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Ann Thorac Surg 2006;81:1697-1699
© 2006 The Society of Thoracic Surgeons

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Original article: Cardiovascular

Reduction of Carbon Dioxide Embolism for Endoscopic Saphenous Vein Harvesting

^a Department of Cardiovascular Surgery, Far Eastern Memorial Hospital, National Taiwan University College of Medicine, Taipei, Taiwan
^b Department of Anesthesia, Far Eastern Memorial Hospital, National Taiwan University College of Medicine, Taipei, Taiwan
^c Department of Anesthesiology, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan

Accepted for publication December 9, 2005.

^_* Address correspondence to Dr Wang, Department of Anesthesiology, National Taiwan University Hospital and National Taiwan University College of Medicine, 7 Chung Shan South Road, Taipei, Taiwan 100; (Email: canon{at}ha.mc.ntu.edu.tw).

	Abstract

Top Abstract Introduction Patients and Methods Results Comment References

 
BACKGROUND: The endoscopic saphenous vein harvesting (EVH) introduced in coronary artery bypass surgery (CABG) is associated with less wound complication and postoperative pain. Carbon dioxide (CO₂) insufflation is used during EVH to facilitate the procedure. The purpose of this study was to determine whether the incidence of CO₂ embolism during EVH with CO₂ insufflation could be reduced with lower CO₂ insufflation pressure.

METHODS: Four hundred and ninety-eight consecutive patients scheduled for elective off-pump CABG were prospectively studied. These patients were randomly assigned into high and low groups in which 15 and 12 mm Hg CO₂ insufflation pressures were used during EVH, respectively. Multiplane transesophageal echocardiography (TEE) with transgastric inferior vena cava view was used to monitor the appearances of CO₂ bubbles. If a burst of many CO₂ bubbles were found by TEE, the CO₂ insufflation would be stopped until detailed examination of the operative field.

RESULTS: The incidence of CO₂ embolisms in the high group of patients (13.3%) was significantly higher than that in the low group (6.5%, p < 0.05). Two episodes of emergent cessation of CO₂ insufflation occurred in the high group of patients. No massive CO₂ embolism with significant hemodynamic alterations occurred in either group.

CONCLUSIONS: The incidence of CO₂ embolisms during EVH could be reduced with lower CO₂ insufflation pressure, which, in combination with increased surgical experience and continuous TEE monitoring of the inferior vena cava, helps to reduce the risks of massive CO₂ embolism.

	Introduction

Top Abstract Introduction Patients and Methods Results Comment References

 
The great saphenous vein is conventionally harvested with the open technique during coronary artery bypass grafting (CABG). The endoscopic saphenous vein harvesting (EVH) recently introduced was associated with less wound complication and postoperative pain [1–3], shorter hospital stay [4], better patient satisfaction [5], and similar graft patency rate compared with the conventional techniques [3]. Carbon dioxide (CO₂₎ insufflation is used during EVH to create a subcutaneous tunnel and to facilitate the harvest of the saphenous vein in CABG. The use of CO₂ insufflation during EVH was reported to reduce hematoma and vein trauma [6]; however, several reports of massive pulmonary CO₂ embolism raise concern about the safety of EVH with CO₂ insufflation [7–9]. In a previous study, we found that CO₂ embolism could be detected with transesophageal echocardiography (TEE) in more than 17.1% of patients who underwent EVH with CO₂ insufflation and 0.5% of patients who developed severe CO₂ embolism necessitating emergent cardiopulmonary bypass [10]. Because CO₂ embolism results from the entry of CO₂ into the circulation during surgical dissection, we investigated whether the incidence and risks of CO₂ embolism during EVH with CO₂ insufflation in CABG could be reduced with lower CO₂ insufflation pressure.

	Patients and Methods

Top Abstract Introduction Patients and Methods Results Comment References

 
Four hundred and ninety-eight consecutive patients scheduled for off-pump CABG surgery from August 2003 to April 2005 were prospectively studied. The study was approved by the Institutional Review Board and written informed consent was obtained from every patient. Patients were excluded if they had prior saphenous vein harvesting for peripheral arterial occlusive disease or CABG. The patients were randomly assigned to two groups of different CO₂ insufflation pressures, which were set at 15 mm Hg (high group) or 12 mm Hg (low group) by the circulation nurse in the operation room. The surgeons and anesthesiologists were not aware of the CO₂ pressure setting until the end of the operation.

General anesthesia was induced in all patients with fentanyl; etomidate and rocuronium were used to facilitate the intubations. Standard monitors including arterial line, rectal temperature, and central venous or pulmonary artery catheters were placed after anesthetic induction. An adult multiplane TEE probe (6T, GE Vingmed Medical, Horten, Norway) was placed after anesthetic induction and intubation. The placement and visualization of the inferior vena cava with the TEE probe was described previously [10]. Briefly, after evaluation of the cardiac function and to avoid the interference from the central venous line, the TEE probe was advanced into the stomach and was rotated with the echo beam angle adjusted to visualize the long axis of the inferior vena cava (IVC). Images during EVH were monitored continuously with the TEE by an anesthesiologist and recorded on super VHS tapes, which were reviewed later by another anesthesiologist who was a qualified perioperative TEE examiner (M-JW) to confirm the findings.

