The bedside management of extremely pre-term neonates relies on the traditional methods of monitoring such as arterial blood pressure, heart rate, pulse oximetry, urine output and evidence of metabolic acidosis. However, these parameters may be delayed or misleading in the detection of poor tissue perfusion. Very frequently even though tissue perfusion may be inadequate, the arterial blood pressure may be in a normal range due to compensatory vasoconstriction. Despite their widespread use, no study has shown that use of these measures improves outcome, and reliance on these measures alone, may result in inappropriate cardiovascular intervention. Tissue spectroscopy can provide a more direct measure of the adequacy of oxygen delivery to tissue, by measuring local, venous-weighted, blood oxygen saturation, and is sensitive to local ischemia. Spectros introduced the first visible light spectroscopy oximeter, T-Stat, in 2006. The T-Stat achieves improved performance by using visible light as opposed to near-infrared (more commonly used in tissue oximetry), and by incorporating broadband spectroscopy (hundreds of wavelengths) to further improve accuracy of the measurement. Spectros is now extending this approach into the infrared with broadband visible/infrared oximetry, allowing for a number of substances to be reliably measured. Impaired intestinal function is a major source of morbidity and mortality in neonatal intensive care. Intestinal dysfunction is manifested by feeding intolerance, poor growth, malabsorbtion, and, in the severest cases, necrotizing enterocolitis (NEC). While NIRS oximetry devices have been applied somatically (renal, gut) in neonates, their inability to compensate for varying levels of fat, water and stool in the tissue has severely limited their utility as monitors of somatic perfusion. It is therefore desirable to develop a non-invasive somatic monitor using the visible/near-infrared portion of the spectrum that achieves the depth of penetration necessary for non-invasive somatic monitoring, but which also incorporates the broadband analysis techniques required to compensate for water, fat and stool that may be present. The impact of this study could be truly significant. This project is designed to study tissue perfusion as a marker for the early identification of circulatory compromise, providing early identification of patients at risk of somatic organ damage. Through the early identification of these patients, we anticipate perfusion targets can be developed to better manage feeding, transfusion, and use of inotropes to significantly improve outcome and reduce hospital costs for these patients.
Aim 1 - To reduce to manufacturing a broadband Vis/NIR tissue oximeter for monitoring the oxygenation of the gut, prototyped in a just-completed NIH feasibility study, with values corrected for stool, fat, and water.
Aim 2 - To determine the efficacy of the broadband oximeter to detect induced changes in tissue perfusion and intestinal blood flow in a premature baboon model for very low birth weight infants.
Aim 3 - To determine the safety of probes used with the T-Stat Perfusion Monitor.
The clinical management of extremely pre-term neonates in the neonatal intensive care unit is challenging. We will test, in a baboon model, the performance of a new device to non-invasively monitor the sufficiency of blood flow to important organs in the premature neonate. As immature hearts and lungs may not have reached the developmental stage that allows them to function without interventions (such as ventilatory support, blood transfusions, and administration of vaso-active drugs), many of the common tools used in adults to assess heart and lung function either cannot be used, or are inadequate for use in these smaller patients. Designed ultimately for use on premature neonates, this device would enable NICU physicians to make more timely and accurate adjustments to care affecting the function of the heart and blood vessels.
