Volume 20, Issue 6 , Pages 709-711, June 2009
Systemic Air Embolism following CT-guided Lung Biopsy
Article Outline
Clinical Case
OUR institutional review board does not require approval for submission of retrospective reports such as this. A 39-year-old female patient with long-term history of heavy smoking presented to the emergency room with dyspnea and underwent a computed tomography (CT) scan of the chest as part of her evaluation. A left upper-lobe peripheral lesion was detected, along with hilar lymph nodes, with possible encasement of the left pulmonary artery by the hilar nodes (not shown). She was referred to the interventional radiology unit for imaging-guided biopsy of the peripheral lung lesion.
The biopsy was performed with CT guidance (Lightspeed 16 detector; GE Healthcare, Milwaukee, Wisconsin). She was positioned supine, and the biopsy was performed with moderate sedation with midazolam and fentanyl, monitored by a nurse. After marking the skin site, which was targeted after a scan using a surface grid, the skin surface was prepared and draped with povidone iodine. Lidocaine was used for local anesthesia.
A 20-gauge, 15-cm coaxial needle kit with a 2-cm throw (Cook, Bloomington, Indiana) was chosen. The 19-gauge needle guide was positioned in the periphery of the lesion, and CT of the region of the biopsy was repeated (Fig 1). The needle tip was repositioned medially, and a core biopsy sample was obtained. (CT fluoroscopy capability is not available on the scanner used.) The stylet of the needle was reinserted, and the sample was transferred from the needle to the slide for touch preparation and staining by the cytopathology technician present at the time. The patient coughed twice at this time. Two more core biopsy samples were obtained. The samples were examined by the cytopathologist and declared adequate for diagnosis. The needle guide was removed, and hemostasis was achieved with local pressure. The needle guide hub was occluded with the thumb during transition between the stylet and the biopsy needle. Also, patient respiration was suspended during needle insertion, repositioning, and biopsy.
Figure 1.
CT scan at time of biopsy with needle guide tip positioned near the periphery of the lesion. The needle tip was angled medially and a biopsy sample obtained.
As per our routine, a CT scan of the entire chest was obtained, with 10-mm-thick sections, to delineate the extent of pneumothorax and hemorrhage arising as a result of the biopsy. A small pneumothorax was seen, along with small intraparenchymal hemorrhage and air within the left ventricle (Fig 2). The patient became agitated and developed mild tachypnea at this time. Her pulse rate increased to 100 beats per minute from a baseline of 65 beats per minute. She also described chest pain and a tingling/burning sensation over her face and upper arms. One hundred percent oxygen was immediately administered via facemask, and she was maintained in supine position and prevented from sitting up. The institutional rapid response team was summoned and the patient was transferred to the intensive care unit, where an emergent echocardiogram was obtained and the cardiology unit was consulted. The echocardiogram demonstrated complete resolution of air within the left ventricle. Her symptoms resolved completely without any other treatment over a period of 20 minutes. A repeat chest CT scan 2 hours later (Fig 3) showed complete absence of air within the vascular structures of the chest. No clinical sequelae resulted. Histopathologic examination of the core biopsy samples showed granulomatous disease.
Figure 2.
Postprocedural CT scan with 10-mm-thick sections demonstrates pneumothorax and intraventricular air.
Figure 3.
CT image obtained two hours after Figure 2 after 100% oxygen therapy and continuous monitoring in the intensive care unit shows complete resolution of symptoms.
What Happened and Why Did It Happen?
The patient developed air embolism. She coughed twice after the first pass of the core biopsy needle. It is likely that transient communication between the pulmonary vein and the biopsy tract may have been present at that time, resulting in alveolar or bronchial air passing into the pulmonary vein, as a result of the increased intrapulmonary pressure induced by the coughing. The air subsequently passed into the left atrium and then into the left ventricle. The subsequent clinical events arose as a result of antegrade propulsion of the air bubbles into the major branches of the aorta. As the patient remained supine throughout the episode and oxygen therapy was initiated as soon as the complication was recognized, it is possible that the air did not pass antegradely from the left ventricle as large bubbles, but dissipated as small bubbles, causing the clinical events described.
Discussion
Pneumothorax and hemorrhage are commonly encountered complications of transthoracic/percutaneous procedures including aspiration and biopsy (1). Air embolism is a known, rare complication of thoracic needle aspiration and biopsy. Its incidence has been noted to be low (2, 3, 4), ranging from 0.02% to 0.4%. Reports in the literature have described fatal outcomes (5) as well as nonfatal and even asymptomatic outcomes (2, 6, 7) following development of the complication. Symptoms and sequelae arise primarily as a result of the obstructive effects of air within the coronary and cerebral circulation, inducing myocardial and cerebral ischemia.
