PRACTICE RECOMMENDATIONS
� To prevent wide fluctuations in glucose levels, combine basal insulin coverage with a bolus of insulin given with each meal. A
� Use 2-hour postprandial blood glucose levels to adjust doses of rapid-acting insulin. A
� Use a basal/bolus regimen for hospitalized patients with insulin-dependent diabetes, adjusted for weight, age, IV glucose amount, meal size, and prehospital insulin regimen. A
Strength of recommendation (SOR)
A Good-quality patient-oriented evidence
B Inconsistent or limited-quality patient-oriented evidence
C Consensus, usual practice, opinion, disease-oriented evidence, case series
Among the many insulin management systems that have been developed, none has been as widely used as the sliding scale. Despite its acceptance by physicians and patients throughout the world, however, there is little evidence of the sliding scale�s efficacy.1-11
A number of studies have focused on potential problems associated with the sliding scale, primarily related to the �roller coaster� blood glucose levels that often result. The authors of a recent literature review concluded that fluctuating glucose levels are more harmful physiologically than levels that are continuously elevated, even when the elevation is mild.12
In this review, we take a closer look at the failings of the sliding scale system and the advantages of adopting an insulin regimen that more closely resembles a natural physiologic state. To enable you to provide optimal support for patients with insulin-dependent diabetes, we highlight 5 principles of insulin management.
Premeal glucose levels do not reflect insulin need
In a sliding scale system, insulin administration is based primarily�and in some cases, entirely�on a single point in time. Blood glucose levels are tested before meals and at bedtime or every 6 hours, and the amount of insulin administered at that time is based on the test result.
But a premeal blood glucose level is not an accurate predictor of the insulin needed at that time; it is simply a reflection of the insulin previously administered. Insulin given in response to the current blood glucose, then, may compound a prior dosing error, leading to serious drops or spikes in blood sugar. These wide fluctuations present challenges in both inpatient and outpatient settings, although each uses a different sliding scale system.
In the hospital, basal insulin is often withheld
In an inpatient setting, an IV insulin protocol is typically used, and patients may be placed on a sliding scale regimen even if their prehospital HbA1c was in a satisfactory range. The sliding scale is usually dependent on blood glucose levels obtained by bedside monitoring,13 tested every 6 hours. Hospitalized patients often receive no basal insulin, and, because rapid-acting insulin lasts only 3 to 4 hours, the results of their glucose tests are based on the intake of short-acting (regular) insulin alone. Short-acting insulin lasts about 6 to 8 hours, depending on dosage.
A sliding scale regimen generally has a cutoff point, below which no insulin is given. But skipping a dose because a patient�s glucose levels dip below the cut point can leave him or her without insulin for many hours, resulting in a spike in blood sugar.
Standing orders: One size does not �fit� all. Failure to individualize the insulin protocol is another problem with the use of sliding scales in an inpatient setting.7 Typically the sliding scale protocol is preprinted on standing orders, which are the same for all patients who require insulin and are under the care of a particular physician. Rarely are the orders adjusted for factors such as age, weight, IV glucose intake, time of day, size of the upcoming meal (or absence of food, at midnight), or type of diabetes. Outcomes studies of a sliding scale protocol in a hospital setting found that its use did not consistently achieve the desired results.7
Outpatient sliding scale fails to normalize blood glucose levels
Unlike the sliding scale regimen commonly used in hospitals, outpatient protocols often incorporate basal insulin. But that fact alone is not enough to eliminate the peaks and dips in blood glucose levels associated with this approach.
The dose of basal insulin�a long-acting or twice-a-day intermediate-acting insulin�is sometimes given on a sliding scale. More commonly, the sliding scale is used to determine the dose of rapid- or short-acting insulin administered prior to meals, based on the preprandial blood glucose reading and/or the expected caloric or carbohydrate intake. The wide fluctuations and excessive spikes in blood glucose levels associated with sliding scale management may cause reactive oxidative stress�a trigger for vascular damage, especially in patients with type 2 diabetes.14,15