Special considerations in the approach to asthma in infancy and early childhood

Continuous nebulization therapy for asthma with aerosols of beta2 agonists

BACKGROUND

Various studies have demonstrated the benefits of continuous nebulization therapy for delivering aerosols of the beta2 agonists such as terbutaline sulfate or albuterol sulfate to patients with severe asthma and/or impending respiratory failure.

OBJECTIVE

The purpose of this investigation was to explicate the operational factors associated with the use of nebulizers for extended aerosol respiratory therapy including those factors that affect the prescribed aerosol dosages and the relationship to actual delivery of prescribed drugs to the respiratory airways of the lungs of a patient under treatment conditions.

METHODS

Operational characteristics and methods have been investigated for use of long-running nebulizers for continuous nebulization therapy. Factors considered were particle size distribution, setup conditions, aerosolization concentrations and rates, delivery fraction of aerosol reaching patient, and changes in medication concentration during extended operation. With a large volume nebulizer, aerosols can be delivered to the patient without dilution via a standard open mask for up to eight hours without refill. The pneumatic HEART nebulizer with 240 mL reservoir was evaluated.

RESULTS

The nebulizer was operated from a single compressed air or oxygen source and found to provide from 10 to 15 L/min of aerosol with 38 to 50 microL of aerosolized medicine per liter of air (or oxygen) and utilize from 30 to 56 mL/hour of medicinal liquid. The mass median aerodynamic diameter of the aerosol droplets was found to be about 2.0 microm (sigma(g) = 2.7). Delivery efficiency to the patient mask was about 90%. The aerosolized medicine delivered to the patient can be increased by adjusting the flow rate of the gas source or changing the solution concentration of medicine. Typically, several milligrams of drug can be delivered to the patient as inhaled aerosol per hour of treatment of which about one-quarter can be expected to be deposited in the lungs. During eight hours of operation the concentration of medicinal solution increased by about a factor of two because of water evaporation.

CONCLUSIONS

Continuous nebulization therapy is an important means of treating patients with severe asthma. Dosage criteria can be established based on the operating characteristics of the nebulizer system, drug solution concentration, and patient respiration.

Therapeutic controversies in the treatment of asthma

OBJECTIVE

To introduce readers to the current controversial topics in the area of asthma therapy. Background is provided such that clinicians are aware of these issues and can make rational decisions.

DATA SOURCES

Pertinent articles were individually identified and reviewed from each journal.

STUDY SELECTION

Relevant studies, determined by topic and other specific criteria, e.g., testing methodology, were included.

DATA SYNTHESIS

Further investigation is required in the areas discussed. Systemic effects, specifically growth suppression (in children), adrenal suppression, and osteoporosis, have been demonstrated with high-dose inhaled glucocorticoids; however, the clinical relevance of such intravenous glucocorticoid formulations via nebulizer have not been demonstrated. Likewise, data on the equivalence of the inhaled glucocorticoids, with regard to efficacy and potential systemic effects, and the differences between metered-dose inhalers and dry powder inhalers, with regard to aerosol characteristics and drug delivery, are unclear. Theophylline, when used with inhaled beta-adrenergic agonists and systemic glucocorticoids for the treatment of acute asthma, as not been shown to provide clear benefit and may result in increased adverse effects. The use of regular (vs. "as needed" or prn) inhaled beta-adrenergic agonists, although shown in two studies to be detrimental to the control of asthma and result in an increased risk of death or near death caused by asthma, has not been conclusively demonstrated to be harmful.

CONCLUSIONS

Monitoring for adverse effects and the use of techniques to minimize systemic absorption (spacers and mouth rinsing) are recommended when high-dose inhaled glucocorticoid therapy is used. Intranasal and intravenous glucocorticoid products are not recommended for administration via nebulizer because of safety concerns. Until further data are available, inhaled glucocorticoids are thought to be equivalent on a microgram-per-microgram basis rather than an actuation-per-actuation basis. Theophylline is no longer recommended for treatment of acute exacerbations in nonhospitalized patients not already receiving the medication, and the link between deterioration of asthma control (and the risk for death) and regular inhaled beta-adrenergic agonists appears weak.

Low-dose beta-agonist continuous nebulization therapy for status asthmaticus in children

The role of continuous nebulization therapy (CNT) with low-dose beta (beta) agonist was retrospectively reviewed in 7 children admitted to a pediatric intensive care unit for treatment of acute severe asthma. Clinical asthma score (CAS), alveolar-arterial oxygen difference (A-aDO2), PaCO2, heart rate, and respiratory rate were recorded at 0, 12, and 24 hr of CNT. All patients had a decrease in CAS at 12 hr (p < 0.008) and decreased A-aDO2, PaCO2, respiratory rate, and heart rate at 24 hr (p < 0.008). No patient required escalation of dosage or additional intervention such as intravenous beta-agonist therapy or mechanical ventilation. No patient experienced significant cardiovascular toxicity or hypokalemia. We conclude that CNT with low-dose beta agonists should be considered in the initial approach to therapy in children with acute severe asthma.

