/// QUARTERLY BEAT / DECEMBER 2022
QUARTERLY BEAT / DECEMBER 2022 ///
for direct blood pressure determinations in an animal with congestive heart failure, oscillometric techniques are commonly inaccurate with small dogs or cats or during ectopy and Doppler techniques are time-consuming and require a patient with respiratory distress to be restrained. Dobutamine, as a continuous rate infusion (CRI) is very useful in dogs with dilated cardiomyopathies. Intravenous fluids should not be administered to a patient with heart failure, although they should be permitted ad lib access to water. Hemodynamically significant arrhythmias should be treated. Patients should be transitioned to long-term medications after stabilization. While an echocardiogram is not considered an emergent procedure, it is useful for if an emergency clinician has access to an ultrasound machine for that individual to gain basic knowledge of echocardiography, including assessment of left atrial size, contractility and presence or absence of pericardial effusion. Non-cardiogenic pulmonary edema may occur for a variety of reasons. In the emergency room, upper airway obstruction, seizures and electric cord injury are common triggers for the development of non-cardiogenic edema. Non-cardiogenic pulmonary edema is typically high-protein and results due to permeability shifts in the capillaries rather than hydrostatic forces as with cardiogenic edema. There is not specific therapy that has been proven beneficial for hastening recovery from non-cardiogenic edema. Treatment recommendations include cage rest and supplemental oxygen. More specific therapy with either diuretics or colloids has been advocated by various clinicians although no consensus statement exists. The vast majority of dogs with non-cardiogenic pulmonary edema will rapidly improve within 24-48 hours. Pulmonary contusions are common after traumatic injury, particularly in dogs. Animals severely affected with pulmonary contusion will be short of breath rapidly after the injury, although radiographically infiltrates will often worsen over the first 12-24 hours. Dogs with contusions commonly have small to moderate volume pneumothoraces as well. Contusions will generally heal rapidly. One study in dogs was unable to support the use of either prophylactic antibiotics or steroids. Diuretics are also not indicated for animals with pulmonary contusion. Dogs with pneumonia may present to the emergency room with respiratory distress. Bacterial pneumonia is very rare in cats. Pneumonia can be sub-divided into community-acquired such as severe bronchopneumonia (infectious kennel cough complex) or aspiration pneumonia in a dog with laryngeal paralysis or megaesophagus or hospital-acquired for a dog that develops pneumonia while hospitalized for treatment of another condition. Therapy for pneumonia includes broad- spectrum antibiotics, physiotherapy and intravenous fluids. Ideally, a bacterial culture is performed prior to the institution of antibiotics.
although flare-ups in some patients do occur. Chronic bronchitis is defined as the presence of a cough on most days for the preceding two months, without evidence of other underlying cause. Canine chronic bronchitis commonly affects small breed dogs. On auscultation, a mitral murmur is commonly heard. Conversely, feline lower airway disease may present as an emergency. In cats, airway disease appears to represent a continuum with some cats having primarily inflammatory airway disease with cough and excessive mucus production, while other cats are the more prototypical “asthmatics” with reversible bronchoconstriction. Cats with severe bronchoconstriction will often present emergently. It is important to distinguish the airway disease from congestive heart failure. Cats with airway disease typically are normothermic and have had a history of cough. Both heart failure and airway disease may be accompanied by crackles. Parenchymal lung disease is often responsible for respiratory distress. Common causes of parenchymal lung disease include pulmonary edema (cardiogenic and non-cardiogenic), pulmonary contusion, pneumonia and neoplasia. Heart failure in cats is usually appreciated by hypothermia combined with an increased respiratory rate and effort. Jugular venous distension may be present. A gallop or a murmur may be ausculted. Due to the hypothermia, cats with congestive heart failure (CHF) will commonly have slow heart rates (130- 140 bpm). Heart disease in dogs is usually either chronic valvular disease or dilated cardiomyopathy. Animals with a history of trauma or possible trauma and that are presenting with respiratory distress can be assumed to have some component of pulmonary contusion (and/or pneumothorax). Therapy for respiratory distress associated with pulmonary infiltrates include supplemental oxygen and therapeutic agents directed towards the presumptive underlying cause. The distribution of the pulmonary infiltrates may be very useful to help determine the underlying problem. In dogs, cardiogenic pulmonary infiltrates will most often surround the perihilar region, while in cats the