What should the NPH insulin dose be for an elderly male patient with impaired renal function, receiving total parenteral nutrition with a high carbohydrate load, and potentially requiring dialysis?

NPH Insulin Dosing for Dialysis Patient on Overnight Tube Feeding

Reduce the NPH dose to approximately 28-34 units (50-60% of current dose) immediately before dialysis, and hold NPH entirely if dialysis is initiated within 4-6 hours of the scheduled dose. 1, 2, 3

Critical Safety Considerations for Dialysis

The combination of dialysis and insulin creates extreme hypoglycemia risk that supersedes standard dosing calculations. 2, 3

• Dialysis removes glucose from the bloodstream across the semipermeable membrane into the dialysate, independent of insulin action, causing precipitous drops in blood glucose. 2
• One case report documented plasma glucose <18 mg/dL (1 mmol/L) with coma when parenteral nutrition with insulin continued during dialysis. 2
• Insulin dose reduction of 0.2-0.3 units/kg is recommended for diabetic patients undergoing hemodialysis, which for this 115 lb (52 kg) patient equals approximately 10-16 units reduction. 3
• Hypoglycemia during dialysis increases mortality and morbidity significantly in CKD patients. 3

Renal Impairment Impact on Insulin Dosing

Severe renal impairment (GFR 10) dramatically reduces insulin clearance, requiring substantial dose reduction from standard protocols. 1

• The American Diabetes Association recommends starting doses of 0.2 units/kg/day for patients with severe renal impairment (this patient: 52 kg × 0.2 = 10.4 units baseline). 1
• Current dose of 57 units represents 1.1 units/kg - approximately 5-fold higher than recommended for this degree of renal dysfunction. 1
• Severe renal impairment prolongs NPH duration of action beyond the typical 12-16 hours, increasing overnight hypoglycemia risk. 1

Tube Feeding Insulin Coverage

For continuous overnight enteral nutrition with 227g carbohydrate, the nutritional insulin component should be calculated separately from correction needs. 4

• Standard dosing is 1 unit per 10-15g carbohydrate for tube feeding coverage. 4
• For 227g carbohydrate: 227 ÷ 12.5 = approximately 18 units would be the nutritional requirement in a patient with normal renal function. 4
• NPH every 8-12 hours is recommended for continuous enteral feeding rather than once-daily dosing. 4, 5

Specific Dosing Algorithm for This Patient

Given the competing factors (high carbohydrate load vs. severe renal impairment and imminent dialysis), use the following approach:

1. If dialysis is NOT happening today: Give 28-30 units NPH split into two doses (15 units at start of tube feeding, 13-15 units 8-12 hours later). 4, 1, 5

2. If dialysis IS happening today:

   • Hold the NPH dose entirely if dialysis starts within 4-6 hours (during NPH peak action). 1, 2
   • If dialysis is >6 hours away, give only 20-25 units NPH, then stop tube feeding 30-45 minutes before dialysis to prevent severe hypoglycemia. 2
   • Provide intradialytic carbohydrate-rich snack if hypoglycemia develops. 3

3. Monitor blood glucose every 2-4 hours while NPO and during dialysis. 4, 1

Correctional Insulin Approach

• Use subcutaneous regular insulin every 6 hours or rapid-acting insulin every 4 hours for hyperglycemia correction. 4
• Apply conservative correction factor of 1 unit per 30 mg/dL above target (rather than standard 1:25) given severe renal impairment. 1
• If tube feeding is interrupted, start 10% dextrose infusion immediately to prevent hypoglycemia. 4

Common Pitfalls to Avoid

• Never continue full-dose insulin during dialysis - this combination has caused coma and death. 2
• Avoid NPH dosing based solely on carbohydrate load without accounting for reduced insulin clearance in ESRD. 1, 3
• Do not use the previous 57-unit dose - this represents dangerous overdosing for this degree of renal dysfunction. 1
• Monitor for nocturnal hypoglycemia as NPH peaks at 4-6 hours and duration is prolonged with impaired renal clearance. 1

Alternative Consideration

If recurrent hypoglycemia occurs with NPH, consider switching to insulin glargine which has demonstrated better glycemic control, reduced hypoglycemia, and improved quality of life in type 2 diabetic hemodialysis patients compared to NPH. 6