Reference values for serum creatinine in children younger than 1 year of age

Reliable reference values of enzymatically assayed serum creatinine categorized in small age intervals are lacking in young children. The aim of this study was to determine reference values for serum creatinine during the first year of life and study the influence of gender, weight and height on these values. Serum creatinine determinations between 2003 and 2008 were retrieved from the hospital database. Strict exclusion criteria ensured the selection of patients without kidney damage. Correlation analysis was performed to evaluate the relation between height, weight and serum creatinine; the Mann–Whitney test was used to evaluate the relation between gender and serum creatinine. A broken stick model was designed to predict normal serum creatinine values. Mean serum creatinine values were found to decrease rapidly from 55 μmol/L on day 1 to 22 μmol/L in the second month of life; they then stabilized at 20 μmol/L until the seventh month, followed by a slight increase. No significant relation was found between serum creatinine and gender, weight and height. We present here reference values of serum creatinine in infants not at risk of decreased renal function. The absence of a relationship with gender, weight and height confirms that height-based equations to estimate glomerular filtration rate are less useful in patients of this age group

Modeling Technique and a Simulation Tool for Analysis of Clock Synchronizaion in Communication Networks

Abstract — Clock synchronization and timing continue to be an active area of research and development. This paper describes a modeling technique and a simulation tool for analysis of clock synchronization in communication networks. The tool supports analysis of stability, quality of control, time to converge, calculations of standard Maximum Time Interval Error (MTIE) and Time Deviation (TDEV) parameters, etc. Initially developed for clock synchronization in communication networks, the tool can be enhanced to address synchronization needs of other applications as well. I

The effects of losartan on renal function in the newborn rabbit.

The low GFR of newborns is maintained by various factors including the renin-angiotensin system. We previously established the importance of angiotensin II in the newborn kidney, using the angiotensin-converting enzyme inhibitor perindoprilat. The present study was designed to complement these observations by evaluating the role of angiotensin-type 1 (AT(1)) receptors, using losartan, a specific AT(1)-receptor blocker. Increasing doses of losartan were infused into anesthetized, ventilated, newborn rabbits. Renal function and hemodynamic variables were assessed using inulin and para-aminohippuric acid clearances as markers of GFR and renal plasma flow, respectively. Losartan 0.1 mg/kg slightly decreased mean blood pressure (-11%) and increased diuresis (+22%). These changes can be explained by inhibition of the AT(1)-mediated vasoconstrictive and antidiuretic effects of angiotensin, and activation of vasodilating and diuretic AT(2) receptors widely expressed in the neonatal period. GFR and renal blood flow were not modified. Losartan 0.3 mg/kg decreased mean blood pressure significantly (-15%), probably by inhibiting systemic AT(1) receptors. GFR significantly decreased (-25%), whereas renal blood flow remained stable. The decrease in filtration fraction (-21%) indicates predominant efferent vasodilation. At 3 mg/kg, the systemic hypotensive effect of losartan was marked (mean blood pressure, -28%), with decreased GFR and renal blood flow (-57% and -51%, respectively), a stable filtration fraction, and an increase in renal vascular resistance by 124%. The renal response to this dose can be considered as reflex vasoconstriction of afferent and efferent arterioles, rather than specific receptor antagonism. We conclude that under physiologic conditions, the renin-angiotensin is critically involved in the maintenance of GFR in the immature kidney