Hypercapnia impact on vascular and neuronal reactivity in patients before and after carotid endarterectomy

Abstract

Hypothesis: Regional cerebral blood flow (rCBF) and vascular reactivity strongly affect neuronal function. The restoration of blood flow values in the cerebral vascular system may be another benefit of carotid endarterectomy (CEA) in a specific group of patients. Animal experiments in dogs have provided evidence of neuronal reactivity depending on rCBF and vascular reactivity. However, as yet, there are no reports on neuronal reactivity changes related to altered perfusion parameters in humans.

Material and methods: The cohort under study consisted of 41 patients after transient ischaemic attack (TIA) or reversible ischaemic neurological deficit (RIND) whose neurological findings were normal (group A) and 17 patients after minor stroke with a mild degree of hemiparesis or hemihypesthesia (mRS<or=2) (group B). All patients were examined 0-2 days before CEA, on postoperative days 3-7 and at 3 months after CEA. The tests included median nerve somatosensory evoked potentials (SEPs) and transcranial Doppler (TCD) at rest, during hypercapnia (et-CO2=7.0-7.5 kPa) and at rest after hypercapnia.

Results: Group A was found to have a significant increase in V(sys), V(mean) and PI in response to hypercapnia in all periods (i.e., 0-2 days before CEA, on postoperative days 3-7 and at 3 months after CEA). N20/P25 amplitude decreased in response to hypercapnia before and early after CEA. Changes in other SEP parametres before and after hypercapnia were non-significant. Group B showed significant differences resulting from hypercapnia before and after CEA only in vasoreactivity (V(sys), V(mean), PI).

Conclusion: In the analysed group of patients high-grade carotid stenosis caused no haemodynamic impairment. Moreover, no evidence was found of artificially increased rCBF being accompanied by an equally significant change in somatosensory evoked scalp response.