Today's Veterinary Practice

NOV-DEC 2015

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tvpjournal.com | November/December 2015 | ToDay's VeTeriNary PracTice aPProach To resPiraTory DisTress Peer reviewed 55 • Airway examination: Upper airway examination, tracheobronchoscopy • Drug trials: Such as bronchodilators, diuretics, and corticosteroids. UPPER AIRWAY OBSTRUCTION Etiology Upper respiratory tract obstruction involves a mechanical or functional obstruction of the upper (large) airways (ie, the pharynx, larynx, or trachea). Nasal disorders are not considered in this article as the animal should always be able to open its mouth and breathe, preventing the development of dyspnea even if the nasal cavity is obstructed. Specifc causes of upper airway obstruction include: • Naso-oropharyngeal disorders, including polyps (especially in cats), masses, and foreign bodies • Severe head trauma that results in bone fractures (especially nasal, jaw, and palatine fractures) and associated hemorrhage and swelling • Laryngeal disorders, including laryngeal paralysis, laryngeal collapse, laryngeal masses (eg, neoplasia, abscesses, granulomas), and laryngeal inflammation • Tracheal diseases, including tracheal collapse, tracheal foreign body, tracheal stenosis, stricture, tracheal tear, or tracheal mass (either intra- or extraluminal) • Brachycephalic airway disease, which involves a combination of primary and secondary anatomic abnormalities of the upper airways, including stenotic nares, an elongated soft palate, everted laryngeal saccules, laryngeal edema and/or collapse and, in some breeds (eg, English bulldog), a hypoplastic trachea. Clinical Signs Characteristic signs in patients with an upper airway obstruction include inspiratory distress and an externally audible noise associated with breathing (eg, stertor, stridor). Tracheal disease is usually associated with a cough. Initial Stabilization Initial stabilization and therapy may involve: • Oxygen administration/securing an airway: Generally administered by face mask (if tolerated), flow-by oxygen, or oxygen cage, with intubation or tracheostomy performed if needed • Sedation: Achieved with anxiolytic drugs, such as acepromazine or dexmedetomidine, or sedative analgesics, such as butorphanol (Table 2) • Cooling: Many dogs with upper airway obstructions become hyperthermic due to inability to dissipate heat through their upper airways; the goal is to reduce body temperature to at least 103°F, while avoiding hypothermia • Corticosteroids: Breathing against an obstruction can result in marked edema of the upper airway soft tissue; therefore, anti-inflammatory doses of corticosteroids (eg, dexamethasone SP, 0.15 mg/kg IV single dose or Q 24 H) can be considered. Diagnostic Approach Once the patient is stable, diagnostic tests can be pursued. Upper airway examination . Examination is performed after preoxygenation under sedation. At its most basic, examination may involve inspection of the oropharynx and larynx with a laryngoscope; in patients with suspected tracheal disease, it Sedation for Patients in Respiratory Distress In dogs, reasonable choices for sedation are butorphanol, acepromazine, or dexmedetomidine, while butorphanol is the drug of choice in cats. Choice of drug(s) used for sedation/anxiolysis should be based on the individual drug's properties, and relative risks versus benefits for the patient. For example: • Butorphanol is a very safe and effective drug at recommended doses; however, it is relatively short acting (often only 1–2 hours) and cannot easily be reversed. • Acepromazine is also very effective; however, it may be more likely to produce undesirable effects, such as hypotension; has a long duration of action (4–6+ hours); and cannot be reversed. • Dexmedetomidine has the desirable quality of being reversible (with atipamezole) and titratable (given a short duration of action); however, it can produce undesirable effects, such as bradycardia and hypotension. Regardless of the chosen drug, in potentially unstable patients, lower doses are given initially and later increased as needed and tolerated by the patient. Table 2. Patients in Respiratory Distress: Sedative Drug Dosages SEDATIVE DRUG DOSE RANGE Butorphanol 0.1–0.4 mg/kg IM or IV Q 1–4 H, as needed Acepromazine 0.005–0.05 mg/kg IM or IV Q 4–8 H, as needed Dexmedetomidine 0.01–0.1 mg/kg/H IV CRI

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