VASOPRESSIN, ATRIAL-NATRIURETIC-FACTOR AND RENAL WATER HOMEOSTASIS INPREMATURE NEWBORN-INFANTS WITH RESPIRATORY-DISTRESS SYNDROME

Arginine vasopressin (AVP), human atrial natriuretic peptide (hANP), a nd body fluid and electrolyte balance were examined during the first f ive days of life in eleven premature infants (birthweight 1610 +/- 240 g, gestation 30 +/- 1 weeks) receiving mechanical ventilation for res piratory distress syndrome (RDS). Plasma hANP and urine AVP concentrat ions were determined by radioimmunoassay on the first, third and fifth days. Arginine vasopressin urine levels remained constantly elevated during the study period (mean +/- SD 13.5 +/- 7.8 day 1, 12.0 +/- 9.9 day 3, 13.2 +/- 5.1 ng/l day 5, p = n.s.), while plasma hANP was signi ficantly increased on the third day (626 +/- 495 vs. 298 +/- 240 pg/ml on day 1, p < .05). Urine sodium concentration, urine osmolality and osmolar clearance were elevated significantly as well on day 3, p < .0 5, and correlated to hANP levels. Body weight decreased during the stu dy by 8.2% on the third day and by 11.3% of birthweight on the fifth d ay. A significant increase in creatinine clearance occured after the t hird day (p < .01), while free water clearance remained essentially th e same during the first five days of life. We speculate that an increa se in plasma hANP concentration on day 3 of life results in a natriure sis and osmolar diuresis without correlations or temporal relationship s to hypervasopressinemia of the premature neonate with RDS.