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Diabetes Point of Care

I. Introduction

Until recently it was unknown as to why complicated disease states such as kidney disease, vision loss and nerve damage were caused by uncontrolled diabetes. It was then decided that the complications occurring from diabetes could be delayed by reducing blood glucose to a normal level. This decision stemmed from the Diabetes Control and Complications Trial of 1993. To obtain levels that are nearly normal, it is important to monitor blood glucose levels several times throughout the day, everyday. For type I diabetes this is important so that insulin levels can be adjusted without causing hypoglycemia. For Type II diabetics this is important because complications may be delayed if glucose levels are kept at a normal level.

Glucose in the body reacts with the amino acids of proteins. The higher the glucose level, the greater the chemical reaction. The damaged proteins can be measured by a test called hemoglobin A1c or glycosulated hemoglobin. This protein damage can thicken the basement membranes around cells and damage blood vessels, nerves, and kidneys. Therefore, decreasing the blood glucose levels of a patient should prevent many of the complications associated with diabetes.

II. Bedside Blood Glucose Meters                              Back to top

Bedside glucose meters have grown in popularity over the past 10 years. Great improvements have been made in the accuracy of both consumer and hospital meters. This includes decreasing user errors with the introduction of the "no-wipe" test strips, decreased specimen volume, ensuring high quality with QC lock-out options, decreased maintenance, and laboratories taking over the administration of blood glucose monitoring in many hospital settings.

Determining blood glucose concentrations in a timely manner is very important when managing a patientís condition. Blood glucose levels can change drastically within 15 minutes depending upon stress levels, insulin doses, or food intake. Therefore, turn-around times are of grave importance for acting upon blood glucose levels that are in need of clinical intervention. The use of blood glucose devices is considered to be the most efficient and quickest way to determine patientís glucose levels. Blood glucose monitoring eliminates delays in coordinating insulin doses and meal times. It can also help regulate glucose levels by the ability to test often and take action immediately when necessary. This can also mean a decrease in hospital days to achieve controlled blood glucose levels. Ultimately, this means a lower cost to the patient and the community.

So, what are some of the advantages and disadvantages of using blood glucose monitors? 

Advantages of Bedside Blood Glucose Monitoring Disadvantages of Bedside Blood Glucose Monitoring
*Immediate results of the test

*Blood volumes are decreased

*Meals and insulin doses are coordinated

*Repeats can be performed immediately

*Hypoglycemia can be detected more rapidly

*Patient education is at bedside

*Less accurate results

*More difficult to manage testing

*Testing is performed by non-laboratorians

*Billing is difficult

*Results may not reach the laboratory record

*More time for training and QA

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The methodologies for bedside Blood Glucose testing have also changed over the recent years. The trend recently is to shift away from the photometer methods, which use light detection, toward the enzyme reactions which couple glucose concentration of the oxidation of dye that changes color. The following illustrations show the Hexokinase Photometric method and the Glucose Dehydrogenase (GDH) electrode method respectively:

Glucose + ATP------Hexokinase--------- Glucose-6-phosphate + ADP

G-6-P + NAD+------------------- 6-Phospho-gluconolactone + NADH

NADH + Oxidized dye---------------------- NAD + Rduced dye

Glucose + Fe 3+(CN)6----------------- Gluconolactone + Fe 2+(CN)6

Fe 2+ (CN)6--------------------------------- Fe 3+ (CN)6 + e-

With the use of bedside blood glucose meters in the healthcare setting it is important to realize that the results from the meter do not exactly match the results obtained from the laboratory on the same specimen. Why is this true? Part of the reason is because meters display a lower accuracy and precision than the referenced laboratory instrument used. There is also a variability in operator technique. There are clinical differences between capillary versus venous specimens and whole blood versus plasma. The limitations on bedside versus laboratory referenced instruments may also affect the results in different ways.

 

III. Clinical Issues of Blood Glucose Monitoring          Back to top

Regardless of where a specimen is obtained, be it venous, capillary, or arterial, the integrity of this specimen is crucial for obtaining accurate reliable results. Venous specimens should only be used on meters that are not affected by low oxygen concentrations. Those meters which use the enzyme glucose oxidase, use oxygen to react with the glucose. Therefore, these meters should not be used with venous specimens. Capillary specimens have a high oxygen concentration and a slightly higher glucose than venous specimens. Itís important to remember a number of key concepts when collecting a capillary specimen:

  • Patient should have adequate circulation and warm hands.
  • The site should be cleaned with alcohol or warm soapy water.
  • Be sure to wipe the first drop off the finger before analyzing the second drop for a glucose concentration.

Arterial blood draws also have a high oxygen concentration and will give a slightly higher glucose reading than a venous specimen. Make sure the meter is compatible with heparin if one is using a blood gas specimen.

IV line draws should also be mentioned here. If one must use a line draw, it should be flushed with at least a 5 mL blood draw before collection of the specimen. If one is suspect that any glucose solutions have been administered through the line, using an alternate type specimen is recommended.

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Once a good clean specimen has been drawn for analysis, it can give a result leading to the diagnosis of Diabetes Mellitus. Diabetes Mellitus is a disease state in which tissues throughout the body are unable to take up glucose due to a lack of insulin or a lack of response to insulin (Insulin is a hormone produced in the pancreas). This causes an excess of glucose to circulate in the bloodstream. If this high glucose concentration remains in the body, tissues become damaged and a number of complications can arise. These include, but are not limited to impaired kidney function, eye damage leading to blindness, damage to blood vessels which could lead to heart attack or stroke, and damage to nerves leading the peripheral circulation problems. The goal in managing Diabetes Mellitus is to control the blood glucose levels as much as possible to prevent or delay the onset of diabetic complications.

The four major categories of diabetes are:

  • Type I- insulin dependent , juvenille. This is due to a lack of insulin because of beta cell destruction in the pancreas.
  • Type II- non-insulin dependent, adult onset. This is associated with insulin resistance and obesity.
  • Gestational- presents itself during pregnancy.
  • Secondary- Related to medications like corticosteroids or to endocrine diseases such as Cushingís Disease.

 

When one thinks about Diabetes and the many complications associated with this disease its common to focus on keeping glucose results from going too high. However, with diabetes the risk of hypoglycemia is always at large. What are some of the causes of low blood glucose levels in diabetics?

*The insulin dose is too high

*Insulin is taken at the wrong time

*Food intake has been changed by skipping meals or vomiting

*Liver failure

*Non selective beta blocker medications

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In Type I diabetes, hypoglycemia is an emergency state because the brain is starved of glucose which can cause seizures, loss of consciousness, and death. Hypoglycemia is the limiting factor in how aggressively blood glucose levels can be controlled in diabetes.

Type II diabetes

The chance of hypoglycemia in a Type II diabetic is not as great. Many of the factors that contribute to the risk of hypoglycemia include treatment with oral diabetes medication and older aged individuals. Studies show that sulfonylureas have a slow onset and reaction and therefore are less likely to produce a hypoglycemic event.

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Diabetes Point of Care
Table of Contents
Introduction Bedside Blood Glucose Meters Clinical Issues Quality Assurance for Blood Glucose Monitoring
  • Policy and procedure
  • Quality control
  • Proficiency testing
  • Personnel training and competencies
  • Establishing reference ranges and critical values

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Last updated: 02/22/2002  Questions or corrections: Webmaster
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