Quantitative assessment of global cerebral metabolic rate of oxygen (CMRO2) in neonates using MRI

The cerebral metabolic rate of oxygen (CMRO₂) is the rate of oxygen consumption by the brain, and is thought to be a direct index of energy homeostasis and brain health. However, in vivo measurement of CMRO₂ is challenging, in particular for the neonatal population, in whom conventional radiotracer methods are not applicable because of safety concerns. In this study, we propose a method to quantify global CMRO₂ in neonates based on arteriovenous differences in oxygen content, and employ separate measurements of oxygenation and cerebral blood flow (CBF) parameters. Specifically, arterial and venous oxygenation levels were determined with pulse oximetry and the novel T₂ relaxation under spin tagging (TRUST) MRI, respectively. Global CBF was measured with phase contrast (PC) flow velocity MRI. The proposed method was implemented on a standard 3‐T MRI scanner without the need for any exogenous tracers, and the total scan duration was less than 5 min. We demonstrated the feasibility of this method in 12 healthy neonates within an age range of 35–42 gestational weeks. CMRO₂ values were successfully obtained from 10 neonates. It was found that the average CMRO₂ in this age range was 38.3 ± 17.7 µmol/100 g/min and was positively correlated with age (p = 0.007; slope, 5.2 µmol/100 g/min per week), although the highest CMRO₂ value in this age range was still less than half of the adult level. Test–retest studies showed a coefficient of variation of 5.8 ± 2.2% between repeated CMRO₂ measurements. In addition, given the highly variable blood flow velocity within this age range, it is recommended that the TRUST labeling thickness and position should be determined on a subject‐by‐subject basis, and an automatic algorithm was developed for this purpose. Although this method provides a global CMRO₂ measure only, the clinical significance of an energy consumption marker and the convenience of this technique may make it a useful tool in the functional assessment of the neonatal population. Copyright © 2014 John Wiley & Sons, Ltd.     

Pulse Oximetry Screening in Wisconsin

Introduction. Pulse oximetry can be used as a screening tool to detect critical congenital heart disease (CCHD) in neonates prior to hospital discharge and the development of symptoms. Newborns suspected of having CCHD based on pulse oximetry screening should have the diagnosis excluded or confirmed with echocardiography. However, echocardiography is not immediately available in all settings in which newborns are delivered and the best course of action in these settings remains to be determined. The purpose of this study was to evaluate the resources available to diagnose and treat newborns with CCHD born in the state of Wisconsin. Methods. We surveyed the nurse managers or administrators of the 99 Wisconsin hospitals in which babies are routinely delivered in the state of Wisconsin. A telephone survey was performed in February and March 2011. The number of births per facility was estimated from the most recent available data (2010). Results. There were 66 179 total births occurring in 106 hospitals in the state of Wisconsin in 2010, with 99 hospitals routinely delivering newborns. Surveys were completed in 88/99 (88.9%), representing 95% of the state's in‐hospital births. All responding hospitals had pulse oximetry available in the nursery. Twenty‐five of 88 (28.4%) of responding hospitals routinely use pulse oximetry to screen for CCHD, representing 35.2% of surveyed hospital births. Same‐day neonatal echocardiography was available at 33/88 (37.5%) of the responding hospitals, representing 74.4% of surveyed hospital births. The average distance to the higher‐level care facility of choice from the hospitals without neonatal echocardiography is 53.1 miles. Conclusion. Pulse oximetry is universally available in Wisconsin newborn nurseries, and pulse oximetry screening for CCHD is currently being performed for many of Wisconsin's newborns. The majority of births in Wisconsin occur in hospitals where same‐day neonatal echocardiography is available for confirmatory diagnosis of CCHD when necessary.