Altered cardiovascular autonomic regulation after 2-week inhaled salbutamol treatment in asthmatic children.

UNLABELLED: We studied the effects of therapeutic 2-week inhaled salbutamol treatment on the cardiovascular and respiratory autonomic nervous regulation in eight children with asthma. In this randomized, double-blind, placebo-controlled crossover study our test subjects inhaled 200 microg salbutamol or placebo thrice daily for 14 days. After the 14-day treatment we continuously measured electrocardiogram, finger systolic arterial pressure (SAP) and flow-volume spirometry at baseline and the response to a single 600 microg salbutamol inhalation. The periodic variability components of R-R intervals (the time between successive heart beats) and SAP in relation to respiration were assessed using spectral analysis. Two-week salbutamol treatment increased baseline low frequency (LF) variability (P < 0.05) and low frequency/high frequency (LF/HF) variability ratio of R-R intervals (P < 0.05) when compared to the placebo treatment. As a response to the single salbutamol inhalation the increase in LF/HF ratio of R-R intervals was smaller after the 2-week salbutamol treatment (P < 0.01). No significant differences were found in the bronchodilatory response after the treatment period. CONCLUSION: Two-week salbutamol treatment shifts the cardiovascular autonomic regulation to a new level characterized by greater sympathetic responsiveness and slight beta2-receptor tolerance. Because these effects were evident 18 h after cessation of the therapy they are likely to reflect the adaptation of organ responses to regular therapy or altered central autonomic regulation rather than direct drug effect. A slight tolerance developed in the sympathovagal cardiac response but not in the bronchodilatory response.

Altered cardiovascular autonomic regulation after salmeterol treatment in asthmatic children.

The effects of therapeutic 4 weeks' inhaled salmeterol treatment on the cardiovascular and respiratory autonomic nervous regulation was studied in 11 asthmatic children using inhaled corticosteroid medication. The study followed a randomized, double-blind, placebo-controlled cross-over design. The salmeterol dose was 50 micrograms twice daily. The 4-week salmeterol treatment increased baseline heart rate, low-frequency/high-frequency (LF/HF) variability ratio of R-R intervals, LF variability of systolic arterial pressure (SAP) and maximum tidal volume during the deep breathing test, as well as morning and evening peak expiratory flow (PEF) values. The 4-week salmeterol treatment decreased baseline HF variability of R-R intervals. As a response to the acute 600 micrograms of salbutamol, the changes in heart rate, HF variability of R-R intervals and diastolic blood pressure were significantly smaller after 4 weeks' salmeterol treatment. In conclusion, 4 weeks' therapeutic salmeterol treatment decreases basal cardiovagal reactivity, increases sympathetic dominance in the cardiovascular autonomic balance and improves pulmonary function. A tolerance develops in the cardiovascular response but not in the bronchodilatory response.

Cardiovascular autonomic regulation in asthmatic children evidenced by spectral analysis of heart rate and blood pressure variability.

The objective of the study was to investigate the features of cardiovascular and respiratory autonomic nervous regulation in asthmatic and control children. Cardiorespiratory reactivity was studied by continuous and non-invasive recording of the electrocardiogram, finger systolic arterial pressure (SAP) and flow-volume spirometry in supine and upright positions and during a deep breathing test in 19 children with bronchial asthma and 10 healthy control children (age 8-11 years). The periodic variability components of R-R intervals (the time between successive heart beats) and SAP in relation to respiration were assessed using spectral analysis techniques. Nine asthmatic children without beta2-agonist medication had a lower respiratory rate and larger high frequency (HF) variability of SAP than the controls, and 10 asthmatic children with beta2-agonist medication had greater low-frequency (LF) variability of SAP and LF/HF ratio of R-R intervals, but their respiratory rate did not differ from the controls. No intergroup differences were found in the postural change of variables. Stable bronchial asthma appears to increase respiratory-induced alterations in systolic blood pressure in children. Beta2-agonist medication, on the other hand, increases sympathetic cardiovascular activity in children with asthma.