Bright Light Exposure in Critical Ill Patients

  • End date
    Jul 16, 2024
  • participants needed
  • sponsor
    University of Colorado, Denver
Updated on 16 May 2022
heart surgery
troponin i


  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.


PER2 transcript and protein levels in patients undergoing cardiac surgery following intense light therapy utilizing blood samples, buccal swaps and right atrial myocardium. In addition, we will examine the correlation of PER2 levels and PER2 related metabolism and perform a whole genome microarray screen from the collected tissue/blood samples.

Patients will be enrolled 10 to 1 days prior to surgery and will either receive an intense (bright light) box or a placebo/control device (dim/night light box). The patient will start using the light box 7 days prior to surgery every morning from 8.30 to 9.00 AM. The patient will need to keep the box as close as possible to their eyes and not walk away during the treatment period.

  1. Blood /buccal swabs will be collected on the day of enrollment (10-1 days prior to surgery) between 7 and 10 AM without any light therapy and on the day of surgery between 7 and 10 AM before anesthesia induction after one week of light/placebo therapy.

A small piece of the right atrial myocardium (which stems from cardiac cannulation and is otherwise discarded) will be put in liquid nitrogen in the OR and stored for further analysis.

In addition, we will draw a blood sample 72 hrs. after surgery and determine Troponin I levels.

Investigating this patient population will give the necessary evidence if light could also be effective in a perioperative setting to prevent or decrease damage to the myocardium during high risk cardiac surgery. In addition, it will help us understand if light could be used in general to prevent or treat heart ischemia.

2. We will use our light boxes for 30 minutes in ICU care patients on the first morning after admission from 8.30 to 9.00 AM. Before light therapy/sunrise and immediately after light therapy, a blood sample is drawn. These samples will be analyzed for melatonin levels. We have demonstrated that effective intense blue intense light therapy significantly suppresses melatonin plasma levels in health human volunteers which is the desired outcome of light therapy. We also have shown that light exposure via windows does not achieve such a result. Light therapy will be continued for up to 10 days, and blood samples are drawn each morning before sunrise and after light therapy. In patients that are sedated and have their eyes closed, eyes will be opened manually and lubricated before light therapy is initiated. The sample size will be n=40 (10 light treatment 5 days, 10 light treatment 10 days and 10 standard room light treatment 5 and 10 days). Additional readouts from plasma sample will be triglyceride and ANGPTL4 levels as we have already shown that intense light significantly downregulates triglycerides in healthy volunteers. Further, we recently discovered ANGPTL4 as major light dependent protein. ANGPTL4 is a key regulator of triglycerides and of endothelial function in humans and triglyceride levels are also indicative of endothelial function. This approach will allow us to evaluate the effectiveness of our light therapy approach and will further give insight into light elicited endothelial mechanisms in humans.

To further study endothelial function, we will use the Endo_PAT device (Itamar Medical Ltd, Franklin, MA) which has been shown to reliably detect endothelial dysfunction and alterations in critical ill patients. This device has been shown to even work when patients who are on vasopressor therapy. This device is noninvasive and works like an SpO2 monitor with built in cuff pressure measurement.

Finally, we will use Actigraphy (Actiwatch, Phillips) to analyze circadian patterns and associated changes following light therapy. We already have purchased FDA approved Actigraphy devices and shown that intense light strengthens the circadian rhythms in healthy volunteers. Watches will be around the wrist for the duration of the light therapy and are noninvasive.

Condition Myocardial Ischemia, Critical Illness, Endothelial Dysfunction
Treatment Placebo Light, Day Light, ICU Intense Light, ICU Placebo light
Clinical Study IdentifierNCT03822949
SponsorUniversity of Colorado, Denver
Last Modified on16 May 2022


Yes No Not Sure

Inclusion Criteria

Patients undergoing primary sternotomy cardiac surgery
Subjects in the range of 18 - 90 years old
Patient need to be in sinus rhythm at the time of surgery

Exclusion Criteria

patients <18 or >90 years old
participation in other clinical trials within the previous 30 days
neurological conditions that could impair weaning from ventilator support
significant CNS disorders or comorbid irreversible conditions with a six-month mortality rate more than 50 percent
prisoners, or subjects with altered capabilities to make decision will be enrolled
medical history of type 2 diabetes
patients with atrial fibrillation or use of class III anti-arhythmic drug
patients with a left ventricle ejection fraction < 40%
patient in emergency condition
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