Increased Blood–Brain Permeability with Hyperosmolar Mannitol Increases Cerebral O2 Consumption and O2 Supply/Consumption Heterogeneity

• Published in: Journal of cerebral blood flow and metabolism 1996-03, Vol.16 (2), p.327-333
• Main Authors: Chi, Oak Za, Wei, Hwu Meei, Lu, Xiaowen, Weiss, Harvey R.
• Format: Article
• Language: English
• Subjects: Animals; Autoradiography; Biochemistry and metabolism; Biological and medical sciences; Blood-Brain Barrier; Capillary Permeability - drug effects; Carotid Artery, External; Catheterization; Central nervous system; Cerebrovascular Circulation; Fundamental and applied biological sciences. Psychology; Hypertonic Solutions; Male; Mannitol - administration & dosage; Mannitol - pharmacology; Oxygen - blood; Oxygen Consumption - drug effects; Rats; Spectrophotometry; Vertebrates: nervous system and sense organs
• ISSN: 0271-678X; 1559-7016
• DOI: 10.1097/00004647-199603000-00019

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 of 14C-α 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 micro-spectrophotometry (N = 7). Vital signs were similar before and after administering mannitol. Ki was significantly higher in the ipsilateral cortex (IC) (22.3 ± 8.4 μl/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 × 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.