Percutaneous transthoracic needle biopsy (PTNB) is an important procedure for diagnosis of pulmonary lesions. PTNB is minimally invasive procedure but sometimes complications can occur. The most common complications include pneumothorax, hemorrhage, and hemoptysis. Air embolism is very rare complication, but it can be a life-threatening if not managed appropriately. So knowledge of air embolism entity may minimize morbidity and mortality after PTNB.
Computed tomography (CT)-guided percutaneous transthoracic needle biopsy (PTNB) is a common and indispensable procedure for pulmonary lesions. It is minimal risk and discomfort to the patient. The most common complications include pneumothorax (27%–49%), hemorrhage (11%), and hemoptysis (7%) [1–3]. Air embolism is a very rare complication (0.02%–0.4%) but potentially life-threatening complication [4,5]. In this paper, we report a case of systemic air embolism occurred after PTNB that was confirmed on pulmonary CT.
A 50-year-old man had been admitted to hospital with Wernicke’s encephalopathy. He had history of pulmonary tuberculosis for 1 year without treatment, and chest radiography showed multiple ill-defined small nodules and consolidations in both lungs. The patient was further evaluated with contrast-enhanced chest CT that showed a 3-cm sized irregular thick walled cavitary mass with peripheral centrilobular nodules at the superior segment of the right lower lobe (RLL) and multiple ill-defined nodular opacity and consolidations in both lungs, and cavitary mass showed wall enhancement and accompanied enlarged lymph nodes was not present (Fig. 1).
On the suspicion of pulmonary tuberculosis, patient isolation and medical treatment was started. After 2 weeks, follow-up chest CT showed improvement of nodular opacities and consolidations in both lungs but still remained cavitary mass in the RLL, and sputum acid-fast bacillus stain and culture was negative.
For excluding malignancy of cavitary mass, PTNB of mass was attempted. The patient was placed in prone position and the lesion was localized using CT with a single inspiratory breath-hold. A coaxial 18-gauge automatic biopsy device (ACECUT; TSK Laboratory, Tochigi, Japan) was used. Two times of core biopsies were performed with same breath-holding at localization.
At second section of biopsy, shortly after biopsy gun was firing, the patient could take a deep breathe with severe cough. Immediately, biopsy needle was removed and post biopsy CT scan was obtained to assess the complications. CT scan showed linear air density in left inferior pulmonary vein adjacent to biopsy lesion and air in nondependent portion of descending aorta, pulmonary trunk, and left atrium (Fig. 2).
While he was being moved on stretcher for treatment, he abruptly showed short of breathe and cyanosis and then respiratory arrest occurred. Resuscitative efforts were started immediately but cardiac arrest occurred 1 hour later.
PTNB is a frequently performed procedure that is accepted as a standard method for the diagnosis of pulmonary nodule, mass, and inflammatory disease. PTNB is a safe and minimally invasive procedure, but some complications can occur after procedure. The most frequent complications is pneumothorax (27%–49%), hemorrhage (11%), and hemoptysis (7%). Most of these complications are easily managed and mortalities are low [1–3].
Air embolism, the entry of gas into the vascular structures, may result from invasive procedures, trauma, and barotrauma of lung . Systemic air embolism after PTNB is a very rare complication that may result in myocardial infarction, stroke, cardiac arrest, or death. The incidence of air embolism is 0.02%–0.4%, and the majority of these patients are symptomatic [4,5].
Rapid diagnosis of air embolism is essential for proper management. In an emergency situation, it is important to familiar with clinical symptoms. Any onset of shortness of breath, substernal pain, arrhythmia, neurological deficit, seizure, or cardiac arrest should make the operator suspicious for air embolism. A pulmonary and/or brain CT scan provides a definitive diagnosis by showing air bubbles in the heart and vessels .
Although there are no established guidelines for immediate management of air embolism, a few reasonable steps have been suggested. Hyperbaric oxygen therapy (HBOT) is the most effective treatment for air embolism. Oxygen is highly soluble within blood, whereas nitrogen is not. Thus, increasing the proportion of oxygen within the vessel will increase the rate of reabsorption. In addition, HBOT decreases hypoxemia in ischemic tissue and maximizes the ability of that tissue to survive and recover. Although HBOT is a relatively safe procedure, there are some contraindications. The absolute contraindication is an untreated pneumothorax because it may progress to a tension pneumothorax. The relative contraindications include chronic obstructive pulmonary disease, claustrophobia, Eustachian tube dysfunction, upper respiratory infection, seizure, and the presence of a pacemaker . In the patient positioning, theoretically Trendelenburg position make the cerebral circulation relatively dependent, but Patel et al.  reported that air embolism affect the cerebral vasculature before symptom onset. Another positioning technique is right-lateral decubitus position, which make the left ventricular outflow tract nondependent, thus trapping air in the apex of the left ventricle. Despite the theoretical advantages of these positioning, supine positioning may still be preferable because supine position is much easier to manage in the setting of respiratory or cardiac arrest .
The mechanism of air embolism after PTNB remains unclear, but formation of a communication between an airway and a pulmonary vein is the assumed mechanism of air embolization. Normal average pulmonary venous pressure is +10 mm Hg and pulmonary airway pressure during respiration can vary from −5 to > +20 mm Hg, which can lead disrupted airway-venous interface by pressure gradient. It can be more easily when airway pressure exceeds the pulmonary venous pressure, such as coughing, valsalva maneuver, and positive pressure ventilation. Other factors such as chronic obstructive pulmonary disease and air trapping may have also contributed to increase airway pressure. An alternate mechanism for air embolization is communication between the atmosphere and a pulmonary vein in case of stylet-biopsy needle used. While the needle stylet is open to the air, if the patient breathes, air embolization may occur .
In this case, it is possible that the coughing episodes contributed to the entry of air into the pulmonary veins by increasing air pressure in the pulmonary airways. There are some case reports showing air embolism in the heart and cerebral arteries [7,8,10], but no reports described air in the pulmonary vein. This case shows air in the pulmonary vein adjacent to biopsy portion, and which may provide clues that air embolism after PTNB is result of broncho-pulmonary-venous fistula formation.
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