Novel application of indocyanine green fluorescence imaging for real-time detection of thrombus in a membrane oxygenator.

Sakurai, Hironobu; Fujiwara, Tatsuki; Ohuchi, Katsuhiro; Hijikata, Wataru; Inoue, Yusuke; Seki, Haruna; Tahara, Tomoki; Yokota, Sachie; Ogata, Asato; Mizuno, Tomohiro; Arai, Hirokuni

Extracorporeal membrane oxygenation (ECMO) is a life support system for severe respiratory or circulatory failure, and it plays an important role in the coronavirus disease 2019 (COVID-19) pandemic. Management of thrombi in ECMO is generally an important issue, however especially in ECMO for COVID-19 patients who are prone to thrombus formation, the thrombus formation in oxygenators is an unresolved issue for medical professionals, and it is very difficult to deal with. To prevent thromboembolic complications, it is necessary to develop a method for early thrombus detection. We developed a novel method for detailed real-time observation of thrombi formed in oxygenators using indocyanine green (ICG) fluorescence imaging. The purpose of this study was to verify the efficacy of this novel method through animal experiments. The experiments were performed three times using three pigs equipped with veno-arterial ECMO comprising a centrifugal pump (CAPIOX SL) and an oxygenator (QUADROX). To create thrombogenic conditions, the pump flow rate was set at 1 L/min without anticoagulation. Diluted ICG was intravenously administered, and the oxygenator was observed with both an optical detector (PDE-neo) and the naked eye every hour until 8 h after measurement initiation. Under ICG fluorescence imaging, the inside of the oxygenator was observed as a white area. A black dot-like area suspected to be the thrombus appeared 6-8 h after measurement initiation. The thrombus could not be recognized in detail with the naked eye observation until the oxygenator was rinsed with physiological saline. The thrombus and the black area on ICG fluorescence imaging were finely matched in terms of morphology. Thus, we succeeded in real-time thrombus detection in an oxygenator using ICG fluorescence imaging. The combined use of ICG imaging and conventional routine screening tests could compensate for each other's weaknesses and significantly improve the safety of ECMO.