ABSTRACT 26

The Cardiovascular Effects of Single Lung Ventilation and Carbon Dioxide Insufflation during Thoracoscopic Internal Mammary Artery Harvesting

Thomas A. Vassiliades, Jr., MD, Pensacola Heart Institute Pensacola, FL

Purpose: Thoracoscopic internal mammary artery harvesting has become an integral part of minimally invasive coronary artery bypass operations. The technique involves the use of single-lung ventilation and carbon dioxide insufflation to maximize exposure and facilitate rapid dissection. The cardiovascular effects of this technique have not been extensively studied.

Patients and Methods: Fifty consecutive patients undergoing a minimally invasive direct coronary artery bypass (MIDCAB) were prospectively studied intra-operatively. Forty- two left, five right and three bilateral thoracoscopic internal mammary harvests were performed in patients with ejection fractions ranging from 15 to 70 %. Carbon dioxide insufflation was introduced in 2mm Hg increments (8- 14mmHg) and the effects on fifteen hemodynamic indicators were recorded every sixty seconds.

Results:  Patients with hypovolemia poorly tolerated carbon dioxide insufflation until their volume status was corrected. Similarly, patients with poor ventricular function (<30% EF) were more sensitive to the negative effects of carbon dioxide insufflation. However, patients with normal ventricular function and normal volume status tolerated carbon dioxide insufflation up to 14mm Hg without any significant deterioration in hemodynamic performance. No patients experienced ischemia as a result of single-lung ventilation or carbon dioxide insufflation.

Conclusions:  Poor left ventricular function and hypovolemia were the two primary risk factors for hemodynamic compromise during carbon dioxide insufflation. However, euvolemic patients with good ventricular function tolerated carbon dioxide insufflation extremely well.