warfarin and Altitude-Sickness

Topics: Aged; Altitude Sickness; Anticoagulants; Cholesterol, HDL; Clinical Trials as Topic; Enoxaparin; Female; Humans; Male; Neoplasms; Popliteal Vein; Pulmonary Embolism; Risk Factors; Sex Factors; Ultrasonography; Venous Thromboembolism; Warfarin; Young Adult

A 35-year-old healthy male with no history of any past medical illness developed severe headache, vomiting and drowsiness while at high altitude (4,572 m) in the eastern Himalayan ranges. He was evacuated to a tertiary-care hospital where he was diagnosed to have cerebral sinus venous thrombosis (CSVT) on magnetic resonance imaging, with deep vein thrombosis (DVT) of his right popliteo-femoral vein on color Doppler study. Investigation for thrombophilia revealed protein S (PS) deficiency in this patient. Family screening revealed low levels of PS in two elder brothers. One brother had a history of 'stroke in young' at the age of 20 years with the other being asymptomatic. This established the hereditary nature of PS deficiency. We are not aware of any previously published report on hereditary PS deficiency combined with CSVT and DVT occurring at high altitude. However, 1 case of protein C deficiency with CSVT has been reported previously.

Topics: Acclimatization; Adult; Altitude Sickness; Anticoagulants; Anticonvulsants; Cerebral Infarction; Family Health; Hemiplegia; Humans; Male; Military Personnel; Papilledema; Protein S Deficiency; Radiography; Recurrence; Sinus Thrombosis, Intracranial; Thrombophilia; Thrombophlebitis; Ultrasonography; Vomiting; Warfarin

Approximately 476,000 people on warfarin therapy visit a resort at altitude (>2400 m) annually in Colorado. Clinicians practicing at altitude have expressed concern that ascent to altitude adversely affects coagulation in patients taking warfarin in both high altitude residents and visitors. We sought to determine the effect of ascent to and descent from altitude on coagulation in warfarin patients, as assessed by the international normalized ratio (INR). A retrospective medical chart review was conducted on all warfarin patients treated between August 1998 and October 2003 at a cardiology clinic in which travel to and from altitude was documented in association with each INR measurement in high altitude residents. Of the 1139 INR measurements in 49 patients, 143 were associated with changes in altitude (in 32 of 49 patients). The odds of an INR measurement being below the prescribed range were 2.7 times (95% CI: 1.2-5.8) higher among warfarin patients with recent ascent to altitude, 2.1 times (95% CI: 1.4-3.2) higher among warfarin patients with atrial fibrillation, and 5.6 (95% CI: 2.3-13.7) times higher among warfarin patients with both atrial fibrillation and recent ascent to altitude. Increasing altitude is a risk factor for subtherapeutic INR in warfarin patients and this risk is doubled in atrial fibrillation patients.

Topics: Altitude; Altitude Sickness; Anticoagulants; Atrial Fibrillation; Blood Coagulation; Colorado; Confidence Intervals; Contraindications; Female; Fibrinolytic Agents; Humans; Male; Odds Ratio; Retrospective Studies; Stroke; Travel; Warfarin