Applied Radiology

Dr. Mangi is a Resident in the Department of Surgery and Dr. Mullins is a Resident in the Department of Radiology at the Massachusetts General Hospital. Both are also Officers at Harvard Medical School. Dr. McLoud is staff radiologist at the Massachusetts General Hospital and Professor of Radiology at Harvard Medical School, Boston, MA.

The inhalation of alkaloid cocaine (free-basing, mixing the solid cocaine salt with a solvent to render it "smokeable") is a recent phenomenon that surged in popularity among recreational drug users in the early 1980s because of its relatively low cost and easy availability. The earliest report of pulmonary complications related to free-basing cocaine was in 1981. ¹ Several additional reports of pneumothorax, pneumomediastinum, and pneumoperitoneum were documented in the 1980s. ^2-8 Retropharyngeal emphysema has also been described in association with cocaine free-basing. ⁹ There have been only two case reports in the past 9 years, however, which may be due to decreased use of the substance. ^10-12

In 1999, the authors evaluated two patients in the Emergency Department (ED) of Massachusetts General Hospital with cocaine-related pneumomediastinum. Both were young males, who had recently used free-based cocaine. They presented several hours thereafter with subcutaneous emphysema, pneumomediastinum, and leukocytosis. The purpose of this report is to re-emphasize the clinical presentation, evaluation, and management of this entity.

Patients and methods

Two patients presented to the ED and were subsequently admitted to the General Surgical and Medical Services for observation. The patients were interviewed directly by one of the authors (surgery housestaff), and the radiological and medical records were reviewed by two of the authors (radiology and surgery housestaff). All authors reviewed radiographic images.

Patient number one

A previously healthy 24-year-old man developed sudden pain in the back of his neck followed by violent coughing after inhaling free-based cocaine. He subsequently noted right facial and neck swelling accompanied by mild substernal chest discomfort, aggravated by coughing and deep breathing. Following 8 hours of sleep, he awoke with extensive swelling over his entire face and anterior chest wall. He initially presented to a community hospital and then transferred to the ED of our institution.

History revealed that he was otherwise healthy, did not take any medications and had no known allergies to drugs. On physical examination, he did not appear to be in any distress, his heart rate was 85 beats per minute (bpm) with a blood pressure of 160/100 mm Hg, and an blood oxygen saturation of 100% on room air. There was extensive subcutaneous air in his cheeks, neck, and upper chest. There was no cardiac rub on auscultation. The patient was able to swallow and no cough was observed. A white blood cell (WBC) count of 16,700 had been recorded at the outside facility and had increased to 18,200 upon presentation to our ED several hours later.

A chest radiograph revealed an extensive pneumomediastinum. A contrast-enhanced chest CT was performed, which excluded mediastinal fluid collection, pneumothorax, pleural effusion, and pneumoperitoneum (figure 1). Mediastinal air was noted to involve the deep fascial layers of the neck and chest, and surrounded the great vessels in
the mediastinum. Gastrografin swallow, followed by a barium swallow, did
not demonstrate any evidence of esophageal tear. The patient was admitted to the hospital and observed overnight. The subcutaneous air resolved, and his WBC count fell to 11,700 the following morning. He was then discharged.

Patient number two

A previously healthy 19-year-old man inhaled free-based cocaine, and while bearing down after inhaling the drug, felt a "pop" in his chest. He subsequently developed constant pleuritic and substernal chest pain. He proceeded to inhale cocaine once more, and then attempted to sleep. Upon awakening, his chest pain had worsened, and he sought medical attention at the ED. The patient's past medical history was remarkable for a congenital atrial septal defect. He did not take any prescription medications and had no known drug allergies.

On examination, the patient was in no apparent distress and was afebrile. The heart rate was 70 bpm, his blood pressure was 110/80 mm Hg, and the room air arterial blood oxygen saturation was 94%. A pericardial rub was noted on auscultation. There was no evidence of subcutaneous emphysema. His WBC count was 15,100.

