Serum potassium levels are considered as a marker of cerebrovascular emergencies but there is less clarity on the association between initial serum potassium levels recorded on patient’s arrival at the emergency department with the type of stroke. This is a case-control study using data of a tertiary care hospital in Japan from April 2018 to September 2019. We identified adult patients with hemorrhagic stroke including subarachnoid hemorrhage (cases) and those with ischemic stroke (controls). Data on age, sex, chief complaints, vital signs, and initial blood tests were collected. We analyzed the association between serum potassium levels and the type of stroke by drawing a LOWESS curve. Additionally, we fitted a logistic regression model to examine the association of interest. There were 416 stroke patients (158 hemorrhagic and 258 ischemic). The median age was 77 years (IQR: 68, 84), and 54% were male. The mean potassium level was 3.69 ± 0.55 mEq/L for hemorrhagic stroke and 4.08 ± 0.65 mEq/L for ischemic stroke. The LOWESS curve showed that the lower initial potassium level was linearly associated with a greater likelihood of hemorrhagic stroke. In the logistic regression model, the odds ratio for the risk of hemorrhagic stroke per 1 mEq/L lower potassium level was 3.31 (95% confidence interval [CI]: 2.24-5.04). This association remained significant in a multivariable model adjusting for other covariates (OR: 2.62 [95% CI: 1.70-4.16]). Initial potassium level was lower in patients with hemorrhagic stroke compared to those with ischemic stroke.
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