Drugs for Respiratory Emergencies

Drugs Used to Treat Respiratory Emergencies

• Respiratory distress is a common presentation in prehospital settings, affecting people of all ages and ethnicities.
• While underlying conditions vary, reversible bronchial constriction (bronchospasm) is a primary focus of prehospital care, excluding acute pulmonary edema.
• Advanced life support (ALS) interventions, including respiratory medications, significantly reduce mortality in patients with respiratory distress.

Oxygen

• Oxygen is the most commonly used medication in prehospital settings.
• Oxygen use carries risks and benefits, and should be used with careful consideration of its pharmacological properties.
• The use of oxygen is increasingly controversial; its use should be carefully titrated to prescribed oxygen saturation ranges, rather than being applied indiscriminately, in situations like neonatal resuscitation, COPD exacerbations, and acute coronary syndrome.
• EMS providers should anticipate guideline updates, reflecting a paradigm shift in oxygen delivery approaches.
• Some patients, especially those with COPD, require continuous oxygen support at home and may need transtracheal catheters for long-term use. Nasal cannulas may be a better option for some.

Bronchodilators

• Asthma and COPD are inflammatory lung diseases, sometimes causing respiratory distress from narrowing of airways, which patients describe as breathing through a straw.
• Bronchospasm (smooth muscle spasm) and airway edema contribute to distress.
• Bronchodilators are medications divided into selective and nonselective agents.
• Selective agents act preferentially on bronchial smooth muscle, minimizing side effects.
• Beta2 agonists are sympathomimetics, relaxing bronchial smooth muscle without significant tachycardia or hypertension. Examples include albuterol (Proventil), terbutaline (Brethine), formoterol (Foradil), and pirbuterol (Maxair).
• Nonselective agents affect alpha, beta1, and beta2 adrenergic receptors. Alpha receptor stimulation causes blood pressure elevation. Beta1 receptor stimulation increases heart rate and cardiac contractility. Beta2 receptor stimulation results in bronchodilation by smooth muscle relaxation, as seen with racemic epinephrine.
• Increased secretions also contribute to patient distress.
• Any reduction of airway radius (bronchospasm or edema) impacts airflow significantly.

Management of Asthma

• A primary goal in asthma management is to avoid triggers and mitigate their effects.

• When EMS is called, treatment focuses on reversing acute bronchospasm.

• Inhaled beta2-specific medications are the first line of treatment.

• Intravenous (IV) medications may be used if inhaled bronchodilators fail to alleviate bronchospasm and inflammation.

• Albuterol (Proventil, Ventolin) is frequently used.

• Levalbuterol (Xopenex) is a newer, purified form of albuterol, believed to cause fewer adverse effects.

• First-generation drugs had significant beta1 effects in addition to beta2 effects.

• Second-generation drugs were more focused on beta2 effects but still could elevate heart rate, potentially requiring delays between doses.

• Third-generation medications predominantly target beta2 receptors.

• Ipratropium bromide (Atrovent) is used for more severe exacerbations of asthma or for situations where the patient doesn't respond well to albuterol. Inhaled ipratropium has a minimal systemic effect.

• In more severe cases, ipratropium bromide is used and can offer greater symptomatic relief over albuterol as a single agent. Albuterol affects the more central bronchial tree, while cholinergic agents like ipratropium are more pronounced in the peripheral airways.

• Combination products like albuterol/ipratropium (Combivent) take advantage of both medications' unique modes of action and anatomic sites of action to improve treatment outcomes.

Second-Line Therapy for Acute Exacerbation of Asthma

• The clinical picture of an acute asthma attack or COPD exacerbation often includes shortness of breath, use of accessory muscles, and wheezing.
• Initial treatment aims at symptom relief, not directly treating the underlying lung condition.
• If prolonged transport time is anticipated, corticosteroids (e.g., methylprednisolone and dexamethasone) may be indicated to manage the inflammatory processes involved in asthma and COPD.
• Peak expiratory flow rate (PEFR) is an objective method to assess exacerbation severity, response to therapy, and timing of steroid administration.
• Corticosteroids should be considered in acute situations when PEFR doesn't improve by at least 10% after bronchodilator therapy, or when PEFR is less than 70% after an hour.
• Aminophylline and other methylxanthines, once frequently used, are less frequently recommended now.
• Magnesium sulfate has been shown to decrease bronchospasm.
• Epinephrine, though useful in initial treatment, should be used carefully with caution, due to its beta1-mediated cardiac effects and short duration.

COPD Management

• COPD, a pulmonary obstruction classification, primarily includes emphysema and chronic bronchitis.
• These conditions cause increased sputum production, bronchospasm, and irritation.
• Severe COPD exacerbations necessitate oxygenation and ventilation support; however, careful administration of oxygen is critical, as patients with chronic COPD often maintain breathing by relying on low blood oxygen levels.
• Bronchodilators and steroids, similar to asthma management, are used in COPD.
• Low 90s SaO2 is considered acceptable in COPD patients when using pulse oximetry; oxygen levels are important, but high oxygen levels can be harmful.

Dexamethasone and Methylprednisolone

• Dexamethasone (Decadron) and methylprednisolone are corticosteroids.
• Both medications work by multiple mechanisms to reduce inflammation.
• They are used in various inflammatory situations.
• Potential adverse effects of both include central nervous system dysregulation.