Effects of long term infusion of sodium nitroprusside on iron and thiocyanate in rabbits

Abstract

The infusion of 0.75 mg/kg/h sodium nitroprusside (SNP) for 40 h in rabbits leads to a significant rise of the plasma thiocyanate concentration, irrespective of whether SNP was infused alone or in combination with sodium thiosulphate (ST). The iron concentration in the plasma is slightly increased, but the iron-binding capacity is not exceeded. The infusion of SNP in rabbits resulted in an elevation of the non-Hb iron in the liver in every case. About 60% of the infused SNP iron is found in the liver, whilst after FeSO₄ infusion only about 30% of the administered iron is deposited in the liver. The higher iron content of the liver after SNP-infusion shows that SNP-iron is not taken up in free ionic form in this organ. The question of whether and to what extent the complex is broken down before being taken up remains unanswered.

Slight but insignificant metabolic acidosis developed only when SNP was infused alone but not when given in combination with hydroxocobalamin (HC) or ST in the molar ratio 1∶5 (SNP : antidote). HC and ST are equally effective in preventing the development of acidosis. However, the strong colouration of the plasma after HC-infusion makes photometric determinations more difficult.