Introduction Ischemic stroke is a prevalent, devastating disease with high morbidity and mortality. Despite extensive research using animal models, there remains significant gaps in understanding processes of stroke in human patients. To address this, we developed a protocol to obtain and to analyze blood immediately proximal in systemic circulation and distal to a thrombus in patients undergoing mechanical thrombectomy (www.clinicaltrials.gov NCT03153683). Our goal for this project was to evaluate blood gas changes and acid/base balance during stroke and how these changes are affected by patient factors.

Methods We analyzed blood samples from the first 62 patients in the BACTRAC registry. Bicarbonate, pO2, and pCO2 values of intracranial (distal) and systemic (proximal) arterial blood relative to the occlusive thrombus were analyzed. Changes were compared in patients according to vascular collateralization as measured by CTA collateral scores.

Results Mean age was 68.9 years (25 – 95 years). 29 were male, 33 were female. 15 were current smokers (24%), and 47 were non-smokers (no smoking within the last 6 months; 76%). Overall, intracranial gas values differed significantly from systemic. Compared to systemic, mean intracranial pO2 was decreased (211.39 vs. 246.91, p<0.001), pCO2 was decreased (32.19 vs. 38.12, p<0.001, and bicarbonate was decreased (18.90 vs. 22.20, p<0.001). Collateralization did not significantly affect distal blood gas values.

Discussion and Conclusion A compensated metabolic acidosis is present in arterial blood gas samples immediately proximal and distal to thrombi in large vessel occlusive stroke. Vascular collateralization may not significantly affect the acid-base environment immediately distal to a large vessel occlusion.

Disclosures R. Spears: None. C. McLouth: None. K. Pennypacker: None. J. Frank: None. B. Maglinger: None. A. Trout: None. J. Roberts: None. A. Stowe: None. S. Grupke: None. J. Fraser: None.