Maintenance Intravenous Fluids in Acutely Ill Patients.

Abstract

To the Editor: The recommendation by Moritz and Ayus (Oct. 1 issue)1 of 0.9% normal saline as default maintenance fluid in acutely ill patients fails to consider the increased risk of hypernatremia and volume expansion that may occur. Both complications may be potentially as damaging as the hyponatremia that the authors seek to avoid.2,3 Hypernatremia accompanies ongoing hypotonic losses, including from sweat and the urea-induced diuresis associated with nutritional supplementation, and the hypertonic gain of 0.9% saline with added potassium. By definition, maintenance represents an amount and content of fluid needed to maintain a steady state. The emergence of iatrogenic hyponatremia or hypernatremia with any one-size-fits-all prescription indicates a miscalculation of maintenance fluids for a given patient. It is necessary to first define and achieve the steady state desired, to measure or estimate all input and output volumes and electrolyte content, and to recalculate at regular intervals. Urinary sodium excretion, potassium excretion, and flow rate allow for simple calculations of a positive or negative electrolyte-free water clearance and isotonic loss. The best guideline to prevent severe complications would be an algorithm for constructing a therapeutic plan for an individual patient.