Pneumomediastinum and subcutaneous emphysema: complication of cocaine use

Abstract

Pneumomediastinum is more frequent in young men and usually presents in association with subcutaneous emphysema. It can occur in case of oesophageal or chest trauma, be iatrogenic or develop spontaneously, in case of emesis, coughing or forceful straining. Use of illicit drugs, such as cocaine, has been associated with multiple respiratory complications, including pneumomediastinum and subcutaneous emphysema. The pathogenesis of subcutaneous emphysema and pneumomediastinum after cocaine inhalation is not completely known, but it is thought that the physical manoeuvers used to increase its absorption and effect may lead to alveolar rupture, resulting in air escaping into the mediastinum and fascial planes of the neck and chest. Chest X-ray is usually diagnostic, but CT can be used as complementary study, allowing evaluation of adjacent structures. A case of pneumomediastinum and subcutaneous emphysema after cocaine inhalation in an otherwise healthy man is presented.

Background

Subcutaneous emphysema and pneumomediastinum are usually caused by oesophageal or chest trauma. Less frequently, these conditions may have an iatrogenic aetiology, as a consequence of assisted ventilation and medical or dental procedures. They may also occur spontaneously, as in cases of emesis, coughing, or forceful straining, such as in childbirth or strenuous exercise. Often no triggering event is identified.^{1 2}

The use of illicit drugs, such as cocaine, amphetamines and their derivatives, has been associated with pneumomediastinum and subcutaneous emphysema. The substance most commonly associated with these complications is crack cocaine.^{3 4}

Spontaneous pneumomediastinum is rare, with an incidence estimated between 0.001% and 0.01% in adult patients. It is more frequent in young men and usually presents in association with subcutaneous emphysema. Chest pain and dyspnoea are common symptoms.¹

Chest X-ray is usually diagnostic, but CT can also be used to demonstrate pneumomediastinum and subcutaneous emphysema, allowing the evaluation of adjacent structures.^{5 6}

Case presentation

An otherwise healthy, 22-year-old man presented to the emergency department with a sudden onset of chest and neck pain that worsened with respiratory movements. He denied history of recent trauma, episodes of coughing or vomiting, and vigorous physical exertion. He admitted occasional use of cocaine, but denied the use of any other drugs or illicit substance. Patient referred cocaine inhalation the night before and use of Müller’s and Valsalva manoeuvers, in order to maximise its absorption and effect.

On physical examination, the patient was alert, oriented and cooperative, with no obvious respiratory compromise. He had a blood pressure of 120/73 mm Hg, a pulse rate of 80 beats/min and a respiratory rate of 15 breaths/min. His oxygen saturation was 99% and he had no fever.

Subcutaneous crepitations were palpable in the anteroinferior aspect of the neck. Cardiac and pulmonary auscultations were unremarkable, as was the rest of the physical examination.

Arterial blood gases on room air were normal. Results from baseline blood tests showed increased lactate dehydrogenase (246 mg/dL) and total creatine kinase (1058 mg/dL), suggesting rhabdomyolysis. ECG showed normal sinus rhythm with no arrhythmias or segmental changes.

Chest radiograph suggested pneumomediastinum, with no pneumothorax associated (figure 1). CT revealed pneumomediastinum (figure 2) and extensive subcutaneous emphysema extending from the mastoid tip to the clavicles; no convincing pneumothorax was identified, and lung parenchyma was normal (figure 3).

Figure 1.

X-ray images in posteroanterior (A) and lateral (B) views show gas outlining mediastinal structures (blue arrow), more obviously seen anterior to the ascending aorta, in lateral view (yellow arrow).

Figure 2.

Axial non-enhanced CT image shows air around mediastinal structures. Technique: axial CT, 200 mA, 120 kV; 3 mm slice thickness.

Figure 3.

Axial non-enhanced CT image shows gas in the subcutaneous tissues of the neck. Technique: axial CT, 200 mA, 120 kV; 3 mm slice thickness.

Outcome and follow-up

The patient was managed conservatively and required oxygen therapy for 2 days. He was kept under clinical surveillance for 5 days and was fully recovered when discharged. Two months later, he had a re-evaluation consultation and was asymptomatic. He was referred to a drug abuse treatment programme.

Discussion

Subcutaneous emphysema associated with pneumomediastinum is a rare condition, also known as Hamman’s syndrome.

