What happens if a patient is infused with D5 (Dextrose 5%) 1/2 normal saline?

D5 1/2 Normal Saline Infusion: Clinical Effects and Considerations

D5 1/2 normal saline (5% dextrose in 0.45% NaCl) provides both glucose supplementation and hypotonic sodium replacement, making it appropriate for specific clinical scenarios including diabetic ketoacidosis after initial resuscitation, pediatric maintenance fluids, and hypernatremic dehydration, but carries risks of hyperglycemia, hyponatremia, and fluid overload that require careful monitoring. 1, 2

Composition and Physiologic Effects

Fluid Characteristics:

• D5 1/2NS contains 50 grams of dextrose per liter plus 77 mEq/L of sodium (half the concentration of normal saline's 154 mEq/L) 2
• The solution is initially hypertonic due to dextrose content, but becomes hypotonic once glucose is metabolized, allowing controlled decrease in plasma osmolality 2
• Delivers approximately 170 calories per liter from dextrose while providing modest sodium replacement 2

Primary Clinical Applications

Diabetic Ketoacidosis Management:

• Switch from normal saline to D5 1/2NS (or D5 with 0.45-0.75% saline) when serum glucose reaches 250 mg/dL during DKA treatment 1, 2, 3
• Add 20-40 mEq/L potassium (2/3 KCl and 1/3 KPO4) to the infusion once renal function is assured 1
• This prevents hypoglycemia while continuing insulin therapy to clear ketoacidosis 1

Pediatric Maintenance Fluids:

• Appropriate for continued rehydration in children after initial volume expansion, particularly when serum sodium is normal or elevated 1
• Infusion rate typically 1.5 times the 24-hour maintenance requirements (approximately 5 mL/kg/h) accomplishes smooth rehydration 1
• Osmolality decrease should not exceed 3 mOsm/kg H₂O per hour to prevent cerebral edema 1

Hypernatremic States:

• Useful for gradual correction of hypernatremia when combined sodium and glucose replacement is needed 1, 2
• The hypotonic nature (after glucose metabolism) helps lower serum sodium without causing rapid osmotic shifts 2

Adverse Effects and Monitoring Requirements

Hyperglycemia Risk:

• Even 500 mL of dextrose-containing solutions can cause significant hyperglycemia, with 72% of non-diabetic surgical patients exceeding 10 mmol/L glucose after infusion 4
• Blood glucose monitoring is mandatory, especially in diabetic patients 3, 5
• Excessively rapid administration may cause hyperosmolar syndrome with mental confusion and loss of consciousness 5

Electrolyte Disturbances:

• The hypotonic nature can worsen or cause hyponatremia if used inappropriately 6
• May cause dilution of serum electrolytes and overhydration 5
• Requires monitoring of serum sodium, particularly in patients with baseline hyponatremia 6

Fluid Overload:

• Can cause pulmonary edema and congested states, particularly in patients with cardiac or renal compromise 5
• Frequent assessment of cardiac, renal, and mental status is required during fluid resuscitation 1

Venous Complications:

• May cause phlebitis and thrombosis at injection site, though less likely than with higher dextrose concentrations 5
• Should be administered through a large vein when possible to minimize venous irritation 5

Critical Monitoring Parameters

Essential Assessments:

• Serum glucose levels hourly during acute resuscitation, then every 2-4 hours once stable 3
• Serum sodium and osmolality to ensure correction rate does not exceed 8 mEq/day for hyponatremia or 3 mOsm/kg H₂O per hour for hyperosmolar states 1, 6
• Fluid input/output and hemodynamic monitoring (blood pressure, heart rate) 1
• Mental status changes that may indicate hyperosmolar syndrome or cerebral edema 1, 5

Contraindications and Cautions

Avoid in:

• Hyponatremia without careful calculation of sodium correction needs 6
• Patients requiring rapid volume expansion (use isotonic saline instead) 1
• Severe hyperglycemia or hyperosmolar states until glucose is controlled 5

Special Populations:

• Geriatric patients require careful monitoring for fluid overload 1
• Pediatric patients under 20 years need particularly close observation for cerebral edema during osmolality correction 1
• Patients with renal or cardiac compromise need frequent reassessment to avoid iatrogenic fluid overload 1, 5