Evaluation of the Multi-Test device for immediate hypersensitivity skin testing

Test-to-test reproducibility, user variability, and the effect of positive reactions on adjacent negative sites were evaluated for the Multi-Test skin testing device. Twenty-five subjects had skin tests with 24 histamine (1 mg/ml), four glycerosaline controls, and four "dry" controls on two testings 7 days apart. To assess reproducibility from large and smaller histamine reactions and/or their effect on adjacent negative controls, 10 of the 25 subjects were retested once with the same testing format, but histamine at 10 mg/ml was substituted. To determine whether large allergen reactions affect adjacent negative controls differently than histamine reactions, 24 additional patients were retested on arms and back with negative controls adjacent to allergens to which they had prior 3+ to 4+ skin test reactions. Conclusions from 2688 skin tests on 49 patients are as follows: large (mean > 10 mm) histamine reactions reproduced better than smaller (mean < 7 mm) responses--coefficients of variation were 12.3 and 21.4 respectively. A 14% user variability occurred when comparing mean wheal sizes from histamine produced by each nurse and 1.2% when comparing their coefficients of variation. Neither small histamine reactions nor large reactions from histamine and allergens affected adjacent negative controls. We conclude that Multi-Test is a highly reliable skin testing technique that provides good reproducibility of results and low user variability.

Clinical observations of nebulized flunisolide in infants and young children with asthma and bronchopulmonary dysplasia

Severe bronchopulmonary dysplasia (BPD) is frequently associated with asthma. The combination is often severe enough to necessitate corticosteroid therapy. There are no commercially available nebulizer solutions of corticosteroids for use in infants and young children. Seven infants and small children with very severe BPD and asthma aged 6-24 months, were treated with flunisolide, 187-250 micrograms q.i.d. in the form of nasal spray delivered by nebulizer. After treatment for 2.5-20 months, four patients showed clinical improvement, one initially improved but later deteriorated and died of cardiac failure, and two patients showed no improvement and died within 3 months. The number of days of hospitalization was significantly reduced from 8.4/month to 2.5/month (P less than 0.05). No side-effects were detected and it was felt that the three patients who died, did so as a consequence of very severe BPD and its cardiac consequences. The suspension remained stable for 80 min when mixed with normal saline, cromolyn sodium, albuterol, or acetylcysteine. It is concluded that nebulized flunisolide is a potentially useful treatment for infants and young children with asthma and BPD.

Nebulised salbutamol does have a protective effect on airways in children under 1 year old

Ten infants under the age of 1 year each of whom gave a history of recurrent wheezing attacks were studied with a total body plethysmograph. All the infants were free of wheeze when studied and were sedated with chloral hydrate. All 10 showed a significant deterioration in lung function when given nebulised water for two minutes with an increase in airways resistance and a decrease in specific conductance at one and five minutes after nebulisation compared with baseline readings. Measurements returned to baseline values within 15 minutes. When the same amount of nebulised water was given 20 minutes after nebulised salbutamol, however, there was no significant deterioration in lung function at one and five minutes after administration of nebulised water. We conclude that the airways were protected against the bronchoconstricting effect of nebulised water by the beta 2 adrenoreceptor stimulant salbutamol.

Respiratory syncytial virus infections in adults

In a retrospective 10-year study of 57 adult patients admitted to Orebro Medical Center Hospital, Sweden, with RS virus infections, pneumonia was diagnosed in 36. A primary episode of obstructive airway symptoms was observed in 20% of the patients with pneumonia. Several patients had a long period of fever and a protracted stay in the hospital. No fatal cases or serious complications were registered. Compromised hosts did not appear to be overrepresented in the material, nor did patients with impaired immune responses seem to be more seriously ill. Laboratory findings indicated that the RS virus pneumonia in adults was in some cases due to a mixed bacterial and RS virus infection, but in a few cases it was caused by the RS virus alone. Positive epidemiologic findings were found only in a few cases. The length of the period between the seasonal peak incidences of RS virus infection varied. A tendency to recurrent long and short intervals between the peak incidences was observed. An IgM antibody response to RS virus was common, and IgM detection was found to be a useful complement in the diagnosis of RS virus disease.

Paradoxical deterioration in lung function after nebulised salbutamol in wheezy infants

In 13 infants with a history of wheezing, airways resistance and specific conductance worsened after administration of nebulised salbutamol (0.5 ml sabutamol respirator solution in 1.5 ml normal saline). This paradoxical bronchoconstriction was greatest at 5 min and lasted for up to 15 min. The nebulised solution was found to be acidic and hypo-osmolar, both of which properties have been linked to bronchoconstriction in asthmatic subjects, but even with an initially iso-osmolar solution osmolality increased with time of nebulisation because of evaporation.

Clinical and immunological characteristics of pre-school asthma

Ninety-two children, sixty-two boys and thirty girls, aged 18 months to 6 years with frequent asthma were studied. Nine were born prematurely and two were ventilated in the neonatal period; two had been admitted to hospital with acute bronchiolitis. Most had an early onset of symptoms, forty-two developing asthma in infancy. Although overall growth was normal, 63% had some chest deformity. Half had past or present eczema and just over half had chronic rhinitis. Upper respiratory infection appeared to be an important precipitant of attacks in all, and 88% had exercise-induced asthma. The majority were atopic, 74% had elevated serum IgE levels, skin-prick tests were positive in 61 of 77 tested and half had eosinophilia. However, allergic factors were clearly identified as causing asthma attacks in only 24%. Immunoglobulin deficiencies were found in thirteen and defective yeast opsonization in eighteen; these children showed no other obvious differences from the remainder. Eighty-two children were followed up and after 1 year fifty-one were receiving inhaled steroids. Measurement of serum immunoglobulin, eosinophil count and skin-prick testing had little influence on management.