distribution of pulmonary edema may vary. Bacterial pneumonias will typically have a cranioventral distribution. Neoplasia will usually result in a nodular pattern, although metastatic disease may appear variable. Animals with suspected cardiogenic pulmonary edema should be treated initially with diuretics (furosemide 1-4 mg/kg iv or im, q 1-6 hours), cage rest and supplemental oxygen. If a rapid improvement is not observed, additional therapy with vasodilators (nitroprusside titrated to effect) is warranted. In practice, despite published guidelines, measurement of blood pressure during infusion of nitroprusside is usually not performed in order to limit patient stress, loss of supplemental oxygen (by opening cage door) and technical difficulties in getting accurate numbers. Specifically, it may be challenging or impossible to place an arterial line
WEBINAR HIGHLIGHTS
Approach to the Small Animal Respiratory Emergency
ELIZABETH ROZANSKI , DVM, DACVIM, DACVECC Tufts University, North Grafton, MA
can not be extubated, due to the higher risk of aspiration pneumonia, it is better to perform a tracheostomy than keep a patient intubated. Conversely, in dogs with severe brachycephalic airway syndrome or tracheal collapse, it may be impossible to remove a tracheostomy tube after placement. This means that its avoidance of a tracheostomy is preferable in these dogs as compared with dogs with laryngeal paralysis. If a tracheostomy is unavoidable; plans should be made for surgical correction of the obstruction as soon as feasible. Brachycephalic dogs may also develop laryngeal collapse, which is not amenable to laryngoplasty, and may ultimately necessitate a permanent tracheostomy. In cats, upper airway obstructions are less common, but may be caused by nasopharyngeal polyps or infiltrative laryngeal diseases (neoplasia or granulomatous). Occasionally, cats with severe pleural effusion will have the appearance of severe inspiratory distress. If sedation for an oral examination for a cat with a suspected upper airway obstruction is planned, then supplies should be collected ahead of time for an emergency tracheostomy. The laryngeal lumen of affected cats can be only a millimeter or two in diameter and may require an urgent tracheostomy. If a biopsy of a laryngeal mass is performed in a cat, a tracheostomy is almost always required due to subsequent airway swelling. Cats may also have a permanent tracheostomy placed, although it less well tolerated than it is in dogs. Respiratory distress may also result from lower airway disease, parenchymal lung disease or pleural space disease. Thoracic radiographs are essential to help clarify the degree of pulmonary or pleural space involvement. However, it is important to recall that radiography can be stressful, particularly in cats that are experiencing respiratory distress. Lower airway diseases include chronic bronchitis and feline asthma. Chronic bronchitis rarely presents emergently,
doses of acepromazine (0.03-0.05 mg/kg intravenously) alone or in combination with butorphanol (0.1 mg/kg intravenously) are often effective. Hyperthermia should be treated by active cooling with room temperature (not cold!) intravenous fluids, and by placing the dog in a cool area. Due to airway swelling and edema, a single dose of short acting anti-inflammatory glucocorticoid is advisable. If the dog has not improved within 15-30 minutes or if distress is worsening, more aggressive therapy is warranted. The dog should be heavily sedated or anesthetized and intubated. The emergency clinician should be competent to evaluate airway function and anatomy and to perform a tracheostomy if needed. Additionally, as many upper airway conditions require management and/or surgical intervention, the emergency clinician should be fluent in discussions with clients concerning long-term outcomes. The most common causes of upper airway obstruction may vary depending on location but in our practice include laryngeal paralysis, tracheal collapse, brachycephalic airway syndrome and severe cellulitis. While a complete discussion on the management of these conditions is beyond the scope of this chapter; however, despite their similarities, some differences due to the underlying disease do exist concerning optimal management of affected patients. Laryngeal paralysis primarily affects older large breed dogs, particularly retrievers. Usually, the clinical signs of noisy breathing have been present for some length of time prior to a crisis. Crises often occur during the first hot and humid days of the spring or summer. Dogs will commonly respond well to sedation. Dogs that do not rapidly improve should be sedated and have laryngeal function evaluated and be intubated. If palliative surgery is not readily available, dogs may have a tracheostomy performed or may be keep briefly sedated/intubated until normothermia and eupnea ensue. In our practice, we will commonly maintain dogs on a propofol CRI in 0.9% saline (20 ml of propofol in 1 liter of NaCl) titrated to effect for 30-60 minutes. If after this time period a dog
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