C43-36 Cocaine-induced Spontaneous Mediastinum: A Rare Manifestation of the Macklin Effect

Spontaneous pneumomediastinum (SPM) is a rare condition defined by the presence of free air within the mediastinum without prior trauma or surgical intervention. The most widely accepted mechanism is the Macklin effect, where alveolar rupture due to elevated intra-alveolar pressure allows air to dissect along peribronchovascular sheaths into the mediastinum. Although SPM is typically associated with asthma, vigorous exertion, or vomiting, illicit drug use—particularly cocaine—has been recognized as an uncommon precipitant. Cocaine’s sympathomimetic properties can lead to increased intrathoracic pressures, bronchospasm, and barotrauma, predisposing to alveolar rupture. We present a rare case of cocaine-associated SPM in a young male, emphasizing the role of the Macklin effect in its pathophysiology. A 19-year-old male with a history of ADHD and substance use disorder presented to the emergency department with sudden-onset severe chest pain. He reported intranasal cocaine use approximately two hours prior. On arrival, he was ill-appearing, diaphoretic, flushed, with bilateral mydriasis. Vital signs revealed heart rate 141 bpm, blood pressure 156/112 mmHg, respiratory rate 27 breaths/min, and oxygen saturation 94% on 2 L nasal cannula. EKG showed sinus tachycardia without ischemic changes. Laboratory results demonstrated normal CBC and cardiac biomarkers, with mildly elevated creatinine. Urine toxicology was positive for cocaine and cannabis. Chest radiograph revealed right supraclavicular subcutaneous emphysema, and CT chest without contrast confirmed a moderate-to-large pneumomediastinum with extensive subcutaneous emphysema. CT esophagram suggested possible distal esophageal injury; however, esophagogastroduodenoscopy revealed intact mucosa. Transthoracic echocardiogram showed normal function (EF 53%) with no wall motion abnormalities. The patient was admitted to the ICU for observation. Thoracic surgery recommended conservative management with supplemental oxygen and clinical monitoring. His symptoms improved, and he was discharged to a sober living facility. Cocaine-induced SPM is an uncommon but clinically significant presentation. The underlying mechanism is best explained by the Macklin effect, where alveolar rupture from increased intra-alveolar pressure during forceful inhalation or Valsalva-like maneuvers results in air migration into the mediastinum. Cocaine use increases this risk through barotrauma, bronchoconstriction, and catecholamine-mediated tachypnea. Most cases are self-limiting and managed conservatively; however, differentiation from life-threatening etiologies such as esophageal rupture or tracheobronchial injury is essential. This case highlights a rare thoracic complication of cocaine insufflation—spontaneous pneumomediastinum mediated by the Macklin effect. Awareness of this phenomenon is crucial for clinicians evaluating acute chest pain in young adults with recent cocaine use. Prompt imaging, exclusion of secondary causes, and multidisciplinary collaboration allow accurate diagnosis and safe, timely management.