Evidence-based patient blood management guidelines commonly recommend restrictive hemoglobin thresholds of 70 to 80 g/L for asymptomatic adults. However, most transfusion trials have enrolled adults across a broad age span, with few exclusive to older adults. Our recent meta-analysis of transfusion trials that focused on older adults paradoxically found lower mortality and fewer cardiac complications when these patients were managed using higher hemoglobin thresholds. We postulate that declining cardiac output with age contributes to deteriorating oxygen delivery capacity which impacts anemia-associated outcomes in older adults and propose a model to explain this age-related difference. We reviewed evidence concerning the pathophysiology of aging to explore the disparity in transfusion trial outcomes related to hemoglobin thresholds in different age groups. The literature was searched for normative cardiac output values at different ages in healthy adults. Using normative peak cardiac output data, we modeled oxygen delivery capacity in young, middle-aged, and older adults at a range of hemoglobin levels. Cardiovascular and pulmonary systems are impacted by age-related pathophysiological changes. Diminishing peak cardiac output associated with aging reduces the maximal oxygen delivery achievable under metabolic stress. Hence, at low hemoglobin levels, older adults are more susceptible to tissue hypoxia than younger adults. Our model predicts that an older adult with a hemoglobin of 100 g/L has a similar peak oxygen delivery capacity to a young adult with a hemoglobin of 70 g/L. Age-related pathophysiological changes provide some explanation as to why older adults have a lower tolerance for anemia than younger adults. This indicates the need for patient blood management hemoglobin thresholds specific to older as distinct from younger adults. The primary application of this model is in the consideration of patients rehabilitating to life outside hospital. It is important to note that pathophysiological changes associated with critical illness and major surgery are more complex than can be described in a simple model based on cardiac output and hemoglobin concentration. However, our review of oxygen transport and delivery in health and disease states allows the model to be considered in the context of treatment decisions for anemic adults in a range of hospital and community settings.

基于证据的患者血液管理指南通常建议无症状成人的血红蛋白限制阈值为70至80 g / L。但是，大多数输血试验都招募了跨年龄段的成年人，只有少数成年人可以接受。我们最近针对老年人的输血试验的荟萃分析自相矛盾地发现，当这些患者使用更高的血红蛋白阈值进行治疗时，死亡率更低，心脏并发症更少。我们假设随着年龄的增长心输出量下降会导致氧气输送能力下降，从而影响老年人贫血相关的预后，并提出了一个模型来解释这种与年龄相关的差异。我们审查了有关衰老的病理生理学的证据，以探讨与不同年龄组的血红蛋白阈值相关的输血试验结果的差异。在文献中搜索了健康成年人不同年龄时的标准心输出量。使用规范的峰值心输出量数据，我们在各种血红蛋白水平下对年轻人，中年和老年人的氧气输送能力进行了建模。年龄相关的病理生理变化会影响心血管和肺系统。与衰老相关的峰值心输出量减少会降低在代谢压力下可达到的最大氧气输送量。因此，在低血红蛋白水平下，老年人比年轻人更容易发生组织缺氧。我们的模型预测，血红蛋白为100 g / L的老年人与血红蛋白为70 g / L的年轻人具有相似的峰值氧输送能力。年龄相关的病理生理变化为为什么老年人对贫血的耐受性比年轻人低提供了一些解释。这表明需要针对老年人的患者血液管理血红蛋白阈值与年轻人不同。该模型的主要应用是考虑使患者在医院外恢复生活。重要的是要注意，与危重病和大手术相关的病理生理变化比基于心输出量和血红蛋白浓度的简单模型所描述的更为复杂。然而，