For many, a frequent practice is to order D5 1/2NS intravenous fluids for maintenance IVFs. An expert review (ML Moritz, JC Ayus. NEJM 2015; 2015: 373: 1350-60) of this topic explains why this was right in the 1950s but is usually the wrong choice today.
- Use of hypotonic maintenance fluids (sodium concentration <130 mmol per liter), “has been associated with a high incidence of hospital-acquired hyponatremia and more than 100 reports of iatrogenic deaths or permanent neurologic impairment related to hyponatremic encephalopathy.”
- Acutely ill patients have “disease states associated with excess arginine vasopressin.”
- Recommendations on the use of hypotonic fluids were “based on theoretical calculations from the 1950s, before the syndrome of inappropriate antidiuresis was recognized as a common clinical entity.”
- “More than 15 randomized, prospective trials involving more than 2000 patients have evaluated the safety and efficacy of isotonic fluids…most of these studies involved children…isotonic fluids were superior.” Limitations: these studies were typically <72 hours and excluded patients with renal disease, heart failure, and cirrhosis.
- The authors also note potential problems with 0.9% NS for rapid infusion, perhaps related in part to the polyvinyl chloride bags which lowers the pH. “0.9% saline, as compared with balance salt solutions, may produce a hyperchloremic metabolic acidosis, renal vasoconstriction, an increased incidence of acute kidney injury requiring renal-replacement therapy, and hyperkalemia.”
- Hypotonic fluids may be appropriate in the setting of established hypernatremia or a clinically significant renal concentrating defect (with free-water losses).
My take: D5 1/2 NS and other hypotonic fluids should not be used commonly as a maintenance fluid.
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