Transcapillary vs. Intravenous Glucose: Understanding the Distinction
I need to clarify that your question appears to contain a conceptual misunderstanding—"transcapillary glucose" is not a method of glucose administration, but rather describes the physiological process of glucose movement from blood vessels into tissues across capillary membranes. The provided evidence focuses on intravenous insulin administration for hyperglycemia management, not glucose administration routes.
What the Terms Actually Mean
Transcapillary glucose refers to the passive diffusion of glucose from the intravascular space (bloodstream) through capillary walls into the interstitial fluid and ultimately into cells. This is a physiological process, not a treatment modality.
Intravenous (IV) glucose refers to the direct administration of dextrose solutions into the bloodstream, typically used to treat hypoglycemia or provide caloric support.
Clinical Context: IV Insulin vs. Subcutaneous Insulin
Since the evidence provided focuses on insulin administration routes rather than glucose administration, I'll address what appears to be the clinically relevant question:
Critical Care Settings
Continuous intravenous insulin infusion is the most effective method for achieving glycemic targets in critically ill patients 1, 2. Key features include:
- Rapid titration capability: IV insulin has a half-life of <15 minutes, allowing flexible dose adjustments for unpredicted changes in patient status 1
- Target initiation threshold: Start insulin when glucose persistently exceeds 180 mg/dL (confirmed twice within 24 hours) 1
- Goal range: Maintain glucose between 140-180 mg/dL for most ICU patients 1, 2
- Monitoring intensity: Requires blood glucose checks every 30 minutes to 2 hours 2
Non-Critical Care Settings
Subcutaneous insulin regimens (basal-bolus) are preferred for non-ICU hospitalized patients 1. The evidence strongly discourages sliding-scale insulin as monotherapy 1, 3.
Critical Pitfalls to Avoid
- Never use subcutaneous insulin in critically ill patients, especially during hypotension or shock, as absorption is unpredictable 1
- Never start insulin before excluding hypokalemia (K+ must be >3.3 mEq/L) to prevent fatal cardiac arrhythmias 3, 4
- When transitioning from IV to subcutaneous insulin, administer the first subcutaneous dose 1-2 hours before discontinuing the IV infusion to prevent rebound hyperglycemia 3, 2, 4
Transition Dosing
Convert to basal insulin at 60-80% of the total daily IV insulin dose when transitioning from continuous infusion to subcutaneous therapy 3, 2. Real-world data suggests clinicians often use lower transition percentages (median 45%), though optimal dosing requires further study 5.