Canadian Blood Services, Ottawa, ON, Canada.
Vox Sang. 2013 Aug;105(2):100-7. doi: 10.1111/vox.12027. Epub 2013 Feb 9.
The '30-min rule' requires discarding red blood cells (RBCs) exposed to uncontrolled temperatures for >30 min to ensure safe RBC transfusion. This study was aimed at determining whether multiple room temperature (RT) exposures promote bacterial growth.
Pooled and split RBC units were inoculated with ~1 CFU/ml of Serratia marcescens, Yersinia enterocolitica, Escherichia coli or Staphylococcus epidermidis. Control units remained in storage, while test units were exposed to RT for six 30-min or three 60-min intervals. Bacterial concentrations and endotoxin levels were determined after each exposure and at 42 days of storage. RBC core temperature and RT were monitored in mock units with Escort iLog temperature loggers. A mixed model was used for statistical analyses.
Red blood cell core temperature reached 10.7 ± 0.4°C and 14.2 ± 0.2°C during 30- and 60-min exposures, respectively. Staphylococcus epidermidis and E. coli did not grow in either control or exposed RBCs. Yersinia enterocolitica concentration and endotoxin levels were similar in both control and test units. Serratia marcescens concentration and endotoxin levels were higher in exposed units; however, differences between units exposed for 30 min or 60 min were not observed.
There is no added risk to RBC safety by increasing RT exposures to 60 min with each removal from storage for up to a total of 3 h during RBC shelf life. Therefore, extending the 30-min limitation in RBCs exposed to uncontrolled temperatures to 60 min should be considered by regulatory agencies.
“30 分钟规则”要求丢弃暴露于不受控制温度下超过 30 分钟的红细胞（RBC），以确保安全输血。本研究旨在确定多次室温（RT）暴露是否会促进细菌生长。
将混合和分离的 RBC 单位用~1 CFU/ml 的粘质沙雷氏菌、小肠结肠炎耶尔森菌、大肠杆菌或表皮葡萄球菌接种。对照单位保持在储存中，而测试单位则暴露于 RT 中，分别进行六次 30 分钟或三次 60 分钟的暴露。每次暴露后和储存 42 天后，测定细菌浓度和内毒素水平。使用 Escort iLog 温度记录仪监测模拟单位的 RBC 核心温度和 RT。使用混合模型进行统计分析。
RBC 核心温度在 30 分钟和 60 分钟暴露期间分别达到 10.7°C±0.4°C 和 14.2°C±0.2°C。表皮葡萄球菌和大肠杆菌在对照或暴露的 RBC 中均未生长。小肠结肠炎耶尔森菌浓度和内毒素水平在对照和测试单位中相似。暴露单位的粘质沙雷氏菌浓度和内毒素水平较高；然而，暴露 30 分钟或 60 分钟的单位之间没有观察到差异。
在 RBC 货架寿命期间，每次从储存中取出并暴露于 RT 中，最多总共 3 小时，将 RT 暴露增加到 60 分钟，不会对 RBC 安全性造成额外风险。因此，监管机构应考虑将暴露于不受控制温度下的 RBC 的 30 分钟限制延长至 60 分钟。
