November/December 2012

Sliding-Scale Insulin:
An Ineffective Practice

By Mark D. Coggins, PharmD, CGP, FASCP
Aging Well
Vol. 5 No. 6 P. 8

In the United States, approximately 26 million people have diabetes mellitus, including 10.9 million adults aged 65 or older.1 The number of those newly diagnosed with diabetes continues to rise, and the Agency for Healthcare Research and Quality reports that over the past decade there has been a 26% increase in the number of patients discharged from hospitals with a primary diagnosis of diabetes.

The overall costs related to diabetes treatment place a tremendous burden on the healthcare system, with one in five US healthcare dollars being spent on the condition. Patients with diabetes typically have medical expenses that are 2.3 times higher than those of nondiabetics,1 and families with a child who has diabetes reportedly spend as much as 10% of their income on the disease.2

Beyond the financial cost, diabetes can have a tremendous negative impact on patients and their families due to associated intangibles that are more difficult to measure, such as pain, depression, anxiety, inconvenience, and a lower quality of life.

Diabetes Complications
The primary goal of diabetes management is to achieve a level of glycemic control that closely mimics that of nondiabetic patients in an effort to prevent the long- and short-term complications associated with the disease. Inadequate blood glucose control over an extended period of time can result in significant long-term complications affecting multiple organ systems with reduced quality of life and increased mortality and morbidity (see Table 1 below). Short-term complications related to the failure to control glycemic levels can result in symptoms associated with periods of hyperglycemia. Issues related to hypoglycemia, when severe and left untreated, can lead to unconsciousness, seizures, coma, or even death.1

Continued Widespread Sliding-Scale Insulin Use
Glycemic control in many hospitalized diabetic patients who are not critically ill remains suboptimal in part due to the continued use of sliding-scale insulin regimens despite more than 40 years’ worth of studies questioning the practice’s effectiveness and numerous diabetic best practice treatment guidelines recommending its discontinuation.3

One of the largest cohort studies done to date found that 76% of general medical inpatients received sliding-scale insulin, with these regimens not only failing to control hyperglycemia but also resulting in more episodes of hypoglycemia and longer hospital stays. Additionally, patients on these regimens experienced blood glucose levels greater than 300 mg/dL at a rate three times that of patients on other insulin regimens that were more intensive and physiological based.4

Clinicians’ failure to adjust sliding-scale insulin to improve glycemic control once these regimens have been implemented is an issue in both hospitals and nursing homes. A retrospective observational study conducted at a large medical center observed 84% of patients on sliding-scale insulin experienced hyperglycemia, with dosage adjustments occurring in only 18% of these patients.5

A longitudinal study reviewed 9,804 diabetic patients aged 65 and older who had resided in a nursing home for at least one month. Fifty-four percent of the patients were started on sliding-scale insulin during their stay, and 22% of all insulin orders in the facilities involved a sliding-scale regimen. Eighty-three percent of the residents started on sliding-scale insulin remained on the regimen at the end of the study. Of those patients not started on it, 33% were later switched from other diabetic regimens to sliding-scale insulin.6

The widespread use of sliding-scale insulin in nursing homes remains persistent despite recommendations from the American Medical Directors Association to avoid the practice. In 2012, the American Geriatrics Society increased its focus on sliding-scale insulin by updating the Beers criteria for potentially inappropriate medication use in the elderly to avoid its use due to a higher risk of patients experiencing hypoglycemia without an improvement in the management of hyperglycemia, regardless of setting.7

The Sliding-Scale Roller Coaster
Sliding-scale insulin often fails to individualize insulin requirements and bases insulin doses on glucose levels prior to meals without regard to a patient’s basal metabolic needs, the types and amounts of food to be consumed, a patient’s weight, or other factors influencing insulin demands such as previous insulin needs, insulin sensitivity, or resistance.8 For example, a patient weighing 80 kg would receive the same insulin dose as a patient weighing 65 kg if their blood glucose levels are within the same range. Subsequently, the 80-kg patient may not receive sufficient insulin, placing him or her at increased hyperglycemia risk, and the 65-kg patient may receive a potentially excessive dose that could result in hypoglycemia.

A typical sliding-scale insulin regimen (see Table 2 below) calls for a progressive increase in the amount of premeal and bedtime insulin (if the patient is eating), with the calculated dose of insulin to be administered based only on the patient’s finger-stick blood sugar taken at that point in time. Patients typically have finger-stick blood sugars done every 6 hours or prior to meals and before bedtime. Premeal blood glucose levels do not accurately predict the insulin needed at that time but rather reflect the activity of insulin previously given. If rapid-acting insulin is given with the previous meal and its effects last only three or four hours, then the patient may experience high blood glucose levels for several hours prior to the next dose of insulin being given.9

Rather than being proactive in preventing wide fluctuations in blood glucose levels, sliding-scale insulin regimens are reactive and work to treat hyperglycemic episodes after they have already occurred. Insulin administered in response to current blood glucose alone can compound a prior dosing error, which can lead to significant fluctuations in high and low blood glucose levels. The risk of hypoglycemia is of significant concern since administering insulin doses without regard to meal intake and other factors can result in excessive doses of insulin being administered.5

Another common sliding-scale insulin scenario occurs when a patient does not receive insulin when his or her glucose level is normal. Within a few hours, his or her glucose level increases, leaving him or her with long periods of high blood glucose levels. Insulin is then administered with the next glucose check, and blood glucose returns to normal. This “roller coaster” effect of fluctuating glucose levels repeats itself with evidence existing now that these fluctuations are more harmful physiologically than blood glucose levels that are continuously elevated, even when the elevation is considered mild.10

Pushing for Structured Insulin Regimens
Best practice guidelines now recommend the use of structured insulin regimens with three components: basal insulin, nutritional insulin, and correctional insulin. Regimens combining these components have been shown to reduce fluctuations in blood glucose levels, increase the number of days patients maintain acceptable blood glucose levels, and reduce the length of non-ICU stays for hospitalized patients.

