Diseases of the Lower Respiratory Tract, Pt. 2 Flashcards
What is the etiology of exercise-induced pulmonary hemorrhage?
alveolo-capillary membrane ruptures due to increased stress on the pulmonary artery and pleural space associated with exercise
- pulmonary artery increases to 90 mmHg
- pleural space decreases to -60 mmHg
What are 3 major risk factors to developing EIPH? What are some others?
- pulmonary capillary hypertension
- rheological properties of blood (increased PCV associated with exercise)
- subatmospheric pleural space
- extra/intra-thoracic airway obstruction
- mild equine asthma
- coagulopathies
- bronchial neovascularization
- pulmonary fibrosis causing altered compliance
- locomotor forces
In what horses is EIPH most common?
horses that run at higher speeds —> more intense exercise = greater proportion developing EIPH
- less common in jumpers and barrel racers
- common in racing Thoroughbreds
What is the pathophysiology of EIPH?
- exercise causes pulmonary capillary rupture
- hemorrhage induces inflammation of fibrosis
- this leads to reduced lung compliance and increased susceptibility to capillary rupture recurring
What are the 2 most common clinical signs of EIPH?
- bilateral epistaxis
- poor performance
- may be none if it it mild enough and horse swallows blood
When should endoscopies be done to diagnose EIPH?
30-120 minutes (or as long at 7 days) after intense exercise
What diagnostic is considered more sensitive than endoscopy for diagnosing EIPH? What should be seen?
cytology of TW or BAL fluid
- RBCs and erythrophages around 1 week
- hemosiderophage around 21 days
(fluid will be red)
What can be seen on pulmonary radiographs in cases of EIPH? When is this a useful diagnostic?
dorso-caudal opacification
when evaluating other secondary issues, like pneumonia
What are the 4 major ways to treat EIPH?
- prevent stress rupture of capillaries by decreasing pressure in pulmonary capillaries and increasing alveolar inspiratory pressure
- decrease inflammation and angiogenesis
- reduce bleeding by controlling coagulopathies and platelet function
- maintain capillary integrity
What drug is most commonly used to decrease pressure in pulmonary capillaries in cases of EIPH? What are other possibilities?
Furosemide (banned in Europe)
- Enalapril
- L-NAME
- Sildenafil
- Pentoxifylline
How is URT alveolar pressure increased to treat EIPH?
flair strips are placed on the nose and used to correct dynamic collapse by widening the nostrils
In what 3 ways is LRT alveolar pressure increased to treat EIPH?
- bronchodilators
- corticosteroids
- reduce environmental dust
What 5 alternative medications may be used to treat EIPH?
- vitamin K
- vitamin C
- aminocaproic acid
- aspirin
- biflavinoid
What is the prognosis of EIPH like?
- may have an effect on racing horse careers with severe episodes associated with poor performance
- 1 episode has the ability to cause more in the future
What is the most common cause of pneumonia in adult horses?
aspiration of bacteria from nasopharynx and oral cavity
- begins at airways as bacterial bronchitis or septic IAD
- then spreads to pulmonary parenchyma and extends to the pleural space
What is the most common bacterial etiology of pneumonia in adult horses?
bet-hemolytic Streptococcus equi subsp. zooepidemicus
What are the 2 most common aerobic Gram-positive bacterial etiologies of pneumonia in adult horses?
- Staphylococcus
- Rhodococcus
What are the most common Gram-negative non-enteric/enteric etiologies of pneumonia in adult horses?
NON-ENTERIC = Pasteurella, Actinobacillus, Pseudomonas (contaminant), Bordetella bronchiseptica
ENTERIC = Klebsiella, E. coli, Enterobacter, Salmonella
What are the 3 most common anaerobe etiologies of pneumonia in adult horses? What are they associated with?
- Bacteroides
- Clostridium
- Peptostreptococcus
less favorable prognosis
In what adult horses is pneumonia most commonly seen?
- younger racehorses that were just undergoin prolonged transportation
- those just under general anesthesia or undergoing upper airway surgery
- recent viral respiratory disease
- aspiration after choke (obstructed esophagus)
What is the pathophysiology of pneumonia in adult horses?
weakened immune defenses and massive numbers of bacteria allows for the colonization of lung by opportunistic bacteria
What is the single most predisposing factor for developing pneumonia associated with long distance transport?
head restraint —> lowered head posture is essential for mucociliary clearance
What are the general steps to the development of pneumonia in adult horses?
- infiltration with inflammatory cells causes damage to epithelium and endothelium
- flooding of inflammatory cells, debris, and fibrin
- this leads to exudative, fibropurulent pleuropneumonia
- fibrin will deposit and lead to the organizational stage (pleural peel)
What are the most common clinical signs of pneumonia in adult horses?
