Siemens Rapidlab 1200, Руководство оператора, Страница: 66 / 448

1-46 Rapidlab 1200 Operator’s Guide: System Overview and Intended Use
02087462 Rev. V
Determining the blood glucose level is helpful in diagnosing many metabolic diseases.
Glucose is elevated in any of the forms of diabetes mellitus, including Type 1, Type 2,
Gestational, or any of the 50 other specific types. More moderate elevations occur in
pre-diabetic conditions known as impaired glucose levels. Diabetics sometimes suffer
acute, life-threatening metabolic crises, such as diabetic ketoacidosis that is typical in
Type 1 or hyperglycemic hyperosmolar nonketotic state that is typical in Type 2. Low
glucose levels most commonly stem from insulin overdose, but also from a number of
disorders collectively known as hypoglycemic disorders. Examples of the latter include
insulinoma, IGF
2
-secreting tumor, factitious hypoglycemia, postprandial syndrome,
severe hepatic disorders, endocrine disorders characterized by deficiencies in
gluconeogenic hormones, and some post-surgical gastric states. Extreme abnormalities of
glucose reflect a potentially life-threatening pathophysiologic state that must be corrected
promptly.
6,17,18
Concentration of Lactate
Lactate acid is an intermediary product of the anaerobic metabolism of glucose.
Glycolysis is the term commonly used to describe the conversion of glucose to lactic acid.
Under normal circumstances, glycolysis occurs during muscle contraction where the rate
of metabolism outpaces the oxygen supply in the cells. During strenuous exercise, the
level of lactic acid increases significantly and passes to the blood where it is transported to
and metabolized by the liver. In normal aerobic conditions, the lactic acid is readily
oxidized in the cell to pyruvic acid, which is eventually degraded to CO
2
and H
2
O.
The concentration of lactate in the blood is affected by the rate of production, the rate of
metabolism, and the availability of oxygen at the cell level.
Determining the blood lactate level is helpful in assessing the supply of oxygen at the
tissue level. Increased oxygen deprivation causes the normal oxidation of pyruvic acid to
lactate and can cause severe acidosis called lactic acidosis. This condition is characterized
by increased lactate levels and an increased lactate:pyruvic ratio in the blood due to the
lack of cellular oxidative process. Elevations of lactate are a sign of inadequate delivery of
oxygen to the peripheral tissues as occurs in respiratory failure, circulatory failure, and
clinical shock.
7
Glucose and Lactate Biosensors
The glucose and lactate biosensors are complete electrochemical cells that incorporate
amperometric technology to measure glucose or lactate concentration in samples. The
biosensors consist of 4 electrodes.
1
1 Platinized activated carbon electrode technology license from Cambridge Life Sciences plc. under U.S. Patent Nos 4,970,145
and 5,160,418 and foreign counterparts.