Antidiuretic hormone (ADH) is a fundamental regulator of fluid and electrolyte homeostasis. Osmotically unregulated ADH secretion during intravenous fluid therapy has been implicated in the development of iatrogenic hyponatraemia. The case report and 3 prospective studies of this thesis provide evidence for this and examine the relative contributions of salinity versus infusion rate of intravenous fluids to the development of hyponatraemia. Two studies of plasma and urinary electrolytes and osmolality during intravenous rehydration of children with gastroenteritis were performed. The first, an observational study of 52 children receiving 0.45% (N/2) saline documented persistently raised plasma ADH concentrations independent of plasma sodium. In both studies, plasma and urinary biochemistry suggested osmotically unregulated ADH action. When N/2 and NS were compared in a randomised study of 102 children, NS emerged as superior in the prevention and correction of hyponatraemia, independent of infusion rate. In the third study, 124 pre-operative children were randomised to receive N/2 or NS intravenously at 100% or 50% of maintenance rates post-operatively. Plasma ADH concentrations increased in all groups, and the plasma and urinary biochemistry indicated persistent non-osmotic ADH activity in some children for up to 24 hours. Baseline urinary tonicity approximated NS. Comparison of urinary tonicity with the infused fluid largely explained changes observed in plasma sodium. The risk of hyponatraemia was decreased by isotonic saline but not fluid restriction; however plasma sodium concentration decreased in the NS 100% group between 8 and 24 hours, suggesting that a decreased rate should be considered during prolonged intravenous fluid administration. Fourteen (23%; 7NS) of those on 50% maintenance were assessed as dehydrated, with hypernatraemia in 3 receiving NS50%. The chloride load associated with NS in the second and third studies was not associated with the development of acidosis. The studies also showed that 2.5% dextrose resolved and prevented hypoglycaemia in children with gastroenteritis but was inadequate to prevent hypoglycaemia and/or ketosis in 38% of children under 6 years when infused at maintenance rates. Non-osmotically regulated ADH activity in hospitalised children is common, in the face of which, isotonic is superior to hypotonic saline in decreasing the risk of hyponatraemia.
| Identifer | oai:union.ndltd.org:ADTP/272559 |
| Date | January 2009 |
| Creators | Neville, Kristen Ann, Women's & Children's Health, Faculty of Medicine, UNSW |
| Publisher | Awarded by:University of New South Wales. Women's & Children's Health |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | Copyright Neville Kristen Ann., http://unsworks.unsw.edu.au/copyright |
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