春口 洋昭

Hiroaki HARUGUCHI

飯田橋春口クリニック

Haruguchi Vascular Access Clinic

キーワード : preoperative evaluation, brachial artery flow, resistance index, surveillance, percutaneous transluminal angioplasty

バスキュラーアクセス（vascular access: VA）における超音波診断の役割は，(1)VA作製前の血管評価，(2)作製後の発育不良の評価，(3)日々のVA管理，(4)トラブル時の診断，に分けて考えることができる．VAの作製前の血管評価では，動・静脈の血管径のみならず，動脈壁の性状，静脈の連続性を検査する．作製後の発育不良は，術後2週間目に上腕動脈血流量とRIを測定し，狭窄の早期発見と介入に役立てる必要がある．日々のVA管理では，理学所見によるモニタリングが主となる．超音波検査はサーベイランスとして用い，可能であれば，定期的な上腕動脈血流量と血管抵抗指数（Resistance index: RI）の測定を行う．上腕動脈血流量500 ml/min未満およびRI 0.6以上はシャント機能低下と判断し，厳重な経過観察が必要となる．穿刺においては，超音波ガイド下穿刺，穿刺前の血管の評価，穿刺後の針先確認などが超音波検査で可能となる．シャントトラブルにおいては，穿刺部位と狭窄の位置関係によって，症状が変化することを認識して超音波検査を行うことが重要となる．一般的に上腕動脈血流量350 ml/min未満，RI 0.67以上では，脱血不良，閉塞の危険，再循環などが生じている可能性を念頭において超音波検査を施行する．

The role of ultrasound diagnosis in vascular access (VA) can be divided into: (1) blood vessel evaluation before VA placement, (2) evaluation of immaturation, (3) daily VA management, and (4) diagnosis when trouble occurs. In the preoperative blood vessel evaluation of VA, not only the vascular diameter but also the properties of the arterial wall and the continuity of the vein are examined. We need to measure brachial arterial blood flow rate and resistance index (RI) at 2 weeks postoperatively, and use it for early detection and intervention of stenosis. In day-to-day VA management, monitoring based on physical findings is the main role. Ultrasound examination is used as surveillance, and brachial artery blood flow rate and RI are periodically measured if possible. If the brachial artery blood flow rate is less than 500 ml/min and RI 0.6 or more, the access function is judged to be degraded, and strict follow-up observation is required. Regarding puncture, ultrasonic-guided puncture, evaluation of a blood vessel before puncture, and confirmation of the needle point after puncture, etc., can be performed by ultrasonic examination. When VA trouble occurs, it is important to recognize that the symptoms change depending on the positional relationship between the puncture site and the stenosis. Generally, when brachial arterial blood flow rate is less than 350 ml/min and RI 0.67 or more, ultrasonic examination is carried out based on a suspicion of poor blood removal, risk of obstruction, or recirculation of VA, etc.