ICG clearance is a relevant outcome prediction tool in cardiac surgery

Objective: Predicting outcome is a significant challenge in cardiac surgery. The plasma disappearance rate of indocyanine green (PDR-ICG) has been shown to predict outcome in subsets of critically ill patients, and derangements of PDR-ICG seem to be associated with adverse outcome in patients undergoing coronary artery bypass grafting. This prospective observational trial was designed to evaluate the potential role of PDR-ICG as an outcome prediction tool in a mixed set of cardiac surgery patients.

Methods: 190 consecutive patients undergoing cardiac surgery were included in this prospective observational trial after informed consent. PDR-ICG measurement along with standard lab values were performed preoperative and on postoperative days one, two, and on discharge from the ICU. Additionally, postoperative complications (i.e. acute renal failure and duration of hemofiltration therapies, use of an intra-aortic balloon pump (IABP), duration of mechanical ventilation) were documented. We build two study groups according to the length of stay (LOS) in the Intensive Care Unit (ICU) (<= 3 days vs. > 3 days (i.e. prolonged LOS)).

Results: The PDR-ICG values differed significantly at all time points. PDR-ICG was the strongest predictor for a prolonged LOS in the ICU in patients over 65 years of age and with a Euro SCORE below 8.5 in a multivariate analysis. The major factors suspected to influence mortality rates after cardiac surgery (i.e. age, preoperative LVEF, and EuroSCORE) were found to differ significantly between survivors and non-survivors in our patient collective, which was also the case for PDR-ICG and R15. Preoperative PDR ICG was also the strongest independent predictor for mortality (in a multivariate analysis including age, cardiac function, and Euro SCORE. A PDR-ICG of less than 8.2%/min was associated with a mortality rate of 46.7%, while in patients with a PDR-ICG of more than 8.2%/min the mortality rate was 6.7%.

Conclusion: The PDR-ICG seems to be an important predictive prediction parameter in addition to the EuroSCORE. Pre- and early postoperative single measurements may help to identify patients at risk for developing perioperative complications. A preoperative PDR-ICG below 8.2%/min is an excellent predictor for mortality after cardiac surgery.