It is more frequent in young men, and chest pain and dyspnoea are typical clinical symptoms.^{1 2} This condition may occur in cases of oesophageal or chest trauma. It may also have an iatrogenic aetiology due to assisted ventilation and medical or dental procedures. In cases of emesis, coughing or forceful straining, such as in childbirth or strenuous exercise, it may also occur spontaneously. Often no triggering event is identified.¹

An uncommon cause of pneumomediastinum is cocaine use, particularly if smoked.³

In frequent consumers, cocaine may have direct toxic effects on lung parenchyma, causing alveolar damage and haemorrhage, which increase the likelihood of alveolar rupture.⁴

The pathogenesis of subcutaneous emphysema and pneumomediastinum after cocaine inhalation is still not completely known, but it is thought to result from the development of a pressure gradient between the alveoli and vasculature surrounding them. In order to maximise the absorption and effect of cocaine, users deliberately produce Müller’s manoeuver, which causes negative pressure during forced inspiration with a closed mouth and nose, and Valsalva manoeuver, creating a positive pressure gradient caused by breath holding. These manoeuvres increase intrathoracic pressure, leading to an increased diffusion of the drug across the alveolar membrane into the bloodstream. This may lead to alveolar rupture, resulting in air escaping into the mediastinum and fascial planes of the neck and chest.⁵

Pneumomediastinum is diagnosed by chest X-ray when lucent streaks or bubbles of gas outline mediastinal structures. Gas may cause lucent areas around the aorta, its branches, pulmonary arteries, trachea and proximal bronchi, sternal insertions of the diaphragm, thymus and the brachiocephalic veins. It often extends into the neck or the chest wall. Sometimes, it is more obvious on a lateral view.

There are some signs that suggest the presence of pneumomediastinum in chest X-ray:

• Pneumopericardium, which corresponds to substernal gas anterior to the heart, may be the only radiographical finding, and its detection requires a lateral view.

• Continuous diaphragm sign, which represents mediastinal gas outlining the superior surface of the diaphragm and separating it from the heart. On lateral view, gas between the diaphragm and the pericardium makes the superior margin of the left hemidiaphragm visible, one that is normally obscured by the heart (left hemidiaphragm sign).

• Naclerio’s V sign, in which gas outlines the lateral margin of the descending aorta and extends laterally between the parietal pleura and the medial left hemidiaphragm.

• Ring-around-the-artery sign refers to gas surrounding the mediastinal portion of the right pulmonary artery.

• There may be an apical extension of the pneumomediastinum, creating a lucent cap bounded by a pleural line. This may be easily mistaken for pneumothorax. However, pneumothorax is usually mobile within the pleural space, whereas extrapleural gas is confined within tissue planes. In the apical extension of pneumomediastinum, the pleural line forms an irregular arc and is almost always bilateral. On the other hand, pneumothorax is usually unilateral and is not accompanied by pneumomediastinum.⁶

CT can also be used to demonstrate pneumomediastinum and subcutaneous emphysema. Its main importance is the detection of secondary causes as it allows the evaluation of adjacent structures.

After the diagnostic approach has ruled out underlying aetiologies, including airway compression, pneumopericardium, oesophageal and tracheobronchial rupture, pneumomediastinum treatment is directed towards symptom relief. Spontaneous emphysema and pneumomediastinum are, in most cases, benign and self-limited conditions.⁷

A rare sequelae is the accumulation of a significant amount of air in the mediastinum, in most cases due to missed oesophageal/pulmonary trauma, which may lead to an important air leak, causing tamponade and airway compression, which may require surgical evacuation.

Other complications of pneumomediastinum include extensive subcutaneous emphysema or pneumothorax. If air dissects the retropharyngeal and retroperitoneal spaces, it can cause discomfort and respiratory compromise. In rare situations, air dissects between the mediastinum and the upper spine, causing pneumorrhachis.

Patient’s perspective.

When I was first observed in the emergency department, I denied prior cocaine use since I did not want others, mainly my family, to know about my addiction. Only when I was told that, after full diagnosis workup, no evident cause was found for the symptoms that I had experienced did I realise that my addiction could be its cause and that it was important for me to come clean with the physicians, so that they could treat me properly.

I did not experience these symptoms before and was not aware that cocaine use could cause this type of condition. When I was on my way to the hospital, I felt truly sick and thought that I might be dying. Fortunately, that was not the case and I was fully recovered after some days in the hospital.

This event was a wakeup call for me and made me realise that I was making myself ill by using this type of substance, so after I was discharged, I initiated a drug abuse treatment programme, which is still in course.

I really hope to overcome my addiction and to live a healthier life from now on.

Learning points.

• Pneumomediastinum is an important differential diagnosis of chest pain in young people.

• Cocaine inhalation is a rare cause of pneumomediastinum and subcutaneous emphysema.

• When evaluating a patient with pneumomediastinum, physicians should always obtain a history of substance use in order to prevent recurrent pneumomediastinum and to provide a better quality of care.

• Diagnosis can be made by chest X-ray, but CT plays an important role to rule out underlying etiologies, since it allows adjacent structure evaluation.

• Non-traumatic or iatrogenic pneumomediastinum and subcutaneous emphysema are benign conditions and are managed conservatively in most cases.