Exam 2 - Equine Bacterial Pneumonia & Pleuropneumonia

Question 1

when does bacterial pneumonia occur?

Answer 1

when pulmonary defense mechanisms are overwhelmed or suppressed

Question 2

what are some examples of overwhelmed pulmonary defense mechanisms?

Answer 2

1. aspiration
2. severe bacteremia

Question 3

what are some causes of aspiration in horses?

Answer 3

pharyngeal/laryngeal dysfunction, dysphagia, choke, general anesthesia

Question 4

what agents are associated with severe bacteremia in respiratory diseases in horses?

Answer 4

corynebacterium pseudotuberculosis & streptococcus equi sub species equi

Question 5

what are some examples of suppressed pulmonary defense mechanisms?

Answer 5

transportation, high intensity exercise, viral infections, stress, inhaled toxins (ammonia), poor ventilation, immunosuppressive drugs/immunosuppresive disorders, & endotoxemia/systemic disease

Question 6

what is the pathophysiology of bacterial bronchopneumonia?

Answer 6

usually associated with opportunistic bacteria that are ubiquitous in the horse’s environment & many are normal inhabitants of URT

Question 7

what is the pathophysiology of anaerobic pneumonia?

Answer 7

normal lung is protect from anaerobes - damaged lung from pneumonia, trauma, ischemia, virus leads to an environment for colonization & multiplication of anaerobes

Question 8

what is the pathogenesis of anaerobic pneumonia?

Answer 8

anaerobes release endotoxins & enzymes (heparinases, collagenases)

leads to pulmonary necrosis & abscess formation

Question 9

what are some risk factors for bacterial pneumonia?

Answer 9

any age, breed, sex, or occupation can be affected

long distance transport

strenuous exercise - racing/EIPH, inhaling dirt

general anesthesia

choke/aspiration

immunosuppresion

viral respiratory infections

Question 10

what is the most common cause of pleural effusion in horses?

Answer 10

1. pleuropneumonia
2. neoplasia - bad prognosis

Question 11

besides pneumonia, why else may a horse develop septic pleuritis?

Answer 11

penetrating wound into the thorax

esophageal rupture

Question 12

what clinical signs are seen with bacterial pneumonia?

Answer 12

fever, tachypnea/tachycardia, nasal discharge/cough, exercise intolerance, respiratory distress, halitosis, ventral edema, endotoxemia SIRS, & pleurodynia

Question 13

what is pleurodynia?

Answer 13

pleural pain

Question 14

what clinical signs are associated with pleurodynia?

Answer 14

pawing/apparent colic

abducted elbows

shallow respirations

reluctance to move

painful palpation of ICS

easily misdiagnosed - colic, myopathy, laminitis

Question 15

what can be heard upon thoracic auscultation of a horse with bacterial pneumonia?

Answer 15

crackles, wheezes, attenuated BV sounds, referred large airways sounds, & radiating heart sounds

Question 16

what may be heard on thoracic percussion on a horse with bacterial pneumonia?

Answer 16

regional dullness in the ventral lung fields

resonance over the dorsal lung fields

may detect pleurodynia

Question 17

what does pleural effusion look like on rads? when is it most useful?

Answer 17

ventral soft tissue opacity that obscures the diaphragm & heart borders

air-fluid interface is uncommon

after pleural drainage

Question 18

what can be recognized on thoracic rads of horses with bacterial pneumonia?

Answer 18

increased opacity from consolidation

loss of clarity of lung fields

air bronchograms

interstitial patterns

lung abscesses

Question 19

what pathology is seen on this thoracic radiograph?

Answer 19

pleural effusion

Question 20

other than ultrasound, what else can you do to better evaluate pleural effusion?

Answer 20

thoracocentesis

Question 21

what anatomic location is commonly used for thoracocentesis?

Answer 21

often 7-8 ICS at the point of shoulder

Question 22

what would you use an edta tube of pleural fluid for? what about a heparin tube?

