Today's Veterinary Practice

TVP_JUL-AUG2018

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FEATURES todaysveterinarypractice.com JULY/AUGUST 2018 49 A single nasal line can provide sufficient oxygen supplementation, but dual lines may improve patient comfort by enabling lower oxygen flow rates. The flow rates used typically are in the range of 50-150 mL/kg/min. Patient discomfort may be noticed with rates exceeding 100 mL/kg per minute.1 Nasal lines can be a very effective method of supplementing oxygen, with 1 line achieving an FiO 2 of 30% to 50% and 2 lines potentially achieving 30% to 70% depending on the rates used. 3 Nasotracheal Oxygen Nasal lines may be of limited value in brachycephalic breeds. An alternative technique for recovery from anesthesia in these breeds is the placement of nasotracheal oxygen. 4 In these cases, a red rubber catheter can be placed extending from the external nares and directed into the trachea, before removal of their endotracheal tube. A red rubber catheter is placed from the external nares caudally, with sufficient length to enter the proximal trachea. With the dog in sternal recumbency, the catheter is advanced until it is visible just beyond the soft palate. The catheter is then exteriorized through the mouth using long forceps before being redirected into the trachea. It is secured in a similar manner to the nasal lines as described above. When the dog is recovered from anesthesia and no longer requires further oxygen supplementation, the tube can be easily removed. Intubation Without Positive- Pressure Ventilation Intubation with 100% oxygen may be necessary in severe cases of upper airway obstruction (e.g., laryngeal paralysis crisis). Not every case with an upper respiratory crisis necessarily requires intubation. In cases refractory to other measures of oxygen supplementation (e.g., sedation and anxiolysis, noninvasive oxygen supplementation), timely endotracheal intubation can be a life-saving measure. Rapid induction of anesthesia is desirable to ensure efficient intubation. Propofol is an excellent induction agent but is associated with profound cardiorespiratory depression. It may therefore be sensible to premedicate the animal if time allows or to perform coinduction with another drug class (e.g., a benzodiazepine) to reduce the dose of propofol required. In cases of profound respiratory distress that are secondary to underlying cardiac disease, propofol may result in severe cardiovascular depression with risk for cardiopulmonary arrest. In such cases, depending on the patient's level of excitement and anxiety, sufficient sedation may be achieved with alternative drugs to propofol (e.g., midazolam 0.3 to 0.5 mg/kg and butorphanol 0.2 to 0.3 mg/kg) or FIGURE 9. Geriatric Labrador retriever mix intubated after an upper respiratory crisis associated with laryngeal paralysis. FIGURE 7. Cadaver image indicating the approximate termination of a red rubber catheter used as a nasal line measured to the medial canthus. FIGURE 8. Cadaver image indicating the approximate termination of a red rubber catheter used as a nasopharyngeal catheter measured to the mandibular ramus. Left top and bottom: Courtesy Bernie Hansen, DVM, DACVECC, DACVIM (2)

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