Brain blood flow and metabolism after global ischemia and post-insult thiopental therapy in monkeys.

Abstract

We measured total and regional cerebral blood flow (CBF, rCBF) and cerebral metabolic rate (CMR) of oxygen (O2), glucose (G), and lactate (L) levels for 4 h after 16 min global brain ischemia in rhesus monkeys with and without post-insult thiopental therapy. Eleven monkeys weighing 4-5 kg anesthetized with 1 percent halothane, 66 percent nitrous oxide and 33 percent oxygen, were subjected to 16 min global brain ischemia by a combination of trimethaphan hypotension (to a mean arterial pressure of 50 torr) and a high pressure (1500 torr) neck tourniquet. Post-ischemia, 7 monkeys were untreated (controls) and 4 received thiopental 90 mg/kg infused intravenously over 60 min, beginning at 5 min post-ischemia. Total CBF and rCBF were measured by continuous monitoring of cerebral venous (torcula) and parietal-occipital (external scintillation) 133Xe activity, respectively, after intra-innominate artery injection of 500 micronCi 133Xe in saline. In control monkeys, hyperemia in rCBF, but not in total CBF was observed at 6-7 min post-ischemia, whereas both total CBF and rCBF increased in thiopental treated monkeys. The hyperemia in thiopental treated monkeys coincided with an increase in CMRG without a proportional increase in CMRO2 or lactate levels. Indeed, CMRO2 was depressed in the first 30 min post-ischemia. At 30 min post-ischemia, CMRO2 rose to twofold greater than pre-ischemia in control monkeys, but only to pre-ischemic levels in thiopental treated monkeys. The data suggest that thiopental therapy improves distribution of brain blood flow and brain glucose uptake early post-ischemia and depresses CMRO2 later post-ischemia.