The critical role of transesophageal echocardiography in diagnosing carbon dioxide gas embolism: a case description and lessons learned

Introduction

Carbon dioxide (CO₂) embolism is a well-documented but uncommon complication during laparoscopic surgery, and its incidence may be underreported (1). It arises primarily from direct intravascular insufflation or the entry of gas through injured venous channels, particularly during pneumoperitoneum establishment (2). Delayed diagnosis and intervention can lead to right heart failure, cardiovascular collapse, or paradoxical embolism causing cerebral injury (3). We report a case in which intraoperative transesophageal echocardiography (TEE) played a decisive role in confirming CO₂ embolism and guiding successful resuscitation. This report aims to reinforce the need for heightened vigilance and advanced monitoring in laparoscopic surgery, especially in procedures involving extensive dissection near major vessels.

Case presentation

All the procedures in this study were performed in accordance with the ethical standards of the institutional national research committee, and with the Declaration of Helsinki and its subsequent amendments. Written informed consent was obtained from the patient for the publication of this article and the accompanying images. A copy of the written consent form is available for review by the editorial office of this journal.

The patient was a 67-year-old male (172 cm, 62 kg) who presented with a pancreatic tumor and was scheduled for laparoscopic pancreatoduodenectomy; he was otherwise in good health. General anesthesia was induced and maintained accorded to standard practice, with invasive arterial and central venous monitoring. Approximately two minutes after CO₂ insufflation (12 mmHg, 15 L/min), the patient developed sudden hypotension [blood pressure (BP) 43–63/22–43 mmHg] accompanied by a rapid decrease in end-tidal CO₂ (EtCO₂) from 35 to 18 mmHg (Figure 1). Initial blood gas analysis showed Partial arterial oxygen pressure (PaO₂) 89.9 mmHg [fraction of inspired oxygen (FiO₂) 40%], partial pressure of carbon dioxide (PaCO₂) in artery 44 mmHg, potassium ion (K) 3.9 mmol/L, hemoglobin (HB) 108 g/L, glucose 4.5 mmol/L, lactate 1.4 mmol/L, and buffuer excess (BE) −1.8. Subsequent analysis revealed PaO₂ 372 mmHg (FiO₂ 100%), PaCO₂ 61 mmHg, K 3.4 mmol/L, HB 123 g/L, glucose 8.5 mmol/L, lactate 1.5 mmol/L, and BE −4.6.

Figure 1 Norepinephrine (20 µg) was administered without response, but epinephrine (200 µg) rapidly restored blood pressure to 177/116 mmHg with tachycardia.

TEE was immediately performed, revealing abundant gas bubbles in the right heart, septal flattening indicating right ventricular pressure overload (Figure 2), and gas in the liver parenchyma, suggesting mesenteric venous insufflation (Figure 3). The patient was placed in the head-down left-lateral decubitus position, given 100% oxygen, and administered 200 µg of epinephrine intravenously, followed by a continuous infusion at 0.05–0.1 µg/kg/min. BP was subsequently maintained within the range of 110–160/50–70 mmHg. Cerebral protection measures included head cooling with an ice cap and close monitoring of pupillary changes. Arterial blood gas analysis was performed to guide acid-base and metabolic management. Mannitol and corticosteroids were administered to mitigate intracranial hypertension and systemic inflammatory response. Over 2 hours, repeat TEE confirmed bubble resolution (Figures 4,5). Post-resuscitation, lung ultrasound showed B-lines suggestive of pulmonary edema, necessitating continued mechanical ventilation (Figure 6). The patient was extubated after 18 hours in the intensive care unit and underwent successful surgery 1 week later.

Figure 2 Findings on mid-esophageal four-chamber view and transgastric short-axis view. Arrows: numerous gas bubbles (carbon dioxide) are present in the right atrium and ventricle. The arial septum is displaced toward the left atrium. Signs of right heart pressure overload: elevated right heart pressure causes a right-to-left shift, with bulging of the interatrial and interventricular septum into the left chambers. Septal dyskinesia is a hallmark sign of acute cor pulmonale resulting from a massive gas embolism.

Figure 3 Findings on the transgastric inferior vena cava view. Arrows: multiple, discrete gas accumulations are observed in the liver parenchyma, and gas bubbles are seen passing through the inferior vena cava. Proposed pathophysiological mechanism: the gas likely originated from an inadvertent injury to a mesenteric vein during the establishment of the pneumoperitoneum. Explained systemic migration route: the entrapped gas traveled via the portal vein to the liver. While some gas was trapped locally, the remainder entered the systemic circulation through two potential pathways: (I) passing through the hepatic sinusoids into the hepatic veins and then to the inferior vena cava. (II) In the presence of portal hypertension, bypassing the liver via portosystemic collateral circulation to reach the inferior vena cava.

Figure 4 Findings on mid-esophageal four-chamber view and transgastric short-axis view. Arrows: the previously noted gas bubbles in the cardiac chambers have almost completely resolved; the interatrial and interventricular septum have returned to their normal convex curvature, bulging toward the right.

Figure 5 The transgastric inferior vena cava view reveals that the gas accumulations in the liver parenchyma have almost disappeared (arrow).

