Hypotonic IV Fluids Confer Increased Risk of Low Sodium Levels

A systematic assessment of bias and a meta-analysis of the randomized controlled trials were completed with hyponatremia as the primary outcome, defined as a serum sodium lower than 135 mmol/L.

The review found an overall greater than two-fold relative risk of hyponatremia in the subjects who received hypotonic fluids, as compared to isotonic fluids. Doing the analysis for risk difference, a risk difference for hyponatremia of 0.19 between the two groups was calculated, giving a number needed to harm of 5.26 when using hypotonic fluids. Hypotonic fluid receipt was also associated with a 6.1-fold risk of moderate hyponatremia, versus receipt of isotonic fluids. The study was presented at the American Academy of Pediatrics (AAP) annual conference, held during October 2013 in Orlando (FL, USA).

“Hyponatremia can cause severe neurologic damage and devastating consequences,” said lead author and study presenter Byron Foster, MD, MPH. “Practitioners should stop using hypotonic fluids because of increased risk of poor outcomes and really no benefit, while there's little risk to using isotonic fluids.”

Hyponatremia is an electrolyte disturbance in which the sodium ion concentration in the plasma is lower than normal. In the vast majority of cases, hyponatremia occurs as a result of a proportional excess of water relative to the plasma sodium, as sodium cannot freely cross from the interstitial space into the cell. Symptoms of hyponatremia include nausea and vomiting, headache, confusion, lethargy, fatigue, loss of appetite, restlessness and irritability, muscle weakness, spasms, or cramps, seizures, and decreased consciousness or coma. Hyponatremia is corrected slowly in order to lessen the chance of the development of central pontine myelinolysis (CPM), a severe neurological disease involving a breakdown of the myelin sheaths covering parts of nerve cells.

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