The incidence of the complication may not be as low as previously described (2). It is more likely to be detected with CT imaging than with fluoroscopy. Air embolism occurring during fluoroscopy-guided biopsy is less likely to be detected, and would have been suspected only if symptoms developed that were clearly differentiable from the effects of biopsy-induced parenchymal hemorrhage and pneumothorax. Imaging during CT fluoroscopy-guided procedures may not detect air embolism in asymptomatic patients because of the focal imaging performed at the site of biopsy, which may exclude air-containing cardiovascular structures from the field of view.
Different mechanisms for development of the complication have been described (2, 7). These include (i) air passage from the exterior through the guide needle during removal/reinsertion of the stylet or insertion of the cutting needle for biopsy, especially if intrapulmonary pressure decreases as a result of patient inspiration; or (ii) development of a transient communication between a bronchus and a pulmonary vein as a result of the needle tip positioned within the vein, especially if intrapulmonary pressure increases, as would occur during coughing.
The likely mechanism in this patient was the development of a transient communication between a pulmonary vein and a bronchus, with passage of air into the vein during coughing. Mechanisms to minimize the likelihood of the complication include (i) passage of the needle guide and cutting needles and performance of the biopsy with suspended respiration; and (ii) covering the hub of the guiding needle with the thumb when a stylet or coaxial needle is not occluding the guiding needle.
Recognition of the complication is important. Prompt scanning of the chest should be performed if the patient coughs multiple times with the needle guide in place.
A CT scan of the entire chest—not just the region of biopsy—obtained at the end of the procedure provides baseline information about the size of pneumothorax. This case suggests that it is also likely to increase the likelihood of detection of air embolism. As most scans for guiding needle placement are obtained with 2.5-mm or 5-mm slices, a chest CT study with 10-mm sections minimizes the radiation while facilitating rapid assessment of the chest for complications. This has been our routine, and likely enabled recognition of the air embolism in this patient simultaneously with development of her symptoms.
Prompt treatment for systemic air embolism includes maintaining the patient in supine position while initiating 100% oxygen therapy with a mask (2, 8). Trendelenburg position and right lateral decubitus position have also been suggested to trap the air in a nondependent position, to reduce the risk of antegrade passage into the coronary and cerebral circulation. Of course, if the complication were to occur with the patient in a prone position, repositioning the patient in a supine position may actually facilitate antegrade passage of the air, and the prone position should be maintained.
Rapid initiation of 100% oxygen facilitates increase in the rate of diffusion of the nitrogen within the embolized air into the surrounding blood, reduction in the size of the bubbles, and increased rate of resorption of the air as a result of the increase in surface area relative to air volume. It is our opinion that all patients should be administered 100% oxygen from the beginning. This could possibly increase the oxygen tension of the blood from the beginning, eliminating the delay in initiation of oxygen therapy resulting from a delayed diagnosis, and the period required for the beneficial effect of oxygenation. Hyperbaric oxygen therapy is indicated as the treatment for the air embolism (7), especially into the coronary and cerebral circulation.
CT scanning of the brain may also be performed while the patient is on the CT table to assess for intracranial air.
In summary, although air embolism is a potentially fatal complication of lung biopsy, its incidence is low. Also, coughing as a result of the hemorrhage induced by the biopsy itself could result in the complication, and is therefore inherently unavoidable, even if operator error is completely eliminated. Prompt recognition of the complication may improve outcomes, as treatment with 100% oxygen can be rapidly initiated. Alternatively, all patients undergoing biopsy could be given oxygen throughout the procedure.
References
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- Nonfatal systemic air embolism complicating percutaneous CT-guided transthoracic needle biopsy: four cases from a single institution. Chest. 2007;132:684–690
- . Percutaneous lung biopsies: a survey of UK practice based on 5444 biopsies. Br J Radiol. 2002;75:731–735
- CT-guided needle biopsy of lung lesions: a survey of severe complication based on 9783 biopsies in Japan. Eur J Radiol. 2006;59:60–64
- . Systemic air embolism after percutaneous transthoracic needle biopsy of the lung. Emerg Radiol. 2008;15:353–356
- Air embolism detected during computed tomography fluoroscopically guided transthoracic needle biopsy. Cardiovasc Intervent Radiol. 2008;31:219–221
- . Massive systemic air embolism treated with hyperbaric oxygen therapy following CT-guided transthoracic needle biopsy of a pulmonary nodule. J Vasc Interv Radiol. 2006;17:1355–1358
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The author has not identified any conflicts of interest.
Sameer Bhatia is a shareholder in J&J (unrelated to this article).
PII: S1051-0443(09)00212-7
doi:10.1016/j.jvir.2009.03.006
© 2009 SIR. Published by Elsevier Inc. All rights reserved.
Volume 20, Issue 6 , Pages 709-711, June 2009