Figure 6 Findings on the chest ultrasound. Arrows: multiple B-lines are present in the lungs. Pathophysiological implication: this sonographic pattern is consistent with pulmonary interstitial edema, reflecting pulmonary complications impaired gas exchange.

Discussion

This case represents the first documented use of transesophageal ultrasound to capture the entire progression of a CO₂ embolism in real time during surgery. The imaging traces the path of the gas as it passes through the liver, enters the inferior vena cava, progresses into the right heart, subsequently migrates to the left heart, and is finally absorbed, completing the full embolic sequence. Studies have reported that the risk of gas embolism is higher in laparoscopic procedures than in open surgery (2). The gold standard for diagnosis is TEE, which can detect air bubbles in the right ventricle (4,5).

Perioperative circulatory failure primarily comprises four types: hypovolemic, distributive, cardiogenic, and obstructive shock. The circulatory failure described in this case corresponds to obstructive shock. On TEE, the manifestations of these different types of shock vary. Hypovolemic shock is mainly characterized by a reduction in both diastolic and systolic cardiac volumes. Distributive shock is mainly characterized by high output and low resistance. Cardiogenic shock is mainly characterized by dysfunction of heart contraction and relaxation. Obstructive shock is mainly characterized by the expansion and failure of the right heart system, and, as in our case, may present with intravascular foreign bodies such as gas and thrombus. A study using TEE detected air bubbles via in 11 of 16 patients undergoing laparoscopic cholecystectomy, suggesting that the actual incidence of CO₂ embolism may be significantly higher than previously recognized (4).

At the onset of circulatory failure, obstruction of the pulmonary circulation reduces gas exchange between the pulmonary blood and alveolar air, resulting in a decrease in EtCO₂, while arterial CO₂ levels remain relatively unchanged. However, because pulmonary arterial blood cannot undergo oxygenation due to the embolism, the oxygenation index (PaO₂/FiO₂) is only around 225. Following adjustment of ventilator parameters and corresponding treatment, CO₂ absorption into the circulation increases, leading to a rise in PaCO₂. As pulmonary circulation obstruction gradually resolves, the oxygenation index also improves. The sudden onset of hypotension and decreased EtCO₂ are classic signs of pulmonary obstruction; however, TEE is 50 to 100 times more sensitive than EtCO₂ monitoring for detecting venous air embolism. In this case, TEE provided definitive visual evidence of intracardiac and hepatic gas, enabling immediate targeted treatment. The presence of gas in the left heart without an evident patent foramen ovale suggests transpulmonary passage due to large embolic load, highlighting the potential for severe systemic complications (6). Fortunately, CO₂ has a solubility approximately five times greater than that of air in the blood, which contributes to a more favorable prognosis in affected patients (7).

The pathophysiology involves gas accumulation in the right heart leading to outflow obstruction, acute cor pulmonale, and reduced left ventricular preload (8,9). Additionally, bubbles obstructing the pulmonary circulation create ventilation-perfusion mismatch (areas with ventilation but no perfusion), leading to dead space ventilation and hypoxemia. Inflammatory activation may further exacerbate pulmonary injury, causing endothelial damage and increased capillary permeability, as observed in our patient’s delayed respiratory compromise. More seriously, platelet activation and aggregation may initiate disseminated intravascular coagulation, transforming a simple gas embolism into a more severe systemic insult (10).

Management priorities for CO₂ embolism include stopping insufflation, repositioning the patient, administering 100% oxygen, and providing hemodynamic support (11,12). Aspiration via central venous may be attempted, and hyperbaric oxygen therapy should be considered if neurological symptoms develop (1,13). Advanced life support protocols should be initiated in the event of cardiac arrest. This case reinforces that high-risk laparoscopic procedures may benefit from routine TEE monitoring to facilitate the early diagnosis of gas embolism. From the surgeon’s perspective, when initiating pneumoperitoneum, the insufflation needle should be moved with a gentle, sweeping motion rather than held stationary to prevent rapid, localized gas delivery.

Conclusions

Although CO₂ embolism is rare, it requires rapid recognition and structured management. TEE is invaluable for real-time diagnosis and for guiding therapy. Anesthesia and surgical teams should maintain a high index of suspicion during pneumoperitoneum, especially in oncologic laparoscopies involving vascular dissection. TEE can generally be performed safely and comfortably only in patients under general anesthesia. Moreover, the physician performing the procedure must possess solid theoretical knowledge and substantial clinical experience to ensure timely and accurate diagnosis. In general, incorporating TEE in selected cases can significantly improve patient safety.

Acknowledgments

None.

Footnote

Funding: The work was supported by the Chongqing Science and Technology Joint Project (No. MSXM20202676).

Conflicts of Interest: Both authors have completed the ICMJE uniform disclosure form (available at https://qims.amegroups.com/article/view/10.21037/qims-2025-1-2732/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. All procedures performed in this study were in accordance with the ethical standards of the institutional national research committee and with the Declaration of Helsinki and its subsequent amendments. Written informed consent was obtained from the patient for the publication of this article and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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