The association between central venous pressure, pneumoperitoneum, and venous carbon dioxide embolism in laparoscopic hepatectomy

Background Laparoscopic hepatectomy (LH) is increasingly used. However, the safety and outcomes of LH have yet to be elucidated. The risk of venous gas embolism is increased during liver parenchymal transection. This risk may be increased with positive pressure carbon dioxide (CO2) pneumoperitoneum (PP). This may be exacerbated further when low central venous pressure (CVP) anesthesia is used to minimize hemorrhage during liver resection. Methods To determine the risk of CO2 venous embolism, hand-assisted laparoscopic left hepatic lobectomy was performed for 26 domestic pigs. They were divided into three groups involving, respectively, positive gradient (normal-pressure PP of 12-14 mmHg and low CVP of 57 mmHg), negative gradient (low-pressure PP of 78 mmHg and normal CVP of 10-12 mmHg), and neutral gradient (normal-pressure PP and normal CVP or low-pressure PP and low CVP). Transesophageal echocardiography (TEE) was used intraoperatively to assess the presence of emboli in the suprahepatic vena cava and the right side of the heart. The TEE was recorded and analyzed by blinded observers. Carbon dioxide embolism also was monitored using end-tidal CO2 and compared with TEE. Results Carbon dioxide embolism was demonstrated in 19 of the 26 cases. The majority of gas emboli were small gas bubbles associated with dissection of the major hepatic veins. No statistically significant difference in the occurrence of gas emboli was observed between the groups. Of the 19 animals, 18 experienced no significant hemodynamic changes. One pig in the positive gradient group experienced hypotension in relation to gas embolism. The effects were only transient and did not preclude safe completion of the operation. Conclusions Carbon dioxide embolism during LH occurs frequently. Clinically, this finding appears to be nominal, but care must be taken when dissection around large veins is performed, and awareness by the surgical and anesthesiology teams of potential venous air embolism is essential. Further evaluation of this phenomenon is required.