Department of Surgery, University of Washington, Seattle, Washington, USA.
Department of Laboratory Medicine and Pathology, University of Washington, Seattle, Washington, USA.
Transfusion. 2023 May;63(5):933-941. doi: 10.1111/trf.17246. Epub 2023 Jan 27.
Pediatric patients on extracorporeal membrane oxygenation (ECMO) often receive repeated red blood cell (RBC) transfusions. This study aims to quantify and characterize causes of RBC loss on ECMO.
This retrospective, single-center, observational study includes 91 ECMO patients (age 1 day-20 years). An RBC loss index (RLI), equal to ml RBCs lost per liter of patient + circuit volume per hour, was calculated from the changes in hematocrit and transfused RBCs. To measure the contribution of RBC injury/activation, RBC extracellular vesicle (REV) generation was measured by flow cytometry.
Median RLI on ECMO was 1.9 ml/L/h, 13-fold higher than normal RBC production rate (0.15 ml/L/h) and equivalent to a 4.6 drop in hematocrit/day. Median RBC loss was higher in patients who died (2.95 ml/L/h) versus survived (1.70 ml/L/h, p = .0008). RLI correlated with transfusion rate (r = 0.71); however, transfusion rate (ml/kg) underestimated RBC loss in patients with large changes in hematocrit and over-estimated RBC loss in neonates where the circuit volume is greater than the patient blood volume. In non-bleeding patients, intravascular hemolysis represented 16% of total RBC loss and diagnostic phlebotomy 24%, suggesting that ~60% of RBC loss was due to other causes. REV generation was increased sevenfold to ninefold during ECMO.
RLI (ml/L/h) is a more reliable quantitative indicator of RBC loss than transfusion rate (ml/kg) for pediatric patients on ECMO. Phlebotomy and intravascular hemolysis only account for 40% of RBC loss in non-bleeding ECMO patients. High REV generation suggests sublethal damage and extravascular clearance may be a cause of RBC loss on ECMO.
接受体外膜肺氧合（ECMO）治疗的儿科患者通常需要反复输注红细胞（RBC）。本研究旨在定量分析并确定 ECMO 治疗中 RBC 丢失的原因。
本回顾性、单中心、观察性研究纳入了 91 例 ECMO 患者（年龄 1 天至 20 岁）。通过血细胞比容和输注 RBC 的变化计算 RBC 丢失指数（RLI），其等于每小时每升患者+回路体积丢失的 RBC 毫升数。为了测量 RBC 损伤/激活的贡献，通过流式细胞术测量 RBC 细胞外囊泡（REV）的生成。
ECMO 期间的中位 RLI 为 1.9 ml/L/h，是正常 RBC 生成率（0.15 ml/L/h）的 13 倍，相当于每天 RBC 比容下降 4.6%。与存活患者（1.70 ml/L/h）相比，死亡患者（2.95 ml/L/h）的 RBC 丢失中位数更高（p=0.0008）。RLI 与输血率相关（r=0.71）；然而，对于血细胞比容变化较大的患者，输血率（ml/kg）低估了 RBC 丢失量，对于 ECMO 中回路体积大于患者血容量的新生儿，则高估了 RBC 丢失量。在非出血患者中，血管内溶血占总 RBC 丢失的 16%，诊断性采血占 24%，这表明~60%的 RBC 丢失是由其他原因引起的。REV 生成在 ECMO 期间增加了 7 倍至 9 倍。
与 ECMO 治疗的儿科患者的输血率（ml/kg）相比，RLI（ml/L/h）是更可靠的 RBC 丢失定量指标。在非出血 ECMO 患者中，采血和血管内溶血仅占 RBC 丢失的 40%。高 REV 生成提示亚致死性损伤，血管外清除可能是 ECMO 中 RBC 丢失的一个原因。