- exercise intolerance, cough, nasal discharge
- fever, anorexia, depression
- tachypnea, dyspnea, shallow breathing
- pleurodynia: pain causes horse to stand with elbows abducted
- sternal edema
- endotoxemia
What changes in pulmonary auscultation and percussion are expected with pneumonia?
decreased breath sounds in lower lung
muffled sounds
What is the prefered respiratory sample for diagnosing pneumonia?
transtracheal washes
How is ultrasound commonly used to diagnose pneumonia?
can be used to observe free fluid in the chest or atelectasis
Pneumonia, radiograph:
What are the 3 basic treatments for pneumonia in adult horses?
- antimicrobial therapy
- pleural drainage with a tube + one way valve
- ancillary NSAIDs and analgesics
What is the recommended antimicrobial therapy and length in adult horses with pneumonia?
broad-sprectrum lineup covering G +/- and anerobes, like Penicillin, Gentamycin, and Metronidazole
minimum 10 days or more
What are the major ancillary treatments recommended in adult horses with pneumonia?
- NSAIDs
- hydration (thoracocentesis can remove a lot of fluids)
- nutrition
- oxygenation
What are the 4 indications for performing pleural drainage in adult horses with pneumonia? When should it be done?
- volume sufficient to cause respiratory distress
- emphysematous
- fetid odor
- evidence of sepsis
early before fibrin develops (guided by ultrasound)
What are some complications associated with pneumonia in adult horses?
- phlebitis
- thrombosis
- diarrhea
- pnuemothroax
- cellulitis
- endotoxemia
- laminitis
- abscess development
When is prognosis with pneumonia particularly low in adult horses?
if there is hemorrhagic necrotizing pneumonia
What is the most common cause of pneumonia in foals? When do they typically develop this?
Rhodococcus equi
infected within the first few days of life and develop clinical signs within 2-6 months
How do foals typically become infected with Rhodococcus? What is important to note about spread on farms?
primary inhalation from the soil and secondary ingestion —> intracellular survival in macrophages
zoonosis is possible for immunocompromised humans
What are the general steps to Rhodococcus pneumonia spread?
- inhalation causes bacteria to go into the lungs
- sputum with the bacteria are coughed up and swallowed
- bacteria replicate in the intestinal tract and are shed in manure and the soil
What is the characteristic sign of Rhodococcus pneumonia? What are some other signs?
chronic suppurative bronchopneumonia leads to extensive pulmonary abscessation
- mild fever, occasional cough, increased RR
- decreased appetite, lethargy
- cough, tachypnea, dyspnea
- acute respiratory distress
- commonly subclinical and slowly progressive (critical mass must be reached)
What is evident on hematology and biochemistry in Rhodococcus pneumonia?
- hyperfibrinogenemia
- increased SAA
- neutrophilic leukocytosis
- ELISA for Vap-specific Ig
What is evident on radiographs in Rhodococcus pneumonia?
alveolar patterns with ill-defined regional consolidation
What is considered the best diagnostic for Rhodococcus pneumonia? What does it show?
ultrasonography (easier to use on young foals)
- irregularities
- focal consolidation
- extra-pulmonary locations
In what 2 ways are transtracheal washes used to diagnose Rhodococcus pneumonia?
- PCR with amplification of Vap A
- culture and sensitivity
What 3 things must tracheal washes be interpreted with for diagnosing Rhodococcus pneumonia?
- clinical signs of lower respiratory disease
- cytologic evidence of septic airway inflammation
- radiographic or ultrasound evidence of bronchopneumonia
What treatment is used for Rhodococcus pneumonia? Which is less commonly used?
macrolides (erythromycin, azithromycin, clarithromycin) + rifampin
erythromycin —> can cause hyperthermia, tachypnea, diarrhea in foals, and colitis in mares that eat manure of treated foals (C. diff)
Why are azithromycin and clarithromycin preferred in treating Rhodococcus pneumonia?
- high oral bioavailability
- prolonged half life
- increased pulmonary epithelial lining fluid concentration
What is treatment of Rhodococcus pneumonia guided by?
- resolution of clinical signs (3-8 weeks)
- normalization of fibrinogen
- resolution of ultrasound and readiographic lesions
How is Rhodococcus pneumonia managed? How are barns typically screened?
ventilation, dust, density, isolation, address pasture contamination
visual inspection, TPR, hematology, fibrinogen, SAA, imaging (radiographs, ultrasounds)
How is Gallium used to treat Rhodococcus pneumonia? Passive immunization?
it is a semi-metal similar to iron that bacteria will take up instead of iron
hyperimmune plasma is given —> 1 L at < 48 hr at 2-4 weeks of age
Why are antimicrobials used carefully in treating Rhodococcus pneumonia?
RESISTANCE —> 80% of subclinical foals recover without treatment
What are the 4 most common causes of pneumonia in neonates (<1 month)?
- hematogenic
- descending lung infection
- iatrogenic aspiration
- in utero infection
In what foals is interstitial pneumonia most common?
1-6 months of age —> form of ALI/ARDS
(sporadically rapidly progresses)
What is Pneumocystic jiroveci (carnii)? In what horses does it commonly cause pneumonia?
rare opportunistic fungus that causes pneumonia in immunocompromised
Arab foals with SCID
