Effect of salbutamol on histamine induced bronchoconstriction in healthy infants

Time to Say Goodbye to Bronchiolitis, Viral Wheeze, Reactive Airways Disease, Wheeze Bronchitis and All That

The diagnosis and management of infants and children with a significant viral lower respiratory tract illness remains the subject of much debate and little progress. Over the decades various terms for such illnesses have been in and fallen out of fashion or have evolved to mean different things to different clinicians. Terms such as "bronchiolitis," "reactive airways disease," "viral wheeze," and many more are used to describe the same condition and the same term is frequently used to describe illnesses caused by completely different dominant pathologies. This lack of clarity is due, in large part, to a failure to understand the basic underlying inflammatory and associated processes and, in part, due to the lack of a simple test to identify a condition such as asthma. Moreover, there is a lack of insight into the fact that the same pathology can produce different clinical signs at different ages. The consequence is that terminology and fashions in treatment have tended to go around in circles. As was noted almost 60 years ago, amongst pre-school children with a viral LRTI and airways obstruction there are those with a "viral bronchitis" and those with asthma. In the former group, a neutrophil dominated inflammation response is responsible for the airways' obstruction whilst amongst asthmatics much of the obstruction is attributable to bronchoconstriction. The airways obstruction in the former group is predominantly caused by airways secretions and to some extent mucosal oedema (a "snotty lung"). These patients benefit from good supportive care including supplemental oxygen if required (though those with a pre-existing bacterial bronchitis will also benefit from antibiotics). For those with a viral exacerbation of asthma, characterized by bronchoconstriction combined with impaired b-agonist responsiveness, standard management of an exacerbation of asthma (including the use of steroids to re-establish bronchodilator responsiveness) represents optimal treatment. The difficulty is identifying which group a particular patient falls into. A proposed simplified approach to the nomenclature used to categorize virus associated LRTIs is presented based on an understanding of the underlying pathological processes and how these contribute to the physical signs.

β2-agonists do not work in children under 2 years of age: myth or maxim?

Wheezy infants do not respond to bronchodilators despite evidence of functioning β-adrenoceptors. This is because the predominant aetiology, bronchiolitis, is characterised by small airway oedema and increased mucus, for which β2-agonists are ineffective. http://bit.ly/2Ws9ffh.

Assessing bronchodilator responsiveness in infants using partial expiratory flow-volume curves

Our objective was to compare the effectiveness of maximum forced expiratory flow measured at functional residual capacity (V'maxFRC) and the ratio of flow at 75% of the forced expiratory volume to peak forced expiratory flow (FEF(75)/FEF(peak)) for detecting bronchodilator-related changes in wheezy infants. In 55 infants (mean age, 7.8 +/- 3.1 months) with a history of recurrent wheezing, V'maxFRC and FEF(75)/FEF(peak) were measured at baseline and 15 min following nebulized albuterol. Mean results from 4 baseline and 4 postalbuterol partial expiratory flow-volume curves were compared at baseline and following bronchodilator challenge. The strength (relative effect size) of each measure for assessing change was quantified by dividing the mean of the pre- to postdifferences by the standard deviation of the differences. Mean percent predicted V'maxFRC was 41.3 +/- 34.3% at baseline and 44.4 +/- 34.0% following albuterol. Mean FEF(75)/FEF(peak) was 26.7 +/- 13.4% at baseline and 35.8 +/- 14.3% following albuterol. The mean percent change from baseline [(post-pre)/pre] in percent predicted V'maxFRC was 18.3 +/- 39.3, and for FEF(75)/FEF(peak), it was 44.1 +/- 36.8. The change in FEF(75)/FEF(peak) following albuterol was significantly greater than the change in V'maxFRC (P < 0.0001). The relative effect size for mean percent change from baseline in V'maxFRC was 0.47, and for FEF(75)/FEF(peak), 1.20. Changes in FEF(75)/FEF(peak) appear to differentiate changes in airway function following administration of a bronchodilator better than do changes in V'maxFRC.

Short acting beta agonists for recurrent wheeze in children under 2 years of age

BACKGROUND

Wheeze is a common symptom in infancy and is a common cause for both primary care consultations and hospital admission. Beta2-adrenoceptor agonists (b2-agonists) are the most frequently used as bronchodilator but their efficacy is questionable.

OBJECTIVES

To determine the effectiveness of b2-agonist for the treatment of infants with recurrent and persistent wheeze.

