1. Elucidate the influence of intense light therapy pretreatment in patients undergoing cardiac surgery. We hypothesize that intense light exposure is associated with the peripheral stabilization of Per2 in human buccal swabs and plasma samples before surgery and with a decrease of Troponin I levels after surgery. In addition, we hypothesize that light therapy leads to Per2 dependent metabolic optimization in the human cardiac tissue. Therefore, a small piece of human heart tissue from the right atrium will be collected during cardiac cannulation, which will be otherwise discarded. 2. Critical illness (being in the intensive care unit) results in circadian malfunction and vessels not working. Vessel function is controlled by the body's circadian clock. Intense light boosts the circadian clock and the vessel function in animal studies. Vessels not working well in critical ill patients results in a myriad of severe diseases (delirium, stroke, heart attack, organ damage etc). Thus we will test if intense light can be used to boost the circadian clock and the associated vessel function in critical ill patients.