Why can't D5 (Dextrose 5%) containing Intravenous Fluid (IVF) be used for neuro patients?

Why D5-Containing IVF Cannot Be Used for Neuro Patients

D5 (5% dextrose) containing intravenous fluids are contraindicated in neuro patients because they are hypotonic solutions that reduce serum sodium, increase brain water content, worsen cerebral edema, and elevate intracranial pressure, ultimately leading to worse neurological outcomes and increased mortality. 1, 2

Mechanism of Harm

Hypotonic solutions like D5W create osmotic gradients that drive water into brain tissue:

• D5W has an osmolarity below 280 mOsm/L (the threshold for isotonic solutions), making it hypotonic relative to plasma 1, 3
• Once the dextrose is rapidly metabolized after infusion, only free water remains, which moves across the blood-brain barrier into cerebral tissue 2
• This water movement increases brain edema and intracranial pressure in patients with acute brain injury 1, 2
• The American Stroke Association specifically identifies 5% dextrose in water as a hypo-osmolar solution that reduces serum sodium and increases both brain water and ICP 1

Evidence of Clinical Harm

Multiple studies demonstrate worse outcomes with dextrose-containing fluids in neuro patients:

• In primates subjected to complete cerebral ischemia, dextrose 5% in 0.45% saline infusion resulted in significantly greater cerebral injury compared to lactated Ringer's solution, with worse neurologic scores (P < 0.05) and histopathology scores (P < 0.05) at 96 hours post-ischemia 4
• Even when blood glucose remained below 250 mg/dL, there was a high correlation between blood glucose levels and worse neurologic function (rs = 0.76; P < 0.005) 4
• In rat models of closed head trauma, D5W administration increased brain edema and worsened neurological severity scores compared to other fluid types 5

Guideline Recommendations

Current guidelines explicitly recommend against hypotonic solutions in brain injury:

• The French Society of Anesthesiology and Intensive Care (SFAR) recommends isotonic crystalloids (osmolarity 280-310 mOsm/L) as first-line fluid therapy in acute brain injury patients, specifically to avoid hypotonic solutions that risk inducing cerebral edema 1, 3
• A multicenter study comparing pre-hospital fluid use in traumatic brain injury patients found higher mortality in those receiving hypotonic Ringer's Lactate versus isotonic 0.9% NaCl (HR 1.78, p = 0.035) 1
• The American Heart Association warns that hyponatremic encephalopathy from hypotonic fluids is a medical emergency that can be fatal or cause irreversible brain injury 6

Recommended Alternatives

Use isotonic crystalloids instead:

• 0.9% normal saline (osmolarity 308 mOsm/L) is the most widely recommended first-line fluid 1, 3, 2
• Plasma-Lyte (osmolarity 294 mOsm/L) and other balanced isotonic solutions are acceptable alternatives that may avoid hyperchloremic acidosis with prolonged use 3
• These isotonic solutions do not create osmotic shifts that worsen cerebral edema 1, 3

Common Pitfalls to Avoid

Do not confuse D5 normal saline (D5NS) with pure D5W:

• D5NS (5% dextrose in 0.9% saline) is technically hyperosmolar initially but becomes hypotonic after dextrose metabolism 5
• In rat studies, D5NS decreased brain edema at 4 hours but caused significant hyperglycemia (1278 mg/dL) and altered sodium levels (131 mEq/L), though it did not worsen mortality 5
• However, the transient hyperglycemia from any dextrose-containing solution can itself worsen neurologic injury in ischemic brain tissue 4

Avoid fluid restriction as a strategy:

• Fluid restriction minimally affects cerebral edema and may cause hypotension, which paradoxically increases ICP and worsens neurologic outcomes 2
• Maintain euvolemia with isotonic fluids rather than restricting volume 3