Small Animal Surgical Respiratory Diseases PDF

Small Animal Surgical Respiratory Diseases Janet A. Grimes, DVM, MS, DACVS-SA Associate Professor, Soft Tissue Surgery College of Veterinary Medicine University of Georgia Learning Objectives  When faced with a dog with tracheal collapse, brachycephalic obstructive airway syndrome (BOAS), or la...

Small Animal Surgical Respiratory Diseases Janet A. Grimes, DVM, MS, DACVS-SA Associate Professor, Soft Tissue Surgery College of Veterinary Medicine University of Georgia Learning Objectives  When faced with a dog with tracheal collapse, brachycephalic obstructive airway syndrome (BOAS), or laryngeal paralysis, students will be able to:  Describe the anatomy and pathophysiology of the disease  Diagnose laryngeal paralysis and identify components of BOAS on an upper airway examination  Formulate a medical treatment plan  Formulate a client education discussion  Understand surgical procedures available upon referral, postoperative long-term management, and prognosis Tracheal Collapse Tracheal Collapse Tobias and Johnston  Normal tracheal width to height ratio is 1:1  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 Tobias and Johnston Pathophysiology  Loss of glycoprotein and glycosaminoglycan leads to loss of water  Equates to loss of rigidity of cartilage  Coughing leads to inflammation  Loss of normal epithelium  squamous metaplasia and loss of cilia  Increased mucous secretion Signalment  Toy and small breed dogs  Yorkies  Mini poodles  Pomeranians  Chihuahuas  Middle-aged vetstreet.com Clinical Signs  Coughing  ‘Goose honk’  Elicited by palpation on exam  Episodic dyspnea  Exercise intolerance  Cyanosis  Syncope Video courtesy Dr. Tracy Hill Normal Respiration  Inhalation  Inhalation  Expansion of the chest by  Collapse of cervical trachea respiratory muscles  Exhalation  Pressure gradient (negative pressure within the chest)  Collapse of the intrathoracic trachea  Thoracic expansion  Cervical region compression  Must take images in both phases  Exhalation is the reverse of respiration Collapsing Trachea  When does the collapse occur?  Extrathoracic trachea  inhalation  Intrathoracic trachea  exhalation Bronchial Collapse  Occurs in up to 83% of dog with tracheal collapse  Pomeranians have a higher incidence of bronchial collapse petmd.com  Bronchial collapse cannot be treated surgically!  So even if tracheal collapse is appropriately treated – coughing will still occur Medical Management  Acute Treatment  Oxygen  Sedatives  Cough suppressants  Short acting corticosteroids  Antiinflammatory dose  Bronchodilators Medical Management  Chronic Treatment  Weight loss  Controlled exercise (when cool)  Harness (no neck leads)  Environmental modifications  No smoke, scented candles, or airway irritants Medical Management  Medications  Cough suppressants  Sedatives  Bronchodilators  Corticosteroids (anti-inflammatory dose for short periods)  Antibiotics (If suspect respiratory infection) Medical Management  71% of cases can be successfully medically managed for > 1 year  Delays need for surgery  May eliminate need for surgery in some cases  Must EXHAUST medical management before attempting surgery  Surgical correction may eventually fail Surgical Procedures – 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 Surgical Procedures – 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 Surgical Procedures – Intraluminal tracheal stent  Postoperative care  Cough suppressants  Sedatives as needed  Tapering dose of anti-inflammatory corticosteroids  Antimicrobials (2 week course)  Regular re-evaluation with radiographs Surgical Procedures – Intraluminal tracheal stent  Complications  Stent fracture  Exuberant granulation tissue  (Stent migration) Questions? Laryngeal Paralysis Laryngeal Anatomy Tobias and Johnston  Complex!  