Small Animal Surgical Respiratory Diseases Flashcards
(42 cards)
describe tracheal collapse
- normal tracheal width to height ratio is 1:1, but once starts to collapse is a progressive, irreversible condition
- laxity of trachealis muscle progressing to weakness of cartilage rings and eventual obliteration of the lumen
- collapse is in a dorsoventral direction
describe pathophysiology of tracheal collapse
- loss of glycoprotein and glycosaminoglycans leads to loss of water
-equates to loss of rigidity of cartilage - coughing leads to inflammation
-loss of normal epithelium leads to squamous metaplasia and loss of cilia
-increased mucous secretion
describe signalment of tracheal collapse
- toy and small breed dogs: yorkies, mini poodles, pomeranians, chihuahuas
- middle-aged
describe clinical signs of tracheal collapse
- coughing: goose honk, elicited by palpation on exam
- episodic dyspnea
- exercise intolerance
- cyanosis
- syncope
contrast normal respiration to respiration with trachea collapse
- inhalation: expansion of the chest by respiratory muscles
-pressure gradient (negative pressure within the chest)= thoracic expansion and cervical region compression - exhalation is the reverse
with tracheal collapse:
-inhalation: collapse of cervical trachea
-exhalation: collapse of the intrathoracic trachea
-MUST TAKE IMAGES IN BOTH PHASES OF RESPIRATION
-fluoroscopy is also helpful
-extrathoracic trachea: collapse on inhalation
-intrathoracic tracheal collapse on exhalation
describe bronchial collapse
- occurs in up to 83% of dogs with tracheal collapse
- pomeranians have a higher incidence of bronchial collapse
- canNOT be treated surgically
-even if tracheal collapse is treated, coughing will still occur
describe medical management of tracheal collapse
- acute treatment: present cyanotic, etc.
-oxygen
-sedatives
-cough suppressants
-short acting corticosteroids: antiinflammatory dose
-bronchodilators - chronic treatment:
-weight loss
-controlled exercise (when cold outside)
-harness: no neck leads
-environmental modifications: no smoke, no scented candles, no airway irritants - medications:
-cough suppressants
-sedatives
-bronchodilators
+/- corticosteroids: anti-inflammatory dose for short periods (not long term CSA)
+/- antibiotics: if suspect respiratory infection
good news: 71% of cases can be successfully managed medically for >1 year; delayed need for surgery and may eliminate need for surgery in some cases
-must EXHAUST medical management before attempting surgery; surgical correction may eventually fail
describe surgical management of tracheal collapse: extraluminal prosthetic tracheal rings
- treats cervical trachea only
-does not treat intrathoracic trachea or bronchial collapse - immediate improvement seen postoperatively
-75-85% success rate - complications: 10-30% of dogs
-laryngeal paralysis
-tracheal necrosis
-pneumothorax
describe surgical manangement of tracheal collapse: intraluminal tracheal stent
- treats entire trachea
-first tracheal ring to bifurcation
-does not treat bronchial collapse
-no incision - immediate clinical improvement: 83-89% success at 1 year
- post-op care
-cough suppressants
-sedatives as needed
-tapering dose of anti-inflammatory corticosteroids
-antimicrobials (2 week course)
-regular re-eval with radiograph - complications:
-stent fracture
-exuberant granulation tissue
-stent migration
describe laryngeal anatomy- cartilage
- epiglottis: rostral most cartilage, rests on the soft palate
- thyroid cartilage:
-largest cartilage
-covers the sides of the larynx (armor to protect the sides) - cricoid cartilage:
-complete ring
-connected to the first tracheal ring caudally - arytenoid cartilage:
-paired
-cuneiform, corniculate, vocal, muscular processes - rima glottidis:
-opening of the larynx through which air passes
-narrowest portion of the larynx
describe the crycoarytenoideus dorsalis muscle
origin: dorsolateral surface of cricoid cartilage
insertion: muscular process of the arytenoid cartilage
function: abduction of arytenoids to open glottis to inhale
innervation:
a. recurrent laryngeal nerves
-arise from the vagus nerve in the cranial thorax
-terminate as caudal laryngeal nerves
-provide motor supply to larynx
b. cranial laryngeal nerves: arise from vagus nerve, mostly sensory and part of cough reflex
describe laryngeal anatomy in cats
arytenoid cartilages do NOT have cuneiform or corniculate processes
describe larynx functions (3)
- assists in swallowing: pulled cranially to allow epiglottic coverage
- controls airway resistance: decreases resistance with abduction during inhalation
- voice production: tension on vocal cords, purring in cats
describe laryngeal paralysis
- loss of ability to abduct arytenoids on inhalation
-degeneration of recurrent laryngeal nerves causes loss of function of cricoarytenoideus dorsalis muscle
describe congenital laryngeal paralysis
- siberian huskies, dalmations, rotweilers, bull terriers
- onset of clinical signs before 1 year of age
- often a component of diffuse neurologic disease
describe acquired laryngeal paralysis
- most common form!
