術中血圧と心筋虚血・MINS：概念・因果・臨床的解釈

Myocardial Injury After Noncardiac Surgery（MINS）and Intraoperative Blood Pressure：Association, Causation, and Clinical Uncertainty

はじめに

　近年よく目にする概念，myocardial injury after noncardiac surgery（MINS）は，不良な患者予後と関連するという報告が複数あり，そこから派生して，術中血圧管理の重要性が着目されている。MINSの定義には歴史的な変化があり，その基盤となる周術期の心筋傷害の概念も揺らぎながら定まってきた経緯がある。本論文ではその概念を整理して，術中管理の実際とどう関連するかを解説する。

　Myocardial injury after noncardiac surgery（MINS）has emerged as an important perioperative concept because of its strong association with adverse postoperative outcomes. The definition of myocardial injury has evolved over time, particularly with the introduction of cardiac troponins, which led to a distinction between myocardial injury and myocardial infarction. MINS is generally defined as a postoperative troponin elevation that does not meet the criteria for myocardial infarction, yet it is strongly associated with increased mortality.

　Pathophysiologically, MINS is closely related to type 2 myocardial infarction, which results from an imbalance between the myocardial oxygen supply and demand. Common contributing factors for MINS include tachycardia, hypotension, anemia, and hypoxemia. This has led to the hypothesis that optimizing perioperative hemodynamics, particularly blood pressure, may reduce MINS.

　Observational studies consistently demonstrate an association between intraoperative hypotension and increased risks of MINS and mortality, especially when the mean arterial pressure falls below approx. 65mmHg. However, randomized controlled trials and meta-analyses have failed to show that interventions targeting blood pressure alone reduce the risks of MINS or improve outcomes. Current guidelines suggest avoiding hypotension, often using a 65-mmHg threshold, but they acknowledge limited causal evidence. Thus, although the intraoperative blood pressure is an important marker, its role as a modifiable determinant of MINS remains uncertain.