Surgery of the thoracic aorta with hypothermic circulatory arrest: experience with retrograde perfusion via the superior vena cava and demonstration of cerebral perfusion

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Abstract
OBJECTIVE: Retrograde cerebral perfusion (RCP) via the superior venacava has been described as an adjunctive technique to enhance the safety ofhypothermic circulatory arrest (HCA), but perfusion of cerebral tissue inhumans during RCP has not been demonstrated to date. We report our clinicalexperience with RCP and our attempt to demonstrate "true" perfusion of thebrain. METHODS: Between April 1993 and June 1995, 49 thoracic aorticprocedures were performed in 48 patients (male:female = 26:22) (emergency:elective = 25:24). The indications for surgery were acute type "A"dissection (18) chronic aneurysm (28) and infected valved conduit (3).Hypothermic circulatory arrest (15 degrees C) and RCP were implemented inall cases (mean HCA time 29 min, range 11-69) (mean RCP time 26 min, range10-65). The 99mTechnetium labelled brain perfusion agent d,l, hexamethylpropylene amine oxime (99mTc-HMPAO) was administered (100 MBq) into thecardiotomy reservoir following institution of HCA (15 degrees C) in threeconsecutive patients and planar dynamic brain imaging with a portable gammacamera was commenced at the start of RCP. RESULTS: Six hospital deaths(12.2%) occurred in the emergency group due to atheromatous embolic strokein one patient, sepsis in one, ruptured infrarenal aortic aneurysm in one,myocardial failure in one, renal failure in one and multi-system organfailure in one patient. The remaining patients suffered no majorneurological complications (median Intensive Care Unit stay 1 day, range1-5). Inspection of the images acquired showed 99mTc-HMPAO activityspreading quickly from the jugular bulb and the superior sagittal sinusthroughout the cerebral white and gray matter. Time-activity curvescalculated for both cerebral hemispheres showed homogeneous regionalcerebral perfusion. CONCLUSIONS: Retrograde cerebral perfusion is easy toestablish, "safe" and provides blood flow to the brain during HCA. The flowquantification and metabolic contribution of RCP require furtherinvestigation.

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