SEARCH STRATEGY

Relevant trials were identified using the Cochrane Airways Group database (CENTRAL), Medline and Pubmed. The database search used the following terms: Wheeze or asthma and Infant or Child and Short acting beta-agonist or Salbutamol (variants), Albuterol, Terbutaline (variants), Orciprenaline, Fenoterol

SELECTION CRITERIA

Randomised controlled trials comparing the effect of b2-agonist against placebo in children under 2 years of age who had had two or more previous episodes of wheeze, not related to another form of chronic lung disease.

DATA COLLECTION AND ANALYSIS

Eight studies met the criteria for inclusion in this meta-analysis. The studies investigated patients in three settings: at home (3 studies), in hospital (2 studies) and in the pulmonary function laboratory (3 studies). The main outcome measure was change in respiratory rate except for community based studies where symptom scores were used.

MAIN RESULTS

The studies were markedly heterogeneous and between study comparisons were limited. Improvement in respiratory rate, symptom score and oxygen saturation were noted in one study in the emergency department following two salbutamol nebulisers but this had no impact on hospital admission. There was a reduction in bronchial reactivity following salbutamol. There was no significant benefit from taking regular inhaled salbutamol on symptom scores recorded at home.

REVIEWER'S CONCLUSIONS

There is no clear benefit of using b2-agonists in the management of recurrent wheeze in the first two years of life although there is conflicting evidence. At present, further studies should only be performed if the patient group can be clearly defined and there is a suitable outcome parameter capable of measuring a response.

Bronchodilator responsiveness in normal infants and young children

Several studies have demonstrated that normal infants exhibit bronchoconstriction after inhalation of nonspecific agonists and that the induced airway narrowing can be reversed by the inhalation of a beta-agonist. However, there are very limited data on baseline airway tone and the airway response to a beta-agonist in this subject population. The purpose of our study was to evaluate in normal infants baseline airway responsiveness to the inhaled beta-agonist, albuterol, using changes in maximal expiratory flows. Forty-one healthy infant volunteers with no history of respiratory disease or recurrent wheezing (ages 5.4 to 141.4 wk) were studied. Maximal expiratory flow- volume curves were obtained at baseline and 10 min after inhalation of albuterol (n = 28) or placebo (n = 13) using a metered-dose inhaler with a spacer. The mean percent change was significantly greater (p < 0.05) in the albuterol versus placebo group for FEV(0.5) (2.2% versus -1.5%), FEF(75%) (10.6% versus -3.1%), and FEF(85%) (12.9% versus 0.5%). Six of 28 albuterol-treated infants demonstrated increases in FEF(75%) greater than two standard deviations from the mean change in FEF(75%) seen in the placebo group. These infants were younger and more frequently exposed to maternal smoking during pregnancy. We conclude that normal healthy infants have overall levels of baseline airway tone that are similar to that reported in adults and older children; however, among the infants we evaluated the response to an inhaled bronchodilator was greatest in the youngest infants and in those exposed to tobacco smoking.

KEYWORDS

airway responsiveness; asthma; tobacco smoke; infant pulmonary function; bronchodilator

Inhaled salbutamol for wheezy infants: a randomised controlled trial

BACKGROUND

Salbutamol is frequently used as a bronchodilator for infants who wheeze. Many single dose studies have questioned its effectiveness.

AIMS

To investigate the response of wheezy infants to salbutamol over an extended time period in order to elucidate either symptomatic relief or a protective effect.

METHODS

Eighty infants under 1 year, with persistent or recurrent wheeze and a personal or family history of atopy, were recruited to a randomised, double blind, cross over, placebo controlled trial. Salbutamol (200 microg three times daily) or placebo were administered regularly over two consecutive treatment periods of four weeks via a spacer and mask. Symptoms of wheeze and cough were recorded in a diary. At the end of the study pulmonary function tests were performed before and after salbutamol (400 microg).

RESULTS

Forty eight infants completed the diary study; 40 infants underwent pulmonary function testing. No difference in mean daily symptom score was observed between the salbutamol and placebo periods. There was no difference in the number of symptom free days. Compliance and forced expiratory flows remained unchanged and resistance increased following salbutamol. There was no relation between the response measured by symptom score or pulmonary function in individual patients.

CONCLUSION

In wheezy infants with an atopic background, there was no significant beneficial effect of salbutamol on either clinical symptoms or pulmonary function. Clinical effects could not be predicted from pulmonary function tests. Salbutamol cannot be recommended as the bronchodilator of choice in this age group.

