COMPLEXITY OF INSULIN THERAPY HAS RISEN SHARPLY IN THE PAST DECADE

From The Editor: The following is from ISMP MEDICATION SAFETY ALERT, published by the Institute for Safe Medication Practices. While they are concerned with all medications, misdosage of diabetes medications can have especially severe consequences.

PROBLEM: Data derived from scientific research, voluntary reporting programs, and technology used to automate the medication use process clearly show that insulin errors are frequent and cause significant patient harm. There is an unmistakable reason for this. While insulin therapy has always required thoughtful management, over the last decade, its complexity has risen sharply. Here's just a sampling of the error-prone nature of insulin therapy today.

The onset of action for various insulin types varies widely. Depending on the product, the onset may vary from mere minutes to eight hours. This makes the typical time for insulin administration and its relationship to meals confusing. As such, our error database has examples of patients who have developed hypoglycemia because they have not eaten within the required time frame, especially after receiving insulin analogs such as ultra-short acting insulin lispro (HUMALOG) or insulin aspart (NOVOLOG). This also has happened when insulin was ordered according to a standard dosing schedule such as "every morning" or "every evening," not a specified mealtime.

The rule that clear insulin can be given IV has changed. Humalog, Novolog and LANTUS (insulin glargine) are clear, but not indicated for IV use as is regular insulin. Also, clear insulins traditionally have been rapid acting, but Lantus is long acting.

There are close to a dozen different types of insulins and several dozen different brands, many of which have names or packages that look or sound alike. Hospitals have reported a pattern of errors related to confusion between LENTE (insulin zinc suspension) and Lantus, and HUMULIN (insulin, human) and Humalog. For example, after clarification with patients, several bedtime orders for "Lenti" and "Lentis," were changed to Lantus, and an order for "Human Log" was changed to Humulin L. In each case, the house officers who ordered the insulin were unfamiliar with the specific type of insulin that the patient reported taking. It's also easy to mix up insulin vials. We recently heard about a hospitalized patient who sustained profound hypoglycemia after her infusion had been prepared using Lantus instead of regular insulin. A vial of Lantus, which had been left under the hood after preparing syringes for a specific patient, had been mistaken as human regular insulin.

Insulin is available in multiple concentrations (100 units/mL and 500 units/mL). For pediatric use, a 10 unit/mL concentration may be prepared to deliver very small doses. Adding to the risk, insulin syringes only measure the most common concentration, 100 units/mL. One recent error clearly describes the risk of multiple insulin concentrations. Sliding scale insulin was prescribed for an infant with potential doses in tenths of a unit. Pharmacy diluted the regular insulin to 10 units/mL and labeled the vial appropriately. Using a tuberculin syringe, the patient received the correct dose for one week. Then he was given 3 units instead of 0.3 units after a nurse withdrew the dose from a vial of regular insulin, 100 units/mL. Confusion also is possible with premixed products of rapid and intermediate acting insulins offered in varying strengths (HUMULIN 50/50 or 70/30, HUMALOG MIX 75/25). Several errors have been reported when clinicians forgot to include the strength or transcribed the order incorrectly.

It's not uncommon for patients to receive widely variable doses and more than one type of insulin concurrently. Patient confusion between several different insulins, and failure to discontinue previous insulin when switching to a new product, may go unnoticed until patient harm occurs. We recently heard about several errors where patients were hospitalized after taking both Humalog and regular insulin, or Lantus insulin along with twice daily NPH insulin. Over-the-counter availability of most insulins (except some ultra-short acting or long acting products) may contribute to the problem.

Sound confusing? If we as clinicians are confused, imagine how bewildered the patient may be. The examples above, and many more avenues of complexity (e.g., using "u" for unit, improper mixing of insulin products, etc.) leave no doubt that insulin is a high alert drug that is prescribed, dispensed, and administered via error-prone processes and to patients who often are at risk for an adverse outcome if an error occurs.

Insulin therapy is a complex, error-prone process for clinicians and patients. With such complexity, it's not surprising that errors with insulin are frequent and characteristically harmful to patients. As such, this high-alert medication requires special handling.

Obtain an accurate history of insulin therapy from patients and follow-up questions to detect possible confusion between the many look and sound-alike insulin products. Whenever possible, encourage patients or families to bring in the insulin for validation.

Communicate prescriptions clearly using the entire product name and always writing out "units." If a nonstandard insulin concentration is needed, list the concentration and the patient's dose in units and volume. Consider the patient's usual times for meals and specify a clear relationship between insulin administration and meals. Use verbal orders only when necessary and spell back the name to avoid confusion with sound-alike insulin products. Establish a standardized sliding scale for insulin coverage used during illness.

Safely store and dispense insulin. Do not keep insulin vials on top of medication carts or counters, or under pharmacy compounding hoods, as insulin could be confused with heparin, which also is measured in units. Put all insulin back in the appropriate storage area immediately after use. If the concentration of an insulin vial/syringe is not 100 units/mL, apply bold warning labels that clearly state the concentration and explicit instructions for measuring the proper dose in units and volume using a specified type of syringe. Use a single standard concentration for all adult IV insulin infusions. In hospitals, have pharmacy prepare and dispense prefilled syringes for once daily doses of long-acting insulin (e.g., LANTUS). For outpatients, encourage prescribers to order insulin cartridges when appropriate (although insurance coverage may be poor).

For neonates, use insulin 100 units/mL for doses 5 units or greater using a U100 insulin syringe. For doses less than 5 units, have pharmacy prepare and label a 10 units/mL concentration and use a 1 mL tuberculin syringe with 0.01 mL graduations (1 unit equals 0.1 mL). Otherwise, consider IV infusion for insulin delivery.

Require an independent double check of all doses before dispensing and administering IV insulin. Build the double check into daily work processes so it can be accomplished without disruptions. "Smart" infusion pumps with set dose limits also can serve as a double check.

Provide staff with ongoing education about insulin products and methods of delivery. Prepare a chart that lists all insulin products used in your facility. Include generic and brand names; concentration; onset, peak, and duration of action; acceptable routes of administration; time of administration in relationship to meals; appropriate drug delivery devices; and special precautions (e.g., measuring the proper dose, mixing instructions, more frequent patient glucose monitoring). Pictures of the boxes in which insulin is packaged also would be helpful. Post the charts in areas where insulin is prescribed, dispensed, and administered.

Educate patients about their insulin therapy and how to prevent and treat hypoglycemia. Reinforce how physical activity and snacks affect glucose levels and how to handle circumstances such as travel and illness. Ask patients to demonstrate glucose monitoring skills and insulin administration, including measuring the correct dose.

Gauge the patient's response to insulin by obtaining blood glucose levels. For hospitalized patients, the nurse who administers the insulin should perform the glucose testing to avoid potential communication failures. Pay special attention to patients at risk for hypokalemia and hypoglycemia (e.g., people who are fasting or have autonomic neuropathy, those taking potassium-lowering drugs). Patients with renal or hepatic impairment may require reduction in total daily doses of all insulin.

Don't assume there are no problems with insulin therapy at your practice site. Audit health records for episodes of hypoglycemia and hyperglycemia, misuse of the abbreviation "u" in prescriptions, the frequency of verbal insulin orders and so on. Proactively anticipate and address problems with insulin use in both inpatient and outpatient settings through the Failure Mode and Effects Analysis process and by discussing insulin errors that have happened in other practice sites. Don't let down your guard with this high-alert medication, even if problems are not obvious today.