Submitted on July 12, 2005
Accepted on November 17, 2005
Near-Infrared Spectroscopy Measurements of Cerebral Blood Flow and Oxygen Consumption following Hypoxia-Ischemia in Newborn Piglets
Kenneth M. Tichauer1*, Derek W. Brown2, Jennifer Hadway3, Ting-Yim Lee2, and Keith St. Lawrence2
1 Imaging Division, Lawson Health Research Institute, London, Ontario, Canada; Department of Medical Biophysics, University of Western Ontario, London, Ontario, Canada
2 Imaging Division, Lawson Health Research Institute, London, Ontario, Canada; Imaging Research Laboratories, Robarts Research Institute, London, Ontario, Canada; Department of Medical Biophysics, University of Western Ontario, London, Ontario, Canada
3 Imaging Division, Lawson Health Research Institute, London, Ontario, Canada; Imaging Research Laboratories, Robarts Research Institute, London, Ontario, Canada
* To whom correspondence should be addressed. E-mail: ktichaue{at}lawsonimaging.ca.
Impaired oxidative metabolism following hypoxia-ischemia (HI) is believed to be an early indicator of delayed brain injury. The cerebral metabolic rate of oxygen (CMRO2) can be measured by combining near-infrared spectroscopy (NIRS) measurements of cerebral blood flow (CBF) and cerebral deoxy-hemoglobin concentration. The ability of NIRS to measure changes in CMRO2 following HI was investigated in newborn piglets. Nine piglets were subjected to 30 min of HI by occluding both carotid arteries and reducing the fraction of inspired oxygen to 8%. An additional nine piglets served as sham-operated controls. Measurements of CBF, oxygen extraction fraction (OEF), and CMRO2 were obtained at baseline, and for six hours following the HI insult. Of the three parameters, only CMRO2 showed a persistent and significant change after HI. Five minutes after reoxygenation, there was a 28 ± 12 % (mean ± SE) decrease in CMRO2, a 72 ± 50% increase in CBF, and a 56 ± 19% decrease in OEF compared to baseline (p < 0.05). By 30 min post-insult and for the remainder of the study there were no significant differences in CBF and OEF between control and insult groups; whereas, CMRO2 remained depressed throughout the 6 hr post-insult period. This study demonstrates that NIRS can measure decreases in CMRO2 caused by HI. The results highlight the potential for NIRS to be used in the neonatal intensive care unit to detect delayed brain damage.
