Alpha Omega Alpha Honor Medical Society

The relationship between administered oxygen levels and arterial partial oxygen pressure to neurocognition in postoperative mechanically ventilated cardiac surgical patients

Investigator: Philip Chan, Tufts University School of Medicine

Mentor: Balachundhar Subramaniam, MD

Oxygen at a high inspired fraction is routinely used throughout the perioperative period for cardiac surgery in order to optimize oxygen delivery. Recent studies in cardiac arrest patients demonstrate that hyperoxia after return of spontaneous circulation may be associated with higher mortality. Although oxygen tension is widely studied in critically ill patients, little is known regarding hyperoxia and neurocognition in patients undergoing coronary artery bypass grafting. Not only may hyperoxia further exacerbate inflammation during cardiac surgery, it is known to increase oxidative stress that form ROS and damage cellular membranes, DNA and signaling proteins. Postoperative cognitive dysfunction may be secondary to inflammatory mediators that cross the weakened blood-brain barrier that directly injure neurons. Investigating hyperoxia and its effects on inflammation, oxidative stress, and neuronal injury in cardiac surgical patients may further explain its effects on postoperative cognitive dysfunction.

Patients undergoing elective or urgent on-pump CABG surgery will be randomized to one of two experimental groups, a normoxia and a hyperoxia arm. In the normoxic group, FiO2 will be set at 0.35 ideally to maintain PaO2 between 70-100 mmHg and saturations from 92-95%, and titrated up if need be to prevent potentially injurious hypoxemia. In the hyperoxic group, FiO2 will be set at 1.0 throughout the intraoperative period, including during CPB and upon arrival to the ICU. Neurocognitive testing, t-MoCA and CAM or 3D-CAM, will be performed daily from postoperative day two until hospital discharge, and by phone at postoperative months one, three and six. Baseline variables, days of mechanical ventilation, length of ICU/hospital stay, and mortality will also be collected.

At the time of writing this report, the study is enrolling patients. Of the 289 patients screened, 143 met exclusion criteria and 146 were approached for consent. Of the 84 patients who consented to the study, 22 withdrew their consent or were withdrawn due to an unexpected problem, and 62 patients were enrolled and have completed the protocol as planned. The total number of subjects to be studied is 100.

The effects of administered oxygen levels and arterial partial oxygen pressure to neurocognition and postoperative cognitive dysfunction in cardiac surgery patients will be assessed when full study sample has been enrolled.

Last modified: 1/30/2017

Updated on January 30, 2017.

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