Carbon dioxide embolism during transanal total mesorectal excision (taTME)
Transanal total mesorectal excision (taTME) is a relatively new surgical approach that has become increasingly common for patients with low rectal cancer. This approach uses subperitoneal carbon dioxide (CO2) to create the pelvic workspace and perform the operation from the anal side. Thereby, a good surgical performance is achieved for a narrow pelvis, which is difficult with laparoscopy from the abdominal side. However, taTME is associated with potentially life-threatening complications, including CO2 embolism , which is not a commonly encountered complication during laparoscopic TME. This complication may be important in a transanal approach, and surgeons performing taTME need to be aware of this potential event to prevent major morbidity. Here, we report our experience with 2 patients who had a sudden drop in end-tidal carbon dioxide (ETCO2) that was suspected to be due to CO2 embolism during taTME.
The patient was a 54-year-old man with low rectal cancer with a main symptom of difficult defecation. His body mass index (BMI) was 23.4 kg/m2. His medical history included appendectomy and bladder carcinoma treated by transurethral resection. The tumor had invaded the prostate and was 7.0 cm from the anal verge. After chemoradiotherapy (CRT), we performed laparoscopic intersphincteric resection and prostate resection with taTME. After placing the patient in the Trendelenburg position, surgery was performed from the abdominal side and perineal side at the same time. On the abdominal side, a 12-mm trocar was inserted through the umbilicus, and pneumoperitoneum was created by insufflation of CO2 via the trocar. The intra-abdominal pressure was maintained at < 10 mmHg. On the perineal side, after purse-string suture of the lower rectum from the anal side, a GelPOINT Mini was placed and pneumoperitoneum was created by insufflation of CO2 using an Air-Seal device with high flow and smoke evacuation settings. The intraperitoneal pressure was maintained at < 15 mmHg.
After dissection near the prostate using an electrosurgical knife, pneumoperitoneum was stopped and purse-string suture was performed again with little bleeding (Fig. 1). When re-insufflation of CO2 for creation of pneumoperitoneum was performed, ETCO2 dropped suddenly from 40 to 29 mmHg and blood oxygen saturation (SpO)2 dropped from 100 to 94% (Fig. 2). The fraction of inspired oxygen (FIO2) was increased and the surgical procedure and insufflation were stopped. Vital signs did not worsen, and SpO2 increased to 100%. At this point, arterial blood gas analysis showed respiratory acidosis, and CO2 embolism was suspected. After about 15 min, arterial blood gas analysis showed a tendency for recovery, and the gradient between partial pressure of carbon dioxide (PCO2) and ETCO2 was decreased. The intraperitoneal pressure was reduced to 10 mmHg, and the operation was restarted and completed without any additional problems. The operating time was 754 min and blood loss was 1560 ml. There were no postoperative complications related to the intraoperative event.
The patient was a 67-year-old man who was indicated for surgery for recurrence of rectal cancer identified by elevated carcinoembryonic antigen. His BMI was 28.6 kg/m2. His medical history included appendectomy. The tumor had invaded the sacral bone and levator ani muscle and was located 7.0 cm from the anal verge. After CRT, we performed abdomino-perineal resection and sacral bone resection with taTME. After placing the patient in the Trendelenburg position, surgery was performed from the abdominal side and perineal side at the same time. The abdominal side was treated with open laparotomy. On the perineal side, the operation was performed in the same setting as the first case.
Bleeding occurred from the right posterior side of the prostate during dissection of the posterior side of the prostate from the rectum to preserve the circumferential margin. This bleeding was stopped immediately using a suction system (Fig. 3). At this point, ETCO2 dropped suddenly from 32 to 16 mmHg and SpO2 dropped from 100 to 97% (Fig. 4). CO2 embolism was suspected. FIO2 was immediately increased and the surgical procedure and insufflation were stopped. A few minutes later, blood pressure decreased from 100/60 to 67/57 mmHg and heart rate increased from 50 to 90 bpm. Ephedrine was administered intravenously, and vital signs recovered. After about 60 min, the intraperitoneal pressure was reduced to 10 mmHg, and the operation was restarted and completed without any additional problems. The operating time was 431 min and blood loss was 1792 ml. There were no postoperative complications related to the intraoperative event.
