Evaluation of hemodynamics: comparison of vacuum and mechanical stabilization in the beating heart

Hemodynamic instability remains a prominent concern for surgeons performing coronary surgery without cardiopulmonary bypass. The purpose of this study was to further elucidate the mechanism of hemodynamic instability by comparing vacuum stabilization to mechanical stabilization.

Four 60-kg swine were placed under general anesthesia. A median sternotomy incision was made, and baseline hemodynamic measurements were recorded. Mechanical and vacuum stabilization of the circumflex distribution were alternately compared with repeated baseline measurements in a counterbalanced method, and 32 experiments were conducted.

There were significant differences between baseline hemodynamics and stabilized hemodynamics for mechanical stabilization versus vacuum stabilization, respectively, for the following parameters: blood pressure (mean decrement), -32.18% (P =.0028) versus -31.3% (P =.0006); cardiac output, -31.03% (P =.0046) versus -35.2% (P =.03); and mixed venous oxygen saturation, -29.8% (P =.008) versus -27.4% (P =.0004). There were no statistical differences between mechanical and vacuum stabilization when their decremental effects on baseline hemodynamics were compared with each other for any of the measured variables.

The mechanisms of hemodynamic compromise during coronary stabilization remain to be fully elucidated. Our study demonstrates no statistical difference between vacuum and mechanical stabilization on the measured hemodynamic values. More sophisticated studies involving detailed analysis of motion and geometry are required so that technical solutions to hemodynamic instability can be developed.