Distinct Alterations in Oxygenation, Ion Composition and Acid-Base Balance in Cerebral Collaterals During Large-Vessel Occlusion Stroke

Purpose: Disturbances of blood gas and ion homeostasis including regional hypoxia and massive sodium (Na⁺)/potassium (K⁺) shifts are a hallmark of experimental cerebral ischemia but have not been sufficiently investigated for their relevance in stroke patients.

Methods: We report a prospective observational study on 366 stroke patients who underwent endovascular thrombectomy (EVT) for large-vessel occlusion (LVO) of the anterior circulation (18 December 2018-31 August 2020). Intraprocedural blood gas samples (1 ml) from within cerebral collateral arteries (ischemic) and matched systemic control samples were obtained according to a prespecified protocol in 51 patients.

Results: We observed a significant reduction in cerebral oxygen partial pressure (-4.29%, p_aO_2ischemic = 185.3 mm Hg vs. p_aO_2systemic = 193.6 mm Hg; p = 0.035) and K⁺ concentrations (-5.49%, K⁺_ischemic = 3.44 mmol/L vs. K⁺_systemic = 3.64 mmol/L; p = 0.0083). The cerebral Na⁺:K⁺ ratio was significantly increased and negatively correlated with baseline tissue integrity (r = -0.32, p = 0.031). Correspondingly, cerebral Na⁺ concentrations were most strongly correlated with infarct progression after recanalization (r = 0.42, p = 0.0033). We found more alkaline cerebral pH values (+0.14%, pH_ischemic = 7.38 vs. pH_systemic = 7.37; p = 0.0019), with a time-dependent shift towards more acidotic conditions (r = -0.36, p = 0.055).

Conclusion: These findings suggest that stroke-induced changes in oxygen supply, ion composition and acid-base balance occur and dynamically progress within penumbral areas during human cerebral ischemia and are related to acute tissue damage.