BMJ  2006;332:853 (8 April), doi:10.1136/bmj.332.7545.853-a

Letter

Disorders of sodium balance

Iatrogenic hyponatraemia—water overload and not enough potassium

The first 150 words of the full text of this article appear below.

EDITOR—Reynolds et al dealt with the important, everyday clinical problem of disorders of sodium balance and clearly stated that most cases of hyponatraemia are iatrogenic.¹ However, they did not clarify the reasons for iatrogenic hyponatraemia: usually a combination of water overload and inadequate potassium replacement. Too many doctors believe that a normal 24 hour requirement for water is 3 l or more, so they prescribe that volume to patients receiving intravenous fluids. If the intravenous fluid used is saline, volume overload can occur rapidly; if it is dextrose solution, the dextrose is metabolised, leaving the water to dilute extracellular fluid.

More importantly, this practice is often accompanied by a failure to provide adequate potassium replacement. The nephron is dedicated to the reabsorption of sodium, but only by exchange excretion of either potassium or hydrogen. The potassium is leached from intracellular fluid to be replaced by sodium to maintain . . . [Full text of this article]

Ninewells Hospital, Dundee DD1 9SY j.a.w.wildsmith@dundee.ac.uk

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Disorders of sodium balance

Rebecca M Reynolds, Paul L Padfield, and Jonathan R Seckl
BMJ 2006 332: 702-705. [Extract] [Full Text] [PDF]