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Diluting and Hydrating Agents |   |
Water is one of the most important and safest agents used to modify the character of respiratory tract secretions. Consumption of adequate amounts of water is crucial for optimal functioning of the respiratory system, and is even more important for a patient who has difficulty mobilizing bronchial secretions. Water can also be vaporized or aerosolized for delivery to patients whose upper airway has been bypassed by intubation. However, caution should be taken to avoid either over- or under-hydration if normal mucus is to be achieved. This is especially true for patients on fluid restriction or with congestive heart failure.
Saline (NaCl) is commonly nebulized for diluting the mucus and enhancing clearance, and small amounts (1-3 cc) of normal saline (0.9% NaCl) are used to dilute other medications for aerosolization. Like water, saline is absorbed into the sol layer to disadhere mucus from the airway. Many clinicians prefer to use half-normal saline (0.45% NaCl) for mucosal hydration, especially with ultrasonic nebulization, because the evaporation of water from droplets of this solution results in a solute concentration like that of normal saline.
Hypertonic saline solutions (1-15% NaCl) are the agents of choice for sputum inductions, because its elevated osmolarity can result in increased movement of fluid into the bronchorrhea. These solutions are obviously contraindicated for sodium-restricted patients.
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Propylene Glycol, which is both a solvent and hygroscopic agent, is used to stabilize aerosol droplets from bronchodilators and to inhibit the potential for bacterial growth. It is safe in low concentrations, creating a soothing effect on the respiratory mucosa. In concentrations greater than 5%, it is often used to induce sputum. |
Ethyl Alcohol (ETOH) is a wetting agent that has been used to destablize the alveolar plasma exudates occurring in cardiogenic pulmonary edema. It acts to destabilize the froth observed in the alveoli and bronchioles in cardiogenic pulmonary edema. Normally, 5-15 mL of 30-50% ETOH is vaporized by positive pressure. Temporary irritation of the airway mucosa is the only side effect experienced in this treatment.
Mucolytics
True mucolytics are drugs intended to control mucus and bronchial secretions. The two primary agent approved for administration as aerosols to treat abnormal pulmonary secretions are acetylcysteine and dornase alfa. Both act to disrupt the disulfide bond in mucus and break down DNA materials in airway secretions.
Acetylcysteine (Mucomyst) is an aerosolized medication indicated for treatment of the thick, purulent, viscous mucus secretions that can occur in COPD, especially chronic bronchitis, tuberculosis, cystic fibrosis, and acute tracheobronchitis. It is also administered orally as an antidote to reduce hepatic injury with overdoses of acetaminophen, and is designated as an orphan drug.
Aerosol doses of mucomyst are available in either 10 or 20% solutions, and normal dosage with 20% solution is 3-5 ml TID or QID, and 6-10 ml TID or QID with the 10% solution. The most serious potential side effect is bronchospasm, especially with hyperreactive airways seen in asthmatics, so using bronchodilators mixed with acetylcysteine or administer previously by MDI or nebulizer is recommended. Other potential side effects include stomatitis, nausea, and rhinorrhea.
Dornase Alfa (Pulmozyme) is an orphan drug that was produced by recombinant DNA techniques, and is indicated for the treatment and management of the viscid respiratory secretions seen in patients with cystic fibrosis (CF). In CF patients, pulmozyme helps reduce the frequency of respiratory infections requiring parenteral antibiotics, and generally improves their overall pulmonary function.
Pulmozyme available as a single use ampule, with 2.5 mg drug in 2.5 ml of clear solution. Recommended dosage is 2.5 mg daily, delivered by nebulizers specifically approved for this use. Few side effects have been observed, including voice alteration, pharyngitis, laryngitis, rash, chest pain, and conjunctivitis.