Epiglottis  Thyroid cartilage  Cricoid cartilage  Arytenoid cartilage  Rima glottidis Laryngeal Anatomy  Complex  Epiglottis  Rostral most cartilage  Rests on the soft palate  Thyroid cartilage  Cricoid cartilage  Arytenoid cartilage  Rima glottidis Tobias and Johnston  Tobias and Johnston Laryngeal Anatomy  Complex  Epiglottis Tobias and Johnston  Thyroid cartilage  Largest cartilage  Covers the sides of the larynx  Cricoid cartilage  Arytenoid cartilage  Rima glottidis  Tobias and Johnston Laryngeal Anatomy  Complex  Epiglottis  Thyroid cartilage Tobias and Johnston  Cricoid cartilage  Complete ring  Connected to first tracheal ring caudally  Arytenoid cartilage  Rima glottidis  Miller’s Anatomy Laryngeal Anatomy  Complex  Epiglottis  Thyroid cartilage  Cricoid cartilage  Arytenoid cartilage  Paired Cuneiform Corniculate  Cuneiform, corniculate, vocal, muscular processes process process  Rima glottidis Tobias and Johnston Laryngeal Anatomy  Complex  Epiglottis  Thyroid cartilage  Cricoid cartilage  Arytenoid cartilage  Rima glottidis  Opening of the larynx through which air passes  Narrowest portion of the larynx Laryngeal Anatomy  Cricoarytenoideus dorsalis  Origin: dorsolateral surface of cricoid cartilage  Insertion: muscular process of the arytenoid cartilage  Function: abduction of arytenoids to open glottis Miller’s Anatomy Miller’s Anatomy Laryngeal Anatomy  Recurrent laryngeal nerves  Arise from the vagus nerve in the cranial thorax  Terminate as caudal laryngeal nn.  Provide motor supply to larynx Miller’s Anatomy  Cranial laryngeal nerves  Arise from vagus nerve  Mostly sensory and part of cough reflex Laryngeal Anatomy - Cats  Cats are different  Arytenoid cartilages do NOT have cuneiform or corniculate processes Cat Dog Physiology  The larynx has three functions  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 Laryngeal Paralysis  Loss of ability to abduct arytenoids on inhalation  Degeneration of the recurrent laryngeal nerves  Loss of function of the cricoarytenoideus dorsalis muscle Miller’s Anatomy Congenital Laryngeal Paralysis  Siberian Huskies, Dalmatians, Rottweilers, Bouvier des Flandres, Bull terriers  Onset of clinical signs before 1 year of age  Often a component of diffuse neurologic disease Acquired Laryngeal Paralysis  Most common  Causes  Labradors, Goldens, Saint  Idiopathic most common Bernards, Irish Setters  Link with hypothyroidism?  Generalized polyneuropathy  Average age 9 years  Geriatric onset laryngeal paralysis  Males > females and polyneuropathy (GOLPP)  Trauma, surgery, tumors, etc. Clinical Signs  Acute or chronic onset of signs  Acute onset is often an aggravation of chronic disease  Early signs  Change in bark  Gagging  Coughing  Decreased exercise Clinical Signs  Later signs  Inspiratory stridor  Dyspnea  Cyanosis  Syncope  Heatstroke Diagnostics – Blood Work  CBC, Chemistry, Urinalysis  Often unremarkable or consistent with hypothyroidism  Thyroid panel  May be hypothyroid Diagnostics – Radiographs  Thoracic radiographs  Aspiration pneumonia  ~8% of cases  Megaesophagus  ~11% of cases Diagnostics – Esophageal Dysfunction  Esophagrams (swallowing study)  Laryngeal paralysis = worse esophageal function  Control = better esophageal function  All control dogs with decreased esophageal function developed laryngeal paralysis  Often not performed clinically Diagnostics – Upper Airway Examination  Performed under light plane of anesthesia  If too deep, normal larynx can appear paralyzed  Premeds  Can make them too deep, be careful  Acepromazine/butorphanol common  Propofol  Induction agent  Doxapram  Main side effect with large bolus: apnea  Stimulates respiratory center in brain if respirations are absent or weak Diagnostics – Upper Airway Examination Normal  Evaluation of arytenoid abduction  Normal: abduction during inhalation, passive relaxation during exhalation Diagnostics – Upper Airway Examination Unilateral laryngeal paralysis  Evaluation of arytenoid abduction  Normal: abduction during inhalation, passive relaxation during exhalation  Laryngeal paralysis: no motion of the arytenoids  Unilateral laryngeal paralysis  Only one arytenoid abducts  Not common – most dogs compensate well Diagnostics – Upper Airway Examination Bilateral laryngeal paralysis  Evaluation of arytenoid abduction  Normal: abduction during inhalation, passive relaxation during exhalation  Laryngeal paralysis: no motion of the arytenoids  Bilateral laryngeal paralysis  Neither arytenoid abducts  Most common presentation Diagnostics – Upper Airway Examination Bilateral laryngeal paralysis with paradoxical motion  Evaluation of arytenoid abduction  Normal: abduction during inhalation, passive relaxation during exhalation  Laryngeal paralysis: no motion of the arytenoids  Bilateral laryngeal paralysis with paradoxical motion  Neither arytenoid abducts, but move with air flow  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 