Bronchodilator responsiveness testing using raised volume forced expiration in recurrently wheezing infants

We hypothesized that a new test of infant lung function, less affected by shifts in lung volume, might better detect bronchodilator effects. Using the raised volume forced expiration technique (RVFET), the effect of a bronchodilator on lung function was studied in 22 infants with a history of recurrent wheeze and five healthy infants. Forced expiratory volume in 0.75 s (FEV0.75), forced expiratory vital capacity (FVC), and forced expiratory flow at 75% of FVC (FEF75%) were measured by forcing expiration, using an inflatable jacket from a lung volume set by an inspiratory pressure of 20 cm H2O. A minimum of five measurements were made at baseline and following the administration of 500 microg of salbutamol from a metered dose inhaler via a small volume metal spacer. Changes in lung function in the group of 25 infants who received salbutamol were compared to seven infants who received placebo aerosol. No significant changes occurred in measures of lung function following salbutamol administration when compared to baseline or placebo despite a significant increase in heart rate. A shift in lung volume is unlikely the reason why infants do not demonstrate a change in forced expiration following bronchodilator administration.

Using low-frequency oscillation to detect bronchodilator responsiveness in infants

The potential of the low-frequency forced oscillation technique (FOT) to measure the response to inhaled salbutamol was studied in 13 infants with a history of recurrent wheeze and nine healthy infants. The input impedance of the respiratory system (Zrs) between 0.5 and 20 Hz was measured at a transrespiratory pressure of 20 cm H2O during a brief Hering-Breuer reflex-induced pause in breathing. Parameters representing the airway resistance (Raw) and inertance (law), and a constant-phase tissue damping (G) and elastance (H) were estimated from the Zrs spectra. Lung function was measured before and after the administration of 500 microg of salbutamol via a small-volume metal spacer. Six of these infants also received a placebo aerosol. A fall in Raw (13% for the entire group) occurred following treatment with salbutamol (p < 0.008) but not placebo. There was no significant difference in the response to salbutamol between the normal infants (7.65% +/- 5.49%) and those with recurrent wheeze (17.58% +/- 8.67%). On grouped data, the fall in G just failed to reach statistical significance (p = 0.05) after correcting the significance level for multiple tests. No significant change occurred in law or H. We conclude that the low-frequency FOT is a suitable methodology for studying bronchodilator responsiveness in infants.

[Comparative study of nebulized sambutol against placebo in the acute phase of bronchiolitis in 33 infants aged 1 to 6 months]

BACKGROUND

The therapeutic role of bronchodilators in bronchiolitis remains controversial. The aim of this study is to evaluate the safety and the clinical response to nebulized salbutamol in infants with mild acute bronchiolitis.

PATIENTS AND METHODS

Thirty-three infants, aged 1 month to 5 months and 22 days (mean: 92.4 days) were included in the study. Patients received either nebulized salbutamol (0.15 mg/kg per dose: 16 infants) or a placebo (normal saline aerosol: 17 infants), delivered by an oxygen propellent, three times at intervals of 1 hour, as part of a double-blind randomized trial. Effect of treatment was evaluated by measuring respiratory and heart rate, clinical scores based on the degree of retraction and wheezing, and oxygen saturation. Clinical assessment was repeated 30 minutes after each nebulization. A nasopharyngeal swab was obtained for detection of respiratory syncytial virus (VRS) antigens by immunofluorescence assay in all patients.

RESULTS

Patients in the salbutamol group exhibited significantly greater improvement in respiratory rate (P = 0.01), accessory muscle score (P < 0.001) and wheezing score (P < 0.001). There was no significant difference in oxygen saturation between both groups. Infants treated with salbutamol exhibited a non-significant increase in heart rate after the three sprays; no other adverse effects were noted. VRS was identified in 78% of the children tested.

CONCLUSIONS

Salbutamol is safe and effective in relieving the respiratory distress of young infants with acute bronchiolitis. Our study confirms previous observations that infants younger than six months of age respond as well as older children when given three doses of nebulized salbutamol. Responders could not be differentiated from non responders by personal or family histories of atopy and VRS isolation. A longitudinal study could establish a correlation between response to bronchodilator therapy and later development of asthma.

Treatment of respiratory syncytial virus infections in children

Treatment of the infections caused by the respiratory syncytial virus (RSV) has varied largely in different centres. Recently, however, management practices have become more clear based on a number of studies. An infant with RSV bronchiolitis should be hospitalized in case of insufficient oxygenation, as measured by pulse oximetry, and additional oxygen should be supplied. Mist treatment and physiotherapy are not beneficial. Bronchodilators seem to be the drug of choice in most infants with bronchiolitis. Use of corticosteroids has not been supported by data received from most studies although they are generally used. Ribavirin should be used only with high-risk patients such as immunosuppressed children. Despite the common prescription of antibiotics, they should only be given to patients with verified bacterial infection. In the future, immunotherapy including aerosolized IgG may be an alternative in treatment of RSV infections. Until an efficient vaccine is brought to clinical use, the best way to limit nosocomial spread of infections is to use cohort nursing and gowns.