• Keith E Gipson, David J Rosinski, Robert B Schonberger, Cathryn Kubera, Eapen S Mathew, Frank Nichols, William Dyckman, Francois Courtin, Bradford Sherburne, Angelique F Bordey, and Jeffrey B Gross.
• Department of Anesthesiology, Hartford Hospital, Hartford, Connecticut; Department of Anesthesiology, University of Connecticut School of Medicine, Farmington, Connecticut. Electronic address: keith.gipson@aya.yale.edu.
• Ann. Thorac. Surg. 2014 Mar 1; 97 (3): 879-86.

BackgroundNumerous gaseous microemboli (GME) are delivered into the arterial circulation during cardiopulmonary bypass (CPB). These emboli damage end organs through multiple mechanisms that are thought to contribute to neurocognitive deficits after cardiac surgery. Here, we use hypobaric oxygenation to reduce dissolved gases in blood and greatly reduce GME delivery during CPB.MethodsVariable subatmospheric pressures were applied to 100% oxygen sweep gas in standard hollow fiber microporous membrane oxygenators to oxygenate and denitrogenate blood. GME were quantified using ultrasound while air embolism from the surgical field was simulated experimentally. We assessed end-organ tissues in swine postoperatively using light microscopy.ResultsVariable sweep gas pressures allowed reliable oxygenation independent of carbon dioxide removal while denitrogenating arterial blood. Hypobaric oxygenation produced dose-dependent reductions of Doppler signals produced by bolus and continuous GME loads in vitro. Swine were maintained using hypobaric oxygenation for 4 hours on CPB with no apparent adverse events. Compared with current practice standards of oxygen/air sweep gas, hypobaric oxygenation reduced GME volumes exiting the oxygenator (by 80%), exiting the arterial filter (95%), and arriving at the aortic cannula (∼100%), indicating progressive reabsorption of emboli throughout the CPB circuit in vivo. Analysis of brain tissue suggested decreased microvascular injury under hypobaric conditions.ConclusionsHypobaric oxygenation is an effective, low-cost, common sense approach that capitalizes on the simple physical makeup of GME to achieve their near-total elimination during CPB. This technique holds great potential for limiting end-organ damage and improving outcomes in a variety of patients undergoing extracorporeal circulation.Copyright © 2014 The Society of Thoracic Surgeons. Published by Elsevier Inc. All rights reserved.

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