural space

• ↑ microvascularity permeability

• Impaired lymphatic drainage from pleural space

• Transdiaphragmatic movement from peritoneal space

Pathophysiology of Parapneumonic Effusion

• Pneumonia or pulm. abscess

• ↑ cap. permeability of lung & visceral pleura

• Favors movement of fluid & protein into pleural space

• ↓ lymphatic drainage of fluid & protein

• Favors accumulation of PF

Pathophysiology of Parapneumonic Effusion

Three Stages

• Exudative stage

• Fibrinopurulent stage

• Organization stage

Stage 1 = Exudative Stage

• Inflammation of lung & visceral pleura

• Neutrophils incite vascular injury => ↑ vascular perm. => outpouring of sterile, protein rich, exudative fluid

• Uncomplicated PE

Pathophysiology of Parapneumonic Effusion

Stage 2 = Fibrinopurulent Stage

• Bacterial invasion & multiplication (complicated PE)

• Influx of neutrophils & clotting factors

• Accumulation of fluid, bacteria, cellular debris

• Fibroblasts deposit fibrin => loculates fluid & compromises lymphatic drainage

Pathophysiology of Parapneumonic Effusion

Stage 3 = Organization Stage

• Growth of fibroblasts into exudate

• Continued deposition of fibrin on pleural surfaces

• "Pleural peel"

• Inelastic fibrous membrane

• Encases lung

• Limits pulmonary expansion

Non-pneumonic Causes of Bacterial Pleuritis

• Penetrating thoracic wounds

• Esophageal rupture

• Primary idiopathic pleuritis

• Bacteremia

Clinical Signs

• Fever of unknown origin

• Lethargy, anorexia

• Tachypnea, tachycardia

• ± Nasal discharge

• ± Cough

• ± Exercise intolerance

• ± Respiratory distress

• ± Weight loss

• ± Halitosis

• ± Sternal edema

• ± Hypovolemia / endotoxemia

• ± Pleurodynia

Clinical Signs

Pleurodynia

• Pawing / apparent colic

• Anxious facial expression

• Abducted elbows

• Shallow respiration

• ↓ chest excursion

• Reluctance to cough, move, lie down, descend

• Painful to palpation of ICS

• Easily misdiagnosed

• Colic, Exert Rhab, Laminitis

Thoracic Auscultation

Rebreathing Bag Helpful!

• Dorsal thorax

• Normal to ↑ BV sounds

• ± Crackles & wheezes

• Ventral thorax

• Attenuated BV sounds

• Referred large airway sounds

• ± Friction rubs

• ± Radiating heart sounds

DDX for Attenuated Lung Sounds

• Pleural effusion

• Pleural abscess

• Pulmonary atelectasis

• Pulmonary abscess

• Pulmonary consolidation

• Pulmonary neoplasia

• Pulmonary granuloma

• Diaphragmatic hernia

• Pericardial effusion (cranioventral)

• Pneumothorax (dorsal)

Thoracic Percussion

• Regional dullness - ventral lung fields

• Resonance over dorsal lung fields

• Focal-multifocal regions of dullness

• Loculations

• Peripheral pulmonary lesions

• May detect pleurodynia

Thoracic Radiography

• Pleural effusion - ventral soft-tissue opacity

• Obscures diaphragm and heart borders

• Air-fluid interface uncommon

• Most useful after pleural drainage

• Loss of clarity of lung fields

• Air bronchograms

• Interstitial pattern

• Lung abscesses

Thoracic Ultrasonography

Useful to localize & characterize disorders of:

• Peripheral lung

• Atelectasis, consolidation, abscessation, necrosis, neoplasia

• Pleural space

• Pleural effusion, "gas echoes," pleural fibrin, loculations, abscessation, pneumothorax

