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Basal-bolus vs. sliding-scale insulin in hospitalized patients: assessment of advantages and disadvantages

By:  Maria Sedky Saad (PharmD Candidate c/o 2021), Shivani Shah (PharmD Candidate c/o 2021)

           Hyperglycemia is a common condition in hospitalized patients whose glucose levels are normally controlled with oral antidiabetic medications, which are often discontinued upon admission. To circumvent hyperglycemic complications in hospitalized patients with type 1 and type 2 diabetes, glucose levels are commonly controlled with insulin in the inpatient setting. A variety of methods are available to regulate hospitalized patients’ glucose levels and prevent the adverse events associated with hyperglycemia.

  A commonly used method to control glucose levels in institutional settings is sliding-scale insulin therapy, which is the administration of rapid-acting insulin 30 minutes before meals, based on the patient’s pre-meal glucose reading.1 Another method that more closely mimics the body’s physiological insulin secretions is basal-bolus insulin therapy. Patients initiated on basal-bolus therapy are given a long-acting insulin either once or twice a day and nutritional or rapid-acting insulin before meals. In addition, patients may receive a correctional or rapid-acting pre-meal insulin dose for unanticipated hyperglycemia.1 It is critical to understand the benefits and harms of both therapy strategies to effectively manage hyperglycemia, as patients with diabetes are often at an increased risk of 30-day readmission following discharge.2

One of the biggest advantages of using sliding-scale insulin regimens in hospitalized type 1 and type 2 diabetic patients is that they are convenient and simple, enabling patients to receive treatment promptly.3 This method is also tailored to each patient, as it considers patient specific insulin sensitivity, daily activity levels, and carbohydrate intake. Patients may also feel more comfortable with this regimen as it allows for a “pre-determined” plan and, therefore, has the potential to improve adherence outcomes.

It is equally important to note that some studies discourage the use of sliding-scale insulin as monotherapy in inpatient settings due to its potential to cause adverse events, particularly in surgical patient populations.4 Current American Diabetes Association (ADA) guidelines also advise against this practice for glycemic control.2 Sliding-scale regimens can lead to fluctuations in glycemic levels because they do not deliver insulin in a physiological manner nor do they mimic the body’s normal response to insulin. As sliding-scale insulin regimens are pre-set, there is limited flexibility with regard to adjusting them according to patients’ increased or decreased food intake, fluctuating stress levels, and physical activity, which can all affect glucose levels.

According to the ADA, basal-bolus insulin therapy is recommended for noncritically ill hospitalized patients with poor oral intake or nothing by mouth (NPO).2 However, the ADA recommends that patients in critical care settings receive continuous intravenous insulin infusions to achieve their glucose targets. The ADA also strongly recommends that protocols for glycemic control in critically ill patients allow for, “predefined adjustments in the infusion rate, accounting for glycemic fluctuations and insulin dose”.2

Basal-bolus insulin therapy more closely mimics the natural secretion of insulin by pancreatic beta cells which occurs continuously throughout the day and in response to meals when additional insulin is needed. In basal-bolus insulin therapy, patients receive a combination of long-acting and short-acting insulin in one regimen. Basal insulin, or long acting insulin, is usually administered once or twice daily to keep glucose levels constant during periods of fasting. In a non-diabetic individual, when the body is in a period of fasting, a constant level of glucose is secreted to provide energy to the cells in the body. Once enough glucose has been secreted to fulfill the body’s needs, insulin gets secreted to regulate and maintain blood glucose levels. In diabetic patients, this physiological process is defective, requiring the administration of basal insulin once to twice a day to maintain an appropriate and constant level of glucose in the body.4 Examples of long-acting insulin include detemir (Levemir®) and glargine (Basaglar®). Bolus insulin, or short acting insulin, is administered immediately prior to breakfast, lunch, and dinner to control glucose levels following major meals.3 Examples of short-acting insulins include aspart (Novolog®) and glulisine (Apidra®). This insulin therapy approach not only reduces mean daily glucose levels, but it also provides a structured method for managing inpatient hyperglycemia and prevents the fluctuations between hypoglycemic and hyperglycemic blood glucose levels, which are seen more frequently with sliding scale insulin monotherapy. In addition, studies have illustrated that basal-bolus insulin therapy is less likely to lead to hypoglycemic episodes when compared to sliding-scale insulin monotherapy.5

Although the ADA currently recommends basal-bolus therapy as the preferred glucose control method in hospitalized patients with type 1 and type 2 diabetes, it requires more frequent insulin injections than sliding-scale insulin regimens and, therefore, is usually not preferred by clinicians in institutional settings. As a result, current practice at most institutions for maintaining glycemic control in non-critically ill patients consists of sliding-scale insulin regimens. When sliding-scale regimens are used as monotherapy, pharmacists can play a role in monitoring glucose levels closely and routinely to prevent fluctuations and personalize their patients’ regimens based on individual factors which can affect glucose levels.  

  ADVANTAGES DISADVANTAGES
Sliding-Scale · Convenient, simple, treatment prompt · Tailored to each patient’s specific parameters · Can improve adherence outcomes · Fewer injections required · Does not mimic body’s natural insulin response leading to fluctuations in glucose levels · ADA advises against using it as monotherapy in hospitalized patients  
Basal-Bolus · More closely mimics the body’s physiological secretion of insulin · Decreases fluctuation between hypoglycemia  and hyperglycemia · Decreased occurrence of adverse events associated with poor glucose level control · Current ADA recommendation for glycemic control in non-critically ill patients in hospitalized settings · More injections needed · Complicated and time-consuming insulin therapy regimens  

SOURCES:

  1. Basal-Bolus Versus Sliding-Scale Insulin Therapy in the Acute Care Hospital Setting: A Review of Comparative Clinical Effectiveness and Cost-Effectiveness. Ottawa (ON): Canadian Agency for Drugs and Technologies in Health; 12. PubMed PMID: 28727401. Accessed on 06/08/2019.
  2. American Diabetes Association. Diabetes Care in the Hospital: Standards of Medical Care in Diabetes-2019. Diabetes Care. 2019;42(Suppl 1):S173-S181. doi: 10.2337/dc19-S015. Accessed on 06/10/2019. 
  3. Badlani, S, Ford, W, Yu, D et al. Evidence for Basal–Bolus Insulin Versus Slide Scale Insulin. Curr Emerg Hosp Med Rep. 2014; 2(1): 26-34. Accessed on 06/08/2019.
  4. Umpierrez GE, Smiley DS, Zisman A, et al. Randomized study of basal–bolus insulin therapy in the inpatient management of patients with type 2 diabetes (RABBIT 2 Trial). Diabetes Care. 2007;30:2181.Accessed on 06/11/2019.
  5. Harbin M, Dossa A, de Lemos J, Drummond I, Paty B, Taylor B. Evaluation of protocol-guided scheduled basal-nutritional-correction insulin over standard care for vascular surgery patients. Can J Diabetes. 2015 Jun;39(3):210-5. doi:10.1016/j.jcjd.2014.10.004.Accessed on06/09/2019.

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