Chapter 46 - Pyothorax

Question 1

Is continuous suction more effective than intermittently suction ?

Answer 1

No proven superiority.

Question 2

Median duration of tube placement and when to remove them?

Answer 2

• 4-8 days (dogs and cats)
• Remove when production < 2-5 mL/kg/day and clinical, radiologic and cytologic improvement (minimal pleural effusion, non-degenerate neutrophils and no evidence of infectious organisms)

Question 3

Benefits of thoracic lavage ?

Answer 3

• Facilitation of drainage,
• Minimization of bacteria and inflammatory mediators in the pleural space,
• Reduction in viscosity of the fluid,
• Prevention of thoracostomy tube obstruction,
• Breakdown of adhesions.

Question 4

How is a thoracic lavage realized ?

Answer 4

• Slowly inject warm sterile isotonic saline (10–20 mL/kg) via the thoracostomy tube
• Retrieval of less than 75% of the volume infused should prompt additional investigation
• Fluid can be left in the pleural space for 10–15 minutes before withdrawal
• 2–3 times daily or more frequently as needed (appearance and volume of the aspirated
  fluid are often used to guide frequency of lavage)

Question 5

Use of fibrinolytics for thoracic lavages ?

Answer 5

Large randomized trial in humans showed that intrapleural fibrinolytics did not reduce mortality, frequency of surgery, or length of hospital stay but were associated with more adverse events (such as fever, pain, and hypersensitivity reactions) [47]. Additionally, the British Thoracic Society meta-analysis concluded that there is no indication for their routine use in adults

Question 6

There is no definitive
criteria exist that dictate ideal therapy between surgical and medical management.
What are the generally accepted indications for surgical treatment ?

Answer 6

• Failure of medical therapy (persistent effusion or
  infection despite appropriate thoracostomy drainage and antimicrobial therapy or failure of clinical improvement in 3 or more days)
• Diagnostic imaging consistent with pulmonary or mediastinal migrating foreign material or abscessation,
• potentially the presence of Actinomyces spp. in areas where migrating grass awns are endemic

British Thoracic Society guidelines for adults and children recommend surgical intervention if patients are showing continued signs of sepsis after 5–7 days of appropriate thoracic drainage and antimicrobials

Question 7

Prognosis ?

Answer 7

Overall survival in dogs is 83% and in cats is 62%.

Question 8

Choice of antibiotics ?

Answer 8

• Broad-spectrum coverage of aerobic and anaerobic organisms
• Empiric antimicrobial therapy: beta-lactam with beta-lactamase inhibitor (e.g. ampicillin/sulbactam): efficacious for Actinomyces spp. (dogs), most anaerobes, and Pasteurella spp. (cats and dogs);
• Addition of a fluoroquinolone such as enrofloxacin will
  improve gram-negative coverage and can be considered

Question 9

Duration of antimicrobial therapy ?

Answer 9

• No consensus
• British Thoracic Society: additional 1–4 weeks of antibiotics to be given at discharge for children and at least 3 weeks in adults,
• Discontinuation based on clinical, biochemical, and radiological response.

Question 10

Etiology of pyothorax in dogs?

Answer 10

• Often undetermined (definitive etiology in dogs : 4–22% of cases, in cats 5–67%)
• Dogs: foreign body migration, penetrating thoracic trauma, hematogenous or lymphatic spread, esophageal perforation, parasitic migration, progression of discospondylitis, parapneumonic spread, neoplasia, ruptured lung abscesses, and iatrogenic causes (thoracic surgery or thoracocentesis). Most common documented cause is a migrating grass awn or plant material.

Question 11

Etiology of pyothorax in cats?

Answer 11

• parapneumonic extension, penetrating thoracic wounds, foreign body migration, parasitic migration, and hematogenous spread.
• Leading cause in cats is currently unknown
• Common belief exists that direct inoculation by cat bites may be a predominant cause (bacterial organisms isolated from pleural infections similar to cat-bite abscesses, cats with pyothorax are 3.8 times more
  likely to live in multicat households, higher
  incidence during fighting and mating period) - BUT no significant increase in risk in outdoor or male cats and recent review : only 15.6% of feline pyothorax cases described in the literature (20 out of 128 total cases) resulted from bite wounds