Glucose monitoring with long-term subcutaneous microdialysis in neonates

Background. Microdialysis is a new approach for continuous monitoring of sm all molecules in the extracellular space, and hypoglycemia is a common prob lem in neonatal intensive care. The objective of this study was to evaluate subcutaneous microdialysis for long-term glucose monitoring in neonatal in tensive care. We determined the relative recovery of the microdialysis syst em in vitro and in vivo, the stability of the relative recovery in vivo dur ing long-term microdialysis, and the correlation between blood and dialysat e concentrations of glucose and urea. Furthermore, we evaluated the sensiti vity and specificy of subcutaneous microdialysis for the diagnosis of hypog lycemia. Patient and Methods. Thirteen infants (10 neonates) with gestational ages o f 30.2 to 45.6 weeks were investigated by microdialysis of subcutaneous adi pose tissue and blood sampling. Subcutaneous microdialysis was performed fo r a median (range) duration of 9 (4-16) days. Results. The application was safe, even in extremely low birth weight infan ts (< 1000 g) with scanty subcutaneous adipose tissue. The mean +/- standard deviation of the relative recovery in vitro was 101 /- 3% for glucose and 100 +/- 2% for urea. Using urea as the internal stand ard, the mean relative recovery in vivo was 96.4 +/- 12.7% at the beginning and remained constant up to 16 days. The correlation between microdialysate and blood was significant for glucos e (r = 0.88) and urea (r = 0.98). Subcutaneous microdialysis allowed the de tection of asymptomatic hypoglycemias. The diagnostic sensitivity of a dial ysate glucose <less than or equal to>2.9 mM to predict a blood glucose leve l less than or equal to2.8 mM was 92.3%, with 88.1% specificy. The positive predictive value with a 13.4% prevalence of a blood glucose < 2.8 mM was 5 4.5%, with a negative predictive value of 98.7% and an accuracy of 88.7%. Conclusions. Subcutaneous microdialysis is a safe method, well suited for l ong-term glucose monitoring in neonates during intensive care. Subcutaneous microdialysis can be used to reduce blood loss and painful stress resultin g from diagnostic blood sampling in high-risk neonates.