ABSTRACT
We attempted to clarify the renal physiologic response to arginine vasopressin (AVP)
in the 12 sick neonates: three with respiratory distress syndrome (RDS), three with
meconium aspiration syndrome, two with transient tachypnea of the newborn, two with
neonatal asphyxia, and two low birthweight infants during the first 2 days of life.
Plasma atrial natriuretic factor (ANF), urinary AVP, osmolality, free water clearance
and cre-atinine clearance (Ccr ) were measured at 8 to 16 hours of life (stage 1) and 24 to 32 hours of I ife (stage
2). Urinary AVP was expressed as the ratio of AVP to Ccr (urine AVP/Ccr ). These subjects were divided into two groups: group A represented five infants with
a urine AVP/ Ccr ratio of 2000 or higher and group B, seven infants with a ratio of less than 2000
at stage 1. Hyponatremia occurred in two infants of group A at stage 2. Number of
infants on mechanical ventilation was four in group A and one in group B. There were
no significant differences in gestational age, birthweight, Apgar scores at 1 and
5 minutes, blood gas pH and mean arterial blood pressure between groups A and B. A
good correlation was observed between logarithm of urine AVP/Ccr ratio and urinary osmolality (p < 0.01). A negative correlation was observed between
logarithm of urine AVP/Ccr ratio and free water clearance (p < 0.01). Body weight of infants of group A at stage
2 was greater than at stage 1 (p < 0.05). Higher plasma ANF concentrations were observed
in infants of group A at stage 2 when compared with those at stage 1 (p < 0.1). These
results suggest that the syndrome of inappropriate excretion of antidiuretic hormone
may occur in the early neonatal age.
