An animal model for measuring the effect of common NICU procedures on ATP metabolism.

Neonates exposed to common neonatal intensive care unit (NICU) procedures show alterations in heart rate, blood pressure, and oxygen saturation. However, it is unclear if these physiologic changes increase adenosine triphosphate (ATP) utilization, thus potentially increasing the risk for tissue hypoxia in medically fragile neonates. Plasma uric acid is a commonly used marker of increased ATP utilization because uric acid levels increase when ATP consumption is enhanced. To examine the effect of a common NICU procedure on plasma uric acid concentration, we developed a model that allows for acute monitoring of this biochemical marker in plasma in 7- to 9-day-old rabbits. In our pilot study, we exposed neonatal rabbits to a single heel lance 2.5 hr after catheter placement. We measured uric acid concentration before and 30 min after the heel lance and compared findings to levels in control animals not exposed to the heel lance. Our pilot data shows a significant difference in uric acid concentration over time between the control and heel lance groups (46.2 ± 7.1 μM vs. 54.7 ± 5.8 μM, respectively, p = .027). Calculation of percentage change from baseline showed uric acid concentration increasing in rabbits exposed to heel lance and decreasing in control rabbits (1.5 ± 4.7% vs. -16.1 ± 4.2%, respectively, p = .03). These data suggest that this animal model can be successfully used to examine the biochemical effect of common NICU procedures, such as heel lance, on markers of ATP breakdown and purine metabolism.