Sliding Scale Insulin and Hypoglycemia in Long-Term Care

The prevalence of diabetes mellitus (DM) continues to increase steadily as obesity reaches epidemic proportions worldwide in all segments of the population, including older adults residing in long-term care facilities.^1-3 Today, approximately 25% of adults aged 65 and older in the United States have diabetes.⁴ The incidence of diabetes will increase exponentially, as noted by Narayan and colleagues⁵: “These increases are largest for the two oldest age groups: 220% among those aged 65 to 74 years and 449% among those aged 75 years and older between 2005 and 2050. In the long-term care setting, the management of type 2 DM is critically important; however, it remains particularly challenging due to the complex and fragile nature of older adults in long-term care settings.^6,7 With a plethora of available medications to treat diabetes, prescribing often hinges on provider preferences, goals of treatment, and individual patient preferences and characteristics. This is exemplified by a recent study highlighting the widespread variability and inconsistency among prescribing patterns in older adults with diabetes in US nursing homes.⁸

In 2012, the American Geriatrics Society (AGS) Updated Beers Criteria for Potentially Inappropriate Medication Use in Older Adults challenged the widely accepted traditional practice of DM management with sliding scale insulin (SSI), which typically consists of providing patients with short-acting insulin from 4 to 6 times per day, based on finger-stick glucose level immediately prior to insulin injections. In this recommendation, the AGS suggested for the first time, and with a strong recommendation, that SSI is a therapeutic approach to be avoided in the elderly because of the “high risk of hypoglycemia without improvement in hyperglycemia management, regardless of care setting.”⁹ Other researchers have also noted that SSIs may provide no benefit and perhaps result in harm.^10-12 The “reactive” SSI approach can lead to rapid changes in blood glucose levels, exacerbating both hyperglycemia and hypoglycemia.^13,14 In the inpatient hospital setting, data suggest that SSIs should not be used on their own and do not provide any added benefit when used with other diabetes medications.^13,15-18 In its position statement on inpatient diabetes and metabolic control, the American College of Endocrinology also strongly discourages the use of SSI, highlighting the lack of evidence to support this therapeutic approach.¹⁹

Although numerous studies have demonstrated that SSIs may result in poor glycemic control and noxious effects, it continues to be the most prescribed insulin regimen, according to several studies.^12,14,15 The reasons for this pattern are not well articulated, and there has been little research on diabetes management in long-term care settings. Specifically, hypoglycemia with the use of SSIs has been poorly defined in elderly residents undergoing subacute rehabilitation in long-term care facilities Annals of Long-Term Care: Clinical Care and Aging^®(ALTC ) had the opportunity to discuss the widespread use of SSIs in the nursing home population with a team of investigators from North Shore LIJ Health System, Manhasset, NY: Santiago Lopez, MD, Renee Pekmezaris, PhD, Liron Sinvani, MD, Jinny Caldentey, MD, and Andrzej Kozikowski, PhD. To illustrate their points, Lopez and colleagues explain the results and clinical implications of a retrospective chart review study that they conducted to assess risk of hypoglycemia when using SSIs in elderly persons with diabetes residing in a skilled nursing facility (SNF) that is part of a large academic health system in the New York metropolitan area. The answers below represent their collective responses.

ALTC: What were the objectives of your study?

In our study, we aimed to evaluate the risk of hypoglycemia when using SSIs in the management of diabetes in elderly residents admitted for subacute care in a long-term care facility after hospitalization. The primary objective of this study was to provide further supporting evidence for the inclusion of SSIs in the Beers criteria. Specifically, we sought to: (1) evaluate the risk of hypoglycemia with the use of SSIs in geriatric residents undergoing subacute rehabilitation in a long-term care facility; (2) assess risk factors for hypoglycemia with SSI when used with additional diabetes medications in elderly residents admitted to a long-term care facility; and (3) evaluate whether the type of SSI (conservative vs aggressive) is associated with disparate glycemic control in the geriatric population.

How did you conduct your study?

