Postnatal course of plasma levels of adrenocortical steroids in premature infants with and without NaCl supplementation

Urinary excretion of aldosterone, arginine vasopressin and cortisol in premature infants with maximum renal acid stimulation

Of 452 low-birth-weight infants who were routinely screened for maximum renal acid stimulation (MRAS) (urine pH < 5.4), 149 episodes of incipient late metabolic acidosis (urine pH < 5.4 on 2 consecutive days) were randomly allocated to either a control group or treatment with NaHCO3 or NaCl (2 mmol/kg/day each) for 7 days. Urinary excretion of aldosterone-18-glucuronide (Aldo), arginine vasopressin (AVP) and cortisol was determined in timed urine samples. On day 1, patients with MRAS showed a tendency towards increased urinary excretion of Aldo compared with infants without MRAS. In patients who received alkali therapy, urinary excretion of Aldo, AVP and cortisol decreased or showed a trend to lower values from day 1 to day 7, whereas in patients with MRAS but no specific therapy, Aldo and AVP showed a tendency to increase. We concluded that persistent MRAS is not only characterized by a reduced rate of weight gain and a tendency to decreased nitrogen assimilation, but also increased secretion of Aldo and AVP.