Irwin R S, Doherty P W, Bartter T, Gionet M M, Collins J A
Department of Medicine, University of Massachusetts Medical School, Worcester.
Chest. 1988 Jun;93(6):1270-5. doi: 10.1378/chest.93.6.1270.
At present, there is no sensitive and specific test to confirm the clinical impression that a respiratory disorder is due to aspiration of gastric contents. Since intravenous technetium pertechnetate (99mTcO4-) has been shown to be safe, actively concentrated in the gastrointestinal tract, and secreted into gastric juice, we sought to determine whether 99mTcO4-, when given intravenously, is suitable to detect pulmonary aspiration of small amounts of gastric contents in rabbits. Biodistribution studies over 24 h revealed that 99mTcO4- persistently appeared in the stomach, thyroid, and salivary glands and did not appear in the lungs. Pharmacokinetic studies showed that 99mTcO4- was rapidly picked up by the stomach wall and secreted promptly into the stomach lumen and that the stomach wall persistently secreted 99mTcO4- into stomach contents for 24 h. By injecting 99mTcO4- through an intratracheal catheter in order to simulate aspiration, the radioactive threshold for imaging intrapulmonary 99mTcO4- was determined to range between less than 0.5 microCi and 2 microCi, depending on the amount of background activity in the blood pool. By measuring the radioactivity in stomach contents (microCi/g), over 24 h after intravenous injection of 2 mCi of 99mTcO4-, we were able to calculate the amount of aspirated stomach contents that our technique should reveal at various time points. We concluded from this preliminary feasibility study that 99mTcO4-, when given intravenously, is suitable to detect pulmonary aspiration of small amounts (less than or equal to 4 ml for 8 h after an intravenous dose of 2 mCi) of gastric contents in human patients. Since our biodistribution studies show that saliva as well as stomach contents are potential sources for any aspirated 99mTcO4-, how to distinguish aspiration of oropharyngeal from stomach contents remains to be determined. It also remains to be determined how long 99mTcO4- remains in the lungs after it has been instilled; clearance that is too rapid significantly decreases the ability of this agent to reveal aspiration.
目前，尚无灵敏且特异的检测方法来证实呼吸紊乱是由胃内容物误吸所致的临床判断。鉴于静脉注射高锝酸盐（99mTcO4-）已被证明是安全的，它能在胃肠道中主动浓聚并分泌到胃液中，我们试图确定静脉注射99mTcO4-是否适用于检测家兔少量胃内容物的肺误吸情况。24小时的生物分布研究表明，99mTcO4-持续出现在胃、甲状腺和唾液腺中，而未出现在肺部。药代动力学研究显示，99mTcO4-被胃壁迅速摄取并迅速分泌到胃腔中，且胃壁持续24小时将99mTcO4-分泌到胃内容物中。通过经气管导管注射99mTcO4-以模拟误吸，根据血池中的本底活性量，确定肺内99mTcO4-成像的放射性阈值在小于0.5微居里至2微居里之间。通过在静脉注射2毫居里99mTcO4-后24小时内测量胃内容物中的放射性（微居里/克），我们能够计算出我们的技术在各个时间点应能检测到的误吸胃内容物的量。从这项初步可行性研究中我们得出结论，静脉注射99mTcO4-适用于检测人类患者少量（静脉注射2毫居里后8小时内小于或等于4毫升）胃内容物的肺误吸情况。由于我们的生物分布研究表明，唾液以及胃内容物都是任何误吸的99mTcO4-的潜在来源，如何区分口咽内容物与胃内容物的误吸仍有待确定。99mTcO4-注入肺内后在肺内停留多长时间也有待确定；清除过快会显著降低该试剂检测误吸的能力。