A CT scan revealed a pneumomediastinum (figure 2A), which was confirmed on contrast-enhanced chest CT (figure 2B). Mediastinal air was noted to extend into the soft tissues of the neck. There was no pleural effusion, pneumothorax, or pneumoperitoneum. A gastrografin swallow was normal. An echocardiogram showed no evidence of cardiac tamponade physiology. The patient was admitted to the medical service. Prior to discharge, his WBC count fell to 6,700. The patient was followed with serial chest radiography that documented decrease in the pneumomediastinum. He was discharged with uneventful follow-up.

Discussion

Mediastinal emphysema may be an ominous finding, suggestive of either traumatic or spontaneous exertional ¹³ tracheobronchial or esophageal disruption. Extrapleural tears of the central major bronchi or distal trachea may occur after severe blunt trauma leading to a pneumomediastinum. Disruption of the esophagus either from instrumentation and balloon dilatation or following violent vomiting (Boerhaave's syndrome) also produces mediastinal emphysema. "Spontaneous" pneumomediastinum usually occurs following a sudden or prolonged increase in intrathoracic pressure (for example, Valsalva maneuver, status asthmaticus, and barotrauma from mechanical ventilation). The mechanism involves the rupture of alveoli within the lung parenchyma with subsequent dissection of air centrally along the bronchovascular bundles to the hila (interstitial emphysema) and rupture into the mediastinum. ^14,15 Mediastinal emphysema following crack cocaine inhalation is due to the latter mechanism.

Pneumomediastinum reported in the setting of free-based cocaine use is thought to develop as the patient performs a Valsalva maneuver in order to intensify the euphoria. The resultant increase in intrathoracic pressure is transmitted to the alveoli, which subsequently rupture, thereby resulting in pneumomediastinum. ^2-5 Mediastinal air then dissects into the planes of least resistance, resulting in cervical subcutaneous emphysema and, occasionally, pneumoperitoneum. Pneumothorax is unlikely as the air tracks centrally along the bronchovascular bundles. True pneumopericardium is uncommon and usually occurs as a result of iatrogenic instrumentation. Pseudopneumopericardium may be effected by adjacent air in the fascial planes of the mediastinum.

Patients who develop subcutaneous emphysema and pneumomediastinum in the setting of cocaine inhalation appear relatively well, despite the impressive amounts of air that are seen in the mediastinum and cervical soft tissues. Dyspnea is rare but intermittent pleuritic substernal chest discomfort and sudden onset of facial and neck swelling are very frequent. Moderate leukocytosis is common, likely secondary to the sympathomimetic effects of the cocaine. ⁵ There is usually no history of chest trauma or a history of antecedent vomiting, but a history of illicit drug use is often difficult to obtain. Physical examination reveals neck and upper torso subcutaneous emphysema without other findings. Patients are most often hemodynamically stable.

The presence of mediastinal air on standard chest radiographs in the absence of a history of other etiologic factors should raise suspicion of free-based cocaine use. Extensive subcutaneous air may obscure a pneumomediastinum and a CT may be confirmatory. Typically, thoracic CT is performed to evaluate mediastinal fluid collections or hematoma, possible tamponade of the heart or vessels, or small pneumothoraces not appreciated on the chest radiograph. In most cases, neck CT would not change management. Echocardiography is recommended if suspicion for tamponade physiology is raised by the clinical evaluation. In the right clinical setting, a gastrografin swallow may be necessary to exclude an esophageal tear in patients who may be intoxicated and whose history is therefore unreliable.

In the acute setting, the patient should be monitored with standard pulse oximetry, cardiac monitoring, and electrocardiogram. Management consists of close observation. The leukocytosis typically resolves quickly, and the pneumomediastinum and subcutaneous emphysema will also quickly resolve without residual effects. The rapid and early institution of drug counseling cannot be overemphasized. AR

References

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2. Salzman GA, Khan IF, Emory C: Pneumomediastinum after cocaine smoking. South Med J 80:1427-1429, 1987.

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15. Seaman ME: Barotrauma related to inhalational drug abuse. J Emerg Med 8:141-149, 1990.