Unexpected Air on Trauma Computed Tomography: Iatrogenic Intravascular Air After Peripheral Venous Cannulation.

Small amounts of intravascular air are occasionally detected on computed tomography (CT), most commonly after intravenous contrast administration. However, intravascular air may also be introduced during routine peripheral venous access before contrast injection. In the trauma setting, this finding may be misinterpreted as traumatic mediastinal or thoracic pathology, particularly in elderly patients. We report the case of an 89-year-old man who presented after a ground-level fall with mild head trauma. A 20-gauge peripheral intravenous catheter was inserted into the left median cubital vein before imaging. Non-contrast head CT demonstrated traumatic subarachnoid hemorrhage. Cervical CT incidentally revealed a small focus of air within the left subclavian vein, and subsequent chest CT demonstrated a new small focus of air within the superior vena cava. Follow-up imaging showed complete disappearance of the air. No pneumomediastinum, pneumothorax, airway injury, esophageal abnormality, or other thoracic traumatic pathology was identified. The patient remained asymptomatic throughout the clinical course and developed no signs of symptomatic air embolism. The anatomical distribution, temporal migration, and spontaneous disappearance of the air suggested a benign iatrogenic origin related to peripheral venous access rather than traumatic pathology or contrast administration. This case highlights the importance of recognizing incidental central venous air as a potential imaging pitfall in elderly trauma patients in order to avoid unnecessary diagnostic workup and overinterpretation.