Blood transfusions recruit the microcirculation during cardiac surgery.
BACKGROUND
Perioperative red blood cell transfusions are commonly used in patients undergoing cardiac surgery to correct anemia caused by blood loss and hemodilution associated with cardiopulmonary bypass circulation. The aim of this investigation was to test the hypothesis that blood transfusion has beneficial effects on sublingual microcirculatory density, perfusion, and oxygenation. To this end, sidestream dark field (SDF) imaging and spectrophotometry were applied sublingually before and after blood transfusion during cardiac surgery.


METHODS
Twenty-four adult patients undergoing on-pump cardiac surgery, including coronary artery bypass grafting, cardiac-valve surgery, or a combination of these two procedures, were included consecutively in this prospective, observational study. Sublingual microcirculatory density and perfusion were assessed using SDF imaging in 12 patients (Group A). Sublingual reflectance spectrophotometry was applied in 12 patients (Group B) to monitor microcirculatory oxygenation and hemoglobin (Hb) concentration.


RESULTS
Blood transfusion caused an increase in systemic Hb concentration (p < 0.01) and hematocrit (p < 0.01). At the microcirculatory level, blood transfusion resulted in increased microcirculatory density (from 10.5 ± 1.2 to 12.9 ± 1.2 mm capillary/mm(2) tissue, p < 0.01) as shown using SDF imaging. In concert with the SDF measurements, spectrophotometry showed that microcirculatory Hb content increased from 61.4 ± 5.9 to 70.0 ± 4.7 AU (p < 0.01) and that microcirculatory Hb oxygen saturation increased from 65.6 ± 8.3% to 68.6 ± 8.4% (p = 0.06).


CONCLUSIONS
In this study we have shown that blood transfusion: 1) improves the systemic circulation and oxygen-carrying capacity, 2) improves sublingual microcirculatory density but not perfusion velocity, and 3) improves microcirculatory oxygen saturation.
Department of Translational Physiology, Academic Medical Center, University of Amsterdam, Amsterdam, the Netherlands. k.yuruk@amc.uva.nl
Koray
K
Yuruk
Emre
E
Almac
Rick
R
Bezemer
Peter
P
Goedhart
Bas
B
de Mol
Can
C
Ince
D000368:Aged; D000740:Anemia / Q000628:therapy*; D016063:Blood Loss, Surgical / Q000503:physiopathology* / Q000517:prevention & control; D001803:Blood Transfusion; D002302:Cardiac Output / Q000502:physiology; D006348:Cardiac Surgical Procedures; D002315:Cardiopulmonary Bypass; D005260:Female; D006801:Humans; D008297:Male; D008833:Microcirculation / Q000502:physiology*; D008875:Middle Aged; D009060:Mouth Floor / Q000098:blood supply; D010092:Oximetry; D011446:Prospective Studies; D011673:Pulsatile Flow / Q000502:physiology; D013053:Spectrophotometry