Sliding (scale) down a slippery slope? Go to proactive glycemic control in pts
April 1, 2007 8 minutes read
Sliding (scale) down a slippery slope? Go to proactive glycemic control in pts
"We really can do better."
Hospitals and their pharmacists need to make a conscious effort to improve glycemic control in hospitalized diabetic patients, moving from a traditional reactive approach to embrace newer, protractive strategies.
That is one of the conclusions of a study at the University of Colorado Hospital in Boulder that looked at the efficiency and effectiveness of current prescribing practices with short - and intermediate - acting insulin to prevent or treat acute hyperglycemic episodes in hospitalized patients with diabetes mellitus or hyperglycemia.1 The authors also sought to identify clinical findings that influence the effectiveness of insulin therapy in these patients.
Lead author Larry Golightly, Pharm.D., tells Drug Formulary Review his investigation of inpatient outcomes associated with using sliding-scale insulin was prompted primarily by a suspicion that the therapy was sub-optimal in this population. Endocrine authorities caution against use of sliding-scale insulin regimens, he says. In addition, concerns have been voiced from both hospital nursing and pharmacy staffs that equipment and personnel constraints were limiting ability to fully adhere to prescribed insulin regimens. Adverse drug reactions were also a concern, he added.
The researchers reviewed medical records for patients' clinical characteristics and response to administered insulin that were recorded during each of the first five days of hospitalization in which sliding-scale insulin therapy was used. One of the difficulties they encountered was that despite immediate or bedside availability of both computerized and manual means to record finger-stick blood glucose levels and insulin injections, uncertainties or missing information related to execution, timing, blood glucose levels, or insulin doses were present in some 30% of all anticipated points of care involving insulin.
Ten episodes of hypoglycemia in six patients were associated with sliding-scale insulin. Appropriately timed, successive glucose measurements documented a decrement in elevated blood glucose values to within a target range after 12% of sliding-scale insulin injections, while glucose levels remained elevated and insulin effects were therefore sub-therapeutic after 84% of injections.
Adjustments rarely made
Despite blood glucose levels that remained persistently elevated, corresponding adjustments in either the timing or the dose of insulin were made infrequently, he says. Sliding-scale insulin regimens were never adjusted in 81% of patients. Through five days of therapy, the proportion of patients who attained good glycemic control ranged from 2% to 10%. The mode of overall glycemic control was poor, with 51% to 68% of patients in this category on any given day. Overall, he says, treated diabetic and hyperglycemic patients were more likely to be poorly controlled than to be relatively well controlled.
According to the study, acutely ill, hospitalized patients are prone to large variances in plasma or blood glucose concentrations. Clinical features that may contribute to a loss of metabolic control include stressors such as disease exacerbation, surgery, pain, infection, or emotional disturbances, as well as administration of agents that may disrupt glucose utilization such as corticosteroids, beta blockers, diuretics, catecholamine-based vasocative agents, and IV fluids containing dextrose. Because of these factors, effective treatment and preventive strategies are required to maintain satisfactory glycemic control in the hospital, Golightly says.
Outcome quality in patients hospitalized for various acute illnesses has proved to be directly related to glycemic control, the research report says. Evidence for this relationship comes from clinical trials, causality investigations, and observational studies that congruently demonstrate significant associations between good glycemic control or intensified treatment and good outcomes, and between less good or poor glycemic control and sub-optimal or poor outcomes.
Still, sliding-scale insulin therapy is well ingrained in medical practice, he notes. Sliding-scale insulin or routine blood glucose monitoring with administration of small doses of subcutaneous short-acting insulin as needed for treating hyperglycemia is recommended in some current medical textbooks as routine therapy for many inpatients, especially during perioperative periods and other times of stress. At the University of Colorado Hospital, pharmacy records show that subcutaneous, human, regular, sliding-scale insulin was prescribed for 197 inpatients by 102 different resident and attending physicians during a one-month period. Based on extended census data, this extrapolates to use of sliding-scale insulin in some 2,500 patients a year or roughly 13% of all admissions, Golightly says.
Despite its broad acceptance, evidence supporting effectiveness of sliding-scale insulin therapy is lacking, he notes. Because of the documented importance of good glycemic control and the disparity between widespread use and uncertain effectiveness of sliding-scale insulin, an evaluation of the therapy was warranted. For managing diabetes in hospitalized patients, he says, endocrine specialists and others have suggested that proactive insulin regimens should be adopted instead of sliding scale insulin. There also should be specific strategies to facilitate implementation of the regimens as feasible.
Researchers examined the medical records of 90 inpatient admissions. Of the 90 patients evaluated in the study, 9% were receiving nothing by mouth and 7% were receiving TPN. The remaining 84% were receiving an oral or enteral diet. For those who were eating, a variety of diets such as regular, diabetic or American Diabetes Association, cardiac, renal, or low-sodium were prescribed.
During hospitalization, oral antidiabetic drugs were administered in 20% of patients. Basal intermediate or long-acting insulins were administered in 34% of patients. Both oral antidiabetics and insulin were administered concurrently in 2% of the patients. Thus, sliding-scale was the sole antidiabetic drug prescribed for 43% of patients. Sliding-scale insulin was provided as regular insulin in 92% of patients and insulin lispro in 8%.