It’s recommended that basal insulin be given routinely to account for patients’ basal metabolic insulin requirements and prevent the liver from overproducing glucose, which leads to hyperglycemic episodes. The use of long-acting basal insulin has been shown to provide glycemic control superior to sliding-scale insulin with less hypoglycemic risk.11

Nutritional or bolus insulin is recommended to cover insulin needs to convert mealtime glucose into energy without postprandial hyperglycemia. Rapid-acting insulin is used to cover nutritional intake and correct hyperglycemia. Basal plus rapid-acting insulin (often called basal/bolus insulin therapy) most closely mimics normal physiologic insulin production and controls blood glucose more effectively. Regular insulin isn’t recommended for the nutritional component because its longer duration doesn’t mimic normal physiologic insulin production.

Correctional insulin is used to provide real-time adjustment of insulin dose based on a patient’s insulin sensitivity. Dosages are individualized using a correction factor (also called a sensitivity factor), which represents the degree to which 1 unit of rapid-acting insulin lowers a patient’s blood glucose level. Correction doses of insulin are based on preprandial blood glucose levels. The nutritional dose is then added to the correctional dose to obtain the total rapid-acting insulin dose required for that meal.

Additional considerations to further individualize insulin therapy are weight-based correction insulin regimens. Weight-based formulas are essential for helping to control hyperglycemia by preventing underdosing and reducing hypoglycemic risks related to overdosing when patient weight is not considered. Other considerations also are taken into account, such as a patient with a muscular frame who may require less insulin than an obese patient with the same weight.

Barriers to Changing the Culture
Barriers to changing the sliding-scale insulin culture to one that embraces newer physiological insulin regimens include practitioners’ resistance to change, fear of hyperglycemia overcorrection and possible hypoglycemia, poor blood glucose monitoring, failure to obtain a patient’s weight, reluctance to spend time calculating nutritional and correctional doses, fear of calculation errors, and lack of understanding of the risk associated with sliding-scale insulin.12

Overcoming these barriers requires buy-in from the entire healthcare team and requires the ongoing education of administrators, prescribers, nurses, dietitians, and pharmacists. A multidisciplinary effort is necessary to push back against the continued use of sliding-scale insulin, and the healthcare team must design and implement adequate policies to promote the use of these newer insulin regimens. Successful implementation of these practices can reduce the burden diabetes places on the healthcare system while improving the patient’s quality of life.

— Mark D. Coggins, PharmD, CGP, FASCP, is a director of pharmacy services for more than 300 skilled nursing centers operated by Golden Living and a director on the board of the American Society of Consultant Pharmacists. He was recognized by the Commission for Certification in Geriatric Pharmacy with the 2010 Excellence in Geriatric Pharmacy Practice Award.

References
1. Centers for Disease Control and Prevention. National Diabetes Fact Sheet: National Estimates and General Information on Diabetes and Prediabetes in the United States, 2011. Atlanta, GA: Centers for Disease Control and Prevention; 2011.

2. Diabetes: the cost of diabetes. World Health Organization website. http://www.who.int/mediacentre/factsheets/fs236/en.

3. Boord JB, Greevy RA, Braithwaite SS, et al. Evaluation of hospital glycemic control at US academic medical centers. J Hosp Med. 2009;4(1):35-44.

4. Queale WS, Seidler AJ, Brancati FL. Glycemic control and sliding scale insulin use in medical inpatients with diabetes mellitus. Arch Intern Med. 1997;157(5):545-552.

5. Golightly LK, Jones MA, Hamamura DH, Stolpman NM, McDermott MT. Management of diabetes mellitus in hospitalized patients: efficiency and effectiveness of sliding-scale insulin therapy. Pharmacotherapy. 2006;26(10):1421-1432.

6. Pandya N, Thompson S, Sambamoorthi U. The prevalence and persistence of sliding scale insulin use among newly admitted elderly nursing home residents with diabetes mellitus. J Am Med Dir Assoc. 2008;9(9):663-669.

7. American Geriatrics Society 2012 Beers Criteria Update Expert Panel. American Geriatrics Society updated Beers Criteria for potentially inappropriate medication use in older adults. J Am Geriatr Soc. 2012;60(4):616-631.

8. Umpierrez GE, Palacio A, Smiley D. Sliding scale insulin use: myth or insanity? Am J Med. 2007;120(7):563-567.

9. Hirsch IB. Sliding scale insulin—time to stop sliding. JAMA. 2009;301(2):213-214.

10. Nalysnyk L, Hernandez-Medina M, Krishnarajah G. Glycaemic variability and complications in patients with diabetes mellitus: evidence from a systematic review of the literature. Diabetes Obes Metab. 2010;12(4):288-298.

11. Maynard G, Lee J, Phillips G, Fink E, Renvall M. Improved inpatient use of basal insulin, reduced hypoglycemia, and improved glycemic control: effect of structured subcutaneous insulin orders and an insulin management algorithm. J Hosp Med. 2009;4(1):3-15.

12. DeYoung J, Bauer R, Brady C, Eley S. Controlling blood glucose levels in hospital patients: current recommendations. American Nurse Today. 2011;6(5):12-14.

Table 2: Typical Sliding-Scale Insulin Regimen

— Information based on author’s experience

— Source: Michota F. What are the disadvantages of sliding-scale insulin. J Hosp Med. 2007;2 Suppl 1:20-22