Rôle de la vitamine C sur les effets corticosurrénaliens de l'étomidate

Abstract

This study was carried out to assess whether the adrenal inhibition induced by etomidate could be prevented by associating ascorbic acid with etomidate, as a protective effect of ascorbic acid administered three hours after etomidate has been described. Sixteen ASA 1 or 2 patients, less than 65 years old, free of endocrine disease, were included. At induction of anaesthesia, eight of them (group B) were given an infusion of ascorbic acid 1 g, in 500 ml of 5 % glucose. Group A patients (n = 8) were given 500 ml of 5 % glucose. Anaesthesia was induced with etomidate 0.3 mg · kg −1, fentanyl 0.005 mg · kg −1 and vecuronium 0.1 mg · kg −1. Maintenance was carried out using a continuous infusion of etomidate (0.1 mg · kg −1 · h −1 for 10 min, followed by 0.01 to 0.02 mg · kg −1 · h −1). Additional boluses of fentanyl or diazepam (10 mg) were administered when arterial blood pressure or heart rate were 20 % greater than preanaesthetic values. The number of injections required was the same in both groups. Plasma cortisol concentrations were measured by radioimmunoassay (RIA) before anaesthesia (T0), 4 h (T4) and 24 h (T24) after the end of surgery. Blood ACTH levels were also assessed by RIA at T0 and T4. The adrenal insufficiency at T4 had completely ended at T24. In fact, the relative decrease in cortisol levels was greater in patients treated with ascorbic acid (T4/T0 : 47.6 ± 9 % in group A vs 76.5 ± 33 % in group B, p < 0.05) ; this was suggestive of a higher degree of adrenal inhibition in patients receiving ascorbic acid. Both groups had similar ACTH levels and cortisol/ACTH ratios, and therefore similar hypophyseal responses. These results may be explained by a concentration-dependent antioxydant effect of ascorbic acid. The routine administration of vitamin C before surgery does not seem prevent the alterations in adrenal activity due to etomidate.