Nnemo (Neonatal Neuromonitor) – A Hybrid Optical System to Characterize Perfusion and Metabolism in The Newborn Brain

Premature birth, defined as a gestational period less than 37 weeks, occurs in 8% of infants born in Canada. These births are associated with a higher risk of developing neurological complications. Infants born with very low birth weights (VLBW, < 1500 g) experience cognitive or behavioural deficits at a rate of 40-50%, while a further 5-10% develop major disorders such as cerebral palsy. The likelihood of injury increases with a shorter gestational period and/or a lower birthweight. Intraventricular hemorrhaging (IVH) occurs in 20-25% of VLBW infants, characterized by bleeding in the germinal matrix and surrounding white matter. This highly vascularized region is particularly susceptible to bleeds due to underdeveloped cerebrovascular structures. Severe IVH causes an inflammatory response and subsequent obstruction of cerebrospinal fluid (CSF) drainage, resulting in enlargement of the brain’s ventricles, referred to as post-hemorrhagic ventricular dilatation (PHVD). PHVD increases intracranial pressure and can result in compression/damage of brain tissue.

Diagnosis of IVH and PHVD is regularly performed using cranial ultrasound. Clinicians can visually assess and grade hemorrhaging/ventricle dilatation. Ultrasound, however, is limited in its ability to continuously monitor and only detects irreversible damage. NNeMo (Neonatal NeuroMonitor) is a hybrid optical device combining diffuse correlation (DCS) and near-infrared spectroscopy (NIRS) to simultaneous monitor cerebral blood flow (CBF) and metabolism at the bedside. DCS analyzes light scatter from red blood cells to infer their motion and calculate CBF while NIRS exploits light absorption properties to quantify changes in oxidized cytochrome c oxidase (oxCCO), a direct marker of energy metabolism. System validation was presented in a piglet model of neonatal hypoxia-ischemia. Clinical translation of NNeMo was demonstrated in PHVD infants during ventricular taps (i.e., CSF drainage). Changes in perfusion and metabolism are presented in premature infants at high risk of IVH within the first 72 hours of life. Lastly, NNeMo was translated to the cardiac operating room, in patients undergoing surgery with cardiopulmonary bypass, to observe metabolic response to large intraoperative changes in CBF. Optical measures of perfusion and metabolism show potential to act as prognostic markers of injury and could aid clinicians in patient management before significant damage persists.