Cyanosis without hypoxemia: Extensive infusaport-associated central venous thrombosis presenting as superior vena cava syndrome

ABSTRACT: Superior vena cava (SVC) syndrome is a potentially life-threatening condition caused by impaired venous return from the head, neck, and upper extremities that can present with prominent facial cyanosis. This finding may be misleading, as it does not necessarily reflect impaired arterial oxygenation. We report a 68-year-old woman with metastatic colorectal cancer receiving chemotherapy through a right internal jugular implantable venous access port who presented with acute dyspnea, weakness, and progressive facial and perioral cyanosis 2 days after completing FOLFOX (A chemotherapy regimen consisting of folinic acid (leucovorin), fluorouracil (5-FU), and oxaliplatin. It is commonly used to treat colorectal cancer) chemotherapy. Given recent chemotherapy exposure, her presentation initially raised concern for hypersensitivity or anaphylactoid reaction. Despite the patient's striking cyanotic appearance, arterial blood gas analysis demonstrated normal oxygenation, whereas venous blood gas revealed marked desaturation with elevated deoxyhemoglobin. Imaging subsequently identified extensive catheter-associated thrombosis involving the bilateral internal jugular, subclavian, and brachiocephalic veins with complete occlusion of the SVC and extension into the right atrium. The patient was treated with systemic anticoagulation and urgent endovascular thrombectomy with the removal of the indwelling port, resulting in rapid clinical improvement. This case emphasizes that in SVC obstruction, visible cyanosis may reflect localized venous congestion rather than systemic hypoxemia. Recognition of discordant arterial and venous oxygenation can help avoid misdiagnosis and facilitate timely intervention, particularly in oncology patients with central venous devices.