A technique used with increasing frequency in the neurosurgical operating room is temporary occlusion of a major intracranial vessel to facilitate the obliteration of a vascular lesion (e.g. cerebral aneurysm). While this is of great help technically, it produces a potential for cerebral infraction (stroke). Under these conditions, collateral blood flow is present, which distinguishes this type of ischemic insults from complete, global ischemia as produced by cardiac standstill. I proposed to explore means of protecting cerebral tissue from such partial or """"""""focal"""""""" ischemia, using measures designed to maximize energy supply via collaterals, and to minimize the energy requirements of the tissue. These techniques are designed to prevent rather than to treat ischemia and have been generally under-utilized. In the initial phase of the proposed study, I will refine an existing model of focal cerebral ischemia in the rabbit to mimic the conditions present when treating patients with cerebrovascular disease, and I will test the effects of three protective measures used singly and in combination. Induced systemic hypertension and intravenous mannitol will be used to improve energy supply by improving collateral blood flow. Mild hypothermia will be used to reduce energy requirements. In the second phase of the study, I propose to use the focal in vivo ischemia model to test the protective effect of replacing the rabbit's red blood cells with polymerized bovine hemoglobin. The resulting reduction in viscosity, without a reduction in oxygen carrying capacity, is expected to increase substantially the rate of blood flow and oxygen delivery (energy supply) via collaterals to ischemic brain tissue. During the later phase of study, several pharmacologic agents which suppress neuronal metabolism will be combined and delivered prior to the induced ischemia. Since it is anticipated that some of the most useful agents will not readily pass the blood-brain-barrier, intra-arterial mannitol will be given prior to the agents to transiently open the barrier and increase the penetration. If effective, this would provide a new method for avoiding cerebral tissue injury and would have the potential for direct application in the operating room where agents could be given prior to an interval of """"""""planned"""""""" focal brain ischemia.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Clinical Investigator Award (CIA) (K08)
Project #
1K08NS001732-01
Application #
2259853
Study Section
NST-2 Subcommittee (NST)
Project Start
1994-04-01
Project End
1999-03-31
Budget Start
1994-04-01
Budget End
1995-03-31
Support Year
1
Fiscal Year
1994
Total Cost
Indirect Cost
Name
Massachusetts General Hospital
Department
Type
DUNS #
City
Boston
State
MA
Country
United States
Zip Code
02199
Quinones-Hinojosa, Alfredo; Malek, Junaid Y; Ames 3rd, Adelbert et al. (2003) Metabolic effects of hypothermia and its neuroprotective effects on the recovery of metabolic and electrophysiological function in the ischemic retina in vitro. Neurosurgery 52:1178-86; discussion 1186-7
Sakakibara, Yohtaro; Mitha, Alim P; Ayoub, Issam A et al. (2002) Delayed treatment with nicotinamide (vitamin B3) reduces the infarct volume following focal cerebral ischemia in spontaneously hypertensive rats, diabetic and non-diabetic Fischer 344 rats. Brain Res 931:68-73
Sakakibara, Y; Mitha, A P; Ogilvy, C S et al. (2000) Post-treatment with nicotinamide (vitamin B(3)) reduces the infarct volume following permanent focal cerebral ischemia in female Sprague-Dawley and Wistar rats. Neurosci Lett 281:111-4
Mokudai, T; Ayoub, I A; Sakakibara, Y et al. (2000) Delayed treatment with nicotinamide (Vitamin B(3)) improves neurological outcome and reduces infarct volume after transient focal cerebral ischemia in Wistar rats. Stroke 31:1679-85
Lee, E J; Ayoub, I A; Harris, F B et al. (1999) Mexiletine and magnesium independently, but not combined, protect against permanent focal cerebral ischemia in Wistar rats. J Neurosci Res 58:442-8
Ayoub, I A; Lee, E J; Ogilvy, C S et al. (1999) Nicotinamide reduces infarction up to two hours after the onset of permanent focal cerebral ischemia in Wistar rats. Neurosci Lett 259:21-4
Maynard, K I; Quinones-Hinojosa, A; Ogilvy, C S (1998) Magnesium plus mexiletine inhibit energy usage and protect retinas against ischemia. Neuroreport 9:4141-4
Smrcka, M; Ogilvy, C S; Crow, R J et al. (1998) Induced hypertension improves regional blood flow and protects against infarction during focal ischemia: time course of changes in blood flow measured by laser Doppler imaging. Neurosurgery 42:617-24;discussion 624-5
Maynard, K I; Arango, P M; Chen, D et al. (1998) Acetylsalicylate administered during simulated ischemia reduces the recovery of neuronal function in the in vitro rabbit retina. Neurosci Lett 249:159-62
Maynard, K I; Chen, D; Arango, P M et al. (1996) Nitric oxide produced during ischemia improves functional recovery in the rabbit retina. Neuroreport 8:81-5