We wanted to study the effects of a 600 micrograms inhaled salbutamol dose on the cardiovascular and respiratory autonomic nervous regulation in eight children suffering from bronchial asthma.
In this randomized, double-blind, placebo-controlled, crossover study we continuously measured electrocardiogram, finger systolic arterial pressure (SAP) and flow-volume spirometry at baseline as well as 20 min and 2 h after the drug inhalation. The R-R interval (the time between successive heart beats) and SAP variabilities were assessed by using spectral analysis. Baroreflex sensitivity was assessed by using cross-spectral analysis.
Salbutamol significantly decreased the total and low frequency (LF) variability of R-R intervals as well as the high frequency (HF) variability of R-R intervals and of SAP. Salbutamol significantly increased the LF/HF ratio of R-R intervals and of SAP, minute ventilation, heart rate and forced pulmonary function in comparison with placebo. The weight of the subjects significantly correlated positively with baroreflex sensitivity and negatively with heart rate after the salbutamol inhalation.
We conclude that the acute salbutamol inhalation decreases cardiovagal nervous responsiveness, increases sympathetic dominance in the cardiovascular autonomic balance, and has a tendency to decrease baroreflex sensitivity in addition to improved pulmonary function.
Spectral analysis of the heart rate variability can be used as a measure of baroreflex sensitivity in ketamine anesthetized rats. Stimulation of delta1-receptors with phenylephrine (0.01 mg/kg, i.v.) results in a rise of the strength of heart rate regulation, principally in the low frequency band. Maximal deviations of spectral indexes from basal level were observed on 4-8 min for low (0.2-1 Hz) and high (1-3 Hz) frequencies bands and on 10-15 min for very low (0.08-0.2 Hz) frequency band after phenylephrine injection.
Background: Interest in determination of baroreflex sensitivity in clinical practice is growing because of its prognostic information in patients with heart disease. The purpose of the present study was to assess the feasibility of cross spectral analysis in the determination of baroreflex gain from spontaneous RR interval and systolic pressure fluctuations, and to compare the results to the traditional pharmacological method in patients with coronary artery disease. Methods. We measured the gain and time lag between RR interval and systolic pressure variabilities in the frequency domain, and compared baroreflex indexes obtained by this technique with standard phenylephrine tests in 32 patients with coronary artery disease. Results. Cross spectral analysis by fast Fourier transform techniques yielded acceptable (> 0.5) coherence between systolic pressure and RR interval in the mid- (0.07-0.15 Hz) and in the respiratory-frequency (0.15-0.40 Hz) band fluctuations in 30 patients (94%), with mean coherences of 0.69 and 0.74. The mean phase difference in the mid-frequency hand was greater than in the respiratory-frequency band (-83 vs -23 degrees, P
We investigated water drinking and arterial blood pressure responses to intravenous infusions of ANG II in young (4 mo), middle-aged adult (12 mo), and old (29 mo) male Brown Norway rats. Infusions of ANG II began with arterial blood pressure either at control levels or at reduced levels following injection of the vasodilator minoxidil. Under control conditions, mean arterial pressure (MAP) in response to ANG II rose to the same level for all groups, and middle-aged and old rats drank as much or more water in response to ANG II compared with young rats, depending on whether intakes were analyzed using absolute or body weight-adjusted values. When arterial blood pressure first was reduced with minoxidil, MAP in response to ANG II stabilized at significantly lower levels compared with control conditions for all groups. Young rats drank significantly more water under reduced pressure conditions compared with control conditions, while middle-aged and old rats did not. Urine volume in response to ANG II was lower, while water balance was higher, under conditions of reduced pressure compared with control conditions. Baroreflex control of heart rate was substantially reduced in old rats compared with young and middle-aged animals. In summary, young rats appear to be more sensitive to the inhibitory effects of increased arterial blood pressure on water drinking than are older animals.
RefSource: Am J Physiol Regul Integr Comp Physiol. 2010 Nov;299(5):R1133-4
We wished to assess the effects of beta-blockade on baroreflex sensitivity and standard tests of integrity of autonomic nervous function in patients with coronary artery disease, and to determine whether the effects of lipophilic (metoprolol) and hydrophilic (atenolol) beta-blockers differ. Beta-blocking drugs increase spontaneous heart rate variability in healthy subjects and in patients with coronary heart disease, but little is known about their effects on baroreflex sensitivity and heart-rate based tests of autonomic integrity. In a randomly allocated double-blind crossover study with three 2-week treatment periods, metoprolol CR 200 mg once a day, or atenolol 100 mg once a day, or placebo once a day, were administered to 18 male patients with stable coronary artery disease. Baroreflex sensitivity was determined from the natural baroreflex challenge of Valsalva strain. Heart rate reactions to standard stimuli were measured. No significant differences were found between the effects of atenolol and metoprolol. Beta-blockade did not significantly affect the baroreflex sensitivity, but it diminished the Valsalva ratio significantly (P
Earlier studies have shown that cardiovascular autonomic regulation is impaired in untreated or poorly controlled systemic hypertension. The purpose of this double-blind, randomized parallel trial was to evaluate whether improved blood pressure (BP) control can reverse this impairment. The study group consisted of 33 patients (age 45 to 63 years) with poor BP control who received randomized metoprolol or enalapril monotherapy. Baroreflex sensitivity (BRS) was assessed by phenylephrine test and time- and frequency-domain measurements of heart rate variability (HRV) were analyzed from 24-hour ambulatory electrocardiographic recordings during monotherapy and after 10 weeks of combination therapy with metoprolol + felodipine or enalaril + hydrochlorothiazide to lower casual BP to