脳動脈瘤患者における一時クリッピング中の局所脳血流変化：H2吸入法による術中評価
In 15 patients with cerebral aneurysms, regional cerebral blood flow (RCBF) was monitored intraoperatively using the H2 inhalation technique during temporary vessel occlusion testing. Following temporary clipping, RCBF fell below critical thresholds in the majority of cases. Upon clip removal from the internal carotid and middle cerebral arteries, marked reperfusion hyperemia was recorded at 298 ± 55 ml/100 g × min. Despite these hemodynamic changes, the rate of postoperative complications attributable to temporary clipping did not increase, suggesting that complication development depends on the duration of cerebral ischemia and the integrity of the blood-brain barrier.
Temporary arterial clipping induces cerebral ischemia with RCBF dropping below critical levels; reperfusion upon clip removal triggers marked hyperemia. Postoperative complications appear linked to ischemia duration and blood-brain barrier integrity rather than the hyperemic response itself.
For inhalation applications of molecular hydrogen, the lower flammability limit (LFL) deserves careful handling. The classical 4% figure applies to closed-system mixtures; the practical inhalation-environment threshold is 10%. Even pure-hydrogen output (the UFL 75% paradox) passes through the flammable range at the air–gas boundary. High-concentration (66% / 100%) inhalers are documented in the Japanese Consumer Affairs Agency accident-information database and are not recommended.
See also:
https://h2-papers.org/en/papers/17125074