The present study was undertaken to assess the effects of acute metabolic acidosis on the activity of the renin-angiotensin-aldosterone system in 12 children with a mean age of 8.9 years who underwent NH4Cl loading test. Ammonium chloride was given in a dose of 0.15 g/kg per day for 3 consecutive days to evaluate renal acidification. Prior to and following NH4Cl administration blood acid-base parameters, plasma and urine electrolytes, creatinine and aldosterone concentrations as well as plasma renin activity (PRA), urine flow rate and net H+ excretion were measured. Ammonium chloride administration significantly depressed blood pH (P less than 0.05), bicarbonate (P less than 0.01) and base excess (P less than 0.01) and resulted in a slight, but significant elevation of plasma potassium concentration (P less than 0.05). Furthermore, NH4Cl ingestion induced a marked increase in urine flow rate (P less than 0.01) and urinary sodium, potassium and chloride excretion (P less than 0.01). In response to NH4Cl metabolic acidosis, PRA doubled (4.72 +/- 1.18 vs 8.13 +/- 1.02 ng/ml per hour, P less than or equal to 0.05) and there was a nearly four-fold increase in plasma aldosterone level (0.49 +/- 0.12 vs 1.52 +/- 0.24 ng/ml, P less than 0.01) and in urinary aldosterone excretion (19.2 +/- 4.3 vs 71.8 +/- 13.8 micrograms/day, P less than 0.01). The elevated aldosterone production observed in this study is assumed to be mediated by the combined effect of sodium and water diuresis-related increased PRA, hyperkalaemia and the direct stimulation of adrenal steroidogenesis by metabolic acidosis.
Aim-To evaluate the reliability of dipstick measurements of urine specific gravity (U-SG). Methods-Fresh urine specimens were tested for urine pH and osmolality (U-pH, U-Osm) by a pH meter and an osmometer, and for U-SG by three diVerent methods (refractometry, automatic readout of a dipstick (Clinitek-50), and (visual) change of colour of the dipstick). Results-The correlations between the visual U-SG dipstick measurements and U-SG determined by a refractometer and the comparison of Clinitek ® -50 dipstick U-SG measurements with U-Osm were less than optimal, showing very wide scatter of values. Only the U-SG refractometer values and U-Osm had a good linear correlation. The tested dipstick was unreliable for the bedside determination of U-SG, even after correction for U-pH, as recommended by the manufacturer. Conclusions-Among the bedside determinations, only refractometry gives reliable U-SG results. Dipstick U-SG measurements should be abandoned. (Arch Dis Child 2001;85:155-157)
We report here 6 cases of critically ill newborn infants with both RDS and acute renal insufficiency, unresponsive to conventional treatment (furosemide, dopamine). Theophylline, an adenosine antagonist, has been shown to prevent hypoxemia-induced renal insufficiency in rabbits and our patients thus received compassionately a low-dose of theophylline (1 mg . kg-1 i.v.). Urinary water excretion and creatinine clearances increased significantly in 5 out of 6 neonates, thus suggesting a beneficial role of theophylline in neonatal prerenal failure.
Aim. Inulin clearance (Cin) is the gold standard for assessing glomerular filtration rate (GFR). Other methods are based on the plasma creatinine concentration (Pcreat), creatinine clearance (Ccreat), the Haycock‐Schwartz formula and the plasma concentration of cystatin C (PcysC), a 13kDa basic protein produced at a constant rate by all nucleated cells. The present prospective study was thus designed to evaluate the reliability of PcysC as a marker of GFR in comparison with that of Pcreat, Ccreat and the Haycock‐Schwartz formula, using Cin as the gold standard. Methods: Ninety‐nine children (51 m/48 f), with a median age of 8.3 y (1.0–17.9) were studied. Using a cut‐off for Cin of 100ml/min per 1.73 m2, 54 children (54.5%) had impaired GFR. Those with normal GFR were comparable for age, height, weight and body mass index. Results: Logistic regression, ROC analysis and linear regression all showed that Ccreat was the best parameter to discriminate between impaired and normal GFR, followed by the Haycock‐Schwartz formula, PcysC, and finally Pcreat, each one being significantly more predictive than the next.
Conclusion: GFR is better assessed by the Haycock‐Schwartz formula than by PcysC or Pcreat alone. It is therefore concluded that when urine collection is not possible, simply measuring the child's Pcreat and height is the best, easiest and cheapest way to assess GFR.
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