Anesth Analg 2003;96:683-685
© 2003 International Anesthesia Research Society
CARDIOVASCULAR ANESTHESIA
Carbon Dioxide Embolism Diagnosed by Transesophageal Echocardiography During Endoscopic Vein Harvesting for Coronary Artery Bypass Grafting
Su-Man Lin, MD,
Wen-Kuei Chang, MD,
Cheng-Ming Tsao, MD,
Ching-Huei Ou, MD,
Kwok-Hon Chan, MD, and
Shen-Kou Tsai, MD
Department of Anesthesiology, Taipei-Veterans General Hospital, National Yang-Ming University and National Taiwan University, China
Address correspondence and reprint requests to Shen-kou Tsai, MD, PhD, Department of Anesthesiology, Taipei-Veterans General Hospital, National Taiwan University and Yang-Ming University, 210, Sec 2, Shih-pai Rd., Taipei, Taiwan 11217, China. Address e-mail to sktsai{at}vghtpe.gov.tw
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Abstract
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IMPLICATIONS: We describe a case of massive carbon dioxide embolism with an abrupt decrease in arterial blood pressure and continuous mixed venous oxygen saturation during endoscopic vein harvesting that was immediately diagnosed by intraoperative transesophageal echocardiography.
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Introduction
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Endoscopic vein harvesting (EVH) is a procedure analogous to a laparoscopic procedure, where carbon dioxide (CO2) is insufflated to obtain vein grafts from lower extremities for coronary artery bypass grafting (CABG) (1–3). This technique seems to be safe because there are no adverse hemodynamic consequences or systemic CO2 absorption during EVH (4). Although CO2 embolism suspected by profound hypotension and decreased ETCO2 during laparoscopy is rare, this complication can be fatal (4–8). We are unaware of reports about CO2 embolism during EVH in lower extremity diagnosed by intraoperative transesophageal echocardiography (TEE). We describe a case of massive CO2 embolism with an abrupt decrease in blood pressure and continuous mixed venous oxygen saturation (SvO2) during EVH that was immediately diagnosed by intraoperative TEE. The possible mechanism and successful management are discussed.
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Case Report
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A 64-yr-old woman with 3-vessel coronary artery disease was scheduled for CABG. The patient had no previous surgery, and her medical history was significant for hypertension and coronary artery disease treated medically for 10 yr. The patient was given lorazepam 2 mg orally on the evening before surgery and morphine 0.1 mg/kg IM plus midazolam 0.05 mg/kg IM upon arriving in the operating room. Intraoperative monitors included five-lead electrocardiography, radial artery catheter, pulmonary artery (PA) catheter with venous saturation and continuous cardiac output monitoring, pulse oximetry (SpO2), capnography (ETCO2), nasopharyngeal, and rectal temperature. Data were continuously recorded using a multichannel recorder; SvO2 data were obtained from the PA catheter with the Baxter Vigilance® monitor (Baxter Healthcare Corp, Round Lake, IL). Continuous TEE was performed after the induction of anesthesia and tracheal intubation using a 5-Hz adult multiplane color flow Doppler transducer (Vingmed Ultrasound; GE, Horten, Norway). The systemic plane TEE images were obtained based on Society of Cardiovascular Anesthesiologists-ASA guidelines (9).
The patient received fentanyl 15 µg/kg IV in divided doses for the induction of anesthesia in addition to propofol 1.5 mg/kg IV until loss of consciousness, followed by propofol 5 mg · kg-1 · h-1 IV. Muscle relaxation was achieved with pancuronium 0.1 mg/kg IV and antibiotic prophylaxis provided with cephazolin 2 g IV.
Anesthesia was maintained with desflurane (6%–8% end-tidal concentration) in 100% O2. Mechanical ventilation was adjusted to maintain ETCO2 between 30–40 mm Hg. Hemodynamic and respiratory variables remained stable during simultaneous EVH and median sternotomy. During the endoscopic part of the operation, a 5-mm port (Stryker Endoscopy, Santa Clara, CA) was inserted through the superficial fascia of the medial aspect of the left calf. Blunt dissection was used to expose the superficial compartment of the calf. CO2 at 3 L/min with 15-mm Hg insufflation pressure (Endomed Electronic Insufflator, Endomed Inc, Phoenix, AR) was then used to develop a potential space. Approximately 10 min after beginning the endoscopic dissection, the blood pressure abruptly decreased from 130/80 mm Hg to 30/16 mm Hg, and the SpO2 decreased from 100% to 85%. PA pressure increased from 36/10 mm Hg to 60/35 mm Hg. Heart rate and ETCO2 remained unchanged at that time, but the ETCO2 decreased from 35 to 28 mm Hg 1 min later. At the same time, TEE demonstrated acute gas emboli entering the right atrium (Fig. 1). Simultaneously, the SvO2 abruptly decreased from 80% to <50%, although the cardiac output decreased by only 15% (Fig. 2). Based on these findings, the diagnosis of CO2 emboli was considered. The insufflation of CO2 was discontinued. The patient was placed in a head-down position. At the time of the event, the median sternotomy had already been performed, so the surgeon was able to place a right atrial vent and aspirate a large amount of air. Internal cardiac massage was initiated, and ephedrine 25 mg was administered IV. The arterial blood pressure returned to normal within 1 min. Repeated TEE examination showed good left ventricular contractility and no more air emboli inside the heart and PA. Surgery was continued and completed in 4 h. The patient fully awoke without neurological sequelae after surgery.
