Subcutaneous Injections of Insulin Regimen

Subcutaneous tissue injection continues to be the most common route for insulin delivery in the pre and post-operative period. Absorption of regular insulin from the subcutaneous tissue is often slow and variable. The coefficient of variation between patients has been shown to exceed 50% and intra-individual coefficient of variation exceeds 25% (45). Greater variability of absorption should be expected in the hospitalized patient.

Sliding-scale insulin regimens based upon retrospective hyperglycemia often fail to achieve the desired degree of glycemic control (12,16,27,44). This technique does not consider

TABLE 5 Fixed-Rate Glucose-Insulin-Potassium (GIK) Infusion Regimen

Replace Chlorpropamide 5 days before surgery with short-acting sulphonylurea. Discontinue Metformin 48 h before procedures associated with renal dysfunction (risk for lactic acidosis). Withhold oral hypoglycemic agent(s) the morning of surgery. If non-emergent surgery, control BG prior to procedure (90-180 mg/dL).

Hold solid food for >8h (longer with history gastroparesis). Clear liquids permitted until 2h before surgery. Antihypertensive and antianginal medication taken with water. Measure fasting BG level with calibrated bedside glucose monitor.

Inject one-half usual morning dose of intermediate-acting insulin upon awakening. Inject one-half of usual morning dose of short-acting insulin if fasting BG level exceeds 200 mg/dL. Hold insulin for fasting BG levels < 100 mg/dL. Insist upon early admission to hospital. Start intravenous infusion of 10% glucose in water or 0.45% saline (5 to 10g/h)

around 7:00 am. Infuse isotonic saline solution if dehydrated due to bowel prep, prolonged fast, or osmotic diuresis. Monitor BG hourly until the induction of anesthesia and surgery.

Replace glucose infusion with "GIK" solution, two hours prior to surgery. Mix glucose (5000 mg), regular insulin (15 Units), and potassium (10mmol KCl) in 500 ml water to form a 10% dextrose "GIK" solution. Infuse at 100 ml/h through a peripheral vein.

Measure BG once-hourly during and immediately following major surgery. Frequency of BG monitoring may be decreased to every 2 to 4 h in fasting patients with residual endogenous insulin production, average insulin sensitivity, and no history of hypoglycemia unawareness.

Determine optimal glycemic range for individual patient. Maintain BG levels within 100 to 200 mg/dL range. Tight BG control

(90 to 110 mg/dL) may be difficult to achieve with this regimen. If BG >200 mg/dL, change "GIK" solution to 20 Units insulin per 500 ml. If BG <90 mg/dL, change "GIK" solution to 5 Units insulin per 500 ml. Inject 25 to 50 ml 50% glucose solution for symptomatic hypoglycemia.

Measure electrolytes daily and change "GIK" solution as necessary. Hyponatremia and hypokalemia are common in the postoperative period. Measure urine for glucose and ketones when BG >200 mg/dL.

Convert "GIK" to a subcutaneous insulin regimen once the patient is able to tolerate solid food. Discontinue "GIK" infusion 30

to 60 min after injecting subcutaneous insulin (Table 6). Adjust subcutaneous insulin-dosage schedule and reinstitute oral hypoglycemic agent(s) prior to hospital discharge.

events that produce an increase in metabolic stress, the timing of meals, and the differences in insulin requirements at different times of the day (12). Despite its lack of recommendation in the recent medical literature, the sliding-scale method remains the most common technique for managing blood glucose levels in the perioperative period (44,59).

In contrast, insulin algorithms take into account patient and surgery specific information. The total amount of daily insulin is based upon the previous 24-h insulin requirement, carbohydrate load, degree of stress, level of patient activity, and presence of gluconeogenic medications (14-17,44). An intermediate-acting or long-acting insulin formulation (NPH or Glargine) is typically injected once to twice per day to supply approximately 50% of the patient's daily needs. Short-acting (Regular) or rapid-acting (Lispro) insulin is typically injected into the subcutaneous tissue prior to each meal or snack. The algorithm recommends small correction doses of short-acting insulin to fine-tune BG control. Regular insulin should be used with caution (or avoided) at bedtime to decrease the risk for early morning hypoglycemia (Table 6) (44,51,53).

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