The study used a retrospective chart review design, conducted in residents with type 2 DM, aged 65 and older, who were transferred from hospitals to a 249-bed SNF for subacute rehabilitation. Residents were excluded if they were admitted to the hospital with a diagnosis of diabetic ketoacidosis, new-onset of type 2 DM, hyperosmolar nonketotic coma, or hypoglycemia. All residents fitting these criteria (N=752) were identified using ICD-9 diagnosis codes from the long-term care facility medical records between August 2011 and August 2012. Of these, 100 charts were randomly selected utilizing the random number generator in Microsoft Excel. The study was approved by the institution’s review board.

Charts were reviewed for past medical history of diabetes and for demographic and epidemiological information such as gender, age, race, weight, height, body mass index (BMI), admitting diagnosis, length of stay in hospital, length of stay in subacute rehabilitation, functionality, and comorbidities. Laboratory information on long-term care facility admission including blood glucose, creatinine, albumin, and glycosylated hemoglobin levels (HbA_1C) were recorded. Chart data were extracted from the nurses’ finger stick logs and insulin administration records in the Medication Administration Record for diabetic regimen, including oral antidiabetics, insulin use (basal/bolus/mixed), and SSI. Use of SSI was then divided into aggressive and conservative categories based on Queale’s study¹⁵ (glucose level <175 mg/dL and glucose level >175 mg/dL, respectively). Finger-stick logs were then reviewed for episodes of hypoglycemia: finger stick <70 mg/dL and hyperglycemia >200 mg/dL. Of note, all finger-sticks are performed on all long-term care residents with diabetes according to the pre-meal institutional schedule. If episodes of hypoglycemia were found, the timing of the hypoglycemic episode, the presence of contributing factors, such as missed meals, and regimen changes following the episodes were assessed and documented.

Functional status and illness severity on admission to the long-term care facility were assessed. Functional status was evaluated by using the New York State Department of Health Hospital and Community Patient Review Instrument to assess independence in activities of daily living.²⁰ Scores range from 4 to 25, with 4 indicating completely independent and 25 indicating entirely dependent. Furthermore, comorbidities were assessed using the Charlson Comorbidity Score, a validated tool to assess increased severity of condition.²¹

What were the characteristics of your study population?

In the 100 residents analyzed, average age was 81.3 years with 56% female and 88% white. Average body weight was 74 kg with BMI of 27.1 kg/m². Average comorbidity index was 5, with moderately impaired function. Median length of stay in the hospital and in long-term care were 6 and 18.5 days, respectively. The most frequent admission diagnoses were elective surgery (19%) and non-elective surgery (16%), followed by respiratory disease (14%) and infectious disease (13%). All residents had a history of diabetes, 60% had diabetes with end organ damage, 47% had myocardial infarction, 31% had a tumor, and 26% had a history of congestive heart failure.

What did the results of your data analysis reveal with regard to treatment type, patient characteristics, and the incidence of hypoglycemia?

The Table shows hypoglycemic episodes according to diabetes treatment regimen. Over half (57%) of the residents received SSIs. The incidence of a hypoglycemic event was 2.65 times greater in the SSI group compared with the non-SSI group (2.28 vs 0.86, respectively, per 100 SNF resident days; P<.05).

The median age for the residents who developed hypoglycemic episodes was 78 years, with an average Charlson Comorbidity Index greater than 4. There were 38 episodes of hypoglycemia (glucose <70 mg/dL) in 18 residents, with approximately half of the episodes occurring between 4 am and 8 am. We observed 70% of residents had a glomerular filtration rate under 50 mL/min and 80% had an HbA_1C level less than 7%. HbA_1C did not significantly differ between residents who received SSIs versus those that did not (P=.341) and it did not differ between residents who experienced one or more hypoglycemic events versus those that had no hypoglycemic episodes (P=.967). Glomerular filtration rate also did not significantly differ between residents on SSI regimens versus those that did not receive SSIs (P=.271), and it did not differ based on hypoglycemic status (P=.199).

