What are the implications of switching from D5LR (5% Dextrose in Lactated Ringer's solution) to PNSS (Peripheral Nutrition Support Solution) in a patient who is already receiving a balanced diet and has a history of diabetes or impaired glucose regulation?

Switching from D5LR to PNSS in a Patient Already Receiving Adequate Oral Diet

If a patient with diabetes or impaired glucose regulation is already consuming a balanced diet that meets their nutritional needs, switching from D5LR to PNSS (plain normal saline without dextrose) is the appropriate choice to avoid unnecessary hyperglycemia and simplify glycemic management. 1, 2

Rationale for Discontinuing Dextrose-Containing Fluids

When a patient is receiving adequate oral nutrition, the dextrose component of D5LR becomes unnecessary and potentially harmful:

• Dextrose infusions cause measurable hyperglycemia even in non-diabetic patients, with 5% dextrose at 100 mL/hr raising serum glucose by approximately 9 mg/dL above baseline, and at 200 mL/hr raising it by 24 mg/dL. 3

• In hospitalized patients without diabetes, dextrose infusion is associated with a 3-fold increase in hospital-related hyperglycemia (fasting plasma glucose ≥126 mg/dL), highlighting the glycemic burden of unnecessary dextrose administration. 4

• The FDA label for dextrose solutions specifically cautions that "solutions containing dextrose should be used with caution in patients with known subclinical or overt diabetes mellitus" and emphasizes the need to "monitor blood and urine glucose and if necessary, add insulin" to minimize hyperglycemia. 2

Clinical Decision Algorithm

Step 1: Assess nutritional adequacy

• If the patient is consuming >50% of meals and maintaining stable weight, oral intake is likely sufficient. 5
• Dextrose-containing IV fluids are only indicated when enteral/oral nutrition is interrupted or insufficient. 1

Step 2: Evaluate insulin requirements

• If the patient is on basal insulin only (not receiving nutritional insulin for tube feeds or TPN), they do not require IV dextrose for hypoglycemia prevention. 1
• The critical indication for continuous dextrose infusion is when a patient receiving nutritional insulin coverage has their enteral nutrition interrupted. 1

Step 3: Switch to PNSS

• For patients eating adequately, plain normal saline provides hydration and electrolyte support without the glycemic burden of dextrose. 5, 2
• Continue monitoring blood glucose every 4-6 hours initially after the switch to ensure stability. 5

Key Monitoring Parameters After Switching

Blood glucose surveillance:

• Monitor blood glucose every 4-6 hours for the first 24 hours after discontinuing dextrose-containing fluids to detect any unexpected hypoglycemia (though this is unlikely if oral intake is adequate). 5
• In patients with diabetes or glucose intolerance, target blood glucose 140-180 mg/dL during hospitalization. 5, 6

Electrolyte monitoring:

• Continue monitoring serum electrolytes (sodium, potassium, chloride, bicarbonate) as clinically indicated, particularly if the patient has ongoing losses or renal impairment. 5

Critical Pitfalls to Avoid

Do NOT abruptly discontinue dextrose if:

• The patient is receiving nutritional insulin coverage (NPH for tube feeds, regular insulin in TPN) and oral intake suddenly becomes inadequate—in this scenario, immediately start D10 at 50 mL/hr to prevent hypoglycemia. 1, 7
• The patient has type 1 diabetes and is NPO—these patients require continuous basal insulin AND dextrose infusion to prevent both hypoglycemia and ketosis. 1

Common misconception:

• Healthcare providers sometimes continue D5LR "just in case" the patient stops eating, but this approach causes unnecessary hyperglycemia and complicates insulin management. 3, 4
• The correct approach is to switch to PNSS when nutrition is adequate, then reinitiate dextrose only if oral intake becomes insufficient. 1

Insulin Adjustment Considerations

If the patient was receiving correctional insulin for D5LR-induced hyperglycemia:

• After switching to PNSS, correctional insulin requirements should decrease significantly. 5
• Continue basal insulin at the usual dose, as this addresses the patient's underlying diabetes, not the IV dextrose. 5, 8

Avoid the sliding scale trap:

• Do not rely solely on correctional insulin without basal coverage, as this approach is associated with worse glycemic control and higher complication rates. 5