Low glomerular filtration rate

NRC 1993 Vieira et al. 1996). Whether differences in xenobiotic metabolism make the child more or less suseeptible also depends on whether the relevant enzymes are involved in activation of the parent compound to its toxic form or in detoxification. There may also be differences in excretion, particularly in the newborn who has a low glomerular filtration rate and has not developed efficient tubular secretion and resorption capacities (Altman and Dittmer 1974 NRC 1993 West et al. 1948). Children and adults may differ in their capacity to repair damage Irom chemical insults. Children also have a longer lifetime in which to express damage Irom chemicals this potential is particularly relevant to cancer. 

Only about 10% of the Na-i- filtered by the glomerulus is reabsorbed by the distal convoluted tubule (DCT) and therefore the capacity of the thiazide group of diuretics to influence the elimination of Na-H in the urine is limited compared to the loop agents. Thiazides can prevent the reabsorption of up to 5% of the total filtered Na+, whereas the equivalent figure for loop diuretics is about 20%. Thiazides can still produce a moderate naturesis and diuresis compared to carbonic anhydrase inhibitors and the K+-sparing agents. Most thiazides are ineffective at low glomerular filtration rates. They also hinder the ability of the kidneys to produce a dilute urine. 

Neonates are particularly sensitive to the effects of iodine, and transient hypothyroidism has often been reported, particularly in pre-term infants (237,252,253). The low glomerular filtration rate in infants can also result in delayed excretion of contrast agents. 

In some cases, such as in pyloric stenosis, which involves obstruction between the stomach and the duodenum with consequent vomiting, leading to loss of hydrochloric acid and volume depletion, a diminished glomerular filtration rate leads to metabolic alkalosis. Because a low glomerular filtration rate affects the secretion of hydrogen ions, the ability to reabsorb bicarbonate is also affected. A low glomerular filtration rate also reduces the quantity of bicarbonate that is filtered. As such, the ability to correct acidosis or alkalosis is affected when glomerular filtration rate is reduced. 

If, for some reason, the diffusible Ca is lowered, the kidney conserves the serum level of calcium, partly because of a lowered filtration rate, but mostly by an increased reabsorption. At a total serum Ca concentration of less than 1.8 mmol/liter the net urinary excretion is almost zero. This regulatory function of the kidney can be disturbed by a low glomerular filtration rate, phosphate retention, acidosis, secondary hyperparathyroidism, and disturbances in the vitamin D metabolism [4],... 

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