Management of the child with bronchial asthma. Pathologic, physiologic and pharmacologic problems

Reversibility of lung function abnormalities in children with perennial asthma

Extrinsic perennial bronchial asthma was studied by whole-body plethysmography in 118 patients to evaluate the degree and character of functional abnormalities during the asymptomatic "interval phase" of the disease. Study patients were divided into three functional subgroups, and the efficacy of albuterol (salbutamol), a beta-2-sympathomimetic drug, on bronchial obstruction of hyperinflation was analyzed. Response to medication was best in the group with predominant bronchial obstruction without hyperinflation. In contrast, patients with hyperinflation in the presence or absence of bronchial obstruction had only partial reversibility of their pathophysiologic alterations. Hyperinflation usually causes only minor clinical symptoms but tends to develop into irreversible lung damage in the form of "loss of elastic recoil." We suggest that early diagnosis and strict medical management in patients with hyperinflation are mandatory.

Controlled assessment of oral bronchodilators for asthmatic children

Various pulmonary function changes were determined in twenty paediatric patients after a single oral dose of theophylline, ephedrine, or their combination in a double-blind crossover study. The possible contributions of guaifenesin and butabarbital, components of some formulations in clinical use, were also examined. Bronchodilatory efficacy in decreasing order, when compared to placebo, was observed for theophylline-ephedrine and theophylline (nearly comparable), and for ephedrine-butabarbital and ephedrine (nearly comparable). Butabarbital and guaifenesin did not enhance or decrease bronchodilatory effect. Adverse reactions appeared to be more frequently related to ephedrine intake, although no serious reactions were noted.

Pharmacokinetic analysis of the disposition of intravenous theophylline in young children

The disposition of a single intravenous dose of theophylline, 3.2 mg/kg, was studied using a high-pressure liquid chromatographic assay in ten asthmatic children one to four years of age. The man plasma theophylline clearance was 0.100 +/- 0.036 l/kg/hr, kel 0.49 +/- 0.30 hr-1, betat1/2 3.38 +/- 1.11 hr, alphat1/2 0.13 +/- 0.09 hr, and V1 0.25 +/- 0.13 1/kg. Plasma theophylline clearance was approximately 40% greater in these children than that reported in adults, mainly due to an increased rate of drug elimination. Large interindividual differences were observed. Analysis of data using either a two- or one-compartment model yielded almost identical dosage regimens designed to rapidly achieve and maintain a chosen plasma theophylline concentration. Calculations based upon mean values of pharmacokinetic constants predict that a maintenance dose rate for aminophylline of 30 mg/kg/day, after a loading dose of 5.6 mg/kg, would rapidly achieve and maintain a mean steady-state plasma concentration of theophylline of 10 mg/1. Potential toxicity of such a regimen has not been excluded, since therapeutic trials (with achievement of steady state) have not yet been conducted.

The use of intravenous isoproterenol in the treatment of status asthmaticus

The use of intravenous isoproterenol in nineteen children with status asthmaticus who did not respond to standard anti-asthmatic therapy is reported. Six of the fourteen patients who responded favorably had normal blood gases within six hours ten within twelve hours and twelve within eighteen hours; all fourteen of the patients who responded favorably had normal blood gases within twenty-two hours after the drug was begun. Clinically, eleven of the fourteen patients who responded favorably showed improvement in respiratory distress within twelve hours of the institution of therapy. All patients who responded favorably showed some improvement within twenty-eight hours of treatment. There were five treatment failures; two were due to cardiovascular toxicity of isoproterenol, and three to progression in symptomatology that necessitated continuous ventilation with respirators.