We propose an in vivo study of hypoxic and ischemic brain injury in anesthesized rats with 31P and 1H NMR spectroscopy.
Our aim i s to evaluate factors that predict and contribute to cerebral damage, and to compare the metabolic protection conferred by thiopental, isoflurane, halothane, and fentanyl. Ketamine, an anesthetic that does not protect the brain, will be studied and compared with the other agents. Four basic questions will be addressed: 1) How do the different anesthetic agents ameliorate hypoxic and ischemic brain injury? 2) How soon can in vivo NMR spectroscopy determine that irreversible injury has occurred? 3) Does hypoxia during anesthesia produce more injury than global ischemia? 4) When hypoxic and ischemic brain damage occur during anesthesia, how much injury during reperfusion? Our study will use a horizontal NMR spectrometer whose magnetic field strength is 5.6 Tesla. Anesthetized rats will be placed prone in a region of high magnetic field homogeneity, and will be studied using a 14 mm low noise surface coil detector. 31P NMR spectroscopy will be performed in vivo during hyperoxia, hypoxic hypoxia, and global ischemia (obtained using Pulsinelli's model), and used to determine intracellular pH and intracellular concentrations of ATP, PCr, Pi, and monophosphate sugars. 1H spectroscopy will be performed separately under similar conditions to study intracellular concentrations of lactate and N-acetylaspartate. Magnetization transfer methods will be used to measure the unidirectional fluxes and unidirectional rate constants for the creatine kinase (CPK) and ATP synthetase reactions. Deterioration and recovery of energy stores will be studied during hypoxia and ischemia, and correlated with invasive post-mortem measurments of membrane phospholipids and free fatty acids, done by collaborators using freeze extraction techniques and HPLC. In vitro studies indicate that metabolic and electrical activity can return to normal in CNS neurons that were deprived of oxygen and glucose for 20 to 60 minutes. Clinical situations involving more than a few minutes of insufficient oxygen or glucose supply often result in permanent damage. We hope that our in vivo studies of different anesthetics will suggest therapeutic strategies for humans that extend the brain's tolerance of oxygen deprivation and reduce the likelihood of intraoperative brain injury.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Unknown (R23)
Project #
5R23GM034767-02
Application #
3447882
Study Section
Surgery, Anesthesiology and Trauma Study Section (SAT)
Project Start
1985-07-01
Project End
1988-06-30
Budget Start
1986-07-01
Budget End
1987-06-30
Support Year
2
Fiscal Year
1986
Total Cost
Indirect Cost
Name
University of California San Francisco
Department
Type
Schools of Medicine
DUNS #
073133571
City
San Francisco
State
CA
Country
United States
Zip Code
94143
Bickler, P E; Litt, L; Banville, D L et al. (1988) Effects of acetazolamide on cerebral acid-base balance. J Appl Physiol 65:422-7
Bickler, P E; Litt, L; Severinghaus, J W (1988) Effects of acetazolamide on cerebrocortical NADH and blood volume. J Appl Physiol 65:428-33
Mills, P; Sessler, D I; Moseley, M et al. (1987) An in vivo 19F nuclear magnetic resonance study of isoflurane elimination from the rabbit brain. Anesthesiology 67:169-73
Litt, L; Gonzalez-Mendez, R; James, T L et al. (1987) An in vivo study of halothane uptake and elimination in the rat brain with fluorine nuclear magnetic resonance spectroscopy. Anesthesiology 67:161-8
Mills, P; Chew, W; Litt, L et al. (1987) Localized imaging using stimulated echoes. Magn Reson Med 5:384-9
Litt, L; Gonzalez-Mendez, R; Weinstein, P R et al. (1986) An in vivo 31P NMR study of cerebral hypoxic hypoxia in rats. Magn Reson Med 3:619-25
Litt, L; Gonzalez-Mendez, R; Severinghaus, J W et al. (1986) Cerebral intracellular ADP concentrations during hypercarbia: an in vivo 31P nuclear magnetic resonance study in rats. J Cereb Blood Flow Metab 6:389-92