Cardiovascular disease is the leading cause of death in the US. Each year, more than 500,000 coronary revascularization surgeries are performed. The in-hospital mortality rate among patients undergoing coronary artery bypass graft (CABG) surgery has declined to less than 6% in recent years, but potentially serious complications still occur and can prolong hospitalization, impair quality of life, and substantially increase medical costs. Excessive postsurgical inflammation can contribute to adverse outcomes, and the investigators hypothesize that exposure of patients to extraneous light at night during in-hospital recovery potentiates the inflammatory response to Coronary artery bypass graft (CABG), aortic valve replacement (aAVR), mitral valve replacement (MVR), CABG with aortic valve replacement (CABG AVR), or CABG with mitral valve replacement (CABG MVR), in turn, compromising several aspects of recovery. This hypothesis is based on our mouse models of brief global and focal cerebral ischemia; mice exposed to dim light at night (dLAN) during ischemic recovery have substantially more inflammation, neurological damage, and functional deficits than mice exposed to dark nights during ischemic recovery. The circadian system of mammals, including mice and humans, is most sensitive to light within the blue range of the spectrum (450- 485 nm); substituting longer wavelength light for nighttime exposures of mice recovering from ischemia eliminates the detrimental effects of the exposure to light at night (LAN). Based on these data, the hypothesis is that filtering the light CABG, AVR, MVR, CABG AVR, CABG MVR, or SAH surgery patients are exposed to at night during in-hospital recovery will reduce inflammation, and in turn improve functional outcome.
Specific Goals To determine if exposure of patients to extraneous LAN during recovery in the hospital potentiates the post- surgical inflammatory response. In the proposed study, consenting patients undergoing elective CABG, AVR, MVR, CABG AVR, CABG MVR, or SAH surgery will be randomly assigned to (1) the control group which will wear goggles for 10h at night that allow the full spectrum of light to pass through or to (2) the experimental group which will wear goggles for 10h at night that filter out wavelengths of light between 450-485 nm (i.e. the part of the spectrum that activates photosensitive ganglion cells and alters entrainment of the circadian clock). Baseline and postsurgical measures of inflammation and cognitive function will be obtained prior to surgery and during recovery in the hospital. If exposure to short wavelength (blue) LAN increases post-cardiac surgery inflammation, then the experimental group with filtered goggles will have lower blood markers of inflammation than the control group. Furthermore, we predict that reduced inflammation among the experimental group will be associated with less severe cognitive deficits on post-surgical day 5 (typically the day before discharge). In summary, this project will determine whether night-time exposure to blue light while recovering from CABG, AVR, MVR, CABG AVR, CABG MVR, or SAH surgery in the hospital affects the post-surgical inflammatory response and outcome. This study is innovative in two regards: 1) it will the first study to determine how a factor of a hospital's physical environment influences recovery from a major surgery and 2) it will be the first CABG study to determine whether reduction of early post-operative inflammation improves heart function and cognitive function after surgery. Elevated post- surgical inflammation is associated with a wide range of negative outcomes. If LAN exposure in the hospital does increase post-surgical inflammation, then adjusting patient exposure to environmental lighting could prove to be an inexpensive and effective way to improve patient outcome for CABG, AVR, MVR, CABG AVR, CABG MVR, or SAH surgery and a wide range of medical conditions that have an inflammatory component.
In summary, the proposed study will determine whether exposure to extraneous LAN exacerbates inflammation and compromises recovery from CABG, AVR, MVR, CABG AVR, CABG MVR, or SAH surgery. Our preliminary data indicated that cardiovascular patients are exposed to extraneous light several times per night while staying in the hospital and that LAN is associated with increased inflammation in both diurnal and nocturnal rodents \[15\]. The proposed project represents a "first step" aimed at determining whether hospital lighting affects inflammation. However, the payoff could be enormous; if manipulating nighttime light in hospital rooms improves patient outcomes, then it would be a relatively easy, inexpensive, innovation that could reduce post-surgical complications and save millions of dollars per year in health care costs by shortening the length of hospital stays and reducing morbidity.
