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.