Distribution of cerebral flow using retrograde versus antegrade cerebral perfusion

Background. This study compared flow to the brain with retrograde and antegrade cerebral perfusion during circulatory arrest. Methods. Twenty-four rabbits were injected with 5 mCi of technetium-99 macroaggregated albumin, a tracer trapped in the capillaries. Group I (n = 6) were maintained normothermic, and the tracer was injected into the ascending aorta. Group II (n = 6) were maintained normothermic, and underwent cannulation of the superior vena cava (SVC), exsanguination through the aorta, and injection of the tracer into the SVC, which was proximally occluded. In group III (n = 6), the animal was cooled to 25°C. The animal was exsanguinated through the aorta and tracer was injected into the ascending aorta. In group IV (n = 6), animals were cooled to 25°C. The animal was exsanguinated through the ascending aorta and tracer was injected into the SVC. Three animals (group V) were exsanguinated through the ascending aorta and a retrograde venogram of the SVC was performed. Scintigraphy of groups I to IV was carried out on a digital gamma camera. Brain trapping of tracer was graded from 0 to 5, with 0 being no tracer in the brain and 5 being dominant tracer trapping in the brain. Results. Tracer trapping in the brain showed group I, 3.67 ± 0.82; group II, 0; group III, 4.67 ± 0.41; group IV, 0.17 ± 0.41 (p< 0.0001). Retrograde venogram of the SVC showed flow into the cerebral veins. Conclusions. Retrograde flow through the SVC reaches the cerebral venous system. Flow arriving in retrograde fashion does not go through the capillary system.