Risposta vasomotoria cerebrale alla stimolazione con CO2 e L-arginina. Valutazione pre e post-operatoria in soggetti con stenosi marcata della carotide interna

Translated title of the contribution: Pre and postoperative assessment of L-arginine and CO2-induced cerebral vascular response in subjects with high grade internal carotid artery stenosis

D. Bosone, G. Micieli, F. Zappoli, A. Argenteri, S. Marcheselli, M. G. Egitto, G. Nappi

Research output: Contribution to journalArticlepeer-review

Abstract

The risk of a first episode of cerebral ischaemia or a recurrence in subjects with severe uni or bilateral stenosis of the internal carotid artery (>70%) is linked to thromboembolic events and the effects of reduced cerebral blood flow, especially in subjects with poor compensation mechanisms orbilateral stenosis or occlusion of the extracranial arteries. These two mechanisms often combine exposing subjects to severe carotid atheromasia and a very high risk of developing transient or permanent cerebral ischaemia with the high human and social costs entailed. In this group of patients thromboendarterectomy is not only thought to reduce the risk, but also to return cerebral vasomotor capacity to normal levels leading to the recovery of good intracranial haemodynamic function. Transcranial Doppler allows non-invasive measurement of blood flow velocity and resistance parameters such as the pulsatility index in the basal cranial arteries. Some studies have demonstrated that CO2-induced flow velocity changes in the middle cerebral artery are a reliable indicator of the cerebral vasomotor reserve. Subsequent investigations showed that the CO2 response was significantly impaired in patients with internal carotid artery occlusion and poor haemodynamic compensation mechanisms. It was recently shown that the aminoacid L-Arginine can induce vasodilation of the resistance vessels, being directly transformed at endothelial level into nitric oxide (an endothelium-derived relaxation factor) by nitric oxide synthase. L-Arginine-induced haemodynamic changes recorded by transcranial Doppler study in the middle cranial artery can be considered a reliable index of endothelial function even in subjects with haemodynamic and/or atherosclerotic cerebrovascular disease. This study aimed to measure CO2 and L-Arginine-induced intracranial haemodynamic changes before and at least three months after thromboendarterectomy to establish the extent to which surgery aids recovery of cerebral vasomotor response and endothelium-mediated vasomotor reactivity. At this preliminary stage we included 8 subjects (16 cerebral hemispheres) (average age 63.5 + 6.26) with non-occlusive stenosis of at least 70% of the carotid artery lumen. The pre-operative work-up in all subjects included brain CT, colour flow Doppler of the supraortic trunks, digital arterial angiography, basal transcranial Doppler and continuous bilateral monitoring of average flow velocity changes induced by inhaling CO2 (RVM-CO2) and L-Arginine infusion (150 mg/kg/i.v./30') (RVM-Arg). In the post-operative stage and at least three months after surgery patients again underwent Doppler colour flow, transcranial Doppler and monitoring under the same conditions as those used before surgery. The vasomotor reserve was (RVM) was calculated as the percentage of maximum flow velocity change after stimulation with respect to the basal velocity. Neither RVM-CO2 or RVM-Arg were significantly changed before and after surgery considering all hemispheres (mean ± SD RVM-CO2 48.25 ± 23.5% and 44.6 ± 20.2%; RVM-Arg 24.2 ± 6.33% and 21.5 ± 9.7%) and considering the stenotic side alone (RVM-CO2 47.7 ± 26.9% and 46.2 ± 23.5%; RVM-Arg 22.7 ± 5.64% and 21.1 ± 9.01%). Comparing the stenotic and non-stenotic sides before surgery RVM-CO2 showed no significant differences (mean ± SD 42 + 23.4% and 55.6 ± 23%) although the reserve tended to improve on the non-stenotic side, whereas RVM-Arg improved significantly on the non-stenotic side (mean ± SD 21.8 ± 7% and 28.3 ± 4% p = 0.05). This weak significance disappeared in the post-operative stage (19.9 ± 10.5% and 22.07 ± 9.2%). There was no significant correlation between CO2 and T-Arginine-induced vasomotor reactivity. In conclusion, both CO2 and L. Arginine stimulate vasodilation of resistance vessels, probably by means of two different endothelium-mediated mechanisms. Both substances can be used to measure cerebral vasomotor response in patients with severe carotid artery stenosis. However, our preliminary results failed to show a significant improvement of the cerebral reserve three months after surgery, suggesting that endarterectomy in these patients reduces the thromboembolic risk, but probably does not affect a stablized haemodynamic situation.

Translated title of the contributionPre and postoperative assessment of L-arginine and CO2-induced cerebral vascular response in subjects with high grade internal carotid artery stenosis
Original languageItalian
Pages (from-to)143-151
Number of pages9
JournalRivista di Neuroradiologia
Volume9
Issue numberSUPPL. 2
Publication statusPublished - 1996

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging
  • Clinical Neurology
  • Radiological and Ultrasound Technology

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