Anterior ischemic optic neuropathy: a complication after extracorporal circulation.

INTRODUCTION: Anterior ischemic optic neuropathy (AION) describes a defect of the optic nerve leading to irreversible loss of vision in most cases. Pathophysiology of this disease is manifold and has been discussed as a posthemorrhagic complication as well as a neurological complication after operations with cardiopulmonary bypass.
METHODS: On the basis of two cases, the clinical picture is described in relation to the available literature. Preoperative risk factors, operative data, cardiopulmonary-bypass, postoperative complications and clinical symptoms are discussed together with ophthalmologic findings in order to elucidate the pathophysiology of this process.
RESULTS: There is no reliable and effective treatment of anterior ischemic optic neuropathy. Neither corticosteroids, osmotic diuretics, hemodilution nor surgical decompression of the optic nerve have proved successful. Hence, measures to avoid ischemic optic neuropathy have priority. The following risk factors were determined: History of glaucoma or other ophthalmological problems, prolonged cardiopulmonary bypass-time and myocardial ischemia, general oedema during cardiopulmonary bypass, excessive hemodilution with low hemoglobin and hematocrit, hypo- or hypertension, systemic hypothermia, need for vasoactive medication.
CONCLUSIONS: Influenced by a variety of factors, pathophysiological microvascular changes provoke anterior ischemic neuropathy with sudden painless loss of vision, irreversible in most cases. Since therapeutic trials have failed, prevention of possible causes is the only way to avoid this rare but severe complication of cardiac surgery.