Can D5W Cause Euvolemic Hyponatremia?
Yes, 5% dextrose in water (D5W) can cause euvolemic hyponatremia, particularly in hospitalized patients with conditions that impair free-water excretion, such as syndrome of inappropriate antidiuresis (SIAD) or postoperative states. 1
Mechanism of D5W-Induced Hyponatremia
D5W is effectively free water once infused because the dextrose is rapidly metabolized, leaving only water behind with no osmotic load. 2 This creates a hypotonic fluid that, when administered to patients with impaired free-water excretion, leads to water retention and dilutional hyponatremia. 1
The key pathophysiologic driver is non-osmotic vasopressin (AVP) release, which occurs commonly in hospitalized patients due to:
- Pain, nausea, and stress 1
- Postoperative states 1
- Pulmonary infections (pneumonia) 1
- CNS disorders (meningitis) 1
- Medications 1
When AVP is elevated, the kidneys cannot excrete free water appropriately. Administering D5W in this setting provides a continuous source of electrolyte-free water that gets retained, progressively lowering serum sodium while maintaining normal volume status (euvolemia). 1
Clinical Context and High-Risk Populations
Pediatric patients are particularly vulnerable. The 2018 AAP/Pediatrics guideline explicitly warns that hypotonic fluids (including D5W with low sodium) administered to acutely ill children frequently causes hospital-acquired hyponatremia, affecting 15-30% of hospitalized patients. 1 The guideline emphasizes that children with acute illnesses have vastly different fluid requirements than the historical calculations suggested, and their impaired free-water excretion makes them susceptible to hyponatremia from hypotonic maintenance fluids. 1
Patients with cirrhosis represent another high-risk group. The 2018 EASL guideline specifically identifies "excessive hypotonic fluids (i.e., 5% dextrose)" as a cause of hypervolemic hyponatremia in cirrhotic patients, though the mechanism involves similar impaired water excretion. 1
Critical Distinction: When D5W is Appropriate vs. Harmful
D5W has legitimate therapeutic uses that must be distinguished from inappropriate use:
Appropriate Use:
- Hypernatremia correction: D5W is the recommended fluid for correcting hypernatremia because it delivers pure free water to lower serum sodium. 2
- Diabetes insipidus: For IV rehydration in diabetes insipidus, D5W (hypotonic fluid) should be used at usual maintenance rates, NOT normal saline. 3
Inappropriate Use Leading to Hyponatremia:
- Maintenance fluids in acutely ill patients: Using D5W as routine maintenance fluid in hospitalized patients with conditions causing SIAD or SIAD-like states (postoperative, pneumonia, meningitis) will cause euvolemic hyponatremia. 1
- Patients with cirrhosis: D5W can worsen or precipitate hyponatremia in decompensated cirrhosis. 1
Evidence-Based Prevention Strategy
The 2018 AAP Pediatrics guideline provides the strongest recommendation: isotonic fluids (sodium 140 mEq/L) should be used for maintenance hydration in hospitalized children rather than hypotonic fluids. 1 This recommendation is supported by large meta-analyses and the randomized controlled trial by McNab et al., which demonstrated significantly lower risk of hyponatremia with isotonic versus hypotonic (77 mEq/L sodium) maintenance fluids. 1
For adults, the same principle applies: avoid D5W or other hypotonic fluids as maintenance therapy in acutely ill hospitalized patients who are at risk for impaired free-water excretion. 1
Common Pitfall to Avoid
Never use D5W as routine maintenance fluid in hospitalized patients with acute illness, postoperative states, or conditions associated with non-osmotic AVP release. 1 The most serious complication is hyponatremic encephalopathy, which can be fatal or cause irreversible brain injury. 1 Instead, use isotonic fluids (sodium 140-154 mEq/L) for maintenance hydration in these populations. 1
The exception is when you are intentionally correcting hypernatremia or managing diabetes insipidus, where D5W's free-water delivery is the therapeutic goal. 3, 2