Symptomatic air embolism after computed tomography-guided four-hook needle localization of a pulmonary nodule: a case description

Introduction

Preoperative pulmonary marking under computed tomography (CT) guidance can be used to identify the location of small pulmonary nodules before video-assisted thoracoscopic surgery (1). Various auxiliary devices, such as hook wires, microcoils, lipiodol, methylene blue, and radionuclides, are employed for this procedure (2,3). The four-hook needle is a new localization device for pulmonary nodules and is as safe, convenient, and effective as is the commonly used hookwire (4). However, preoperative pulmonary marking is an invasive procedure, with the principal complications being pneumothorax and pulmonary hemorrhage (1,4). Systemic air embolism is a rare complication, and to our knowledge, only a few cases attributable to hookwire localization have been reported (5-9). Here, we report a case of systemic air embolism during pulmonary marking with a four-hook needle under CT guidance. The clinical features and treatment experiences are also described.

Case presentation

A 62-year-old man visited our hospital for the treatment of a ground-glass pulmonary nodule with an 8-mm diameter in the left upper lobe. The nodule was found incidentally and increased in size, with the patient exhibiting no relevant symptoms during the health checkup. As the nodule was too small to be palpated by an examining finger, we planned video-assisted thoracic surgery (VATS) wedge resection after localization of the nodule with the four-hook needle under CT guidance. The results of the routine laboratory tests revealed no abnormalities.

On the day of the operation, the patient was placed in the supine position on the CT table, and an initial thin-section CT image (Figure 1A) was obtained to determine the puncture point and direction while cardiac and respiratory parameters were monitored. After injection of a local anesthetic, a four-hook anchor claw with a tricolored suture was delivered via a coaxial needle (Guiding-Marker System; SensCure Biotechnology, Ningbo, China) during a single inspiratory breath hold. Movement and coughing were not observed during the procedure. An immediate CT scan was performed to confirm the proper location of the marker and check for any possible complications (Figure 1B). The patient did not complain of any discomfort, but the CT images revealed air-fluid levels in the aortic root (Figure 2A). He was shifted to the right lateral decubitus and Trendelenburg position, and 100% oxygen was administered via a face mask. The second chest and brain CT indicated massive air in the left ventricle, right coronary artery, left internal mammary artery, and left external carotid artery (Figure 2B,2C), indicating a diagnosis of arterial air embolism. One minute later, the patient experienced facial numbness accompanied by a lack of consciousness and a transient decrease in blood pressure and blood oxygen saturation, which completely recovered in less than 2 minutes without the use of norepinephrine. Disappearance of the air in the aortic root, right coronary artery, left internal mammary artery, and left external carotid artery was confirmed on the postlocalization CT images; moreover, the volume of air in the left ventricle was significantly reduced (Figure 2D). We monitored the patient for an additional 30 minutes, and there were no unusual changes on the electrocardiogram or any deficit in the neurologic examination. VATS wedge resection was performed for the lesion 16 hours later and pathologically diagnosed as lung adenocarcinoma. The patient was discharged 6 days after the surgery with no complications.

Figure 1 A 62-year-old female with a ground-glass nodule in the left upper lobe underwent CT-guided localization with a four-hook needle. (A) The lesion (arrow) observed on an axial CT image. (B) Postlocalization CT showed the location of the released anchor claw (arrow). The bronchial passage was visible within the pulmonary nodule, and small pulmonary veins could be seen in front of the nodule (arrowhead in A). CT, computed tomography.

Figure 2 The chest and brain CT revealed systemic air embolism after four-hook needle localization. (A) An air-fluid level was observed at the aortic root (arrow). (B) A mass of air was visible in the left ventricle (arrow), the right coronary artery (arrowhead), and the left internal mammary artery (red arrow). (C) Air embolism was also detected in the left external carotid artery (arrow). (D) Forty minutes after the initial brain CT scan, a second CT scan showed the disappearance of air in the aortic root, right coronary artery, left internal mammary artery, and left external carotid artery; moreover, the volume of air in the left ventricle was significantly reduced (arrow). CT, computed tomography.

All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Helsinki Declaration (as revised in 2013). Written informed consent was obtained from the patient for publication of this article and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Discussion

The four-hook needle is a novel device used for localizing lung nodules (10). It consists of a coaxial needle, an anchor claw, a suture, a pusher, and a protection tube and is essentially similar to the hook-wire. There is no significant difference in the incidence of pneumothorax and pulmonary hemorrhage between the two methods. However, the four-hook needle has a flexible tricolored suture that exerts a slight pulling force on the anchor claw, preventing it from falling off or shifting. Additionally, the operator can lift the tricolored suture to expose the operative field and raise the lung tissue in the focal area due to the strong hooking action of the anchor claw on the surrounding lung tissue (11). Furthermore, the posterior connection of the four-hook needle consists of a soft line instead of the hard wire of the hookwire. This allows it to be released into the chest cavity during localization procedures, reducing stimulation to the pleural wall and significantly alleviating the patient’s chest pain (4). Systemic air embolism is an extremely rare complication of preoperative pulmonary marking and can result in serious morbidity, even death. Thus far, most of the reported cases were associated with lung biopsy (12), and only a few cases occurred after preoperative pulmonary marking with hookwire (5-9,13). To our knowledge, this is the first report of systemic air embolism occurring in four-hook needle localization.

