Higher brain extracellular potassium is associated with brain metabolic distress and poor outcome after aneurysmal subarachnoid hemorrhage

INTRODUCTION: Elevated brain potassium levels ([K(+)]) are associated with neuronal damage in experimental models. The role of brain extracellular [K(+)] in patients with poor-grade aneurysmal subarachnoid hemorrhage (aSAH) and its association with hemorrhage load, metabolic dysfunction and outcome has not been studied so far. METHODS: Cerebral microdialysis (CMD) samples from 28 poor grade aSAH patients were analyzed for CMD [K(+)] for 12 consecutive days after ictus, and time-matched to brain metabolic and hemodynamic parameters as well as corresponding plasma [K(+)]. Statistical analysis was performed using a generalized estimating equation with an autoregressive function to handle repeated observations of an individual patient. RESULTS: CMD [K(+)] did not correlate with plasma [K(+)] (Spearman’s ρ = 0.114, P = 0.109). Higher CMD [K(+)] was associated with the presence of intracerebral hematoma on admission head computed tomography, CMD lactate/pyruvate ratio >40 and CMD lactate >4 mmol/L (P < 0.05). In vitro retrodialysis data suggest that high CMD [K(+)] was of brain cellular origin. Higher CMD [K(+)] was significantly associated with poor 3-month outcome, even after adjusting for age and disease severity (P < 0.01). CONCLUSIONS: The results of this pilot study suggest that brain extracellular [K(+)] may serve as a biomarker for brain tissue injury in poor-grade aSAH patients. Further studies are needed to elucidate the relevance of brain interstitial K(+) levels in the pathophysiology of secondary brain injury after aSAH.