Abstract
ObjectiveThe goal was to elucidate predictors of decreased free water clearance (DFWC) in very low birth weight (VLBW) infants. We hypothesized that DFWC and fluid retention are linked to the severity of pulmonary problems and prolonged respiratory support, especially to nCPAP treatment.MethodsThe investigation was carried out at Tampere University Hospital between 2001 and 2006. The study population comprised 74 VLBW infants born at 29.21 (24.57–34.14) weeks of gestation. Median birth weight was 1175 (575–1490) grams. We measured plasma and urine osmolality and 24-hour urine volume to calculate free water clearance (FWC) for each infant. If FWC was less than 30 ml/kg/day the infant was classified as having DFWC.ResultsThere were 38 (51.4%) infants with DFWC in the study population. The median duration of the observed DFT period was 14 (4–44) days. The gestational age at birth was lower for DFWC infants compared to infants with normal FWC (NFWC), 28.29 (24.57–32.86) vs. 30.00 (25.57–34.14) weeks (p = 0.001). DFWC infants also needed longer ventilator treatment, 2 (0–23) vs. 0.50 (0–23) days (p = 0.046), nCPAP treatment 30 (0–100) vs. 3 (0–41) days (p<0.0001) and longer oxygen supplementation 47 (0–163) vs. 22 (0–74) days (p = 0.011) than NFWC infants. All values presented here are medians with ranges.ConclusionsDFWC appears to be frequently connected with exacerbation and prolongation of pulmonary problems in VLBW infants. Cautious fluid administration seems to be indicated in VLBW infants with prolonged respiratory problems and DFWC.
Highlights
Infants with bronchopulmonary dysplasia (BPD) appear to suffer transiently from decreased free water clearance (DFWC) on certain occasions [1,2]
This stress response appears to be purposeful and is physiological, unlike the fluid retention with very low birth weight (VLBW) infants observed in our present study
Infants were considered small for gestational age (SGA) if they were in the lowest 10th percentile of birth weight and appropriate for gestational age if they were above 10th percentile for each gestational week stratified by infant gender [19]
Summary
Infants with bronchopulmonary dysplasia (BPD) appear to suffer transiently from decreased free water clearance (DFWC) on certain occasions [1,2]. This is manifested by systemic and pulmonary edema, oliguria, hyponatremia and hypertension, often currently managed with diuretics [3]. Earlier studies on fluid balance have concentrated on fluid management during the first days after the birth and have shown that restriction of fluid intake decreases the mortality and morbidity in preterm infants [5,6]. In our two earlier studies we showed AVP hypersecretion to induce transient fluid retention in response to prolonged or otherwise stressful birth in healthy term infants [7,8]. This stress response appears to be purposeful and is physiological, unlike the fluid retention with VLBW infants observed in our present study
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