Answer 22

edta - cytology, cell counts, protein concentration, & gram’s stain

heparin - biochemical testing

Question 23

what are the normal parameters for pleural fluid?

Answer 23

colorless to pale yellow, transparent, odorless, sterile, normal cell morphology

TNCC 0-10,000/uL

protein concentration 0-4.7 g/dl

Question 24

how is parapneumonic effusion characterized?

Answer 24

cloudy, yellow to bloody, may smell, exudative, neutrophilia +/- degenerative changes

TNCC > 10,000/uL

protein > 4.0 g/dl

may see bacteria on cytology

Question 25

what biochemical parameters of pleural fluid are suggestive of sepsis?

Answer 25

pH < 7.1 glucose < 40 mg/dl increased lactate

Question 26

what is a pleuroscopy used for?

Answer 26

visual assessment of lung & pleurae

Question 27

what is the therapeutic management used for bacterial pneumonia?

Answer 27

antimicrobials, supportive care, rest, & monitoring

Question 28

why start systemic antimicrobials before culture results?

Answer 28

broad spectrum combinations used based off of prevalence & susceptibility testing to cover gram positives, gram negatives, & anaerobes

Question 29

what is the most common isolate from horses with bacterial bronchopneumonia?

Answer 29

streptococcus equi sub species zooepidemicus

Question 30

what is the most common gram-positive aerobic isolate in a horse with bacterial pneumonia?

Answer 30

streptococcus equi sub species zooepidemicus

Question 31

what are some common gram-negative aerobic isolates in a horse with bacterial pneumonia?

Answer 31

pasteurella spp. escherichia coli, klebsiella pneumoniae, enterobacter spp., & actinobacillus spp.

Question 32

what are some common anaerobic isolates in a horse with bacterial pneumonia?

Answer 32

bacteroides fragilis & peptostreptococcus anaerobius

Question 33

what should be considered after getting culture results before deciding in antimicrobials?

Answer 33

1. specific isolates & susceptibilities 2. drug's ability to distribute & kill bacteria at the site of infection 3. ease of administration 4. toxicity & cost

Question 34

what are some systemic antibiotics that are used for the first 1-3 weeks?

Answer 34

aminoglycosides, beta-lactams, & metronidazole

Question 35

what are some systemic antibiotics that are used long-term?

Answer 35

chloramphenicol metronidazole enrofloxacin + metronidazole + beta-lactams or doxycycline or rifampin

Question 36

what medication should be avoided when using intrapleural antimicrobials?

Answer 36

oxytetracycline

Question 37

why use intrapleural antimicrobials?

Answer 37

achieve higher concentrations in the pleural space combine with systemic therapy use lavage to improve pleural micro-environment

Question 38

what are some examples of intrapleural antimicrobials?

Answer 38

gentamicin injectable metronidazole

Question 39

why use aerosolized antimicrobials?

Answer 39

adjunct therapy higher drug concentrations in bronchial secretions & PELF minimize systemic toxicity

Question 40

what are some characteristics of septic pleural effusion?

Answer 40

empyematous, putrid odor, cytologically visible bacteria, positive cultures glucose < 40mg/dl ph < 7.1 elevated lactate poor response to conservative therapy

Question 41

what are some indications for pleural drainage?

Answer 41

voluminous pleural effusion, respiratory distress, & poor response to conservative therapy

Question 42

why use pleural lavage?

Answer 42

facilitate drainage of thick, viscous pleural effusion, fibrin, & necrotic debris improve pleural microenvironment - enhances penetration & action of antimicrobial agents

Question 43

what is the technique used for pleural lavage?

Answer 43

5-10 L warm LRS every 12-24 hours - monitor how well the horse tolerates lavage

Question 44

what is intrapleural fibrinolytic therapy?

Answer 44

recombinant tissue plasminogen activator - 12 mg diluted in 2 L of saline safe, variable effect on fibrin quantity & organization

Question 45

what are some potential sequelae to pleuropneumonia in horses?

Answer 45

endotoxemia antimicrobial associated enterocolitis laminitis thrombophlebitis pneumothorax pericarditis