Eur J Vasc Surg 7, 252-256 (1993) Post-carotid Endarterectomy Hyperperfusion Syndrome" Preliminary Observations for Identifying at Risk Patients by Transcranial Doppler Sonography and the Acetazolamide Test* E. Sbarigia, F. Speziale, M. F. Giannoni, M. Colonna, M. A. Panico and P. Fiorani University of Rome "La Sapienza", Rome, Italy Patients at risk of hyperperfusion syndrome after carotid endarterectomy are often severely hypertensive and have a high grade internal carotid artery stenosis with disordered autoregulation due to a loss of reserve capacity (RC). Cerebral RC can be studied by sophisticated and expensive technical devices (SPECT, PET). Recently it has been demonstrated that the transcranial Doppler (TCD) and acetazolamide provocation test can be used to assess RC. From September 1991 to January 1992, 36 patients were ~tudied by the TCD and acetazolamide test prior to carotid endarterectomy to identify patients at high risk of the hyperperfusion syndrome. Preoperatively, the patients were studied by TCD at rest and after vasolidation with acetazolamide l g intravenously (i.v.). Mean blood flow velocity on the middle cerebral artery (MCAv) was recorded for the following 20 min at 5 min intervals. MCAv at rest was 49 + 17 cm/s. After acetzaolamide infusion in 33 patients (92 %), the mean MCAv was 62 + 19 crn/s with an increase of 19 + 13 cm/s (normal RC). In three patients (8%), the mean MCAv was 43 + 22 cm/s with a decreaseo f - 6 + 3 cm/ s with respect to base values (reduction of RC). (t = 3.30; p = 0.0022). All these patients were hypertensive (BP >180/ lOOmmHg) and had a carotid artery stenosis >90%. Postoperatively, the three patients with reduction of RC complained of homolateral headache. TCD showed a mean MCAv of 67 +_ 17 cm/s, an increase compared to the preoperative rest values of 17 + 8cm/s, the 33 patients with normal RC showed a mean change in MCAv -2 + 12cm/s. The difference between the postoperative recorded mean MCAv in the two groups was statistically significant (t = 2,556, p = 0.0339). In this preliminary study, TCD associated with the acetazolamide test was demonstrated to be an inexpensive, easily performed and repeatable technique useful in assessing the patient at risk of hyperperfusion syndrome. Key Words: Carotid endarterectomy; Hyperfusion syndrome; Transcranial Doppler; Acetazolamide test; Cerebral reserve capacity. Introduction Most postoperative neurological complications of ca- rotid endarterectomy (CEA) are related to embolisa- tion or inadequate cerebral protection in patients with poor collateral supply. Those complications that occur some hours or days after operation are gener- ally associated with ischaemic events due to throm- bosis or embolisation from the endarterectomy site. 1,2 In a small subset of patients, however, the cause of delayed neurological deficit may be related to * Presented at the 6th Annual Meeting of the European Society for Vascular Surgery, Athens, September 1992. Please address all correspondance to: E. Sbarigia, I Cattedra di Chirurgia Vascolare, Policlinico Umberto I, viale del Policlinico, 00185 Roma, Italia. hyperperfusion syndrome in patients with lack of autoregulation (loss of reserve capacity, RC). 3-5. The clinical nature of this syndrome is character- ised by a triad of unilateral head, eye and face pain, contralateral seizures and delayed intracerebral haemorrhage. 6-1° Patients threatened by this syn- drome are often severe and longstanding hyperten- sives, have a high grade internal carotid stenosis (>90%) and poor collateral blood flow that often causes a reduction or loss of RC. 11-13 Loss of RC is related to a massive chronic vasodilatation in an effort to compensate reduced perfusion of the ischaemic hemisphere. 4"14"15 This derangement of autoregula- tion results in a massive increase in cerebral blood flow after removal of a tight stenosis. 4"6' 13 The result- ing increase in permeability of the capillary bed leads to cerebral oedema and, if long lasting, to intracere- bral haemorrhage. 0950-821X/93/070252+05$08.00/0© 1993 Grune & Stratton Ltd.