Adaptive changes in kidney function (increases in sodium (Na) reabsorption and glomerular filtration rate;GFR) are delayed in premature newborns. In the premature newbom lamb model, the time course for postnatal renal adaptation after 10 hr, and the effect of variations in ventilation style on cardiovascular, endocrine and/or kidney adaptations is not known. Preterm lambs (131 d; term=150 d GA; 5-6/group; total n=62) were delivered by cesarean section, surfactant-treated, and ventilated to maintain PaCO2=40-50 mmHg for 2, 5, 10 or 24 hr as follows: high-frequency oscillation (HFO; 12 Hz), high rate (HR; 50 breaths/min; tidal volume (TV)= 9 ml/kg), or low rate(LR; 15 breaths/min; TV=15 ml/kg). Although plasma vasopressin levels decreased from 2-10 hr (i.e. HFO=81±16 to 23±5 pg/ml) and Na reabsorption increased (fractional Na excretion;FENa to <1.0%;Figure) by 16 hr, there were no differences among groups. Mean blood pressure, cardiac output, renal blood flow, filtration fraction, and GFR (Figure) did not change over time, and did not differ among groups. Conclusions: In preterm lambs; 1) The ventilation style employed does not affect the time course for renal adaptation, and 2) Adaptive changes in kidney sodium reabsorption are GFR independent.

figure 1