BACKGROUND: Neurological injury after cerebral air embolism may be due to thromboinflammatory responses at sites of air-injured endothelium. Because heparin inhibits multiple thromboinflammatory processes. we hypothesized that heparin would decrease neurological impairment after cerebral air embolism. METHODS: Anesthetized rabbits received either heparin (n=14) or saline (n=13), 5 minutes before air injection (150 microliter/kg). Heparin was given as a 200 IU/kg bolus and followed by a constant infusion of 75 IU/kg/h for 2 hours. Equal volumes of salines were given to saline group. Two hours later, anesthesia was discontinued. Rabbits were neurologically evaluated 24 hours after air embolism. RESULTS: Heparin group had significantly less neurological impairment at 24 hours (34 14) than saline controls (52 8) (p=0.0013). CONCLUSIONS: When given prophylactically, heparin decreases neurological impairment caused by severe cerebral arterial air embolism.