Summary
Three different responses to sodium nitroprusside as a hypotensive agent during anaesthesia in children are described. A constant high dose (> 3 mg/Kg) response to, abnormal resistance to and tachyphylaxis to the drug are recognised and are dangerous and potentially lethal. They are probably related to abnormalities of cyanide-thiocyanate metabolism resulting in cyanide accumulation. The abnormal responses produce metabolic acidosis, an increase in mixed venous oxygen tension and a decrease in arterial-mixed venous oxygen content difference. Tachyphylaxis may be due to depletion of endogenous thiosulphate and was reversible by sodium thiosulphate therapy (150 mgm/Kg) in two cases in which it was used.
Résumé
Notre expérience avec le Nitroprussiate de Na, chez les enfants, nous a permis de classifier les patients selon leur réponse à cet agent.
Un groupe de patients a une réponse adéquate avec une dose totale plus petite que 3 mg/kg.
D’autres requièrent une dose élevée constante conduisant à une dose totale plus grande que 3 mg/kg. Chez d’autres patients il y a résistance anormale au Nitro-prussiate. Enfin, l’apparition d’une tachyphylaxie est observée dans un dernier groupe de patients.
Les réponses observées chez ces trois derniers groupes de patients sont probablement liées à un métabolisme anormal de l’agent avec accumulation de cyanure. Il y a alors production d’acidose métabolique, le Po2 du sang veineux mixte s’élève, et la différence artério-veineuse en oxygène diminue.
Une déplétion du thiocyanate endogène peut conduire à une tachyphylaxie. De fait on a pu renverser une tachyphylaxie chez deux enfants en administrant du thiocyanate de sodium à la dose de 150 mg/kg.
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Davies, D.W., Greiss, L., Kadar, D. et al. Sodium nitroprusside in children: Observations on metabolism during normal and abnormal responses. Canad. Anaesth. Soc. J. 22, 553–560 (1975). https://doi.org/10.1007/BF03013408
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DOI: https://doi.org/10.1007/BF03013408