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Figure 1. The mid-esophageal four-chamber view of transesophageal echocardiography (TEE) demonstrating a massive gas embolism entered into right atrium (RA; arrow) with bulging the interatrial septum into the left atrium (LA).
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Figure 2. Continuous mixed venous oxygen saturation (SvO2) trend tracing. SvO2 abruptly decreased to less than 50% when transesophageal echocardiography (TEE) was shown in Figure 1. The arrow indicates onset of CO2 embolism. CO, cardiac output.
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Discussion
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Our case report confirms the value of TEE compared with the highly variable effect of ETCO2 during CO2 embolism in a patient with EVH. In this case, early diagnosis of CO2 embolism during EVH for CABG was immediately made by the TEE image and SvO2 changes. Early treatment was instituted with sternotomy, direct venting of gas from the right atrium, internal cardiac massage, and placing the patient in head-down position. When CO2 embolism was suspected, CO2 insufflation was immediately discontinued. The successful resuscitation included aspiration of gas bubbles from the right atrial cannula, inotropic drugs, and positioning of the patient in left decubitus or head-down position. Cardiopulmonary bypass using femoral access or extracorporeal membrane oxygenation may be required if the patient does not respond to initial resuscitation efforts (10).
CO2 embolism is a well known complication of laparoscopy. A sudden decrease in ETCO2 and profound hypotension were noted because of decreased pulmonary flow from the vapor lock caused by the CO2 bubbles resulting in decreased cardiac output and increased dead space. Although a decrease in ETCO2 is a standard method for detection of gas emboli during laparoscopic procedures (8,11), an increase in ETCO2 was observed in two cases of suspected CO2 embolism (10,11). ETCO2monitoring to detect CO2 embolism was systematically studied in a pig model that showed TEE to be the "gold standard" monitor with earlier detection of gas emboli than ETCO2 change (12). The delayed change of ETCO2 during CO2 embolism is because of dissolved CO2 because CO2 is highly soluble in blood and rapidly absorbed from the bloodstream. The average time to the acute change (increase or decrease >3 mm Hg) of the ETCO2 nadir was approximately 45.1 seconds in pigs (12). In our case, the TEE image demonstrated acute massive gas emboli of CO2 entering the right atrium when the ETCO2 was still unchanged until one minute later when it decreased from 35 to 28 mm Hg. The mean quantity of CO2 required to elicit a positive response for ETCO2 in pigs was 0.66 mL/kg but only 0.26 mL/kg in the TEE (12). There is also a time lag between TEE image and the ETCO2 change during acute CO2 embolism. Therefore, TEE is the most sensitive method to detect CO2 embolism compared with ETCO2 and mean PA pressure changes (12). In addition, TEE also offers the advantage of detecting paradoxical embolism caused by a patent foramen ovale.
Profound hypotension will occur in CO2 embolism not only because of the mechanical obstruction of venous and pulmonary circulation by CO2 bubbles, but also because of the direct vasodilatory effect of CO2 to decrease systemic vascular resistance. In our case, besides the TEE finding, the initial presentation of presumptive CO2 embolism was a dramatic decrease in SvO2, which was likely a result of decreased cardiac output, hypovolemia, hypoxemia, and anemia (13). The large amount of CO2 from insufflation into the vein that was perforated in the leg because of blunt dissection of the posterior compartment of the calf enabled entry of CO2 into the venous circulation to the heart during EVH and produced dramatic hemodynamic changes including sudden decreases in blood pressure, cardiac output, and SvO2. The continuous cardiac output measurement showed only a 15% decrease in our case. The abrupt decrease in SvO2 with a less dramatic decrease in cardiac output suggests that the SvO2 may have been artifactually decreased by the presence of CO2 bubbles in the PA. Therefore, the abrupt decrease in SvO2 may also suggest the presence of CO2 embolism clinically if TEE is not available.
In summary, venous CO2 embolism during EVH is rare but can be a potentially fatal occurrence. TEE and continuous SvO2 monitoring can provide early diagnosis. Early diagnosis and effective treatment with air removed from the right atrium provided complete recovery from CO2 embolism without neurologic sequelae. The use of EVH is increasing, and awareness of the potential for CO2 embolism may reduce the sequelae of this complication.
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References
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Accepted for publication November 15, 2002.
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Abstract
Introduction
