Modeling the glucose regulatory system in extreme preterm infants
BACKGROUND: Premature infants represent a significant proportion of the neonatal intensive care population. Blood glucose homeostasis in this group is often disturbed by immaturity of endogenous regulatory systems and the stress of their condition. Hypo- and hyperglycemia are frequently reported in very low birth weight infants, and more mature infants often experience low levels of glycemia. A model capturing the unique fundamental dynamics of the neonatal glucose regulatory system could be used to develop better blood glucose control methods. METHODS: A metabolic system model is adapted from adult critical care to the unique physiological case of the neonate. Integral-based fitting methods were used to identify time-varying insulin sensitivity and non-insulin mediated glucose uptake profiles. The clinically important predictive ability of the model was assessed by assuming insulin sensitivity was constant over prediction intervals of 1, 2 and 4 hours forward and comparing model-simulated versus actual clinical glucose values for all recorded interventions. The clinical data included 1,091 glucose measurements over 3,567 total patient hours, along with all associated insulin and nutritional infusion data, for N=25 total cases. Ethics approval was obtained from the Upper South A Regional Ethics Committee for this study. RESULTS: The identified model had a median absolute percentage error of 2.4% [IQR: 0.9%-4.8%] between model-fitted and clinical glucose values. Median absolute prediction errors at 1, 2 and 4-hour intervals were 5.2% [IQR: 2.5%-10.3%], 9.4% [IQR: 4.5%-18.4%] and 13.6% [IQR: 6.3%-27.6%] respectively. CONCLUSIONS: The model accurately captures and predicts the fundamental dynamic behaviors of the neonatal metabolism well enough for effective clinical decision support in glycemic control. The adaptation from adult to a neonatal case is based on data from literature. Low prediction errors and very low fitting errors indicate that the fundamental dynamics of glucose metabolism in both premature neonates and critical care adults can be described by similar mathematical models.