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A Denise Buonocore, MSN, ACNP-BC, CCRN, replies:

Evidence shows that tight glycemic control is of benefit in patients in the hospital setting. The parameters for control of hyperglycemia in the hospital setting have been outlined by 2 organizations, the American College of Endocrinology (ACE) and the American Diabetes Association (ADA). The current recommendation from the ADA for critically ill patients is that blood glucose levels should be kept as close to 110 mg/dL as possible and always lower than 180 mg/dL. These patients will usually require intravenous insulin. In noncritically ill patients premeal blood glucose levels should be kept as close to between 90 and 130 mg/dL (midpoint of 110 mg/dL) as possible given the clinical situation and postprandial blood glucose levels should be lower than 180 mg/dL. Insulin should be used as necessary.¹

In a 2004 consensus statement, the ACE recommended an upper limit for glycemic control in critically ill patients of 110 mg/dL; for noncritically ill patients, the upper limit recommended for preprandial and maximal glucose levels was 110 mg/dL and 180 mg/dL, respectively.² Although it may appear that these limits were set randomly, both organizations’ recommendations were largely influenced by the first major randomized controlled study by Van den Berghe et al³ (the Leuven protocol) of a surgical intensive care unit population and more recently by the second study by Van den Berghe et al⁴ in the medical intensive care unit population.

A recent meta-analysis published in JAMA⁵ concluded that tight glycemic control does not reduce hospital mortality. An in-depth analysis of this meta-analysis is beyond the scope of this article; however, be aware that in the group of 29 studies used in the meta-analysis, a large proportion of blood glucose measurements fell outside the target range. Also, unacceptably high hypoglycemia rates existed in some of the studies, which may have negatively influenced the findings. In addition, the mean glucose level achieved in the usual care group from these studies ranged from 124 to 205 mg/dL, which is far better than what usual care was like before the first studies on tight glycemic control. In short, these studies were comparing supertight glucose control with good glucose control. What this analysis did point out is that overall tight glucose control significantly reduced risk of septicemia; however, it significantly increased the risk of hypoglycemia.

The "NICE SUGAR" study, due to be released in early 2009, may shed more light on the subject of tight glycemic control. This will be a large randomized control trial with more than 6000 patients enrolled in 4 countries. In the meantime, it would appear to be extremely important to do everything possible to minimize the risk of hypoglycemia especially in high-risk patients that may be more prone to risk such as liver failure patients and patients with acute neurological injuries.

There is no specific protocol recommendation for either insulin infusion or intermittent injection. However, here are some considerations when looking to choose a protocol.

Although there has been no randomized controlled trial of comparing insulin infusion protocols, many protocols are published in the literature. Choose one that fits your specific hospital, taking into consideration your staffing and ability to monitor your patients closely. Ideally, intravenous insulin protocols should consider both the glucose level and its rate of change from the previous blood glucose level. For all protocols, frequent bedside glucose testing is required but the ideal frequency is not known.

The protocols I have used in my practice recommended hourly blood glucose testing until a stable glucose level is achieved. Then the testing can be reduced to every 2 hours. However, more frequent glucose testing is initiated with any major change in patient clinical status (eg, hypotension, addition or decrease in medications such as pressors or steroids or in nutrition, blood transfusions). Because no protocol can account for the specific patient changes that can influence blood glucose levels, the astute critical care nurse is essential to the success of achieving tighter glucose control.

In regards to intermittent insulin injection, we know that a traditional sliding-scale insulin regimen has been shown to be ineffective. The current recommendation is to use a basal, mealtime, correction insulin regimen using long-acting insulin, and to schedule short-acting insulin for meal time coverage and premeal correction insulin. Correction insulin usage is assessed on a daily basis and if frequently required, adjustment is made to the scheduled insulin regimen. If regular insulin is used as the short-acting insulin there is a greater risk of "insulin stacking" when the next blood glucose measurement is performed 4 to 6 hours later because of its longer duration of action.

Remember, this is an evolving science as new technologies are currently being developed, and new studies will hopefully shed more light on exactly where our glucose targets should be in specific patient populations. The question is whether less than 110 mg/dL is really any better than just less than 140 to 150 mg/dL. Stay tuned.

References

1. American Diabetes Association. Standards of medical care in diabetes—2006. Diabetes Care. 2006;29(suppl 1):S4–S42.[Free Full Text]
2. American College of Endocrinology Task Force on Inpatient Diabetes and Metabolic Control. American College of Endocrinology position statement on inpatient diabetes and metabolic control. Endocr Pract. 2004;10:77–82.[Medline]
3. Van den Berghe G, Wouters P, Weekers F, et al. Intensive insulin therapy in the critically ill patients. N Engl J Med. 2001;345:1359–1367.[Abstract/Free Full Text]
4. Van den Berghe G, Wilmer A, Hermans G, et al. Intensive insulin therapy in the medical ICU. N Engl J Med. 2006;354:449–461.[Abstract/Free Full Text]
5. Wiener RS, Wiener DC, Larson RJ. Benefits and risks of tight glucose control in critically ill adults: a meta-analysis. JAMA. 2008;300(8):933–944.[Abstract/Free Full Text]

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