ObjectiveTo determine circulating atrial natriuretic factor (ANF) concentrations in the postoperative state and to define potential hemodynamic determinants of regional plasma ANF concentrations.DesignCohort study.SettingPediatric ICU in a university hospital.PatientsTwenty-two children, mean age 4.2 yrs (range 0.9 to 13.5), were studied 18 hrs after corrective surgery on cardiopulmonary bypass. The underlying cardiac malformations were ventricular septum defect (n = 5), transposition of great arteries (n = 5), tetralogy of Fallot (n = 4), pulmonary stenosis (n = 3), and miscellaneous (n = 5).InterventionsIn addition to the commonly monitored variables in postoperative cardiac patients, blood volume was estimated by the125I albumin method, and plasma samples for radioimmunoassay determination of ANF concentrations were taken simultaneously from indwelling catheters.Measurements and Main ResultsCompared with normal age-matched values, plasma ANF concentrations were increased in all patients, with values tending to be highest in the left atrium, followed by systemic artery, superior vena cava, and pulmonary artery (345 ±PT 158, 333 ±PT 169, 311 ±PT 154, and 272 ±PT 160 pg/mL, respectively [mean ±PT SD; NS]). Simple regression analysis demonstrated a moderate correlation between blood volume and the concentration of ANF in the superior vena cava (p< .05). Stepwise multivariate analysis showed no significant independent predictor of plasma ANF concentrations.ConclusionsPlasma ANF concentrations are increased after open-heart surgery in children, with moderate direct correlation to blood volume. The wide scatter of increased hormone concentrations may be explained by the many factors known to influence circulating ANF concentrations, such as age, underlying disease, cardiovascular state, and drugs.