[Bronchomotor tonus: per-operative bronchospasm].

The comprehension of the occurrence of bronchospasm during surgery is based on the knowledge of the factors which control bronchomotility: parasympathetic or cholinergic system, essentially bronchoconstrictor; sympathetic adrenergic system, with beta-2 effect, bronchodilator, and with alpha-bronchoconstrictor effect. It is also worth bearing in mind the chemical midiators, in particular, histamine contained in the mast cells, "slow reacting substance of anaphylaxis" which is a bronchoconstrictor substance of slow and prolonged action, Serotonin whose role is more modest. The last mediators known, prostaglandins, play an important role in the regulation of bronchomotility, PGE' are bronchodilators, PGF 2 alpha are bronchoconstrictors. With reference to the development of bronchospasm during anesthesia, one must bear in mind the background, and in particular of the allergy, of a past history of asthma and of the pre-operative functional respiratory condition. One must also bear in mind the anaesthesia, and the pharmacodynamic action of the substances used which can interfere with the phenomena controlling bronchomotor tone.