Effect of erythropoietin on anaemia in patients with myeloma receiving haemodialysis.

Discussion This study had investigated the dual role of parasympathetic efferent activity and plasma adrenaline in the pathogenesis ofnocturnal asthma. Parasympathetic blockade in this study caused a significant reversal ofthe nocturnal fall in peak flow rate as shown in our previous work.3 In the first arm of the study parasympathetic blockade reversed completely the nocturnal fall in peak flow rate, but the effect was not complete in the second arm. Infusions ofadrenaline in a dose more than sufficient to reverse the nocturnal fall in plasma adrenaline both before and after parasympathetic blockade produced no significant increase in the peak flow rate at 4 am. Thus, although infusions of adrenaline in higher concentrations can cause bronchodilatation in both normal and asthmatic subjects (fig 2),'4'5 alterations of plasma adrenaline within the concentrations seen on a diurnal basis do not have any significant physiological effect on expiratory airflow limitation either by direct action on bronchial smooth muscle, modulation of vagal neurotransmission,8 mediator release from inflammatory cells,4 16 or by increasing microvascular leakage.9 Our results agree with the earlier observation that a diurnal variation in pulmonary function can occur after adrenalectomy,'7 again confirming a lack of a primary role for adrenaline in nocturnal asthma. These observations do not detract from the therapeutic benefit of oral or inhaled 2 agonists in nocturnal asthma, when (as in this situation) pharmacological concentrations of the agonist are achieved at the receptor. We conclude that the nocturnal fall in plasma adrenaline does not account for the other factor(s) that act with parasympathetic nervous activity to increase airflow limitation at night in asthma. The effect of the a sympathetic and non-adrenergic non-cholinergic nerves and also the study of diurnal variation of airway oedema and inflammatory mediators in nocturnal asthma may be of relevance for future research.