• Cranial mediastinum

• Effusion, abscessation, neoplasia

Thoracic Ultrasound

Normal lung

Comet tails

Clusters of Comet Tails

Consolidation

Consolidation

Consolidation

Pulmonary abscess

Necrotizing Pleuritis, Tetanus

Necrotizing Pleuritis, Tetanus

Pleural effusion, atelectic lung

Pleural effusion

Pleural effusion, lymphosarcoma

Site selection of thoracocentesis

Gas echoes

Loculations

Fibrin loculae

Pleural fibrin & comet tails

Pleuritis

Thoracocentesis

Site Selection

• Localization

• Ultrasonography

• Percussion

• Blind site selection

• 7-8 ICS below pt of shoulder

Thoracocentesis

Technique

• Aseptic technique

• Local anesthetic

• Stab incision

• Instruments

• Teat cannula

• Chest tube

• IV catheter

• Hypodermic needle

• Stopcock

• Use caution to avoid pneumothorax

U/S site selection

Pleural effusion & ascites

Pleural Fluid Analysis

Submission to Lab

• EDTA tube

• Cytology & cell counts (total & diff)

• Protein conc.

• Gram's stain

• Heparin tube

• Biochemical testing

• Aerobic culture & MIC

• Anaerobic culture

Normal Equine Pleural Fluid

• Colorless - pale yellow

• Transparent

• Odorless

• Protein conc. = 0 - 4.7 g/dl

• TNCC = 0 - 10,000/ul

• Sterile

• Normal cell morphology

Parapneumonic Effusion

• Cloudy

• Yellow - bloody

• ± Putrid odor

• Exudative

• TNCC > 10,000/ul

• Protein > 4.0 g/dl

• Neutrophilia ± degenerative changes

• ± Cytologically-visible bacteria

Biochemical Testing

• Rapid assessment of:

• Sepsis & need for drainage

• Stage of disease

• Micro-environment

• Parameters

• pH

• HCO3

• Glucose

• LDH

• Lactate

• PCO2

Biochemical Testing

Brumbaugh & Benson, AJVR, 1990;51:1032

• Non-septic PF

• PF values similar to venous blood

• pH, HCO3, PO2, lactate, glucose

• Septic PF

• PF values compared to venous blood

• ↓ pH

• ↓ glucose

• ↑ lactate

• ↑ PCO2

• ↓ HCO3

Biochemical Testing

• Suggested PF parameters to determine sepsis

• pH < 7.1

• Glucose < 40 mg/dl

• LDH > 1000 IU/L

• Lactate increased

Tracheobronchial Aspiration

Purpose

• Retrieve airway secretions for:

• Cytologic examination

• Grams stain

• Aerobic culture

• Anaerobic culture

• Kirby-Bauer antimicrobial susc.

• Min. inhibitory conc. (MIC)

Techniques

• Percutaneous transtracheal aspirate (TTA)

• Trans-endoscopic tracheal aspiration

• Guarded swabs/brushes/catheters

• Polyethylene tubing

• Bronchoalveolar lavage (BAL)

• "Blind" BAL catheter

• Tans-endoscopic BAL

Percutaneous Transtracheal Aspiration

• Advantages

• Allows aseptic sampling

• Samples pooled secretions from entire lung

• Disadvantages

• SQ cellulitis / abscess / emphysema

• Cytologic findings often differ from histopathologic findings in small airways

Transendoscopic Tracheal Aspiration

• Advantages

• Avoid complications of TTA

• Direct visualization of collection site

• Disadvantages

• Contamination from endoscope or URT

• Samples are less suitable for culture

Bronchoalveolar Lavage

BAL vs. TBA

Rossier et al, JAVMA 1991

• 22 horses with bacterial pneumonia or pleuropneumonia

• BAL detected cytologic abnormalities in 10/22

• TTA detected cytologic abnormalities in 22/22

• BAL may not detect focal or multifocal pulmonary disorders

Cytology

• Neutrophilic infiltration

• Degenerative neutrophils

• Bacteria

• Intracellular

• Extracellular

Culture Results

Interpretation

• Positive culture alone does not necessarily indicate bacterial pneumonia

• Interpret cultures in conjunction with:

• Method of collection

• Clinical signs

• Other clinical findings

• Cytologic findings

Should we culture TBA or PF or both?

