Glucose Monitoring in Neonates:
Glucose determination in the blood or plasma is used in the diagnosis, monitoring and treatment of persons with diabetes mellitus. Neonates (full term birth to 30 days old) and premature infants (gestational age in weeks at birth up to original due date) represent a mixed group of individuals in whom glucose monitoring is crucial and who have a physiology that differs significantly from older children and adults. Prevention or treatment of hypoglycemia (low blood sugar) in this group is just as important as the recognition and treatment of hyperglycemia (high blood sugar.)
Most full term neonates are born with glucose reserves that last for about 6-24 hours and if feeding or intravenous nutrition is not started in that time period, glucose levels can fall dangerously low. Since if left untreated the child can die or survive with serious impairment, it is common practice to measure the blood glucose of neonates.
When “bedside” glucose monitors were first used for neonates, it was discovered that increased hematocrit levels could interfere with the function of some glucose monitors and produce false low glucose results. The precise mechanism of this interference is debated and may be method dependant. Some people think that the blood may interfere with color based reactions by interfering with light transmittance. An analogy is trying to count the raised fingers on someone’s hand when seen through glass versus tissue paper. In the first case it is easy. In the second situation the hand with some fingers may be recognized but the precise number is undefined. For other methods the blood may be too thick for the chemical reactions to go to completion so less glucose is detected.
FDA has published guidelines to aid the makers of these devices and several have been cleared for use in the neonatal period.
Clinicians should carefully review the claims made to help determine if the device in question is appropriate for neonatal use. It is also a good idea to perform a literature search to see if there are studies published in refereed journals investigating the candidate glucose meter in the population in question (e.g.: healthy full term newborns or critically ill preterm neonates.) Even so, no matter what device is used it is crucial that the end user clinicians validate the meters they are considering for use. The clinicians should work closely with the central lab and compare candidate devices against their central laboratory’s current reference method. Given the acuity of care, it may also be a good idea to periodically reevaluate these meters against the reference standard and to develop quality assurance and quality control programs.
In closing, increased hematocrit may interfere with some blood glucose meters. If a result does not make sense the clinician needs to do two things. First, reassess the patient. Second, if it is clinically appropriate, get a new sample and verify the result using an accepted reference method.
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