Laryngeal Paralysis  Four diagnoses:  Normal  Unilateral laryngeal paralysis  Bilateral laryngeal paralysis  Bilateral laryngeal paralysis with paradoxical motion Treatment  Emergency management  For dyspneic animals  Inflammation and swelling exacerbate dypsnea  Medical therapy  Acepromazine/butorphanol for sedation  Oxygen  Cooling  Corticosteroids to decrease swelling  Intubate or temporary tracheostomy if deteriorates Treatment  Medical management  For dogs that are mildly symptomatic  Weight loss  Exercise restriction  Avoid being outside in the heat  Will likely progress with time  Unilateral disease  bilateral disease Treatment – Surgery Tobias and Johnston  Unilateral arytenoid lateralization – referral procedure  Cricoarytenoid lateralization  Suture from the cricoid cartilage to the muscular Tobias and Johnston process of the arytenoid  Mimics action of cricoarytenoideus dorsalis muscle  Causes permanent abduction of the arytenoid  Does not restore function  Decreases airway resistance Miller’s Anatomy Unilateral arytenoid lateralization 8nL Resistance to Flow R= π r4  How far to abduct? Tobias and Johnston Too wide – epiglottis Good won’t cover entirely coverage of when swallowing – airway by Pre-operative Post-operative unilateral ↑↑↑ risk aspiration epiglottis airway opening arytenoid lateralization Treatment – Post-Operative Care  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 Treatment – Post-Operative Care  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 Complications  Aspiration pneumonia: 8-21%  Persistent recurrent respiratory  Lifelong risk signs: up to 33%  Esophageal dysfunction not corrected with surgery  Failure of surgery  Suture breakage  Persistent coughing or  Cartilage breakdown gagging: up to 33% Outcomes  90% of animals improve after unilateral arytenoid lateralization  70% still alive at 5 years Long-Term Outcomes  Acquired laryngeal paralysis is one component of a peripheral neuropathy (GOLPP)  31% have peripheral neurologic signs at diagnosis  Scuffing pelvic limb toes, ataxia, hind limb weakness – lower motor neuron disease  Owners typically attribute to old age or arthritis  100% have neurologic signs at 1 year  Slowly progressive Questions? Brachycephalic Obstructive Airway Syndrome Janet A. Grimes, DVM, MS, DACVS-SA Associate Professor, Soft Tissue Surgery College of Veterinary Medicine University of Georgia Brachycephalic Obstructive Airway Syndrome Clinical Signs  Stertorous breathing  Dyspnea  Cyanosis  Collapse Physical Examination  Respiratory rate, effort, and quality  Auscultation  Referred upper airway sounds (stertor)  Palpation of trachea  Evaluation of nares  Body temperature Pathophysiology  Increased resistance to airflow = increased pressure gradient during inhalation  Leads to tissue inflammation  Laryngeal saccule eversion  Tonsil eversion  Pharyngeal mucosal hyperplasia  Larynx and trachea can weaken and collapse Pathophysiology Primary abnormalities obstruct airflow Soft tissues drawn into Negative pressure lumen and become Increased airway resistance exceeding resistance of hyperplastic surrounding structures Collapse of secondary structures Resistance to Airflow  Normal dogs  Nasal cavities: 76%  Larynx: 5%  Bronchi/bronchioli: 19%  Essentially the same for inhalation/exhalation Uosyte 2015 VetRadUS 8nL Resistance to Flow R= π r4 Brachycephalic Obstructive Airway Syndrome  Four main components  Other findings  Stenotic nares  Altered turbinate anatomy  Elongated soft palate  Redundant/hyperplastic pharyngeal mucosa  Everted laryngeal saccules  Macroglossia  Hypoplastic trachea  Everted tonsils Brachycephalic Obstructive Airway Syndrome  Elongated soft palate = 94%  Stenotic nares = 77%  Everted laryngeal saccules = 66%  Everted tonsils = 56% Medical Management  Non-emergency cases  Weight loss  Restrict exercise  Walk in morning or evening (when cooler)  Cool, shaded, air-conditioned environment  No neck leads  Harness Treatment of Respiratory Distress  Emergency treatment  Oxygen  Cool environment  Acepromazine/butorphanol for sedation  Dexamethasone to reduce laryngeal swelling  Intubate Diagnosis  Upper airway examination under heavy sedation  Thorough evaluation of  Nares  Palate  Pharynx  Larynx (+ function)  Surgery performed during same anesthesia Anesthesia  High risk patients  Especially on recovery  Don’t do late in the day or on Fridays!  