Amounts of insulin prescribed and administered tended to remain constant throughout the study period. Despite clinically documented glucose levels that often remained persistently elevated, corresponding adjustments in insulin doses were made only sporadically. Golightly tells DFR the evaluation focused primarily on data related to objective responses to insulin administration and indicators of insulin efficiency. With the exception of symptomatic hypoglycemia, he says, the overall clinical impact of the measures could not be determined from the data. However, substantial previous evidence has demonstrated the good glycemic control is associated with good clinical outcomes and poor glycemic control often leads to poorer outcomes. He says the research highlighted several concerns associated with sliding-scale insulin therapy, centering on the therapy's efficiency and effectiveness.
Although the exact origin of sliding-scale insulin therapy isn't known, it is generally believed to be carried over from an era in which ambulatory patient self-monitoring was performed using urine glucose measurements. The original name for sliding-scale insulin therapy - rainbow insulin - may have come from the practice of "chasing the rainbow," in which the amounts of short-acting insulin to be administered were determined according to various rainbow colors produced by copper sulfate test tablets when immersed in urine.
The practice of administering small, graded doses of regular insulin based on positivity of urine glucose readings was likely safe in relatively stable patients, since any evidence of glycosuria implies that the concurrent blood glucose level is likely to be quite high. However, that differs from the practice of administering prompt-acting insulin to acutely ill patients with precise blood glucose values that often are lower than the glycosuric threshold. The difference raises questions about the rationale behind sliding-scale insulin therapy.
Another argument suggesting that sliding-scale insulin therapy is based on flawed premises is the fact that insulin is only given in response to hyperglycemia after it has occurred. Thus, sliding-scale insulin does not prevent elevation of glucose levels. When given without food, short-acting insulin may cause hypoglycemia, especially when administered in dosages that are based on assumptions that all patients have similar sensitivities to insulin actions and not adjusted according to past requirements or recent responses. Hypoglyecmia, in turn, may lead to counter-regulatory processes that ultimately lead to rebound hyperglycemia. Thus, Golightly argues, use of sliding-scale insulin therapy, despite its perceptions of clinical convenience and adequacy, may lead to diabetic instability in some patients.
Hospitalized patients with diabetes and/or hyperglycemia should be managed with antidiabetic regimens other than sliding-scale insulin, he emphasizes. Most diabetic patients who can be treated with subcutaneous insulins should receive body weight or insulin sensitivity-determined basal doses supplemented if needed by carbohydrate- and blood glucose-adjusted amounts of rapid insulin. Regimens, he says, should be frequently and carefully readjusted according to response. Pre-printed orders, he says, are a convenient method to offer prescribers a means to tailor such regimens to individual patient needs.
Benefits of proactive approach
"Changing from a reactive approach to management of blood glucose to a more proactive one requires trust that newer insulin regimens can improve glycemic control and a firm commitment to enable and fully implement that improvement," he says. "We really can do better. To be sustained, these changes require support from virtually everyone involved in patient care in the hospital, including administrators, physicians, nurses, pharmacists, and diabetes educators, as well as the support staff associated with all of these disciplines. Leaders usually should be endocrine or diabetes specialists, although committed pharmacists or nurses can and should have a major impact in directing these efforts.
Based on available evidence and experience, experts from the American Diabetes Association's Diabetes in Hospitals Writing Committee have said that sliding-scale insulin is ineffective at best and dangerous at worst and this research supports that view. In addition, he says, the findings reveal outcomes associated with sliding-scale insulin that are widely variable, often ineffectual, and prone to deficiencies in monitoring, documentation, and perhaps most important, sound prescribing rationale and practice.
"This information demands remedial corrective action and improvement in the care of patients with hyperglycemia," he says. "Some suggest that programs to standardize or intensify sliding-scale insulin regimens lead to improved outcomes. Although clearly an improvement on the traditional theme of sliding-scale insulin therapy, we believe that such efforts are misguided. What is needed are individualized treatment regimens consisting of basal insulin along with scheduled prandial insulin doses given in relation to anticipated insulin responsiveness and carbohydrate intake, with adjustments made consistently according to point-of-care glucose levels."
At the University of Colorado Hospital quality-of-care issues related to sliding-scale insulin are being addressed with implementation of a multidisciplinary diabetes care team headed by members of the department of endocrinology. The team consists of dedicated healthcare professionals with direct responsibility for the full range of endocrine-related care of all hospital inpatients with diabetes mellitus and/or hyperglycemia.
The team uses a protocol-driven order set including not only weight-based daily insulin for all diabetic patients, but also high- or low-insulin sensitivity-determined and blood glucose- and carbohydrate-adjusted subcutaneous insulin lispro with every meal. The order set supplements traditional subcutaneous sliding-scale insulin.
Additional improvements in patient management are anticipated with the scheduled implementation of electronic recording of all point-of-care monitoring and therapy. Additional research is warranted to determine if this newer approach to managing glycemic control in hospitalized patients is safe and effective, Golightly says.
[Editor's note: Contact Golightly at (303) 315-2399 or e-mail him at [email protected].]
Reference
- Golightly LK, Jones MA, Hamamura, DH, et al. Management of Diabetes Mellitus in Hospitalized Patients: Efficiency and Effectiveness of Sliding-Scale Insulin Therapy. Pharmacotherapy. 2006;16(10): 1421-1432.
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