CO2 embolism during taTME was suspected in the two cases above, because ETCO2 suddenly decreased during insufflation after surgical dissection. A sudden drop of ETCO2 is an important sign for early detection of venous CO2 embolism, which is caused due to the reduction of pulmonary perfusion and increased alveolar dead space. Symptomatic CO2 embolism can occur during the early period of insufflation. Vital signs usually recover quickly, but CO2 embolism can be fatal if not treated immediately. Therefore, CO2 embolism should be suspected whenever a sudden change of ETCO2 occurs during insufflation in laparoscopic surgery. Transesophageal echocardiography (TEE) is the most reliable diagnostic method for CO2 embolism . TEE can detect intravenous gas in the inferior vena cava, right ventricular, and pulmonary artery, but is not used routinely in intraoperative monitoring because of its high cost and technical complexity. In our two cases, TEE was not used for diagnosis.
The pelvic workspace in taTME is created by delivering CO2, and this can lead to CO2 embolism . Surgery in the perineal cavity is associated with venous CO2 embolism, with many cases reported in laparoscopic radical prostatectomy and laparoscopic hysterectomy. The risk of injury to the venous complex may be high in procedures with transection and dissection close to the perineal cavity. Moreover, venous pressure is low in the Trendelenburg position to secure space for visualization, and CO2 may easily enter the veins . If bleeding created by pneumoperitoneum is stopped using suction, positive pressure during insufflation in the perineal cavity may allow gas to enter the veins and damage tissue. Because the pressure of insufflation is higher in a small space, CO2 embolism may be a major risk in taTME.
In our cases, a drop in ETCO2 occurred during and after dissection near the prostate with insufflation. The taTME procedure was performed from the anal side with dissection close to the prostate, and this procedure may have risk of injury to the venous complex. Therefore, there may be a higher risk of CO2 embolism in taTME compared with conventional laparoscopic surgery. An incorrect dissection layer may cause bleeding easily, and good understanding of the pelvic anatomy and surgical skills is required, in addition to noticing vital signs of CO2 embolism during surgery in the perineal cavity. The AirSeal® system can reduce CO2 consumption and maintain stable intraabdominal pressure during surgery, whereas a conventional laparoscopic system often cannot maintain intraabdominal pressure, leading to a delay of insufflation after suction and changing of forceps. Such a delay results in a longer operation and higher insufflation pressure. The AirSeal system responds immediately to the slightest change in intraabdominal pressure and provides continuous pressure sensing, stable pneumoperitoneum, and continuous smoke evacuation . This contributes to good surgical performance and easier anesthetic management due to reduction of the intraoperative blood CO2 increase compared with conventional laparoscopic surgery. However, this system was used in both of our cases, but CO2 embolism still occurred. At the time when it occurred, the intraperitoneal pressure was < 15 mmHg. Lower pressure might have to be maintained, because high pressure is associated with the incidence of embolism , and the AirSeal system results in safe surgical procedures at low intraabdominal pressure . This system may reduce laparoscopic complications, but surgeons need to keep in mind that CO2 embolism might still occur in surgery with AirSeal in high-risk patients.
In conclusion, surgeons and anesthetists should recognize that surgery on the perineal cavity, including taTME, is associated with the risk of gas embolism. Particular care is needed when the pressure is ≥ 15 mmHg when performing taTME near the prostate. In the future, it will be important to find identifiable and preventable risk factors for this complication.
All authors declare that they contributed to this article and approved the final submitted version. TS and YN collected data, wrote the manuscript, and contributed equally to the manuscript.
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Conflict of interest
Dr. Ito is on the speakers’ bureaus of Johnson & Johnson K.K., Eisai Co., Ltd., Olympus Corporation, Medtronic plc, Chugai Pharmaceutical Co., Ltd., KAKEN PHARMACE, UTICAL CO., LTD., Stryker Japan K.K., Covidien Japan, TAIHO PHARMACEUTICAL CO., LTD., Yakult Honsha Co., Ltd., Fujita Medical Instruments Co., Ltd., Japan Medical Engineering Institute, MSD K.K., Merck Serono Co., Ltd., Medical Leaders Co., Ltd., Takeda Pharmaceutical Company Limited, Applied Medical, MC Medical, Inc., EA Pharma Co., Ltd., and ConMed Japan KK. He received Grants of ConMed Japan KK, Mitsubishi Precision, MURANAKA MEDICAL INSTRUMENTS, FUJITA MEDICAL INSTRUMENTS, and A1 Technica. He has an equity interest in A-Trantion. Drs. Shiraishi, Nishizawa, Yamamoto, Tsukada, and Sasaki have no conflicts of interest or financial ties to disclose.
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