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blood glucose testing

Controlling blood glucose in hospital patients

By: Cynthia Worrell Sanborn

Over time, uncontrolled diabetes mellitus (DM) damages blood vessels, potentially affecting the heart, eyes, kidneys, nervous system, and legs. Two landmark studies in outpatients with type 1 and type 2 DM provided early evidence that controlling blood glucose helps avert such complications.

We’re learning that controlling blood glucose is just as important for hospital patients as for outpatients, and can dramatically affect their outcomes. Various factors can lead to hyperglycemia in hospital patients. (See Common causes of inpatient hyperglycemia.) This article discusses glycemic control in nonpregnant, non-critical-care, hospitalized adults.

Evaluating blood glucose control

Blood glucose control is evaluated with blood tests, including plasma glucose (usually venous and capillary samples) and glycosylated hemoglobin (HbA1c) levels. In the hospital, blood glucose levels can be tested by laboratory instruments and point-of-care bedside glucose meters. Immediate results from glucose meters are used to assess glycemic control and drug effects, improving on-the-spot treatment decisions (especially regarding insulin therapy) to allow more timely and effective patient care.

Used to measure average blood glucose over time, HbA1c testing helps identify patients at risk for diabetes complications. It measures in percentage points the mean blood glucose absorbed by hemoglobin in red blood cells over the previous 2 to 3 months. By comparing results over time, clinicians can evaluate long-term treatment efficacy and, as needed, make changes in therapy and self-care.

Categories of hyperglycemic patients

Hospital patients with hyperglycemia fall into several categories:

  • those with previously diagnosed DM
  • those with previously unrecognized DM that’s confirmed after discharge (a fasting blood glucose of 126 mg/dL or higher or a random level above 200 mg/dL in the hospital)
  • those with hospital-related hyperglycemia (a fasting glucose of 126 mg/dL or higher or a random level above 200 mg/dL during hospitalization that normalizes after discharge).

Hitting the target

To maintain glycemic control, glucose levels should be kept as close as possible to normal and HbA1c should be less than 7% with minimal hypoglycemia episodes. As a general guide for adults, diabetes organizations recommend blood glucose and HbA1c target goals based on both study results and expert consensus.

In hospital patients, safe and effective targets are controversial because tight glycemic control has the potential to increase the hypoglycemia risk. Hypoglycemia can arise quickly, requires immediate treatment, and may cause severe neurologic consequences unless recognized quickly and treated properly. That’s why hospital patients receiving antihyperglycemic medications must be assessed closely. More frequent glucose monitoring is especially crucial for those who are receiving insulin, have impaired mental status, or can no longer recognize hypoglycemia symptoms.

What the evidence shows

Evidence for specific blood glucose targets during hospitalization varies by patient population and illness severity. Targets will remain open to debate until further inpatient studies link populations with specific targets and optimal insulin delivery methods that produce the best outcomes.

Studies of inpatients on general medical-surgical units link hyperglycemia with higher infection rates, longer hospital stays, increased need for intensive care, and greater mortality. Those with preexisting DM or new hyperglycemia had greater hospital mortality, suggesting hyperglycemia predicts a poor outcome in these patients.

Until more specific evidence is available for noncritically ill inpatients, the American Diabetes Association (ADA) recommendations for blood glucose goals seem reasonable. ADA’s 2009 Standards of Medical Care in Diabetes recommend keeping fasting glucose levels in these patients below 126 mg/dL and keeping all random blood glucose levels below 180 to 200 mg/dL.

Strategies to achieve control

Strategies for maximizing outcomes for inpatients with hyperglycemia vary with the specific medical condition and severity of illness. Insulin is recommended because most oral antihyperglycemics have limitations when used in the hospital; generally, they’re not flexible enough to manage acute blood glucose changes in inpatients. Subcutaneous basal-bolus insulin therapy for inpatients has been shown to safely and effectively control glucose levels. Prescribed as intermediate or long-acting insulin, basal insulin gives background glycemic control for metabolism requirements between meals and at night. Bolus insulin is short or rapid-acting insulin used to correct hyperglycemia and cover postprandial blood glucose spikes after meals.

