Bronchial artery perfusion during cardiopulmonary bypass does not prevent ischemia of the lung in piglets: assessment of bronchial artery blood flow with fluorescent microspheres.
OBJECTIVE
Blood supply of the lungs during total cardiopulmonary bypass (CPB) is limited to flow through the bronchial arteries. This study was undertaken to assess the bronchial artery blood flow during CPB with fluorescent microspheres in a piglet model.


METHODS
We subjected ten piglets (mean weight 5.0+/-0.5 kg) to 120 min of normothermic, total CPB without aortic cross-clamping, followed by 60 min of post-bypass perfusion. Fluorescent microspheres were injected into the left atrium or the aortic cannula or distal to the cannula to assess bronchial artery blood flow before, during and after CPB. The reference samples were taken from the descending aorta. We compared the different sites of injection. Tissue samples of the lungs were taken before and 60 min after CPB.


RESULTS
Before CPB, total bronchial artery perfusion was 43.6+/-14.1 ml/min (4.8+/-1.3% of cardiac output) as by injection distal to the aortic cannula. These values were not different when microspheres were injected into the left atrium or the aortic cannula. There was no difference in scatter or in the amount of microspheres in the reference samples among the three injections sites. During CPB, bronchial artery perfusion was significantly decreased (4.4+/-2.4 ml/min vs. 40.0+/-5.0 ml/min before CPB) and returned to baseline values 60 min after CPB. Light microscopy of the tissue samples revealed alveolar septal thickening and a decrease in alveolar surface area after 60 min of reperfusion which was associated with a decreased capacity to oxygenate blood.


CONCLUSIONS
(1) Bronchial artery blood flow can quantitatively be assessed during CPB when microspheres are injected into the ascending aorta and the reference samples are taken from the descending aorta. (2) Despite adequate perfusion pressure bronchial artery blood flow is decreased substantially during CPB. (3) The decrease in blood flow and the ultrastructural changes present at the end of CPB suggest the presence of low-flow ischemia of the lung during total CPB.
Department of Cardiovascular Surgery, University of Freiburg, Hugstetter Strasse 55, D-79106, Freiburg, Germany. schlensa@ch11.ukl.uni-freiburg.de
C
C
Schlensak
T
T
Doenst
S
S
Preusser
M
M
Wunderlich
M
M
Kleinschmidt
F
F
Beyersdorf
D000704:Analysis of Variance; D000818:Animals; D000831:Animals, Newborn; D001783:Blood Flow Velocity; D001981:Bronchial Arteries / Q000503:physiopathology*; D002315:Cardiopulmonary Bypass / Q000009:adverse effects / Q000379:methods*; D004195:Disease Models, Animal; D005453:Fluorescence; D007511:Ischemia / Q000473:pathology / Q000517:prevention & control*; D008168:Lung / Q000098:blood supply*; D008863:Microspheres; D015425:Myocardial Reperfusion / Q000379:methods*; D011336:Probability; D012680:Sensitivity and Specificity; D013552:Swine