Sweeney et al, JAVMA, 1991;198:839

• 327 horses: TBA

• 91% positive

• 127 horses: PF

• 66% positive

• 111 horses: TBA & PF

• 43% TBA positive & PF negative

• 5% TBA negative & PF positive

• Recommend culture & cytology of both

Pleuroscopy

• Visual assessment of lung & pleurae

• Procedure

• Rigid laparoscope / flexible endoscope

• Standing w/ sedation

• Aseptic technique

• 10th ICS

• Pneumothorax facilitates exam

Therapeutic Management

• Varies depending on:

• Severity & duration

• Causative bacteria

• Character & volume of PE

• Fibrin deposition

• Pleural micro-environment

• Severity of lung pathology

• Sequelae

• ** Antimicrobial therapy

• ** Supportive care

• ** Rest

• ** Monitoring

• ± Pleural drainage

• ± Pleural lavage

• ± Ancillary therapy

• ± Thoracostomy

Systemic antimicrobials

Selection

• Before obtaining culture results:

• Broad-spectrum

• Prevalence & susceptibility data

• After obtaining culture results:

• Isolates & MIC patterns

• Distribution

• Drug & host related factors

• Site of infection

• Microenvironment

• Ease of administration

• Toxicity

• Cost

Antimicrobial Selection

Commonly used antimicrobials

• Aminoglycosides

• Penicillins

• Cephalosporins

• Trimethoprim sulfa

• Metronidazole

• Chloramphenicol

• Enrofloxacin

• Doxycycline

• Rifampin

Antimicrobial Therapy

Intrapleural

• Achieve higher concentration in pleural space

• Sodium penicillin G (10-20 MU) IP q 12 hrs

• Combined w/ systemic therapy

Pleural drainage materials

Indications

• Voluminous PF => resp. distress

• Complicated PE

• Empyematous

• Putrid odor

• Cytologically-visible bacteria

• Positive cultures

• Glucose < 40 mg/dl

• pH < 7.1

• Elevated lactate

• Poor response to conservative therapy

Placing chest tube

Suturing chest tube

Chest tube w/ Heimlich valve

Pleural drainage

Pleural Lavage

• Facilitates drainage of:

• Thick, viscous PE

• Fibrin

• Necrotic debris

• Improve pleural micro-environment

• 5-10 L warm sterile LRS q 12-24 hrs

• Contraindication: BPC

Fibrinolytic Therapy

Intrapleural

• Human patients

• Streptokinase 100-250 U q 12 hrs

• Enzymatic debridement

• Lyse adhesions

• Promote drainage of loculae

• Equine patients?

• $$$$$$$$$$

• Recombinant tPA?

Supportive Care

• IV / oral fluid therapy

• NSAIDs

• DMSO

• Polymyxin B (endotoxemia)

• Bronchodilators

• Pentoxyphylline

• Nutritional support

• Probiotics (Sacchromyces bullardii)

• Intranasal oxygen

• Inhalant therapy

• Rest

• Controlled environment

• Monitor for sequelae

Sequelae of Pleuropneumonia

• Endotoxemia

• Antibiotic-associated enterocolitis

• Laminitis

• Thrombophlebitis

• Pleural fibrosis

• Pleural abscesses

• Pulmonary abscesses

• Cranial thoracic masses

• Broncho-plerual communications

• Pneumothorax

• Pericarditis

Pleural or Pulmonary Abscess

• Diagnosis: ultrasonography / radiography

• Treatment:

• Systemic antimicrobials

• Drainage via trocars / tubes

• Suction

• Lavage

• Thoracostomy

Cranial Thoracic Abscesses

Byars et al, EVJ, 1991;23:22-24

• Clinical signs

• Tachycardia

• Pointing of forelimb

• Pectoral & forelimb edema

• Jugular distension / thrombosis

• Caudal displacement of heart

• Diagnosis: ultrasound

• Treatment: antimicrobials & drainage

Cranial thoracic mass

Cranial thoracic mass (yearling with CTA)