All the EVH procedures were performed by surgeons who had experiences of more than 100 patients. The Vasoview Uniport System (Guidant, Menlo Park, CA) was used in all patients. After insertion of a port to achieve the air seal through the skin incision, CO₂ was insufflated to facilitate the creation of a subcutaneous tunnel. The great saphenous vein was dissected with the working endoscope up to the groin region and the branches were identified and divided with bipolar scissors. Another skin incision was made over the proximal end of the vein and the saphenous vein was ligated proximally and divided. During the EVH procedure, any appearance of bubbles was reported to the surgeons. If a burst of many CO₂ bubbles appeared in the IVC (Fig 1), the CO₂ insufflation was stopped immediately and was resumed only after careful examination of the operative field for possible openings on the saphenous vein.

View larger version (73K): [in this window] [in a new window]   Fig 1. Transesophageal echocardiography; transgastric view of the IVC and the hepatic vein. Several carbon dioxide bubbles (arrows) were visible in the IVC. Numbers 2, 4, 6 indicate the depth of the echo image, and V indicates the normal left right orientation of the echo image. (IVC = inferior vena cava.)

	Results

Top Abstract Introduction Patients and Methods Results Comment References

 
Table 1 summarizes the demographic and operative data of the patients. There was no significant difference between the two groups in these preoperative variables. One and two patients were excluded from the study in the high and low groups of patients, respectively, due to conversion to the "open" or "bridging" method of vein harvesting because of technical difficulties.

	Comment

Top Abstract Introduction Patients and Methods Results Comment References

 
The main finding of this study was that the incidence of the CO₂ embolism was reduced with the application of lower insufflation pressure during EVH with CO₂ in CABG. When compared with the conventional "open" or "bridging" method, the EVH was associated with less postoperative pain and wound complication, shorter hospital stay, and comparable graft patency rate [1–4]. Carbon dioxide has been adopted during endoscopic surgery to create working space and facilitate the procedure. It is used during EVH in CABG for the harvest of the saphenous vein to reduce trauma and hematoma [6]; however, several case reports of massive CO₂ embolism raised concern about its safety [7–9]. In our previous study [10], in which 15 mm Hg of insufflation pressure was used during EVH with CO₂, we found CO₂ embolism occurred in 17.1% of patients, while devastating CO₂ embolism presenting as sudden cardiovascular collapse happened in 0.5% of patients [10]. Because of the technical difficulties in creating the subcutaneous tunnel if the insufflation pressure was set at 10 mm Hg or lower in our experience, we used 12 mm Hg in the current study to determine whether lower insufflation pressure was helpful in reducing the risks of CO₂ embolism. Our results demonstrated that lower CO₂ insufflation pressure did reduce the incidence of CO₂ embolism. In addition, the similar incidence of CO₂ embolism (13.3% vs 17.1%) between the patients using the same 15 mm Hg as the insufflation pressure in the current and previous studies [10] suggested that the most important factor for the reduction of CO₂ embolism is the lower CO₂ insufflation pressure.

Another important finding of the current study is that no more massive or life- threatening CO₂ embolism happened in either group of patients. Massive CO₂ embolism is most probably caused by the direct rapid entry of CO₂ into an injured vessel [7–10]. Since there was no massive CO₂ embolism in either group of patients, we cannot be sure whether the reduction of the CO₂ insufflation pressure was also helpful in reducing the risks of massive CO₂ embolism. However, the finding that there were two episodes of CO₂ embolism requiring immediate cessation of CO₂ insufflation only in the high group suggested that lowered CO₂ pressure was also helpful in reducing the risks of massive CO₂ embolism. Since the entry rate of the CO₂ into the venous circulation was dependent on the pressure difference between the insufflation and the venous pressure, 15 mm Hg was used in four of the five cases of massive CO₂ embolism during EVH reported in the literature [7–10]. Considering that there might be more vascular trauma when the EVH was performed by inexperienced operators and with regard to the safety during EVH, we think that 12 mm Hg instead of 15 mm Hg should be used routinely during EVH in CABG.

Transesophageal echocardiography was found to be the most sensitive tool in detecting venous CO₂ embolism [[11]. We use the transgastric IVC view to continuously monitor CO₂ bubbles during EVH. This view is easily obtained, not interfered by microbubbles from the central venous pressure lines, and very sensitive to monitor the appearance of CO₂ bubbles in the IVC. Because the reduction of the CO₂ insufflation pressure alone to 12 mm Hg cannot prevent the occurrence of CO₂ embolism [7], continuous monitoring of the appearance of gas bubbles by TEE in the IVC is necessary during the EVH procedure. With the TEE monitoring, two episodes of CO₂ embolisms were prevented from progression into the massive form, which may cause abrupt hemodynamic alterations and cardiovascular collapse caused by the "gas lock" effect. We conclude that the incidence of CO₂ embolisms during EVH could be reduced with lower CO₂ insufflation pressure, which, in combination with increased surgical experience and continuous TEE monitoring of the IVC, helps to reduce the risks of massive CO₂ embolism.

	References

Top Abstract Introduction Patients and Methods Results Comment References

 

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				M. Tamim, M. Omrani, A. Tash, and A. El Watidy Carbon dioxide embolism during endoscopic vein harvesting Interactive CardioVascular and Thoracic Surgery, August 1, 2008; 7(4): 659 - 660. [Abstract] [Full Text] [PDF]

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This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Kuan-Ming Chiu Shu-Hsun Chu Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Chiu, K.-M. Articles by Chu, S.-H. Search for Related Content PubMed PubMed Citation Articles by Chiu, K.-M. Articles by Chu, S.-H. Related Collections Coronary disease