Bilateral Increase in CO 2 Reactivity After Unilateral Carotid Endarterectomy

Abstract

Background and Purpose A low or absent CO 2 reactivity is considered indicative of a compromised hemodynamic compensatory capacity in patients with internal carotid artery (ICA) stenosis or occlusion. The aim of the present study was to investigate whether patients with preoperatively decreased or absent CO 2 reactivity show an improvement of CO 2 reactivity 3 months after carotid endarterectomy (CEA) and whether the preoperative CO 2 reactivity is correlated with clinical classification and hemodynamic factors. Methods A group of 65 patients with >70% ICA stenosis was studied. CO 2 reactivity was measured by bilateral transcranial Doppler sonography before and 3 months after CEA. Results The preoperative CO 2 reactivity was not significantly different in subgroups formed according to the presenting clinical symptoms. Patients with severe ICA stenosis with contralateral ICA occlusion had mean low preoperative CO 2 reactivity on both sides. Furthermore, patients with reversed flow in the ophthalmic artery had low mean preoperative CO 2 reactivity on the same side. The CO 2 reactivity was not significantly different in the subgroups of patients with signs of collateral blood flow through the anterior or posterior communicating artery. In particular, patients with low preoperative CO 2 reactivity (approximately <30%) showed an evident increase after the operation. Such an inverse correlation was found bilaterally, although it was more pronounced on the CEA side. Conclusions CEA can increase CO 2 reactivity in both hemispheres. This effect is most pronounced in patients with low (<30%) preoperative CO 2 reactivity. If this group represents patients who would be at risk from low-flow stroke, then testing of CO 2 reactivity might help select a subset of patients with an especially high probability of benefit from CEA.