Special needs of the newborn infant in fluid therapy

Reference distribution of the bioelectrical impedance vector in healthy term newborns

Bioelectrical impedance vector analysis (BIVA) is a new method that is used for the routine monitoring of the variation in body fluids and nutritional status with assumptions regarding body composition values. The aim of the present study was to determine bivariate tolerance intervals of the whole-body impedance vector and to describe phase angle (PA) values for healthy term newborns aged 7-28 d. This descriptive cross-sectional study was conducted on healthy term neonates born at a low-risk public maternity. General and anthropometric neonatal data and bioelectrical impedance data (800 μA-50 kHz) were obtained. Bivariate vector analysis was conducted with the resistance-reactance (RXc) graph method. The BIVA software was used to construct the graphs. The study was conducted on 109 neonates (52.3% females) who were born at term, adequate for gestational age, exclusively breast-fed and aged 13 (SD 3.6) d. We constructed one standard, reference, RXc-score graph and RXc-tolerance ellipses (50, 75 and 95%) that can be used with any analyser. Mean PA was 3.14 (SD 0.43)° (3.12 (SD 0.39)° for males and 3.17 (SD 0.48)° for females). Considering the overlapping of ellipses of males and females with the general distribution, a graph for newborns aged 7-28 d with the same reference tolerance ellipse was defined for boys and girls. The results differ from those reported in the literature probably, in part, due to the ethnic differences in body composition. BIVA and PA permit an assessment without the need to know body weight and the prediction error of conventional impedance formulas.

Effect of a 24-hour infusion of an isotonic electrolyte replacement fluid on the renal clearance of electrolytes in healthy neonatal foals

OBJECTIVE

To determine the effects of a 24-hour infusion of an isotonic electrolyte replacement fluid (IERF) on weight, serum and urine electrolyte concentrations, and other clinicopathologic variables in healthy neonatal foals.

ANIMALS

4 healthy 4-day-old foals.

DESIGN

Prospective study.

PROCEDURE

An IERF was administered to each foal at an estimated rate of 80 mL/kg/d (36.4 mL/lb/d) for 24 hours. Body weight was measured before and after the infusion period. Urine was collected via catheter during 4-hour periods; blood samples were collected at 4-hour intervals. Variables including urine production; urine and serum osmolalities; sodium, potassium, and chloride concentrations in urine and serum; urine and serum creatinine concentrations; urine osmolality-to-serum osmolality ratio (OsmR); transtubular potassium gradient (TTKG); and percentage creatinine clearance (Cr(cl)) of electrolytes were recorded at 0, 4, 8, 12, 16, 20, and 24 hours during the infusion period. Immediately after the study period, net fluid and whole-body electrolyte changes from baseline values were calculated.

RESULTS

Compared with baseline values, urine and serum sodium and chloride serum concentrations, urine and serum osmolalities, OsmR, and percentage Cr(cl) of sodium and chloride were significantly increased at various time points during the infusion; urine production did not change significantly. After 24 hours, weight, TTKG, serum creatinine concentration, and whole-body potassium had significantly decreased from baseline values.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that administration of an IERF containing a physiologic concentration of sodium may not be appropriate for use in neonatal foals that require maintenance fluid therapy.

Bioelectrical impedance spectroscopy for the assessment of body fluid volumes of term neonates

The assessment of fluid volume in neonates by a noninvasive, inexpensive, and fast method can contribute significantly to increase the quality of neonatal care. The objective of the present study was to calibrate an acquisition system and software to estimate the bioelectrical impedance parameters obtained by a method of bioelectrical impedance spectroscopy based on step response and to develop specific equations for the neonatal population to determine body fluid compartments. Bioelectric impedance measurements were performed by a laboratory homemade instrument. The volumes were estimated in a clinical study on 30 full-term neonates at four different times during the first month of life. During the first 24 hours of life the total body water, extracellular water and intracellular water were 2.09 +/- 0.25, 1.20 +/- 0.19, and 0.90 +/- 0.25 liters, respectively. By the 48th hour they were 1.87 +/- 0.27, 1.08 +/- 0.17, and 0.79 +/- 0.21 liters, respectively. On the 10th day they were 2.02 +/- 0.25, 1.29 +/- 0.21, and 0.72 +/- 0.14 liters, respectively, and after 1 month they were 2.34 +/- 0.27, 1.62 +/- 0.20, and 0.72 +/- 0.13 liters, respectively. The behavior of the estimated volume was correlated with neonatal body weight changes, leading to a better interpretation of such changes. In conclusion, this study indicates the feasibility of bioelectrical impedance spectroscopy as a method to help fluid administration in intensive care neonatal units, and also contribute to the development of new equations to estimate neonatal body fluid contents.

Neonatal diuretic therapy may not alter Children's preference for salt taste

Human neonates are occasionally treated with diuretics, and we investigated whether this causes a long-term enhancement of salt preference. Salt preference was examined in children aged 4-11 years. Twenty one of the children had received furosemide therapy as preterm neonates, and 24 were preterm neonates from the same ward that had no furosemide therapy. No differences were found between the two groups in preferred concentration of NaCl in soup, in consumption of salty items, and in blood and urine sodium and creatinine. However, in a tested subsample, fractional excretion of sodium (FENa) was higher in the neonatally treated children, suggesting increased salt intake. Reported severity of morning sickness in the mother when pregnant with the child, the child's history of diarrhoea and vomiting and degree of dietary salt exposure were obtained by questionnaire. These variables also did not influence salt preference, or blood and urine sodium and creatinine, except for a correlation between dietary salt exposure and blood sodium concentration. We conclude that while the physiological evidence suggests increased salt intake in children treated neonatally with furosemide, more sensitive tests of salt preference at this age are required to reveal any influence early mineralofluid loss may have on salt preference in childhood.