CEREBRAL HEMODYNAMICS IN INTERNAL CAROTID-ARTERY TRIAL OCCLUSION

The purpose of this study was to analyse the cerebral haemodynamic cha nges brought about by trial occlusion of the internal carotid artery ( ICA). Sixteen patients with surgically inaccessible cerebral aneurysms , carotid cavernous fistulas or neck neoplasms were monitored with tra nscranial Doppler ultrasonography (TCD) during 90-120 s angiographic I CA balloon occlusion or ICA closure with a Selverstone clamp. The bloo d velocity (V) was registerrd continuously in bath middle cerebral art eries (A ICA) while the pulsatility index (PIMCA) and haemodynamic ten sion (U-hemMCA) were calculated. ICA closure led to an instantaneous d rop in the ipsilateral V-MAC, PIMCA and U-hemMCA. The V-MCA thereafter increased gradually until reaching a stable level. The subjects were grouped into those with initial drops in V-MCA to greater than or equa l to 60% of pre-occlusion value (group 1) and those that fell to < 60% (group 2), respectively. In group 1 autoregulatory mechanisms made th e PIMCA decline further, while the U-hemMCA remained unaltered during ICA closure. In group 2, however, the PIMCA did not change further, wh ile the U-hemMCA increased slightly. The cerebral haemodynamic feature s during ICA test occlusion were thus essentially different in the two groups. On re-opening the ICA. there was an overshoot in V-MCA and U- hemMCA. Contralaterally, the V-MCA was increased during ICA occlusion. Seven of the patients later had their ICA closed permanently; While n one of five group 1 patients developed haemodynamic complications, two group 2 individuals experienced harmodynamic stroke. Assuming ICA sac rifice is feasable when test occlusion results in an ipsilateral initi al reduction in V-MCA to greater than or equal to 60% of preocclusion value, the corresponding limit for the U-hemMCA is greater than or equ al to 40%. In the pre-operative evaluation of the haemodynamic risk re lated to ICA loss, TCD emerges as a reliable method. It also seems to allow for the reduction of test occlusion time to 90-120 s.