Background: Rapid correction of dysnatraemias is frequently associated with increased morbidity and mortality. Therefore, it is important to estimate the proper volume and type of infusate required to change the serum sodium concentration predictably. The aim of this study is to evaluate the utility or/and the accuracy of the Adrogue-Madias formula in managing patients with hyponatraemia and hypernatraemia.
Methods: Among the 317 patients who either on admission to our internal medicine clinic or during their hospitalization were found to have hyponatraemia or hypernatraemia, we studied 189 patients (59.6%) in whom the administration of intravenous solutions was required for the correction of dysnatraemias.
Results: Twelve hours after starting the administration of intravenous solutions the anticipated as well as the achieved serum sodium concentration were as follows: in volume depleted patients 130.2+/-4.1 vs 131.3+/-5.2 meq/l (n = 45; P = NS), in syndrome of inappropriate antidiuretic hormone secretion (SIADH) patients 127.4+/-5.7 vs 128.9+/-5.9 meq/l (n = 10; P = NS), in patients with diuretic-induced hyponatraemia 123.8+/-6 vs 125.5+/-5.6 meq/l (n = 29; P = NS), in patients with primary polydipsia 122.5+/-0.7 vs 129+/-1.4 meq/l (n = 2; P = 0.02), while in patients with hypernatraemia 153.6+/-7.5 vs 156.5+/-8.9 meq/l (n = 92; P = 0.021). Furthermore, 24 h from the initiation of the therapeutic intervention the expected and the achieved serum sodium concentrations were 130+/-4 vs 135.6+/-3.3 meq/l (n = 15; P = 0.002) in patients with volume depletion, 128.1+/-4.8 vs 130+/-4.5 meq/l (n = 15; P = NS) in patients with diuretic-induced hyponatraemia and 151.5+/-6.4 vs 153.3+/-8.3 meq/l (n = 67; P = NS) in patients with hypernatraemia.
Conclusions: The formula that has been proposed by Adrogue and Madias predicted with relative accuracy the changes in serum sodium concentration in almost all patients. Thus, it should be considered as a very useful tool for the management of dysnatraemias. However, special attention should be paid when this equation is used in patients with hyponatraemia due to extracellular volume depletion after euvolaemia's restoration and primary polydipsia in order to avoid rapid correction of hyponatraemia.