- labradors, goldens, saint bernards, irish setters
- average age 9 years; males > females
- causes:
-idiopathic most common: potential link with hypothyroidism, generalized polyneuropathy, GOLP
-trauma, surgery, tumors, etc.
describe clinical signs of laryngeal paralysis
- acute or chronic onset of signs
-acute onset is often an aggravation of chronic disease - early signs:
-change in bark
-gagging or coughing bc things feel weird back there
-decreased exercise - later signs:
-inspiratory stridor/dirty panting (can be subtle change!)
-dyspnea
-cyanosis
-syncope
-heat stroke: panting = cooling, no pant = no cool (tends to be spring/early summer dz)
describe laryngeal paralysis diagnostics
- CBC/chem/UA: often unremarkable or consistent with hypothryoidism
- thyroid panel: may be hypothyroid
- thoracic rads:
-check for aspiration pneumonia or megaesophagus (in about 10% of cases) - esophageal dysfunction
-esophagrams (swallowing study)
-laryngeal paralysis = worse esophageal function, could be an indicator, often more research setting and not clinically - upper airway examination
-performed under light plane of anesthesia
-if too deep, normal larynx can appear paralyzed
-premeds: can make them too deep so be careful, usually use acepromazine/butorphenol
-propofol: induction agent but WATCH apnea side effect with bolus! give doxapram to stimulate respiratory center in brain if respirations absent or weak
describe upper airway exam to diagnose laryngeal paralysis
-performed under light plane of anesthesia
-if too deep, normal larynx can appear paralyzed
-premeds: can make them too deep so be careful, usually use acepromazine/butorphenol
-propofol: induction agent but WATCH apnea side effect with bolus! give doxapram to stimulate respiratory center in the brain if respirations absent or weak
describe the 4 diagnoses of laryngeal paralysis
- normal: abduction during inhalation, passive relaxation during exhalation
- unilateral laryngeal paralysis: only one arytenoid abducts, not common and most dogs compensate well
- bilateral paralysis: neither arytenoid abducts, most common presentation
- bilateral laryngeal paralysis with paradoxical motion: neither arytenoid abducts, but moves with airflow
–can look like normal!!
–as animal breathes in, vocal folds appear to adduct, as animal breathes out air passively forces larynx open, mimicking abduction; MUST match breathing in or out with the motion
describe treatment of laryngeal paralysis
- emergency management
-for dyspneic animals: inflammation and swelling can exacerbate dyspnea
-medical therapy: acepromazine/butorphenol for sedation, oxygen, cooling, corticosteroids to decrease swelling
-intubate or temporary tracheostomy if deteriorates - medical management: for dogs that are mildly symptomatic
-weight loss
-exercise restriction
-avoid being outside in heat
-will likely progress with time (unilat to bilat)
describe surgical treatment of laryngeal paralysis: unilateral arytenoid lateralization
a referral procedure!!
- cricoarytenoid lateralization
-suture from the cricoid cartilage to the muscular process of the arytenoid: mimics action of cricoarytenoideus dorsalis muscle- FYI
-causes permanent abduction of the arytenoid- understand this part
-does not restore function: just decreases airway resistance
-how far to abduct?
-too wide = epiglottis won’t cover entirely when swallowing so risk aspiration (only do unilaterally, not bilaterally to avoid risk!)
-even a small change will magnify to a much larger effect!!
describe post-op care of tie back surgery
- no food or water until morning after surgery
-if coughing or gagging after drinking/eating, hold off and try again later
-offer meatballs of food (preformed bolus)
–meatballs for 2-4 weeks
–canned food for 2-4 weeks
–can slowly reintroduce kibble - avoid heavy sedation
-want to maintain swallowing reflexes
-decrease risk of vomiting - no neck leads!
-risk of damaging suture holding the arytenoid in abduction - no swimming
-uncontrolled intake of water can increase risk of aspiration pneumonia - monitor for aspiration pneumonia:
-coughing, fever, lethargy, anorexia
describe complications and outcomes of tie back surgery
complications:
1. aspiration pneumonia
-lifelong risk
-esophageal dysfunction not corrected with surgery
- persistent coughing or gagging
- persistent recurrent respiratory signs
- failure of surgery:
-suture breakage
-cartilage breakdown
outcomes:
-90% of animals improve after unilateral arytenoid lateralization
-70% still alive at 5 years
-long term: acquired laryngeal paralysis is one component of a peripheral neuropathy (GOLPP); some have peripheral neurologic signs at diagnosis that owners typically attribute to old age or arthritis and 100% have neuro signs at 1 year (slowly progressive, will die of something else)
