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- Title
Body fluid osmolality and tonicity in preterm infants.
- Authors
Semama, D. S.; Bouziane, M.; Allaert, F. A.; Gouyon, J.-B.
- Abstract
In adult patients, a recent physiological approach for the osmoregulatory system based on body fluid tonicity (the so-called effective osmolality) seems to provide better information on water movements than does the classical body fluid osmolality. To evaluate whether plasma or urinary tonicities could give a better assessment of osmoregulation than plasma and urine osmolalities in sick preterm infants cared for in a NICU. A prospective study was conducted in 30 preterm infants (BW=1284±377 g; GA=28.8±1.7 weeks). Fifteen consecutive 8-h urine collections were performed for each infant from the 8th h of life (450 periods). A plasma sample was obtained at the end of each urine collection. Sodium, potassium, creatinine, osmolality and tonicity were measured or calculated in urine and blood samples as often as possible. Hypernatremia (P[sub Na] =146–149 mmol/l) was observed in seven infants (23.3%) and in 5.9% of the periods. Fifty-three percent of the infants and 20.4% of the periods presented with plasma hyperosmolality (>300 mosmol/kg H[sub 2] O). The relationship between P[sub osm] and P[sub Na] was significant, but the clinical relevance was weak (r[sup 2] =0.411; P<0.001). Plasma osmolality (P[sub osm] ) positively correlated with urine osmolality (U[sub osm] ), but did not correlate significantly with C[sub H2O] /100 ml GFR. Plasma tonicity (2×(P[sub Na] +P[sub K] )) positively correlated with both urine tonicity (2×(U[sub Na] +U[sub K] )) and effective water clearance (EWC/100 ml GFR). On an individual basis, the linear relationship between urine and plasma osmolalities was significantly weaker than the relationship between urine and plasma tonicities. This study suggests that the calculation of plasma and urine tonicities allows a better assessment of water movements in body fluid compartments than plasma and urine osmolalities.
- Subjects
BODY fluid analysis; OSMOREGULATION; PREMATURE infants; HEALTH
- Publication
Pediatric Nephrology, 2001, Vol 16, Issue 11, p906
- ISSN
0931-041X
- Publication type
Article
- DOI
10.1007/s004670100695