To explore the measurement of atrial natriuretic peptide(ANP)in umbilical cord blood of premature neonates in monitor the balance between water and sodium and its clinical significance.

80 premature neonates were divided into three groups, the simple premature group, the premature plus asphyxia group and the premature plus infection group. Another 30 normal neonates are as control group. The samples of umbilical cord blood of premature neonates were collected at the time of delivery and the ANP levels in them were measured by radioimmunoassay. The sodium levels in their peripheral vein were measured simultaneously. Then compared with the control group.

The ANP levels of the simple premature group(ANP 1. 36 ng/ml ± 0. 35 ng/ml), the premature plus asphyxia group(ANP 1. 64 ng/ml ± 0. 37 ng/ml)and the premature plus infection group(ANP 0. 78 ng/ml ±0. 29ng/ml)are significantly higher than those in the normal neonates(ANP 0. 78 ng/ml ± 0. 24ng/ml), especially in those premature plus asphyxia groups(t=8. 49, P<0. 01). And the sodium levels decreased correspondingly. There is a negative correlation between ANP and sodium levels(r=-0. 97).

ANP is the main mediator of the balance between water and sodium in the premature neonates. ANP increased significantly in the umbilical cord blood of premature neonates, especially incorporate asphyxia and infection factor, and can lead hyponatremia. So early measurement of ANP has a guidance effect on the salvage and treatment of premature neonates.