「無益性の閾値」を超えて：大量輸血意思決定のための倫理的枠組み

Massive transfusion can be lifesaving and resource-intensive, undertaken under time pressure, prognostic uncertainty, and variable system capability. Recent literature suggesting unit-based "futility thresholds" risks translating population-level mortality correlations into bedside stopping rules.

This essay distinguishes three ethically distinct rationales commonly conflated under "futility": (1) physiologic futility-inability to reach the intended clinical goal; (2) potentially inappropriate treatment-contestable judgments about benefits, burdens, and values; and (3) stewardship/rationing-opportunity costs due to scarcity.

It introduces a fourth category: "system-limited salvageability," where transfusion cannot bridge to hemorrhage control within existing infrastructure, distinguishing capability-time mismatch from patient-centered futility. A capability-sensitive massive transfusion protocol (MTP) time-out is proposed, triggered by clinical trajectory rather than unit count, requiring clear rationale labeling, rapid capability assessment, and minimal documentation to support accountability.

When limitations reflect capability gaps rather than patient physiology, institutions should treat these as sentinel events requiring structured review and potential systems improvement. This framework addresses the risk that unit-based thresholds become self-fulfilling limits or mask implicit rationing. By clarifying whether stopping reflects patient physiology or system constraints, it appropriately assigns accountability and enhances transparency in scarcity-driven decisions while maintaining rapid clinical judgment.