[Carbon monoxide in the expiratory gas during laparoscopic surgery]

One of the complications of laparoscopic surgery is carbon monoxide (CO) production under the use of electrocautery. We experienced a case in which high levels of CO were detected in the expiratory gas. An 80-year old, 33 kg female was scheduled for laparoscopic nephrectomy. Anesthesia was induced with thiopental and vecuronium and maintained with nitrous oxide 60% in oxygen and isoflurane. The concentrations of CO in the anesthetic circuit were examined with CO sensor (XC-341, Shinkosumosudenshi, Tokyo). The CO concentrations were not detected at the start of operation. About 140 minutes after carbon dioxide pneumoperitoneum, the CO concentration increased up to 170 ppm accompanying a high Paco level. The high concentrations, however, decreased immediately after ending of pneumoperitoneum. The HbCO levels were unchanged. Subcutaneous emphysema was noted at the end of surgery. This is because CO is more absorbable in the subcutaneous tissue than in the peritoneal cavity. We consider that CO was absorbed in subcutaneous emohysema during pneumoperitoneum and exhausted in the expiratory gas. When subcutaneous emphysema occurred during laparoscopic surgery, we should be aware of absorption of CO.