To the Editor: Carbon dioxide (CO2) embolization is a complication of endoscopic saphenous vein harvesting with CO2 insufflation during coronary artery bypass surgery (1,2). Lin et al. (3), using transesophageal echocardiography (TEE) to monitor CO2 bubbles in the inferior vena cava and hepatic vein, demonstrated a 4% incidence of significant CO2 embolism during endoscopic saphenous vein harvesting with CO2 insufflation procedures. An abrupt decrease in end-tidal CO2 can be a sensitive monitor for detecting CO2 embolism if the cardiovascular function, body temperature, and respiratory status remain stable. However, in the presence of hemodynamic instability capnography can be unreliable. TEE is the most reliable and sensitive method to detect CO2 embolism and is now considered to be the “gold standard” for diagnosis (4). A 78-yr-old woman with a history of angina and hypertension presented for coronary artery bypass surgery. Cardiac catheterization revealed 80% occlusion of the left anterior descending artery, 90% stenosis of the circumflex artery, and 40% stenosis of the right coronary artery. The reported ejection fraction was 60%. She was scheduled for endoscopic saphenous vein harvesting and coronary artery bypass graft surgery. Intraoperative monitors included five-lead electrocardiogram (ECG), radial artery catheter, pulmonary artery catheter, pulse oximetry, capnography, temperature, and TEE. After induction of anesthesia, her baseline TEE revealed good left ventricular function, and normal segmental wall motion in all 16 segments. Color Doppler imaging and agitated saline injection failed to demonstrate a patent foramen ovale (PFO). Endoscopic saphenous vein harvesting with CO2 insufflation at 12 mm Hg was begun. Approximately 30 min after beginning dissection, we noted a transient decrease in her arterial blood pressure from 100/60 to 70/40 mm Hg, accompanied by an increase in end-tidal CO2 to 57 mm Hg. Oxygen saturation remained at 99% with a Fio2 at 100%. This was accompanied by severe bradycardia, and ST segment changes. Mid-esophageal four-chamber views demonstrated severe biventricular global hypokinesis, with diffuse echogenic bubbles completely filling the right atrium and partially filling the right ventricle. Bubbles we seen crossing a PFO into the left atrium and left ventricle, with subsequent macroembolization to the aorta and coronary arterial system. CO2 insufflation was discontinued and cardiopulmonary resuscitation was initiated. The patient was treated with atropine, 1 mg IV push, and epinephrine and norepinephrine IV infusions. Within several minutes the bubbles cleared from the cardiac chambers, right ventricle and left ventricle wall motion normalized, as did the ECG and arterial blood pressure. Subsequent repair of the four vessels, as well as a 2.3 cm PFO, proceeded without incident. The patient was tracheally extubated 12 hours after surgery, and had no neurological sequelae. She was discharged home on the 11th postoperative day. Yoshio Okumura, MD Rodney A. Batchelder, CRNA, MS Department of Anesthesia William Beaumont Hospital Troy, Michigan [email protected]