Is d1/2 (half normal saline) NS (normal saline) suitable for patients who are NPO (nothing by mouth)?

D1/2 NS (Half-Normal Saline) for NPO Patients

D1/2 NS (dextrose 5% in half-normal saline) should NOT be used for NPO patients; instead, use normal saline (0.9% NaCl) at 75-100 mL/h as the standard maintenance fluid. 1

Why Normal Saline is Preferred

Avoid glucose-containing solutions in NPO patients, particularly those with acute neurological conditions or critical illness:

• Glucose can have detrimental effects in acute brain injury of all types, making D5W and D1/2 NS inappropriate choices 1
• The American Heart Association explicitly recommends IV fluids as normal saline at 75-100 mL/h for NPO patients, specifically avoiding dextrose-containing solutions 1
• This infusion rate maintains normovolemia and helps prevent hypotension and cerebral hypoperfusion 1

Risks of Hypotonic Solutions

Half-normal saline (0.45% NaCl) carries significant risks even without dextrose:

• Hypotonic fluids consistently result in falls in serum sodium and are the main factor contributing to hospital-acquired hyponatremic encephalopathy 2
• Over 50 patients have suffered death or permanent neurological injury from hospital-acquired hyponatremia, largely preventable by using 0.9% saline instead of hypotonic fluids 2
• Prospective studies in over 500 surgical patients demonstrate that normal saline effectively prevents postoperative hyponatremia, while hypotonic fluids consistently cause sodium drops 2

Additional Concerns with D1/2 NS

The dextrose component poses specific problems:

• Patients with diabetes or stress hyperglycemia require insulin management when NPO, not glucose-containing IV fluids 1
• Pramlintide and exenatide would not be appropriate for NPO patients, and glucose-containing fluids complicate glycemic management 1
• Basal insulin or basal-plus-bolus correction insulin is the preferred treatment for NPO patients with diabetes, not glucose infusions 1

Clinical Algorithm for NPO Fluid Selection

For standard NPO patients:

• Use 0.9% normal saline at 75-100 mL/h as first-line maintenance fluid 1
• Monitor intake and output closely 1
• Avoid all hypotonic solutions (including 0.45% NaCl and D1/2 NS) 2

For patients with hypernatremia (Na >150 mEq/L):

• Consider hypotonic solutions only in this specific context, with close monitoring 3
• Even then, quarter-normal saline (0.225% NaCl) shows evidence of minor hemolysis and requires further safety research 3

For patients requiring free water:

• Provide adequate free-water separately rather than using hypotonic maintenance fluids 2
• Hospital-acquired hypernatremia occurs when patients have restricted fluid access with ongoing losses 2

Common Pitfalls to Avoid

• Never use "routine" hypotonic fluids for postoperative patients, those with volume depletion, or CNS/pulmonary diseases—these patients have impaired free-water excretion 2
• Do not assume D1/2 NS provides "maintenance" electrolytes—it creates more problems than it solves 2
• Hyponatremic encephalopathy is a medical emergency requiring hypertonic saline, never fluid restriction alone 4
• The only scenario where hypotonic solutions might be considered is established, symptomatic hypernatremia with close monitoring 3