ニカルジピンの内頸動脈血流速度，局所脳血流量，二酸化炭素反応性に及ぼす効果

The Effect of Nicardipine on Internal Carotid Artery Blood Flow Velocity, Local Cerebral Blood Flow and Carbon Dioxide Reactivity

I．はじめに

　構造的にニフェジピンと類似しているカルシウムチャンネルブロッカーは麻酔中の高血圧，心筋虚血，冠動脈攣縮の治療に適していると報告されている^12）．ニカルジピンは水溶性のdihydropuridine calicium channelblockerで強い血管拡張作用を有している^3）．脳動脈瘤手術の麻酔管理では動脈瘤の術中破裂を予防するためにtransmural pressureを注意深く管理する必要がある．術中の高血圧は脳動脈瘤の術中破裂を引き起こす誘引となる可能性があるため速やかに治療する必要がある．この目的でニカルジピンは投与されるが，この薬剤のクリッピング術中の脳血流量，血流速度に及ぼす影響についての報告は少ない．今回ニカルジピンの局所脳血流量，二酸化炭素反応性，内頸動脈血流速度（ICBFV）に及ぼす影響について検討した．

To study the effect of nicardipine on the blood flowvelocity of the internal carotid artery , on local cerebralblood flow (LCBF), and on carbon dioxide reactivity , aninitial dose of 0.5ug/kg/min of nicardipine was adminis-tered in patients for scheduled craniotomy for cerebral aneurysm clipping under isoflurane anesthesia. This agent was administered until the mean arterial blood pressure decreased and could be maintained at about 75% of the initial value until the completion of aneurysm clipping. The measurements of hemodynamics and LCBF were performed after the exposure of the internal carotid artery (T₀), and 10 min, 30min after the starting of nicardipine (n=13), (T₁, T₂ respectively), before aneurysm clipping (T₃) and 30 min after its discontinua-tion (T₄). Local cerebral blood flow was measured by the thermal gradient blood flow meter. The blood flow velocity of the internal carotid artery was measured at T₀ and T3 by a 20MHz pulsed ultrasound Doppler Flow-meter under surgical microscope. Carbon dioxide reactiv-ity was evaluated with %△ LCBF/ △ PaCO2 (%/mmHg) at T₀, T₃ and T₄. Mean arterial blood pressure decreased after nicardipine infusion. Local cerebral blood flow did not change during nicardipine infusion, but blood veloc-ity increased significantly after nicardipine infusion from 43 ± 12 to 55 ± 12 cm/sec (p = 0.024). Carbon dioxide reactivity did not change after nicardipine infusion but had a close correlation with LCBF before (rs = 0.64, p＜ 0.05), during (rs = 0.84, p＜ 0.01) and after hypotension (rs = 0.65, p＜ 0.05). These results suggest that nicardi-pine may be a useful agent to treat perioperative hyper-tension during cerebral aneurysm surgery, because nicar-dipine did not change local cerebral blood flow and car-bon dioxide reactivity, but increased blood flow velocity.