Transitory cerebral microvascular blockade after cardiopulmonary bypass.

Dogs were submitted to cardiopulmonary bypass (CPB) carried out under conditions calculated to generate large numbers of microbubbles and microemboli. On the day following the procedure the dogs showed evidence of neurological damage including impaired consciousness and ataxia. These abnormalities largely cleared within a week. When the animals were sacrificed at intervals after the procedure, the cerebral microvasculature was demonstrated by injecting a suspension a lamp black into the carotid artery. This revealed that multiple filling defects were present in the microcirculation of the brain immmediately after CPB and for two days thereafter. However, by seven days the microvascular blockade had disappeared, and the vascular blockade had disappeared, and the vascular pattern of the brain had returned to normal. Neuropathological findings were sparse and restricted to the cerebellum. This study suggests that the transient neurological syndromes that sometimes follow cardiopulmonary bypass for heart surgery may be due to a transient microvascular blockade, perhaps by microbubbles and microparticles.