Why are dextrose (glucose) containing intravenous (IV) fluids contraindicated in neurosurgical patients?

Dextrose-Containing IV Fluids in Neurosurgical Patients

Dextrose-containing IV fluids are contraindicated in neurosurgical patients because they are hypotonic relative to plasma, which directly worsens cerebral edema by promoting water movement from the intravascular space into brain tissue, ultimately increasing morbidity and mortality. 1

Primary Mechanism: Osmolarity and Cerebral Edema

The fundamental issue is osmolarity management—the osmolarity of administered IV fluids has a direct impact on water movement between plasma and brain tissue, cerebral water content, and risk of edema. 1

Why Hypotonic Solutions Worsen Outcomes:

• Hypotonic solutions (including dextrose-containing fluids) decrease plasma osmolarity, creating an osmotic gradient that drives water into brain tissue 1
• The 2024 British Journal of Anaesthesia guidelines provide a strong recommendation against use of hypotonic solutions in neurosurgical patients (moderate quality evidence) 1
• Research demonstrates that 0.45% saline and 5% dextrose in water significantly worsen brain edema after closed head trauma, decreasing brain tissue specific gravity (indicating increased water content) compared to isotonic solutions 2
• Even when dextrose is combined with 0.9% saline (D5NS), the mortality rate increases to 50% with hypotonic solutions like 0.45% saline, while also significantly decreasing blood osmolality and sodium 3

Secondary Concern: Hyperglycemia

While osmolarity is the primary concern, hyperglycemia from dextrose administration also poses risks:

• Perioperative cerebral ischemia in the context of hyperglycemia worsens neurological prognosis 4
• Administration of just 500 ml of 5% dextrose in 0.9% saline causes significant hyperglycemia (mean 11.1 mmol/L), with 72% of patients exceeding 10 mmol/L 5
• The FDA drug label explicitly states that concentrated dextrose solutions should not be used when intracranial hemorrhage is present 6

The Hypoglycemia Myth

A common pitfall is the fear of hypoglycemia justifying dextrose use—this concern is unfounded:

• Studies show no cases of perioperative hypoglycemia occur in neurosurgical patients undergoing craniotomy for average fasting times of 17-18 hours without glucose administration 4
• Patients remain normoglycemic throughout surgery lasting 4-5 hours without dextrose-containing fluids 4
• Non-diabetic patients undergoing elective surgery with fasting times of almost 13 hours had no preoperative hypoglycemia when receiving non-dextrose crystalloids 5

Recommended Fluid Management

The primary goal for fluid therapy during neurosurgery is to maintain normal blood volume, optimize cerebral blood flow, and avoid reduction in plasma osmolarity. 1

First-Line Fluid Choice:

• 0.9% saline is recommended as first-line fluid therapy in patients with traumatic brain injury (weak recommendation, moderate quality evidence) 1
• Buffered isotonic solutions (such as Plasmalyte®) may be superior as they avoid hyperchloremic metabolic acidosis and adverse renal effects associated with 0.9% saline 1
• Hypotonic solutions such as Hartmann's or Ringer's lactate are commonly avoided due to their lower osmolarity 1

Critical Caveat for Hypoglycemia Management:

In the rare event of documented hypoglycemia in neurosurgical patients, blood glucose <100 mg/dL in neurologic injury patients should be treated immediately by stopping insulin infusion and administering 10-20 g of hypertonic (50%) dextrose, titrated to avoid overcorrection and iatrogenic hyperglycemia 1

Clinical Bottom Line

Avoid all hypotonic and dextrose-containing maintenance fluids in neurosurgical patients. 1 The risk of worsening cerebral edema through decreased plasma osmolarity far outweighs any theoretical benefit, and hypoglycemia does not occur with appropriate fasting protocols. 2, 3, 4 Use isotonic crystalloids (0.9% saline or buffered isotonic solutions) exclusively for perioperative fluid management in this population. 1