Purpose Hemoglobin (Hb) transfusion thresholds are established in intensive care units. A restrictive transfusion threshold (Hb 70–75 g/l) is recommended in septic patients, and a liberal transfusion threshold (Hb 90 g/l) for cardiogenic shock. It is unclear whether these historically adopted transfusion thresholds meet the challenges of individual patients. Methods We evaluated microvascular flow index (MFI) and proportion of perfused vessels (PPV) in the sublingual microcirculation with CytoCam-IDF microscopy and near-infrared spectroscopy (NIRS). A study team-independent, treating intensivist assigned a total of 64 patients to 1 of 2 two transfusion thresholds, 43 patients to the Hb 75 g/l threshold and 21 patients to the Hb 90 g/l threshold, at a surgical intensive care unit. We performed microcirculatory measurements 1 h before and 1 h after transfusion of 1 unit of red blood cells. Results Microcirculatory flow variables correlated negatively with pre-transfusion flow variables (ΔMFI: ρ = − 0.821, p < 0.001; ΔPPV: ρ = − 0.778, p < 0.001). Patients with good initial microcirculation (cutoffs: MFI > 2.84, PPV > 88%) showed a deteriorated microcirculation after red blood cell transfusion. An impaired microcirculation improved after transfusion. At both transfusion thresholds, approximately one third of the patients showed an initially impaired microcirculation. In contrast, one third in every group had good microcirculation above the cutoff variables and did not profit from the transfusion. Conclusion The data suggest that the established transfusion thresholds and other hemodynamic variables do not reflect microcirculatory perfusion of patients. Blood transfusion at both thresholds 75 g/l and 90 g/l hemoglobin can either improve or harm the microcirculatory blood flow, questioning the concept of arbitrary transfusion thresholds.

中文翻译：

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舌下微循环不能反映重症监护病房的红细胞输血阈值——重症监护病房的一项前瞻性观察研究

目的 血红蛋白 (Hb) 输血阈值是在重症监护病房中建立的。脓毒症患者推荐限制性输血阈值（Hb 70–75 g/l），心源性休克患者推荐自由输血阈值（Hb 90 g/l）。目前尚不清楚这些历史上采用的输血阈值是否能满足个体患者的挑战。方法 我们使用 CytoCam-IDF 显微镜和近红外光谱 (NIRS) 评估了舌下微循环中的微血管流动指数 (MFI) 和灌注血管 (PPV) 比例。一名独立于研究团队的重症监护医师在外科重症监护病房将总共 64 名患者分配到 2 个输血阈值中的 1 个，其中 43 名患者达到 Hb 75 g/l 阈值，21 名患者达到 Hb 90 g/l 阈值. 我们在输注 1 个单位的红细胞前 1 小时和后 1 小时进行了微循环测量。结果 微循环血流变量与输血前血流变量呈负相关（ΔMFI：ρ = - 0.821，p < 0.001；ΔPPV：ρ = - 0.778，p < 0.001）。初始微循环良好的患者（临界值：MFI > 2.84，PPV > 88%）在红细胞输注后显示出微循环恶化。输血后受损的微循环得到改善。在两个输血阈值下，大约三分之一的患者最初显示微循环受损。相比之下，每组中的三分之一在截止变量以上具有良好的微循环，并且没有从输血中获益。结论 数据表明，建立的输血阈值和其他血流动力学变量不能反映患者的微循环灌注。在 75 g/l 和 90 g/l 血红蛋白这两个阈值下输血可以改善或损害微循环血流，质疑任意输血阈值的概念。