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 c ava has been described as an adjunctive technique to enhance the safet y of hypothermic circulatory arrest (HCA), but perfusion of cerebral t issue in humans during RCP has not been demonstrated to date. We repor t our clinical experience with RCP and our attempt to demonstrate ''tr ue'' perfusion of the brain. Methods. Between April 1993 and June 1995 , 49 thoracic aortic procedures were performed in 48 patients (male:fe male=26:22) (emergency: elective=25:24). The indications for surgery w ere acute type ''A'' dissection (18) chronic aneurysm (28) and infecte d 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 bra in perfusion agent d,l, hexamethyl propylene amine oxime (Tc-99m-HMPAO ) was administered (100 MBq) into the cardiotomy reservoir following i nstitution of HCA(15 degrees C) in three consecutive patients and plan ar dynamic brain imaging with a portable gamma camera was commenced at the start of RCP. Results. Six hospital deaths (12.2%) occurred in th e emergency group due to atheromatous embolic stroke in one patient, s epsis in one, ruptured infrarenal aortic aneurysm in one, myocardial f ailure in one, renal failure in one and multi-system organ failure in one patient. The remaining patients suffered no major neurological com plications (median Intensive Care Unit stay 1 day, range 1-5). Inspect ion of the images acquired showed Tc-99m-HMPAO activity spreading quic kly from the jugular bulb and the superior sagittal sinus throughout t he cerebral white and gray matter. Time-activity curves calculated for both cerebral hemispheres showed homogeneous regional cerebral perfus ion. Conclusions. Retrograde cerebral perfusion is easy to establish, ''safe'' and provides blood flow to the brain during HCA. The flow qua ntification and metabolic contribution of RCP require further investig ation.