We also did not find significant associations between hypoglycemic status and age (P=.113), sex (P=.350), weight (P=.910), BMI (P=.977), and Charlson Comorbidity Index (P=.327). None of the diseases in resident medical history with the exception of liver disease (P=.049) were significantly associated with hypoglycemic status in residents who received SSIs.

Did you note any significant differences with regard to hypoglycemia in aggressive versus conservative SSIs?

In our study, 26% of residents were on aggressive SSI regimens and 31% were on conservative SSI regimens (Table). A higher percentage of residents on aggressive SSI regimens had one or more hypoglycemic episodes (44.4%) compared with those on conservative regimens (27.8%).

Can you speak briefly to the importance of HbA_1C levels in guiding treatment, including in those who receive SSI regimens?

The basis of the 2012 AGS’ updated Beers criteria recommendation regarding SSIs was a 1997 study by Queale and colleagues.¹⁵ These authors sought to identify predictors of hypoglycemic and hyperglycemic episodes and analyzed glycemic control and SSI use in 171 medical inpatients with DM. The researchers found that although SSIs were commonly prescribed, they provided no benefit and seemed to be associated with episodes of both hyperglycemia and hypoglycemia.¹⁵ While Queale’s study included different epidemiologic and laboratory data, it did not consider HbA_1C levels.¹⁵ Various studies have shown the importance of HbA_1C in guiding the treatment of type 2 diabetic older adults. The ADVANCE trial (Action in Diabetes and Vascular Disease: Preterax and Diamicron MR Controlled Evaluation), ACCORD trial (Action to Control Cardiovascular Risk in Diabetes, and VADT trial (Veterans Affairs Diabetes Trial) are among the trials that have helped to define the importance of individualizing the management of type 2 DM in elderly patients while accounting for HbA_1C levels.^22-24 The American Diabetes Association recommends a target HbA_1C less than 7% for healthy older adults with a life expectancy of more than 10 years and less than 8% for frail elderly patients with a shorter life expectancy.²⁵ Since HbA_1C levels are important in guiding the treatment of type 2 DM, it may also be important to monitor the HbA_1C levels while using SSIs in this population.

What are the practical implications of your study?

This study shows a markedly increased risk of hypoglycemia in elderly diabetic residents admitted to a long-term care setting receiving SSIs, thus medical professionals in long-term care settings should follow the recommendations in the AGS Beers criteria by avoiding the use of SSIs in older adults with diabetes. Moreover, medical professionals should provide elderly residents with type 2 DM with individualized treatment, considering HbA_1C levels, frailty, and life expectancy in order to determine personalized target HbA_1C levels to avoid hypoglycemic episodes and adverse outcomes.               

Did you identify any limitations of your study?

Given the small sample size and the retrospective design utilized, findings from our study should be considered as preliminary and should be confirmed by larger studies. Additionally, we utilized a chart review methodology, which can provide incomplete data due to unrecorded information.²⁶ However, chart review methodology does allow for the collection of rich and readily available data that may not be accessible and/or ethical through other approaches, such as random assignment.²⁷

The updated AGS Beers criteria, which lists SSIs as a potentially inappropriate medication for older patients, was published during our data collection period; therefore the impact of the criteria will not be reflected in our results. Further research should investigate if prescribing patterns have changed as a result of the Beers criteria recommendations.

Why do you think the use of SSIs persists in the long-term care setting despite evidence against its use, and what will it take for facilities to phase out SSI prescribing?

The use of SSIs has persisted for generations mostly due to tradition, convenience, and the ability to rapidly initiate treatment. This practice has been passed down from attending physicians to residents and continues to this day. Patients are usually provided with SSIs in the acute care hospital setting and this order is often transmitted at time of transfer into long-term care. Unfortunately, the provision of SSIs is ingrained in the culture of diabetes management without sufficient evidence for its practice.

We believe that educating experienced medical professionals and those still in training, as well as establishing institutional protocols, are key to breaking the cycle of decades-long SSI provision. The use of other medications, including basal insulin, prandial insulin, and correction-dose insulin, should be part of an institution-wide protocol that all hyperglycemic residents receive. Without such measures, SSIs will likely continue to be provided to residents.

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