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[Hemodynamic changes during bypass surgeries in the beating heart]
Object:
To study the effect of surgical manipulations on patient hemodynamics during beating-heart CABG surgery.
Methods:
We continuously monitored the systemic arterial pressure (SAP, n = 31), the pulmonary arterial pressure (PAP, n = 31) and the mixed venous oxygen saturation (SvO2, n = 6) using an Oxymetrix catheter.
Results:
Patients age ranged from 53 to 85 years old (mean 66.4 +/- 8.5) to whom 3.0 +/- 0.8 distal anastomoses were performed per patient. Stabilization of the heart were done using a "fork-type" stabilizator in all patients, and the target coronaries were clamped proximally and distally to the anastomosis site without pre-conditioning. A SAP decrease was found during the procedure and differed on the coronary territory being worked on: left anterior descending (LAD) (-11 +/- 19%), diagonal (Diag) (-13 +/- 27%), circumflex marginal (CM) (-19 +/- 17%) and right coronary (RC) or posterior descending artery (PDA) (-17 +/- 14%). PAP increase was maximal with the Diag (+47 +/- 84%) and was more important during LAD (+30 +/- 36%) and CM (+21 +/- 48%) than RC/PDA revascularization (+10 +/- 24%). On the other hand, SvO2 changes were found unchanged with any coronary territory. These changes occurred during the stabilization period before vessel occlusion, and were well tolerated by all patients, whom rarely needed inotropic support. No correlation between SvO2, SAP, PAP and occlusion time was found.
Conclusion:
The mobilization and stabilization of the heart using a "fork-type" stabilizator, rather than clamping the coronaries, during beating-heart CABG surgery were responsible for a decreased in SvO2, the SAP and an increase of the PAP. The marked elevation of PAP during revascularization of the diagonal and LAD territory may be explained by a compression of the left ventricle outflow tract. The Trendelenburg maneuver used during revascularization of the marginal and PDA territories may improve hemodynamics by relieving such pressure on the outflow tract and improve venous return.