Pre-oxygenate  Steroids to decrease swelling Main Components of BOAS Stenotic Nares  Abnormally narrowed nostrils  Axial deviation of dorsolateral nasal cartilage (wing of the nostril)  Subjective Stenotic Nares  Causes significant upper airway obstruction  Greater inspiratory effort required  Increased negative pressure  Laryngeal and tracheal collapse  Supraphysiologic stress Stenotic Nares  Treatment: surgical correction  Wedge resection  Horizontal, vertical  Dorsal offset rhinoplasty  Trader’s technique  Amputation of the wing  Can use blade, laser, or electrosurgery Horizontal Wedge Elongated Soft Palate  Normal length  Soft palate no longer than caudal aspect of tonsillar crypt  The tip of the epiglottis should rest on the soft palate  Elongated soft palate  Covers the bulk of the epiglottis  May enter the rima glottidis/larynx Elongated Soft Palate  Palate pulled caudally during inhalation  Obstructs dorsal aspect of glottis  Laryngeal mucosa becomes inflamed/edematous Elongated Soft Palate Tonsil  Staphylectomy (soft palate resection)  How long should it be?  Caudal 1/2-1/3 of the tonsils is appropriate length  Stationary measurement tool  Pulling on tongue can move larynx/ventral structures  Tonsils are stationary Staphylectomy Everted Laryngeal Saccules  Secondary change due to increased respiratory effort  Prolapse of the mucosa lining the laryngeal crypts  Increased intraluminal pressure causes saccules to evert  Obstruct ventral glottis Everted Laryngeal Saccules  Surgical excision  Resection with scissors  No closure required  Can recur if airway resistance is not reduced  Should address stenotic nares and elongated soft palate at the same time Hypoplastic Trachea  Small tracheal lumen compared to dog size  Ratio of tracheal diameter to thoracic inlet  Normal dogs = 20%  Brachycephalic dogs = < 16%  English bulldogs = 12.7%  Not treatable – fact of life Hypoplastic Trachea  Ratio of tracheal diameter to thoracic inlet Post-operative care  Corticosteroids to reduce swelling  Dexamethasone (0.05 – 0.1 mg/kg IV)  Extubate only when the patient is FULLY awake  Keep calm!  Butorphanol  Acepromazine or dexmedetomidine andreasleak.wordpress.com Complications of BOAS Surgery  Dyspnea  Can occur if soft palate swells after staphylectomy  May require temporary tracheostomy until swelling resolves  Death  Aspiration pneumonia  Failure to recover from anesthesia Other Findings in BOAS Dogs Abnormal Nasal Conchae  Brachycephalic dogs also have intranasal obstruction from abnormal conchal development  Normal conchae packed into a significantly shorter space  Increased contact between conchae  increased obstruction Dolichocephalic Dog Brachycephalic Dog Abnormal Nasal Conchae  Mucosal contact points Uosyte 2015 VetRadUS Normocephalic dog Brachycephalic dog Everted Tonsils  Secondary change due to inflammation and airway pressure  Most commonly not treated  Treatment of elongated palate, everted saccules, and stenotic nares should lead to resolution Laryngeal Collapse  Most common in brachycephalic dogs due to chronic upper airway resistance and breathing effort  Normal Laryngeal Collapse  Stage I: laryngeal saccule eversion  Stage II: cuneiform processes of arytenoids collapse and displace medially  Stage III: corniculate processes of arytenoids collapse and displace medially  End stage brachycephalic airway disease Laryngeal Collapse Treatment Laryngeal collapse is a secondary disease - must treat the primary disease Brachycephalic obstructive airway syndrome Medical management Surgery Permanent tracheostomy Unilateral arytenoid lateralization? NOT effective Gastrointestinal Signs  Relationship between respiratory and gastrointestinal disease  More severe respiratory signs = more severe GI signs  Increased intrapleural pressure from upper airway obstruction  Esophageal deviation, gastroesophageal reflux, hiatal hernia, esophagitis, pyloric mucosal hyperplasia  Treating BOAS may reduce/eliminate GI signs  May require medical therapy for GI signs BOAS at UGA  198 dogs operated between 2007-2016  12 (6%) required temporary tracheostomy post-op  No difference in mortality between groups  1 dog in each group died (overall 1% mortality rate) BOAS at UGA  Risk factors for needing temporary tracheostomy  Age  Post-operative corticosteroids  Post-operative pneumonia Questions?