Retinal Artery Air Embolism in Dogs

Abstract

Cerebral air embolism can cause cerebral complications after open heart surgery.The duration of cerebral artery occlusion by air embolism is thought to vary depending on the conditions. However, no study has evaluated factors affecting the duration of occlusion. In this study, we examined the effects of blood pressure and hemodilution on the duration of retinal artery occlusion caused by air embolism in dogs. The duration of retinal artery occlusion caused by the injection of 0.6 mL of air into the common carotid artery was measured by fluorescein angiography and compared among the following three periods: a control period, during which the mean blood pressure (MBP) was maintained at 80 mm Hg; a hypotension period, during which MBP was decreased to 60 mm Hg by exsanguination; and a hypotension plus hemodilution period, during which an additional exchange of blood with hydroxyethyl starch solution was performed and MBP was maintained at 60 mm Hg. When MBP was lowered from 80 to 60 mm Hg, the duration of retinal artery occlusion was prolonged from 34 +/- 39 to 166 +/- 90 s (P < 0.01). In dogs with MBP of 60 mm Hg, hemodilution (12.0 +/- 0.9 to 7.3 +/- 0.5 g/dL hemoglobin concentration) shortened the duration from 166 +/- 90 to 75 +/- 50 s (P < 0.05). Our results demonstrate that hypotension prolongs and hemodilution shortens the duration of retinal artery occlusion caused by air embolism. Implications: We evaluated the effects of blood pressure and hemodilution on the duration of retinal artery occlusion caused by air embolism by retinal fluorescein angiography. Hypotension prolonged and hemodilution shortened the duration of retinal artery occlusion caused by air embolism. (Anesth Analg 1999;88:1004-10)