Which Mechanically Ventilated Patients Should Receive Bronchodilators?
Abstract & Commentary
By David J. Pierson, MD, Editor, Professor, Pulmonary and Critical Care Medicine, Harborview Medical Center, University of Washington, Seattle, is Editor for Critical Care Alert.
Synopsis: Of 206 intubated, ventilated medical ICU patients without evidence for obstructive lung disease or a known indication for bronchodilator therapy, 36% received inhaled albuterol and/or ipratropium bromide (usually every 4-6 h), at an added cost of about $450 per patient.
Source: Chang LH, et al. Utilization of bronchodilators in ventilated patients without obstructive airways disease. Respir Care. 2007;52(2):154-158.
Inhaled bronchodilators are the cornerstone of managing acute airway obstruction, and their use in intubated, mechanically ventilated patients with asthma and COPD is a standard of care. However, inhaled bronchodilators are commonly administered to mechanically ventilated patients without known obstructive lung disease, perhaps because they have a history of smoking or simply for "routine" care. Clinical evidence for benefit from these drugs administered under such circumstances is lacking. Chang and colleagues at the University of North Carolina undertook this study to determine the prevalence of inhaled bronchodilator administration to mechanically ventilated medical patients without obstructive lung disease, as well as the costs associated with this practice.
The authors prospectively determined, in the medical ICUs of 2 tertiary-care academic medical centers, how often albuterol and ipratropium bromide were administered to intubated patients without a recognized indication who were ventilated for more than 24 h during a 6-month observation period. Clinical evidence of obstructive lung disease was defined as either a documented history of asthma or COPD; the presence of wheezing noted on ICU admission; or ongoing outpatient therapy with a bronchodilator prior to admission. In these units, bronchodilators were administered by metered-dose inhaler, and the investigators determined the number of individual inhalations administered to each patient. Cost assessment was based on pharmacy acquisition costs for the drugs plus the cost of respiratory therapist or nurse administration.
Of 435 intubated, ventilated patients admitted to the 2 ICUs during the study period, 137 had clinical evidence of obstructive lung disease and were thus excluded. Another 44 were ventilated for more than a day in another location, 37 were ventilated < 24 h, and 11 were ventilated on more than 1 occasion, leaving 206 patients with no evidence of obstructive lung disease who were ventilated > 24 h. Of these 206 patients, 74 (36%) received inhaled albuterol and/or ipratropium bromide; 65 of them received both agents. Most patients were administered the bronchodilators on a scheduled basis every 4-6 h, and in 58 of 74 (78%) the drugs were started within the first 3 d on the ventilator.
Patients who received bronchodilators had worse oxygenation (measured by arterial PO2/FIO2 ratio: 188 vs 238 mm Hg, P = 0.004) than those who did not, and were more likely to have pneumonia during their ICU admission (53% vs 33%, p = 0.007), However, there were no differences in age, sex, race, or APACHE II score between the 2 groups. Patients receiving bronchodilators had median duration of mechanical ventilation of 8 d (interquartile range, 4-14 d), compared to 3 d (2-8 d) for those not administered bronchodilators. Patients receiving bronchodilators were not more tachycardic, had no greater incidence of tachyarrhythmias, and did not require more potassium replacement, than patients not receiving them. There were no differences in the incidence of ventilator-associated pneumonia, tracheostomy, or mortality. Total extra cost for bronchodilator administration was $449.35 per patient.
Commentary
The findings of this study are consistent with what goes on in the institution in which I practice. Many ventilated patients without known asthma or COPD wind up on inhaled bronchodilators, and once they are started they are seldom stopped as long as the patient remains in the unit. In our ICUs the agents used are generic albuterol and ipratropium bromide, but I have the impression that in many institutions more expensive, brand-name drugs are commonly used. Even if inhaled bronchodilators are not "expensive" in comparison with some of the other agents we use in the ICU, the time spent in delivering them takes the respiratory therapist or nurse away from other tasks, and that time is wasted if the therapy does not help the patient.
We tend to be less precise in using inhaled bronchodilators than we are in the administration of other kinds of drugs, not only in how they are ordered ("albuterol nebs q 4 h") but also in how we decide to start them and how infrequently we monitor their potential effects. Clinically important airway obstruction during mechanical ventilation causes audible wheezing, prolongation of expiration, dynamic hyperinflation (measurable as auto-PEEP), high peak- and plateau airway pressures, increased work of breathing, and hemodynamic compromise.1
Studies have shown that these things can readily be monitored at the bedside,2,3 and that whether bronchodilators are having a detectable effect can be determined objectively. As demonstrated in these and other studies, attempting to predict which ventilated patients will show measurable improvement with bronchodilators is generally unsuccessful. Thus, it is reasonable to do a therapeutic trial, and to continue bronchodilator administration if wheezing is clearly reduced, plateau pressures are decreased, auto-PEEP is diminished, or there is evidence of improvement in venous return from less hyperinflation. However, bronchodilators should not be given for days or weeks just because the patient is a smoker (only a minority of such individuals have COPD), is elderly, or has respiratory secretions.
Numerous studies have compared small-volume nebulizers and metered-dose inhalers for delivering inhaled bronchodilators—in various settings and patient populations, including with intubated, ventilated ICU patients—and their results consistently show these devices to be therapeutically equivalent.4 Metered-dose inhalers are generally less expensive and do not require interruption of the ventilator circuit for administration, but the choice of device is not as important as assuring that it is used correctly. A common mistake is to shake the metered-dose inhaler, place it in line, and then rapidly give several puffs into the circuit; this essentially gives one puff of medication and several additional puffs of propellant. The scientific background and practical application of aerosol administration during mechanical ventilation have recently been reviewed in detail.4
References
- Dhand R. Bronchodilator therapy in mechanically ventilated patients: patient selection and clinical outcomes. (Editorial) Respir Care. 2007;52(2):152-153.
- Wollam PJ, et al. Prediction and assessment of bronchodilator response in mechanically ventilated patients. Respir Care. 1994;39:730-735.
- Dhand R, et al. Bronchodilator delivery by metered-dose inhaler in ventilator-supported patients. Am J Respir Crit Care Med. 1995;151(6):1827-1833.
- Dhand R, et al. Principles and practice of mechanical ventilation, 2nd ed. New York, McGraw Hill;2006:1277-1310.
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