Heparin Reduces Neurological Impairment After Cerebral Arterial Air Embolism in the Rabbit

Abstract

Background and Purpose 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 To first establish a dose of air that would cause unequivocal neurological injury, anesthetized New Zealand White rabbits received either 0, 50, 100, or 150 μL/kg of air into the internal carotid artery (n=5 in each group). One hour later, anesthesia was discontinued. Animals were neurologically evaluated at 24 hours with the use of a scale ranging from 0 (normal) to 97 (coma) points. In a subsequent experiment, anesthetized rabbits received either heparin (n=17) or saline (n=15) 5 minutes before air injection (150 μL/kg). Heparin was given as a 200-IU/kg bolus and followed by a constant infusion of 75 IU · kg −1 · h −1 for 2 hours. Equal volumes of saline were given to control rabbits. Two hours later, anesthesia was discontinued. Animals were neurologically evaluated 24 hours after air embolism. Results There was a monotonic relationship between dose of air and severity of neurological impairment at 24 hours ( P =1.1×10 −7 ). Animals receiving 150 μL/kg of air were unequivocally injured (score, 60±16). In the second experiment, heparin animals had significantly less neurological impairment at 24 hours (34±14) than saline controls (52±8) ( P =.0013). Conclusions When given prophylactically, heparin decreases neurological impairment caused by severe cerebral arterial air embolism.