Microcirculation of the Sternum Following Harvesting of the Left Internal Mammary Artery

 

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Abstract

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.

References

• 1 Baskett R J, MacDougall C E, Ross D B. Is mediastinitis a preventable complication? A 10-year review.  Ann Thorac Surg. 1999;  67 (2) 462-465
  CrossrefPubMedGoogle Scholar
• 2 Gummert J F, Barten M J, Hans C, Kluge M, Doll N, Walther T, Hentschel B, Schmitt D V, Mohr F W, Diegeler A. Mediastinitis and cardiac surgery - an updated risk factor analysis of 10,373 consecutive adult patients.  Thorac Cardiovasc Surg. 2002;  50 (2) 87-91
  Article in Thieme ConnectPubMedGoogle Scholar
• 3 Ridderstolpe L, Gill H, Granfeldt H, Ahlfeldt H, Rutberg H. Superficial and deep sternal wound complications: incidence, risk factors and mortality.  Eur J Cardiothorac Surg. 2001;  20 (6) 1168-1175
  CrossrefPubMedGoogle Scholar
• 4 Frank K H, Kessler M, Appelaum K, Dümmler W. The erlangen micro-lightguide spectrophotometer EMPHO I.  Phys Med Biol. 1989;  34 1883-1900
  CrossrefPubMedGoogle Scholar
• 5 Krug A. Quantitative optische Gewebemessungen am Herzen und an der Leber. Dissertation. Friedrich-Alexander-Universität Erlangen-Nürnberg 1998: 45-56
  Google Scholar
• 6 Shepherd AP, Öberg PA (Eds.) Laser-Doppler Blood Flowmetry. Kluwer Academic Publishers, Norwell 1990
  Google Scholar
• 7 Bonner R, Nossal R. Model for Laser Doppler measurements of blood flow in tissue.  Applied Optics. 1981;  20 (12) 2097-2107
  PubMedGoogle Scholar
• 8 Gandjbakhche A H, Bonner R F, Arai A E, Balaban R S. Visible-light photon migration through myocardium in vivo.  Am J Physiol. 1999;  277 (46) H698-H704
  PubMedGoogle Scholar
• 9 Burton A C. The vascular bed. In: Physiology and biophysics of the circulation Chicago, IL; Year Book Medical 1965
• 10 Parish M A, Asai T, Grossi E A, Esposito R, Galloway A C, Colvin S B, Spencer F C. The effects of different techniques of internal mammary artery harvesting on sternal blood flow.  J Thorac Cardiovasc Surg. 1992;  104 (5) 1303-1307
  PubMedGoogle Scholar
• 11 Takami Y, Ina H. Effects of skeletonization on intraoperative flow and anastomosis diameter of internal thoracic arteries in coronary artery bypass grafting.  Ann Thorac Surg. 2002;  73 (5) 1441-1445
  CrossrefPubMedGoogle Scholar
• 12 Wendler O, Tscholl D, Huang Q, Schafers H Q. Free flow capacity of skeletonized versus pedicled internal thoracic artery grafts in coronary artery bypass grafts.  Eur J Cardiothorac Surg. 1999;  15 (3) 247-250
  CrossrefPubMedGoogle Scholar
• 13 Pevni D, Mohr R, Lev-Run O, Locer C, Paz Y, Kramer A, Shapira I. Influence of bilateral skeletonized harvesting on occurence of deep sternal wound infection in 1000 consecutive patients undergoing bilateral internal thoracic artery grafting.  Ann Surg. 2002;  237 (2) 277-280
  PubMedGoogle Scholar

Karsten Knobloch, MD 

Departement of Thoracic and Cardiovascular Surgery, Hannover Medical School

Carl-Neuberg-Straße 1

30625 Hannover, Germany

Phone: +49 (511) 532-4580

Fax: +49 (511) 532-5404

Email: knobloch@thg.mh-hannover.de