Air embolism can occur during a marking procedure when gas enters the systemic circulation from the pulmonary vein (6). However, it can be difficult to confirm this communication through images alone. Due to the rarity of systemic air embolism after lung localization procedures, most of the reports in the literature are based on single cases or small case numbers. However, systematic that have been conducted to investigate the occurrence and risk factors of systemic air embolism after lung biopsy. Some potential risk factors include intraoperative movement, coughing during the puncture procedure, the number of needle insertions, and a relative position of the lesion above the level of the left atrium (14,15). There are three possible ways for air to enter the systemic circulation through the pulmonary vein during a given medical procedure. First, the air may enter the pulmonary vein directly through the puncture needle, but this is relatively rare because it is unlikely that a large amount of air can be sucked into the vein through the needle (13). Second, the gas may enter the pulmonary vein from the pulmonary artery via pulmonary microcirculation or pulmonary arteriovenous fistulas, but this rarely occurs during lung puncture (16). The third and most likely way is that the pulmonary vein communicates with the bronchus, bronchiole, or airspace along the puncture channel (6,9). In our case, the needle appears to have damaged the pulmonary vein and the adjacent lung tissue, leading to a short-term connection between the vein and either the alveolar or bronchial airways. As a result, a significant amount of air rapidly entered the pulmonary venous circulation. Upon reviewing the CT images of this case, we observed that the bronchial passage was visible within the pulmonary nodule, and small pulmonary veins were visible in the front of the nodule (Figure 1A). Additionally, the patient’s deep inspiration might have decreased the pulmonary vein pressure and elevated airway pressure.

There are no known basic preventive measures for systemic air embolism in lung localization procedures. However, preoperative planning should involve identifying and avoiding visible pulmonary veins and bronchi during the puncture path. Additionally, preventing a positive gradient between alveolar pressure and pulmonary venous pressure may help in reducing the occurrence of systemic air embolism. The following are some recommendations: First, the number of needle insertions should be reduced to lower the probability of damage to the pulmonary veins. If repositioning is necessary, the needle should be moved slowly. Second, adequate subcutaneous anesthesia should be ensured to prevent body movements or coughing that could cause injury around the needle tract. Third, an end-expiratory breath hold is advised to help lower alveolar pressure (17). Finally, if appropriate, adopting an ipsilateral-dependent position can reduce the incidence of systemic air embolism (14).

Systemic air embolism can cause neurological deficits or even death. However, some patients may not show any symptoms even if systemic air is detected in the heart through CT images (18). It is crucial to carry out chest and head CT scans after completion of the pulmonary marking. Hyperbaric oxygen therapy is now regarded as the first-line and definitive treatment; it provides oxygen at a pressure higher than atmospheric pressure and a concentration of 100%, enabling a considerably high level of systemic hyperoxia. This degree of hyperoxia allows nitrogen to transfer from inside the bubbles with a significant gradient, which in turn reduces the size of the bubbles and the degree of obstruction in the arterial blood flow. Furthermore, by increasing the pressure, the volume of the bubbles decreases according to Boyle’s Law (the volume of a gas is inversely proportional to its pressure at a constant temperature), and the concentration of dissolved oxygen in the plasma increases, thereby enhancing oxygen supply to ischemic tissues (19). Early (4–6 hours) hyperbaric oxygen therapy can improve the prognosis of patients with cerebral vascular air embolism, as its efficacy tends to diminish over time. High-flow 100%-oxygen therapy plays a similar role in treatment by increasing the partial pressure of oxygen in the blood and decreasing the partial pressure of nitrogen. This results in nitrogen diffusing from inside the bubbles into the blood, thereby reducing the size of the bubbles and accelerating the absorption of air (8,19). High-flow 100%-oxygen therapy should be administered immediately, as examination rooms are typically equipped with the necessary facilities. In our case, once systemic air embolism was diagnosed, the patient was immediately administered 100% oxygen with a mask under close monitoring. Subsequently, the symptoms disappeared completely, and so hyperbaric oxygen therapy was not performed. The right lateral decubitus and Trendelenburg position are recommended, as this theoretically traps bubbles in the upper part of the left ventricle, preventing them from entering the left ventricular outflow tract. However, this may be controversial since air bubbles may not be sufficiently buoyant to counteract the flow of arterial blood (7). In our case, gas entered the external carotid artery, and we believe that the Trendelenburg and the right lateral decubitus positions are beneficial in preventing gas from entering the intracranial artery. Due to the uncertainty of its mechanism and its potential to be fatal or cause neurological deficits, being familiar with the management of systemic air embolism is critical. The flowchart in Figure 3 summarizes the management of this case.

Figure 3 Flowchart depicting the management of systemic air embolism after the lung localization procedure.

We encountered a case of systemic air embolism caused by preoperative pulmonary marking with a four-hook needle. The patient was promptly placed in Trendelenburg and right lateral positions and administered 100% oxygen, which resolved the symptoms without any sequelae. As pulmonary marking with the four-hook needle is becoming increasingly common, it is critical to reassess the associated risks. Clinicians should enhance their knowledge of systemic air embolism and be aware that early detection and treatment of this complication can mitigate its effects and reduce mortality rates.

Acknowledgments

Funding: This work was funded by the Zhejiang Provincial Health Department (No. 2022KY486).

Footnote

Conflict of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://qims.amegroups.com/article/view/10.21037/qims-24-949/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 and/or national research committee(s) and with the Helsinki Declaration (as revised in 2013). Written informed consent was obtained from the patient for 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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