To the Editor:-Harvest of the greater saphenous vein is a commonly performed procedure in patients undergoing coronary artery bypass grafting (CABG). Minimally invasive video-assisted removal of the saphenous vein in these patients is believed to be associated with decreased complications and greater patient satisfaction than with traditional harvesting techniques. [1–3] 

A new endoscopic vein harvesting system (Guidant Corporation, Menlo Park, CA) uses carbon dioxide (CO2) to aid in the visualization and dissection of the saphenous vein along its linear course. CO2is insufflated at 12–15 mmHg/min, and 10–20 l of CO2may be insufflated during this 45- to 60-min procedure.

Increases in minute ventilation required to maintain preinsufflation arterial carbon dioxide tension (PaCO2) during laparoscopic cholecystectomy have been reported. [4–6]We have observed a 10–20% increase in the baseline end tidal carbon dioxide (ETCO2) levels, as measured by capnography, in patients undergoing endoscopic saphenous vein harvesting with CO2insufflation. However, early in the learning curve, greater total amounts of CO2are insufflated because of increased time needed to master the dissection process. Hence, we have observed even greater increases in ETCO2.

At our institution, concomitant with saphenous vein dissection, the Internal Mammary Artery (IMA) is being exposed by the cardiac surgeon. We routinely decrease the patient's tidal volume (TV) during this time to assist the surgeon in his or her visualization of the IMA. Increases in the ETCO2from this decrease in TV compounded by the increase in ETCO2resulting from the endoscopic saphenous vein harvest may lead to notable changes in ETCO2and alterations in hemodynamics. If video-assisted endoscopic saphenous vein harvest becomes routine in CABG surgery, precautionary measures (such as increases in respiratory rate) should be anticipated.

James M. Gayes, M.D.

Department of Anesthesiology; Abbott Northwestern Hospital; Chicago Avenue at 28th Street; Minneapolis, Minnesota 55404

(Accepted for publication December 1, 1997.)

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