[Acid-base balance immediately after administration of an oral contraceptive (author's transl)]

An increase in breathing activity has often been described for the secretory phase of the menstrual cycle, for gravidity and after intramuscular application of corpus luteum and follicle hormone. The reason for this has been assumed to be a direct interaction of the hormones in the respiratory center. A shortly published paper dealing with 50 women under long-term treatment with a combination of oestrogenes and gestagenes for oral contraception leads the author to the assumption, that a metabolic acidosis is the primary reaction, followed by an increase in breathing activity for respiratory compensation. In a long-term study it is difficult to differentiate between primary and secondary effects. Therefore in the present experiments arterial blood has been analyzed for PaO2, PaCO2, pH and hemoglobin in 49 subjects on day 1 without hormone administration and on day 2 prior to (9.00 a.m.) after (11.00 a.m., 1.00 p.m., 4.00 p.m.) administration of a combination of oestrogene and gestagene. From the measured values O2-saturation, standard-bicarbonate, buffer bases and base excess have been calculated by the Thews nomogram. By comparison of the results before and after hormone administration it was shown, that the primary effect is a metabolic acidosis, partly compensated during the next 7 h by respiratory adaptation. There is no indication for a primary respiratory alkalosis.