Increased blood-brain permeability with hyperosmolar mannitol increases cerebral O2 consumption and O2 supply/consumption heterogeneity.
This study was performed to evaluate whether increasing the permeability of the blood-brain barrier by unilateral intracarotid injection of hyperosmolar mannitol would alter O2 consumption and the O2 supply/consumption balance in the ipsilateral cortex. Rats were anesthetized with 1.4% isoflurane using mechanical ventilation. Retrograde catheterization of a unilateral external carotid artery was performed to administer 25% mannitol at a rate of 0.25 ml/kg/s for 30 s. The blood-brain barrier transfer coefficient (K(i) of 14C-alpha aminoisobutyric acid was measured in one group (N = 7) after administering mannitol. Regional cerebral blood flow (rCBF), regional arterial and venous O2 saturation and O2 consumption were measured in another group using a 14C-iodoantipyrine autoradiographic technique and microspectrophotometry (N = 7). Vital signs were similar before and after administering mannitol. K(i) was significantly higher in the ipsilateral cortex (IC) (22.3 +/- 8.4 microliters/g/min) than in the contralateral cortex (CC) (4.4 +/-1.1). rCBF was similar between the IC (105 +/- 21 ml/g/min) and the CC (93 +/- 20). Venous O2 saturation was lower in the IC (43 +/- 7%) than in the CC (55 +/- 4%). The coefficient of variation (100 x SD/mean) of venous O2 saturation was significantly elevated in the IC (32.3) compared with the CC (18.2), indicating increased heterogeneity of O2 supply/consumption balance. O2 consumption was higher in the IC (9.6 +/- 3.0 ml O2/100 g/min) than in the CC (6.7 +/- 1.5). Our data suggested that increasing permeability of the blood-brain barrier increased cerebral O2 consumption and the heterogeneity of local O2 supply/consumption balance.
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Department of Anesthesia, University of Medicine & Dentistry of New Jersey-Robert Wood Johnson Medical School, New Brunswick 08903-0019, USA.
Wei
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Weiss
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D000818:Animals; D001345:Autoradiography; D001812:Blood-Brain Barrier; D002199:Capillary Permeability / Q000187:drug effects*; D002342:Carotid Artery, External; D002404:Catheterization; D002560:Cerebrovascular Circulation; D006982:Hypertonic Solutions; D008297:Male; D008353:Mannitol / Q000008:administration & dosage / Q000494:pharmacology*; D010100:Oxygen / Q000097:blood*; D010101:Oxygen Consumption / Q000187:drug effects*; D051381:Rats; D013053:Spectrophotometry
D006982:Hypertonic Solutions; D008353:Mannitol; D010100:Oxygen