Nitrous oxide misuse: a clue not to be missed in young patients with venous thromboembolism.

A 27-year-old man presented with altered mental status and unilateral right lower limb swelling. Brain imaging and cerebrospinal fluid analysis were unremarkable. He reported history of nitrous oxide misuse after he recovered from his delirium. The diagnosis of drug induced psychosis was made. The right lower limb swelling was found to be due to extensive deep vein thrombosis. In another case, a 21-year-old woman presented with headache, vomiting and dipoplia. Brain imaging showed extensive cerebral venous sinus thrombosis. She also misused nitrous oxide. Both cases had low-normal vitamin B12 and elevated methylmalonic acid, consistent with nitrous oxide misuse. The woman was found to have elevated homocysteine because of functional vitamin B12 deficiency. Homocysteine was not measured in the man. Raised homocysteine is associated with increased thrombosis risk. Fourteen cases of nitrous oxide misuse associated arterial and venous thrombosis have been reported. These two cases highlighted the importance of inquiring about recreational drug use in young patients who presented with apparently unprovoked venous thromboembolism.

Extended-duration rivaroxaban thromboprophylaxis in acutely ill medical patients: MAGELLAN study protocol.

Patients with acute medical illnesses are at increased risk of venous thromboembolism (VTE), a significant cause of morbidity and mortality. Thromboprophylaxis is recommended in these patients but questions remain regarding the optimal duration of therapy. The aim of this study is to determine whether oral rivaroxaban is non-inferior to standard-duration (approximately 10 days) subcutaneous (s.c.) enoxaparin for the prevention of VTE in acutely ill medical patients, and whether extended-duration (approximately 5 weeks) rivaroxaban is superior to standard-duration enoxaparin. Patients aged 40 years or older and hospitalized for various acute medical illnesses with risk factors for VTE randomly receive either s.c. enoxaparin 40 mg once daily (od) for 10 ± 4 days or oral rivaroxaban 10 mg od for 35 ± 4 days. The primary efficacy outcomes are the composite of asymptomatic proximal deep vein thrombosis (DVT), symptomatic DVT, symptomatic non-fatal pulmonary embolism (PE), and VTE-related death up to day 10 + 4 and up to day 35 + 4. The primary safety outcome is the composite of treatment-emergent major bleeding and clinically relevant non-major bleeding. As of July 2010, 8,101 patients from 52 countries have been randomized. These patients have a broad range of medical conditions: approximately one-third were diagnosed with acute heart failure, just under one-third were diagnosed with acute infectious disease, and just under one-quarter were diagnosed with acute respiratory insufficiency. MAGELLAN will determine the efficacy, safety, and pharmacological profile of oral rivaroxaban for the prevention of VTE in a diverse population of medically ill patients and the potential of extended-duration therapy to reduce incidence of VTE.