Does poor oxygenation during one-lung ventilation impair aerobic myocardial metabolism in patients with symptomatic coronary artery disease?

One-lung ventilation is used during a variety of surgical procedures, even in patients with pre-existing coronary artery disease. The study purpose was to elucidate if myocardial metabolism crosses the anaerobic threshold under hypoxemia during one-lung ventilation. Therefore, we determined myocardial metabolism as a marker for anaerobic myocardial metabolism in patients with significant multi-vessel coronary artery disease undergoing one-lung ventilation during minimally-invasive coronary artery bypass grafting. Twenty patients with multi-vessel coronary artery disease underwent minimally-invasive revascularisation on cardiopulmonary bypass. One-lung ventilation was used for at least 45 min prior to cardiopulmonary bypass. Blood samples were drawn from arterial and coronary sinus blood at various times throughout the procedure to determine myocardial metabolism. After institution of one-lung ventilation arterial partial pressure of oxygen decreased significantly, down to levels between 50 and 70 mmHg. During one-lung ventilation, pH and lactate levels in both arterial and coronary sinus blood remained constant. Significant changes of pH and lactate levels were observed only after cardiopulmonary bypass. No clinically significant signs of myocardial ischemia occurred in any patient. Aerobic myocardial metabolism was unaffected during one-lung ventilation in all patients. Therefore, one-lung ventilation can be applied to patients with multi-vessel coronary artery disease with an acceptable risk of turning myocardial metabolism to an anaerobic state.