Monitoring cardiac output in beating heart coronary artery bypass graft surgery: use of pulse contour cardiac output

Introduction

Coronary artery bypass grafting is the gold standard for myocardial revascularization. Coronary revascularization with the heart beating avoids cardiopulmonary bypass and its complications, but requires active participation by the anaesthetist to manipulate the cardiovascular physiology and maintain haemodynamic stability. The present study evaluates the pulse contour cardiac output (PiCCO) monitor in measuring haemodynamic changes during off-pump coronary artery bypass graft (CABG) surgery.

Methods

Patients (n = 9) undergoing beating heart surgery were anaesthetized in theatre with invasive blood pressure monitoring. The right internal jugular vein was cannulated using the Seldinger technique, and a quadruple lumen catheter was inserted using aseptic technique. A thermodilution arterial catheter (PULSIOCATH, Pulsion Medical Systems AG, München, Germany) was inserted into the right femoral artery. The Octopus^® III Tissue Stabilization System (Medtronic Inc, Minneapolis, MN, USA) was used to stabilize the heart during grafting. Measurements of haemodynamic parameters were made at several time points.

Results

A decrease in systolic blood pressure was found, and differed according to the coronary territory being grafted. The percentage changes from baseline were as follows: left anterior descending (LAD; -14.77% ± 28.4%), circumflex marginal (CM; -24.28% ± 26.1%) and right coronary artery (RCA; -15.17% ± 21.3%). There was a mean percentage decrease in cardiac index when the CM (-7.15% ± 22.59%) was being grafted, compared with the other two arteries: LAD (10.78% ± 37.9%) and RCA (7.49% ± 27.5%). There were also reductions in stroke volume during the procedure: LAD (-5.11% ± 21%), CM (-21.42% ± 8.14%) and RCA (-8.06% ± 20.63%). The systemic vascular resistance index was reduced during revascularization: LAD (-20.22% ± 27.1%), CM (-20.95% ± 18.41%) and RCA (-13.16% ± 27.5%).

Conclusion

Cardiovascular monitoring may be difficult during off-pump CABG surgery. Manipulation of the heart results in a change in the cardiac axis, and therefore precordial electrocardiogram. ST-segment analysis may be unreliable. Central venous pressure and pulmonary artery pressure may be elevated because of myocardial displacement, as opposed to decreased ventricular compliance. The PiCCO uses transpulmonary thermodilution and arterial pulse contour for measurement of stroke volume, continuous cardiac output, systemic vascular resistance, intrathoracic blood volume and extravascular lung water. The present results correspond to those of other groups using pulmonary artery floatation catheters [1] for monitoring cardiac output during off-pump CABG surgery. The PiCCO monitor offers a less invasive method of continuous haemodynamic monitoring during beating heart surgery.