Medication Summary
Pharmacotherapy for cardiogenic pulmonary edema and acute exacerbations of chronic obstructive pulmonary disease (COPD) is discussed here. The goals of therapy in cardiogenic pulmonary edema are to achieve a pulmonary capillary wedge pressure of 15-18 mm Hg and a cardiac index greater than 2.2 L/min/m2 while maintaining adequate blood pressure and organ perfusion. These goals may have to be modified for some patients. Diuretics, nitrates, analgesics, and inotropes are used in the treatment of acute pulmonary edema.
Diuretics, Other
Class Summary
First-line therapy generally includes a loop diuretic such as furosemide, which inhibits sodium chloride reabsorption in the ascending loop of Henle.
Furosemide (Lasix)
Administer loop diuretics such as furosemide intravenously (IV) because this allows both superior potency and a higher peak concentration despite an increased incidence of adverse effects, particularly ototoxicity.
Metolazone (Zaroxolyn)
Metolazone has been used as adjunctive therapy in patients initially refractory to furosemide. It has been demonstrated to be synergistic with loop diuretics in treating refractory patients and causes a greater loss of potassium. Metolazone is a potent thiazide-related diuretic that sometimes is used in combination with furosemide for more aggressive diuresis. It is also used for initiating diuresis in patients with a degree of renal dysfunction.
Nitrates
Class Summary
Nitrates reduce myocardial oxygen demand by lowering preload and afterload. In severely hypertensive patients, nitroprusside causes more arterial dilatation than nitroglycerin. Nevertheless, in view of the possibility of thiocyanate toxicity and the coronary steal phenomenon associated with nitroprusside, IV nitroglycerin may be the initial therapy of choice for afterload reduction.
Nitroglycerin sublingual (Nitro-Bid, NitroMist, Nitrostat, Nitrolingual)
Sublingual nitroglycerin tablets and spray are particularly useful in the patient who presents with acute pulmonary edema with a systolic blood pressure of at least 100 mm Hg. As with sublingual nitroglycerin tablets, the onset of action of nitroglycerin spray is 1-3 minutes, with a half-life of 5 minutes. Administration of the spray may be easier, and it can be stored for as long as 4 years.
Topical nitrate therapy is reasonable in a patient presenting with class I-II congestive heart failure (CHF). However, in patients with more severe signs of heart failure or pulmonary edema, IV nitroglycerin is preferred because it is easier to monitor hemodynamics and absorption, particularly in patients with diaphoresis. Oral nitrates, because of their delayed absorption, play little role in the management of acute pulmonary edema.
Nitroprusside sodium (Nitropress)
Nitroprusside produces vasodilation of venous and arterial circulation. At higher dosages, it may exacerbate myocardial ischemia by increasing heart rate. It is easily titratable.
Opioid Analgesics
Class Summary
Morphine IV is an excellent adjunct in the management of acute pulmonary edema. In addition to anxiolysis and analgesia, its most important effect is venodilation, which reduces preload. It also causes arterial dilatation, which reduces systemic vascular resistance and may increase cardiac output.
Morphine sulfate (Duramorph, Astramorph)
Morphine sulfate is the drug of choice for narcotic analgesia because of its reliable and predictable effects, safety profile, and ease of reversibility with naloxone. Morphine sulfate administered IV may be dosed in a number of ways and commonly is titrated until the desired effect is obtained.
Inotropic Agents
Class Summary
The principal inotropic agents are dopamine, dobutamine, inamrinone (formerly amrinone), milrinone, dopexamine, and digoxin. In patients with hypotension who present with CHF, dopamine and dobutamine usually are employed. Inamrinone and milrinone inhibit phosphodiesterase, resulting in increased intracellular cyclic adenosine monophosphate (cAMP) and altered calcium transport. As a result, they increase cardiac contractility and reduce vascular tone by vasodilatation.
Dopamine
Dopamine is a positive inotropic agent that stimulates both adrenergic and dopaminergic receptors. Its hemodynamic effects depend on the dose. Lower doses stimulate mainly dopaminergic receptors that produce renal and mesenteric vasodilation; higher doses produce cardiac stimulation and renal vasodilation. Doses of 2-10 µg/kg/min can lead to tachycardia, ischemia, and dysrhythmias. Doses higher than 10 µg/kg/min cause vasoconstriction, which increases afterload.
Norepinephrine (Levophed)
Norepinephrine is used in protracted hypotension after adequate fluid replacement. It stimulates beta1- and alpha-adrenergic receptors, which leads to increased cardiac muscle contractility and heart rate, as well as vasoconstriction. As a result, norepinephrine increases systemic blood pressure and cardiac output. Adjust and maintain infusion to stabilize blood pressure (eg, 80-100 mm Hg systolic) sufficiently to perfuse vital organs.
Dobutamine
Dobutamine produces vasodilation and increases the inotropic state. At higher dosages, it may cause increased heart rates, thus exacerbating myocardial ischemia. It is a strong inotropic agent with minimal chronotropic effect and no vasoconstriction.
