Monitoring
Self-Monitoring of Blood Glucose Concentration
Self-monitoring of blood glucose concentration has revolutionized the management of diabetes. It actively involves patients in the treatment process, allows more rapid treatment adjustments, and reinforces dietary changes. Self-monitoring provides patients with the tools necessary to assist in man- agement of the disease; it is especially useful during periods of stress and for patients who are susceptible to hypoglycemia. Urine glucose testing provides only a gross approximation of recent glucose status and should be used only in patients who cannot or refuse to test their blood.
Newer glucose meters are small, portable, and reliable; they provide a digital readout and have a computerized memory to facilitate recordkeeping. Blood sampling is facilitated (and made less painful) by automated, spring- operated lancet devices and the option of testing at sites other than the finger (e.g., the arm), which are less painful. Self-monitoring of blood glucose con- centration is of maximal value if patients perform tests on a regular basis, can accurately measure glucose levels, and can make use of the results. Patients must become familiar with what a normal glucose value is, what the glucose targets are, and how levels can vary with changes in diet or activity and insulin absorption. At a minimum, patients should be able to adjust to repetitive pat- terns of hypoglycemia or hyperglycemia, as well as to periods of stress and illness (“sick days”).
Continuous Glucose Monitoring
Traditional self-monitoring of blood glucose concentration is often inade- quate to optimize metabolic control. Continuous glucose monitoring of inter- stitial fluid has revealed that tight glycemic control is often achieved at the expense of unacceptably high rates of nocturnal hypoglycemia, and postpran- dial glucose excursions are often larger than expected. To minimize these highs and lows, continuous glucose monitoring systems have been approved for clinical use, despite some limitations in accuracy. Data from the first genera- tion of “real-time” glucose sensors were evaluated post hoc, similar to a cardiac Holter monitor, to alert clinicians to previously undetected nocturnal hypogly- cemia and postprandial glucose elevations. Current models are needle-like percutaneous glucose sensors inserted under the skin by the patient; the sensors use an enzyme (glucose oxidase) coupled to electrochemical detectors to measure glucose levels for several days to 1 week before they must be replaced. Mechanical continuous glucose sensors give patients (and parents of young children) the ability to view real-time glucose levels (every 5 minutes), review trends and fluctuations in recent blood glucose levels, and receive alerts when blood glucose levels become too high or too low. Recent clinical trials suggest that continuous glucose monitoring, if used daily, helps patients improve glycemic control without increasing the near-term risk of hypoglycemia. 4