Microcirculation of the sternum following harvesting of the left internal mammary artery.
BACKGROUND
Internal thoracic arterial grafts (ITA) in coronary artery bypass surgery provide excellent long-term patency results. Due to the elevated incidence of sternal infections following pedicled ITA harvesting, blood supply to the sternum has gained the focus of attention. This study sought to evaluate real time parameters of sternal microcirculation prior and immediately after harvesting of the ITA by a novel laser Doppler flowmetry and remission spectroscopy system (Oxygen-To-See (O2C), LEA Medizintechnik, Giessen).


METHODS
21 patients (16 males, age 63 + 4 years, mean NYHA 2.3 +/- 0.3) scheduled for coronary artery bypass grafting (CABG) were enrolled into the study. After median sternotomy, the probe was placed sequentially pre- and retrosternally for measurements of tissue oxygen saturation (sO2), hemoglobin concentration (rHb), superficial (2 mm) und deep (8 mm) blood flow. Measurements were performed and analyzed before and after surgical harvesting of the ITA with a pedicle.


RESULTS
Baseline pre- and retrosternal tissue oxygen saturation (sO2) were 90 +/- 3 % and 87 + 4 %, respectively (n. s.). After left ITA harvesting, presternal sO2 remained unchanged (90 + 4 %, n. s.), whereas retrosternal sO2 decreased significantly (54 + 4 %, p < 0.001). Simultaneously, retrosternal post-capillary venous filling (rHb) increased significantly after ITA harvesting (86 +/- 2 vs. 93 + 2, p < 0.05), whereas presternal rHb remained unchanged. Retrosternal superficial and deep blood flow also decreased significantly (75 +/- 5 vs. 41 +/- 4, and 94 +/- 5 vs. 52 +/- 6) in contrast to comparable presternal blood flow before and after ITA harvesting. There were neither superficial nor deep sternal wound infections occurred in the studied patient population.


CONCLUSIONS
The pedicled harvesting of ITA leads to a significant decrease of microcirculatory blood flow, retrosternal tissue oxygen saturation, and an increase in post-capillary venous filling. Parameters of microcirculation in the presternal area after ITA harvesting remained unchanged compared to baseline values. Hence, the incidence of sternal infections after ITA harvesting in coronary surgery may well be explained by a significant decrease of sternal blood supply in the retrosternal area. Further prospective randomized studies are needed to elucidate the potential role of skeletonized ITA preparation in sternal microcirculation.
Departement of Thoracic and Cardiovascular Surgery, Hannover Medical School, Hannover, Germany. knobloch@thg.mh-hannover.de
K
K
Knobloch
A
A
Lichtenberg
M
M
Pichlmaier
H
H
Mertsching
A
A
Krug
U
U
Klima
A
A
Haverich
D000368:Aged; D005260:Female; D006801:Humans; D007387:Internal Mammary-Coronary Artery Anastomosis / Q000379:methods*; D017078:Laser-Doppler Flowmetry; D008297:Male; D008323:Mammary Arteries / Q000601:surgery*; D008833:Microcirculation; D008875:Middle Aged; D010100:Oxygen / Q000032:analysis / Q000378:metabolism*; D010865:Pilot Projects; D013057:Spectrum Analysis; D013249:Sternum / Q000098:blood supply* / Q000000981:diagnostic imaging; D020858:Tissue and Organ Harvesting / Q000009:adverse effects* / Q000379:methods; D014463:Ultrasonography
D010100:Oxygen