Beta2 Agonists
Class Summary
Bronchodilators are an important component of treatment in respiratory failure caused by obstructive lung disease. These agents act to decrease muscle tone in both small and large airways in the lungs. This category includes beta-adrenergics, methylxanthines, and anticholinergics.
Terbutaline (Brethaire, Bricanyl)
Terbutaline acts directly on beta2 receptors to relax bronchial smooth muscle, relieving bronchospasm and reducing airway resistance.
Albuterol (Proventil)
Albuterol is a beta-agonist useful in the treatment of bronchospasm. It selectively stimulates beta2-adrenergic receptors of the lungs. Bronchodilation results from relaxation of bronchial smooth muscle, which relieves bronchospasm and reduces airway resistance.
Xanthine Derivatives
Class Summary
Xanthine derivatives may relax smooth muscle of the bronchi.
Theophylline (Elixophyllin Elixir, Theo-24)
Theophylline has a number of physiologic effects, including increases in collateral ventilation, respiratory muscle function, mucociliary clearance, and central respiratory drive. It partially acts by inhibiting phosphodiesterase, elevating cellular cAMP levels, or antagonizing adenosine receptors in the bronchi, resulting in relaxation of smooth muscle. However, its clinical efficacy is controversial, especially in the acute setting.
Anticholinergics, Respiratory
Class Summary
Anticholinergics antagonize the action of acetylcholine with muscarinic receptor on bronchial smooth muscle.
Ipratropium bromide (Atrovent HFA)
Ipratropium bromide is an anticholinergic medication that appears to inhibit vagally mediated reflexes by antagonizing the action of acetylcholine, specifically with the muscarinic receptor on bronchial smooth muscle. Vagal tone can be significantly increased in COPD; therefore, this can have a profound effect. Ipratropium can be combined with a beta-agonist because it may require 20 minutes to begin having an effect.
Corticosteroids
Class Summary
Corticosteroids have been shown to be effective in accelerating recovery from acute COPD exacerbations and are an important anti-inflammatory therapy in asthma. Although they may not make a clinical difference in the emergency department (ED), they have some effect 6-8 hours into therapy; therefore, early dosing is critical.
Methylprednisolone (Solu-Medrol, Depo-Medrol, Medrol)
Methylprednisolone is usually given IV in the ED for initiation of corticosteroid therapy, although in theory, oral administration should be equally efficacious.
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Bilateral airspace infiltrates on chest radiograph film secondary to acute respiratory distress syndrome that resulted in respiratory failure.
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Extensive left-lung pneumonia caused respiratory failure; the mechanism of hypoxia is intrapulmonary shunting.
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A 44-year-old woman developed acute respiratory failure and diffuse bilateral infiltrates. She met the clinical criteria for the diagnosis of acute respiratory distress syndrome. In this case, the likely cause was urosepsis.
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This patient developed acute respiratory failure that turned out to be the initial presentation of systemic lupus erythematosus. The lung pathology evidence of diffuse alveolar damage is the characteristic lesion of acute lupus pneumonitis.
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A Bilevel positive airway pressure support machine is shown here. This could be used in spontaneous mode or timed mode (backup rate could be set).
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Headgear and full face mask commonly are used as the interface for noninvasive ventilatory support.
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Bilevel positive airway pressure (BiPAP) and inspiratory positive airway pressure (IPAP) settings are shown. IPAP or expiratory positive airway pressure (EPAP) and frequency can be preset.
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Noninvasive ventilation with bilevel positive airway pressure for acute respiratory failure secondary to exacerbation of chronic obstructive pulmonary disease.
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Wave forms of a volume-targeted ventilator: Pressure, flow, and volume waveforms are shown with square-wave flow pattern. A is baseline, B is increase in tidal volume, C is reduced lung compliance, and D is increase in flow rate. All 3 settings lead to increase in peak airway pressures. Adapted from Spearman CB et al.
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The cause of respiratory failure may be suggested by spirometry.
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A 65-year-old man developed chronic respiratory failure secondary to usual interstitial pneumonitis. Loss of normal architecture is seen upon biopsy. Also seen are varying degrees of inflammation and fibrosis.
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Lung biopsy from a 32-year-old woman who developed fever, diffuse infiltrates seen on chest radiograph, and acute respiratory failure. The lung biopsy shows acute eosinophilic pneumonitis; bronchoscopy with bronchoalveolar lavage also may have helped reveal the diagnosis.
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Lung biopsy on this patient with acute respiratory failure and diffuse pulmonary infiltrates helped yield the diagnosis of pulmonary edema. Therefore, cardiogenic pulmonary edema should be excluded as the cause of respiratory failure prior to considering lung biopsy.
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Pressure-volume curve of a patient with acute respiratory distress syndrome (ARDS) on mechanical ventilation can be constructed. The lower and the upper ends of the curve are flat, and the central portion is straight (where the lungs are most compliant). For optimal mechanical ventilation, patients with ARDS should be kept between the inflection and the deflection point.
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Surgical lung biopsy was performed in the patient described in Image 3. The histology shows features of diffuse alveolar damage, including epithelial injury, hyperplastic type II pneumocytes, and hyaline membranes.
