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Defective cerebrovascular autoregulation after carotid endarterectomy
1Department of Vascular Surgery, Rigshospitalet 2102, University of Copenhagen, Denmark.
Insights
Cerebral hyperperfusion after carotid surgery can cause symptoms due to impaired autoregulation. Reducing blood pressure in affected patients normalized middle cerebral artery flow velocity, resolving symptoms.
Area of Science:
- Neurology
- Vascular Surgery
- Cerebrovascular Physiology
Background:
- Carotid endarterectomy corrects stenosis but can lead to cerebral hyperperfusion.
- Defective cerebrovascular autoregulation is implicated in post-operative hyperperfusion syndrome.
- Transcranial Doppler (TCD) is used to monitor cerebral blood flow velocity.
Purpose of the Study:
- To investigate the relationship between carotid endarterectomy, cerebral hyperperfusion, and cerebrovascular autoregulation.
- To assess the impact of ipsilateral middle cerebral artery mean flow velocity (Vmean) changes on post-operative symptoms.
- To evaluate the efficacy of blood pressure reduction in managing hyperperfusion syndrome.
Main Methods:
- Ninety-five patients undergoing carotid endarterectomy were monitored using TCD for middle cerebral artery Vmean.
- Vmean was measured pre- and post-operatively, focusing on symptomatic (headache, hypertension) and asymptomatic patients.
- Hemodynamic parameters and Vmean were analyzed in relation to blood pressure and autoregulation.
Main Results:
- Symptomatic patients exhibited significantly higher mean pressure difference across the stenosis compared to asymptomatic patients.
- Ipsilateral Vmean increased significantly post-operatively in symptomatic patients, indicating hyperperfusion.
- Reduction of arterial pressure with labetalol led to a significant decrease in ipsilateral Vmean, resolving symptoms like headache and seizures.
Conclusions:
- Post-endarterectomy cerebral hyperperfusion is linked to defective ipsilateral autoregulation.
- Ipsilateral middle cerebral artery Vmean is pressure-dependent in patients with hyperperfusion syndrome.
- Reducing arterial pressure is an effective strategy to manage symptoms of cerebral hyperperfusion, even in normotensive patients.
Abstract:
Correction of high grade carotid artery stenosis may result in cerebral hyperperfusion because of defective vascular autoregulation. Thus, transcranial Doppler was used to determine mean arterial flow velocity (Vmean) of the middle cerebral artery in 95 patients before and after carotid endarterectomy. Attention was focused on postoperative episodes of ipsilateral headache and hypertension. Symptoms of cerebral hyperperfusion lasted for 3 (1.5-5) h (median and range) in nine patients, and for 12 (8-14) days in nine other patients. Of these later patients, two developed seizures on the 5th and 6th postoperative day, respectively. The mean pressure difference across the stenosis was 31 (0-63) mmHg in the symptomatic group (n = 18) as opposed to only 10 (0-60) mmHg in the asymptomatic group (n = 77) (p < 0.01). In the 18 patients with headache after surgery, ipsilateral Vmean increased to 177 (130-332)% of the preoperative value (p < 0.0001), while the contralateral Vmean remained unchanged. After blood pressure was reduced in symptomatic patients with labetalol, ipsilateral Vmean decreased from 92 (69-124) to 56 (32-93) cm s-1 (p < 0.0001) as systemic arterial pressure decreased from 101 (80-128) to 88 (60-103) mmHg, with no change in contralateral Vmean. Normalisation of Vmean via reduction of arterial pressure ended episodes of headache and seizure in symptomatic patients. Thus, in patients who developed post-endarterectomy hyperperfusion, these findings clearly demonstrated that ipsilateral middle cerebral artery mean flow velocity was pressure dependent. This substantiates the hypothesis of defective autoregulation in the ipsilateral hemisphere after carotid endarterectomy, and in turn demonstrates an immediate cessation of symptoms with reduction of arterial pressure even in normotensive patients.