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

Objective. Retrograde cerebral perfusion (RCP) via the superior vena cava has been described as an adjunctive technique to enhance the safety of hypothermic circulatory arrest (HCA), but perfusion of cerebral tissue in humans during RCP has not been demonstrated to date. We report our clinical experience with RCP and our attempt to demonstrate ''true'' perfusion of the brain. Methods. Between April 1993 and June 1995, 49 thoracic aortic procedures 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 in all cases (mean HCA time 29 min, range 11-69) (mean RCP time 26 min, range 10-65). The (99m)Technetium labelled brain perfusion agent d,l, hexamethyl propylene amine oxime (Tc-99m-HMPAO) was administered (100 MBq) into the cardiotomy reservoir following institution of HCA(15 degrees C) in three consecutive patients and planar dynamic brain imaging with a portable gamma camera was commenced at the start of RCP. Results. Six hospital deaths (12.2%) occurred in the emergency group due to atheromatous embolic stroke in one patient, sepsis in one, ruptured infrarenal aortic aneurysm in one, myocardial failure in one, renal failure in one and multi-system organ failure in one patient. The remaining patients suffered no major neurological complications (median Intensive Care Unit stay 1 day, range 1-5). Inspection of the images acquired showed Tc-99m-HMPAO activity spreading quickly from the jugular bulb and the superior sagittal sinus throughout the cerebral white and gray matter. Time-activity curves calculated for both cerebral hemispheres showed homogeneous regional cerebral perfusion. Conclusions. Retrograde cerebral perfusion is easy to establish, ''safe'' and provides blood flow to the brain during HCA. The flow quantification and metabolic contribution of RCP require further investigation.