Saddle Pulmonary Embolism Secondary to Nitrous Oxide Use: A Case Report and Literature Review

Saddle pulmonary embolism (SPE) is a rare but life-threatening presentation of venous thromboembolism (VTE). Recreational nitrous oxide (N₂O) use has become increasingly common and can cause a functional vitamin B12 deficiency that leads to elevated homocysteine levels and a prothrombotic state. We describe a 31-year-old man with ongoing N₂O abuse who presented with dyspnea and calf pain and was found to have a saddle pulmonary embolus and right leg deep vein thrombosis. Laboratory studies showed low vitamin B12 and high homocysteine levels. He was treated with anticoagulation and discharged in stable condition. This case highlights the need to consider N₂O exposure in patients with unexplained thrombosis, particularly in younger adults.