Pneumothorax

• Etiology

• Bronchopleural communication

• Indwelling chest tubes

• Thoracostomy

• Clinical signs

• None => tachypnea, respiratory distress

• Diagnosis

• Auscultation, ultrasound, radiography

• Treatment

• Evacuation of pleural air

Broncho-pleural Communications

• Necrotizing pleuropneumonia

• CS: cough, ND, pneumothorax

• Dx: IP infusion of fluorescein

• Tx: aspirate free air

Pericarditis

• Clinical signs

• Muffled heart sounds

• Pericardial friction rubs

• RHF

• ECG electrical alternans

• Diagnosis

• echocardiography

• Treatment

• Antimicrobials

• Pericardial drainage / lavage

• Instillation of antimicrobials

Prognosis

• Patient Considerations

• Occupation

• Duration

• Pleuropulmonary damage

• Sequelae

• Owner considerations

• Financial commitment

• Medical considerations

• Early diagnosis

• Aggressive therapy

• Ultrasound monitoring

Prognosis

• Early dx & aggressive tx

• Good - excellent for survival

• Good for return to athletic fxn

• Advanced case with sequelae

• Fair - good for survival

• Fair - poor for athletic fxn

Prognosis

Raphel & Beech, JAVMA, 1982

• Survival: 38/90 (42%)

• Not associated with outcome

o Breed , occupation

o PF: volume, WBC, TP

o Blood: PCV, TPP, WBC, Fibrinogen

o Bacterial isolates

• Associated with outcome

o Isolation of E. coli

• Athletic function

• 16/38 (42%) returned to normal performance

Prognosis

Sweeney et al, JAVMA, 1985;187:721-724

• 46 horses w/ anaerobic cultures

• Anaerobic isolates: 33% survival

• No anaerobic isolates: 67% survival

• Foul smell

• Survival = 2/13 (15%)

Prognosis

Reef, Proc. ACVIM 1990;8:573-575

• Survival assoc. w/ absence of:

• Pleural effusion

• Fibrin

• Loculi

• Gas echoes

• Lung necrosis

• Return to athletic fxn assoc. w/ absence of:

• Pleural fluid

• Lung consolidation

• Lung necrosis

• Gas echoes

Prognosis

Collins et al, JAVMA, 1994;205:1753

• 43 cases

• 22/43 (61%) discharged

• Anaerobes - no effect on survival

Prognosis

Carr et al, Proc AAEP, 1994

• 21 horses w/ hemorrhagic pulmonary infarction

• Recent transport or exercise

• Peracute onset

• Rads & US: pulm consolidation & PE

• Serosanguinous ND & PE

• ↑ PT, PTT, FDP

• Necropsy: arterial thrombosis => infarction, hemorrhage, necrosis, sepsis, PE

• Guarded to poor prognosis

Prognosis

Seltzer & Byars, JAVMA, 1996

Byars, Proc Dubai Int Eq Symp, 1997

• Survival of tx horses = 134/140 = 96%

• 4/6 non-survivors died w/I 48 hrs

• Survival of long-term tx = 134/136 = 98.5%

• 70 TBs of racing age

• 43/70 = 61% raced

• 24/43 = 56% won a race

• Indwelling drains / dur of tx = no effect

• CTM: 1/8 raced

• BPC: 0/2 raced

Surgical management

Thoracostomy

• Pleuritis cases that develop pleural abscesses that are refractory to medical management

• Alternative to euthanasia

• Evacuation of adverse material from thorax

• Too large for tube drainage

• Viscous or inspissated exudate

• Fibrinopurulent material

• Necrotic tissue (lung)

Thoracostomy-Case Selection

Proper case selection is critical

• Not recommended for:

• Primary form of tx

• Acute or diffuse pleuritis

• Removal of fibrin

Thoracostomy-Case Selection

Proper case selection is critical

• Most effective for subacute-chronic cases

• Stable systemic condition

• Signs of endotoxemia resolved

• No laminitis or major organ dysfunction

• One hemithorax mostly healed

• Remainder of ipsilateral thorax mostly healed

Thoracostomy-Case Selection

Proper case selection is essential

• Persistent mass(es) of inspissated exudate and necrotic debris

• Too large for drainage via chest tubes

• Refractory to medical tx

• Unilateral & localized

• Complete mediastinum

• Visceral-parietal seal

• Walled off from ipsilateral lung

Preoperative Assessment

Sonographic mapping

• Assess number, character, and location of thoracic mass(es)

• Localize boundaries of thoracic mass

• Assure mass is encapsulated from ipsilateral and contralateral pleural space

• Simultaneous infusion of LRS

• Map boundaries of infused fluid

• Assess BP communication

• Scan cranial mediastinal region

Thoracostomy

Surgical position

• Standing

• Less risks of general anesthesia

• Less expensive

• Gravity aids in removal of necrotic material

• General anesthesia

• IPPV-control of ventilation

• Controlled patient compliance

Thoracostomy

Surgical approach

• Intercostal

• Less invasive

• Smaller cosmetic defect

• Reduced postoperative morbidity

• Can always progress to rib resection if needed

Thoracostomy

Surgical approach

• Partial rib resection

• Improved exposure

• Complete removal of necrotic material

• Selection of optimum approach

• Location, size & character of necrotic material within thx

Thoracostomy

Surgical site

• Sonographic mapping

• Usually rib #6, 7 or 8

• Most ventral aspect of cavity

Thoracostomy

Standing position

• Standing in stocks

• Xylazine ± detomidine

• Detomidine ± butorphanol

• Local anesthesia

• Carbocaine®

• Line block-skin, SQ, muscles

Thoracostomy

Intraoperative mgt

• Plan ahead!!! Be prepared!!!

• Monitor MM, HR, RR & respiratory effort

• Sonographic assessment of pneumothorax

• Control of pneumothorax

• Suction unit, teat cannulas

• Supplement oxygen

• IPPV & general anesthesia

• Blood transfusion

Thoracostomy-Surgical Technique

Standing open thoracostomy-intercostal approach

• Aseptic prep & local anesthesia

• Vertical incision in ICS

• Lateral thoracic vein-ventral extent of latisimus dorsi

• Control hemorrhage

• Sharp division of cutaneous trunci & intercostal muscles

• Probe into thoracic cavity

• Enlarge incision as needed

• Remove debris & lavage

• Pack with lap sponge

• Cover with self-adhering bandage

Thoracostomy-Surgical Technique

Open thoracostomy & partial rib resection

• Aseptic prep & local anesthesia

• 25-40 cm vertical skin incision over rib

• Sharp dissection to periosteum of rib

• Elevate & reflect periosteum

• Gigli wire-transect proximal rib

• Reflect rib ventrally & disarticulate at CC jxn

• Remove 15-30 cm segment of rib

• Incise parietal pleura 12-25cm

• Explore pleural cavity

• Manually evacuate necrotic material

• Gentle manual debridement & lavage

• Partial closure of incision

• Pack incision with sterile dressing

Thoracostomy

Post-operative care

• Antimicrobials/ NSAID

• Supportive care

• Stall rest-followed by hand walking

• Manual debridement & lavage q 12-24 hours

• Hydrotherapy

• Change dressings & packing

• Keep incision open until cavity has granulated

• Cavity granulates and closes in 3-8 wks

Survival

Short term outcome (n=22)

• 18 horses - discharged alive

• 19 horses - resolution of thx disease

• 20 horses - improved thx disease

• 2 cases with poor outcome were examples of poor case selection

Survival

Long-term outcome (n=18 survivors)

• All 18 had complete resolution of thoracic disease

• 12 returned to same athletic function

• 3 returned to lesser athletic function

• 3 retired to pleasure or breeding