• Bektaş Atasever, Christa Boer, Peter Goedhart, Jules Biervliet, Jan Seyffert, Ron Speekenbrink, Lothar Schwarte, Bas de Mol, and Can Ince.
• Department of Translational Physiology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands. b.atasever@vumc.nl
• J. Cardiothorac. Vasc. Anesth.. 2011 Oct 1;25(5):784-90.

ObjectiveThe authors hypothesized that cardiopulmonary bypass (CPB) (on-pump) is associated with more severe changes in the microcirculatory blood flow and tissue oxygenation as compared with off-pump coronary artery bypass surgery.DesignAn observational study.SettingA university hospital and teaching hospital.ParticipantsPatients undergoing on-pump (n = 24) or off-pump (n = 24) cardiac surgery.InterventionsMicrocirculatory measurements were performed before CPB and 10 minutes after the switch to CPB or before and during cardiac luxation in off-pump patients.Measurements And Main ResultsSublingual microcirculatory perfusion was investigated using side-stream dark field imaging, and sublingual microcirculatory oxygenation was measured using reflectance spectrophotometry. Conversion to CPB resulted in an increase in cardiac output from 4.0 ± 0.2 to 4.8 ± 0.3 L/min (p < 0.01) and a 40% reduction in arterial hemoglobin concentration. Cardiopulmonary bypass was associated with an increase in venular blood velocity from 349 ± 201 μm/s to 563 ± 227 μm/s (p < 0.05), a reduction in functional capillary density of 43%, and an increase in hemoglobin oxygenation of the red blood cells in the remaining filled capillaries from 47.2% ± 6.1% to 59.7% ± 5.2% (p < 0.001). The decrease in cardiac output during cardiac luxation from 4.5 ± 1.7 to 1.8 ± 0.8 L/min (p < 0.01) without hemoglobin changes was associated with a complete halt of capillary blood flow and a reduction in maximum capillary blood velocity from 895 ± 209 to 396 ± 178 μm/s (p < 0.01). The functional capillary density remained unchanged, whereas the hemoglobin oxygenation declined from 64.2% ± 9.1% to 48.6% ± 8.7% (p < 0.01).ConclusionsOn-pump and off-pump cardiac surgery are associated with distinct alterations in sublingual microcirculatory perfusion and hemoglobin oxygenation. Although on-pump surgery results in a fall out of capillaries resulting in decreased oxygen extraction, off-pump surgery results in a cessation of flow during luxation resulting in decreased convection of oxygen transport.Copyright © 2011 Elsevier Inc. All rights reserved.

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