Non-invasive assessment of changes in left ventricular diastolic time intervals after acute blood volume reduction in haemodialysis

The effects of acute blood volume reduction induced by haemodialysison diastolic time intervals were studied in 19 patients by echo-and phonocardiography. Haemodialysis significantly decreasedleft ventricular diameters. The isovolumic relaxation time wasprolonged and negatively correlated with left ventricular enddiastolic dimensions. To study the effect of load reductionon left ventricular filling time, cardiac cycles with the sameR–R interval, before and after haemodialysis, were compared.At any given R–R interval dialysis resulted in a significantprolongation of the filling time. This study shows that diastolictime intervals are dependent on left ventricular loading conditions,and this effect should be considered when these time intervalsare evaluated in the clinical setting.     

Comparative study of the effects of nedocromil sodium (4 mg) and sodium cromoglycate (10 mg) on adenosine-induced bronchoconstriction in asthmatic subjects

The effect of nedocromil sodium (4 mg; 7.8 × 10⁻⁶ m ) on adenosine-induced bronchoconstriction was compared with that of a higher dose of sodium cromoglycate (10 mg; 24.1 × 10⁻⁶ m ). Eleven allergic asthmatic patients (mean age 26.28 ± 12.21 years) were studied. Adenosine (0.03–4.00 mg) was administered as nebulized aerosol. The dose of adenosine producing a 20% change in FEV₁(PD₂₀) was calculated from the individual semi-logarithmic dose-response curves. Patients were studied on 4 separate days. On the first day the adenosine challenge was performed; on subsequent days patients were pretreated (20 min before challenge) with either placebo or test drug (nedocromil sodium 2 × 2 mg or sodium cromoglycate 2 × 5 mg) administered by pressurized aerosol in a randomized, double-blind manner. Statistical analysis was performed by two-way analysis of variance. Neither sodium cromoglycate nor nedocromil sodium showed a significant bronchodilator effect. In patients treated with placebo, inhalation of adenosine produced a dose-related bronchoconstriction with a geometric mean PD₂₀ of 0.42 mg. After drug administration the mean PD₂₀ values were 1.29 mg with sodium cromoglycate and 2.30 mg with nedocromil sodium. Both drugs produced a significant increase in mean PD₂₀ value in comparison with placebo and baseline ( P < 0.01). These results demonstrate that nedocromil sodium (4 mg) is significantly more potent than a larger dose of sodium cromoglycate (10 mg) in inhibiting adenosine-induced bronchoconstriction ( P < 0.05).     

Relationship of Qrs amplitude to left ventricular dimensions after acute blood volume reduction in normal subjects

The relationship between the acute reduction in left ventriculardimensions induced by intravenous frusemide and scalar electrocardiographicQRS amplitude was studied in 14 normal subjects. The major electrocardio–graphicchange was a significant increase in QRS voltages inverselyproportional to the changes in left ventricular dimensions.This effect was opposite to the change predicted by the Brodyeffect. Surface electro–cardiographic voltages are greatlyinfluenced by myocardial cell orientation and the effectivedipoles of the wave of activation are parallel to the long axesof cardiac fibres. As in the normal ventricle the arrangementof fibres is mainly circumferential, the body surface potentialsare strongly affected by longitudinal wave front voltages. Wesuggest that during acute reduction of blood volume the inverserelationship of left ven–tricular volume and QRS amplitudecan be explained by a reduced short-circuiting effect of bloodmass on a longitudinally directed wave of activation.     

Effect of nedocromil on bronchospasm induced by inhalation of substance P in asthmatic subjects

Several studies have demonstrated that neuropeptides are present in peptidergic fibres of bronchial tissue. The aim of the present study was to evaluate in vivo the effect of nedocromil sodium (2 × 2 mg) on bronchospasm induced by inhalation of substance P. Six moderate asthmatic patients, mean age 25.17 years, were studied. Airway response was measured as FEV₁ and the dose of substance P (using a dose range of 23–736 nmol) producing a 20% decrease in FEV₁ (PD₂₀) was calculated from the individual semilogarithmic dose-response curves. Patients were studied on 3 separate days in a randomized, double-blind manner. On the first day a baseline PD₂₀ value was determined. On subsequent days substance P challenge was performed after pretreatment (20 min before challenge) with either placebo or nedocromil sodium. Student's paired t -test and Wilcoxon's test were used for statistical analysis. The results of this study demonstrated that inhalation of substance P causes a dose-dependent bronchoconstriction and that the bronchoconstriction induced by substance P can be prevented by pre-treatment with nedocromil sodium.