Be aware that outdated “sliding-scale” insulin without basal insulin is ineffective because it treats rather than prevents hyperglycemia and doesn’t provide meal coverage. Regular “sliding-scale” insulin is linked to a greater incidence of hypoglycemia than rapid-acting insulin.

Use of standardized order sets for basal-bolus insulin therapy can help establish a guide for prescribing safe and effective insulin therapy. Multidisciplinary collaboration to develop such standards can improve blood glucose management. Staff education regarding blood glucose goals, insulin use, and hypoglycemia prevention is pivotal to the success and safety of glucose management.

I.V. insulin infusion

I.V. insulin infusion is recommended for numerous clinical situations, mostly involving critically ill patients or other situations calling for intensive glycemic control. Many facilities have insulin protocols for implementation by nurses, but no comparison studies have been done to identify an ideal guideline. Most patients receiving insulin infusions are housed in critical care units where they can be closely monitored, but some facilities use such protocols in general medical-surgical units. (See Indications for I.V. insulin infusion.)

Monitoring guidelines

Blood glucose monitoring should be ordered for all inpatients with diabetes or hyperglycemia and for those at high risk for hyperglycemia. Point-of-care results need to be readily available to all staff to identify the patient’s response to treatment, hyperglycemia trends, and hypoglycemia episodes.

In general, premeal and bedtime testing is recommended for patients who are eating, whereas testing every 4 to 6 hours is advised for those who can’t have oral intake. Patients receiving insulin infusions must be monitored closely—hourly in many cases—as such intensive treatment carries a high hypoglycemia risk.

Continuous glucose monitoring systems have become more widely available, although they haven’t been evaluated for hospital use. They’re being used more frequently for outpatient diabetes management, most commonly with insulin pump therapy.

Preventing and treating hypoglycemia

Hypoglycemia prevention should be part of the treatment plan for managing blood glucose levels. Causes of inpatient hypoglycemia include use of an inappropriate insulin type, mismatch between insulin type and/or timing to nutritional intake, and altered nutritional intake without insulin dosage adjustment.

Many facilities have protocols for hypoglycemia treatment, which nurses should use to reverse hypoglycemia. The frequently used “rule of 15” recommends giving 15 g of a simple carbohydrate (such as fruit juice or glucose tablets), followed by blood glucose testing in 15 minutes, with repeat treatment and monitoring as needed until blood glucose reaches a set goal. The patient should receive a snack or meal as soon as glucose normalizes to prevent hypoglycemia recurrence. Treatment for patients who can’t have oral intake may include I.V. dextrose 50%, glucagon injection, or a simple carbohydrate given by feeding tube.

“Survival skills” education

“Survival skills” diabetes education should be included in discharge planning for all patients with hyperglycemia. Although individualized, it may include instructions in the basic definition of diabetes and hyperglycemia, blood glucose goals, hyperglycemia complications, prescribed medication, proper nutrition, blood glucose monitoring, hypoglycemia recognition and treatment (if the patient takes glucose-lowering drugs), hyperglycemia problem-solving, and follow-up care. Because most deaths in diabetic patients are related to cardiovascular events, teach patients about the importance of blood pressure and lipid control and smoking cessation. When possible, educate the family and significant others, too.

Discharge plans for patients with previously unrecognized and hospital-related hyperglycemia are essential. Those with newly diagnosed diabetes or evidence of poor management need referrals for ongoing medical follow-up and comprehensive diabetes education. Those with hospital-related hyperglycemia need medical follow-up, as some will be diagnosed with new-onset diabetes or will be discharged on short-term drugs to treat hyperglycemia.

Managing blood glucose in the hospital can be challenging because of patient circumstances and environmental factors that alter glucose levels. More research is needed to find better care-delivery systems for inpatient hyperglycemia management.

Selected references

American Diabetes Association. Standards of medical care in diabetes—2009. Diabetes Care. 2009;32(suppl 1):S13-S61. Accessed April 21, 2009.

Inzucchi S. Management of hyperglycemia in the hospital setting. N Engl J Med. 2006;355:1903-1911.

Umpierrez G, Smiley D, 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;30:2181-2186.

Cynthia Worrell Sanborn is a diabetes nurse specialist in Adult Inpatient Services at the University of Virginia Health System in Charlottesville.

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