[In vivo blood histamine during anesthesia].

The authors studied the variations in histaminaemia in the plasma on the one hand, and in whole blood on the other hand: In volunteers:-after administration of histamine in an intravenous infusion ranging from 18 to 90 ng/min/kg;-after administration of thiopental, methohexital and propanidide. In volunteers, by means of the different parameters measured, the authors found that the mean plasma concentration was 0.69 +/- 0.26 ng/ml. In the whole blood, the histaminaemia was 54 +/- 18 ng/ml. The perfusion of histamine up to 45 ng/kg/min led to no symptomatology in 3 volunteers. Propanidide led to an average increase of 350 p. 100 in the initial normal figure of plasma histaminaemia approximately 5 minutes after the beginning of the injection. But there is no agreement between the figures obtained and the clinical signs (tachycardia, mild hypotension). The injection of thiopental led to an analagous symptomatology: i.e. tachycardia and mild hypotension, arising before the maximum increase in plasma histaminaemia. Methohexital, and althesin are also histamine-liberators. Only estomidate, a new pure hypnotic product as yet not commercialised, did not lead to histamine-liberation.