Aortic air embolus following pulmonary tumor radiofrequency ablation.

Aortic air embolism following a computed tomography (CT) guided percutaneous transthoracic procedure is a rare occurrence, but one that can have dire consequences. We present a case of a 48-year old female diagnosed with aortic air embolism during percutaneous radiofrequency ablation of a pulmonary mass. A large amount of intra-aortic air can be seen on the CT images just before the patient suffered acute cardiac arrest. Although this is a rare occurrence, recognition and management of this complication is important for physicians who perform any percutaneous transthoracic procedures.

Case report

History

A 48-year-old man with history of colorectal carcinoma presents with multiple lung lesions, one which was recently biopsied and proven to be colorectal carcinoma metastasis. The patient was scheduled for ablation of multiple metastases in the left lung.

Procedure

The patient was placed in the prone position. Initial scans of the left lung were performed to localize the 2 largest lesions, which lie in the superior and posterior aspect of the left lower lobe. A 17-ga needle 10 cm in length with a 3 cm in ablation cool-tip electrode was advanced into the lung (Fig. 1). The electrode was placed initially approximately 5 mm from the medial aspect of the lesion. A second attempt was made, and the electrode was reintroduced within the tumor lesion (Figs. 2 and 3). Immediately after the scan was completed, the anesthesiologist noted blood in the endotracheal tube, at which point the patient was found to be in cardiopulmonary arrest. The patient was then placed in supine position, and the cardiopulmonary resuscitation was started. During the resuscitation process, it was noted that the computed tomography (CT) scan showed air within the descending thoracic aorta and intercostal arteries which were consistent with massive air emboli (Fig. 4). The findings were promptly relayed to the code team, and the patient was placed immediately in a Trendelenburg position. The patient regained a heart rhythm, and he was immediately transferred to a hospital with hyperbaric chamber.

Fig. 1

Radiofrequency probe is positioned adjacent to the liver mass. Large amount of intraluminal air is seen within the aorta.

Fig. 2

A portion of the radiofrequency probe is again seen near the lung mass with some minor intraparanchymal pulmonary hemorrhage. Large amount of intraluminal air within the aorta.

Fig. 3

Large amount of intraluminal air within the aorta with a small amount of air seen extending into a right lumbar artery.

Fig. 4

Large amount of intraluminal air within the aorta with air extending into a right lumbar artery. Minimal intraparanchymal pulmonary hemorrhage near the radiofrequency probe and lung mass.

Discussion

CT-guided needle biopsy of the lung is a useful procedure commonly performed to diagnose pulmonary lesions. The most common side effects of this procedure are pneumothorax (35%), but other serious complications such as air emboli and hemothorax can occur [1]. Air emboli can be classified into 2 types venous and arterial. There are multiple etiologies of arterial emboli including the direct introduction of air into arteries by surgery or trauma. Pulmonary barotrauma results in alveolar rupture and is associated with positive pressure ventilation. Alveolar rupture can result in pneumothorax, air cysts, or even air embolism as is seen in our case. Hiraki et al. [2] found the incidence of systemic air embolism after a CT-guided transthoracic needle biopsy to be approximately 0.4%. Anzueto et al. [3] determined that barotrauma is more closely associated with a patient's underlying medical condition than to the ventilator parameters.

The organ systems most affected by air emboli are the cardiovascular, respiratory, and central nervous system. The cardiac effects include ST wave segment changes or right ventricular strain patterns [4]. Arterial air embolization into the coronary arteries can induce a specific drum-like or “millwheel” murmur as well [5]. Pulmonary manifestations include dyspnea, gasp reflex due to hypoxemia, and pulmonary edema.

At last, neurologic symptoms can be seen and may be due to cardiovascular collapse resulting in cerebral hypoperfusion or due to the embolism itself [4]. Intraoperative arterial air emboli should be suspected when there is unexplained hypotension or a sudden drop in end-tidal CO2 (ETCO2) [4]. The decrease in ETCO2 correlates to volume of the air embolus. Pulse oximetry, which measures arterial oxygen saturation, is not able to detect an embolus and ETCO2 [5].

Precordial Doppler ultrasound is sensitive in detecting intracardiac air and can be used intraoperatively. Echocardiograph is even more sensitive, which can detect embolisms as small as 5 μme. The treatment of an air embolism begins with preventing further air entry and providing hemodynamic support. Covering the surgical field with saline soaked dressing and tilting the table may also be beneficial [4]. The position is also crucial. The left lateral decubitus and the supine positions are the best for venous and arterial emboli, respectively. Hyperbaric chambers are the mainstay of treatment. Administration of 100% oxygen can decrease the bubble size, and it also increases the gradient for the diffusion of nitrogen from the bubbles [5]. Timing is extremely important, with early hyperbaric oxygen showing significantly better outcomes in patients with air emboli, more so for venous emboli than arterial. In one study, venous embolisms treated with hyperbaric oxygen within 6 hours resulted in recovery 74% of the time versus 44% of the time for those treated after 6 hours. However, data on arterial emboli are not as clear. That same study found recovery in 33% of those treated within 6 hours, versus 36% treated after 6 hours [6]. Regardless, hyperbaric oxygen treatment continues to be the mainstay of treatment. This is also the treatment initiated in our patient.