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Hypokalemia and potassium excretion in stroke patients
S E Gariballa1, T G Robinson, M D Fotherby
1University Department of Medicine for the Elderly, Selly Oak Hospital, Birmingham, UK.
Insights
Hypokalemia, low potassium levels, is common in stroke patients compared to heart attack or hypertension patients. Lower potassium levels upon hospital admission are linked to a higher risk of death after stroke.
Area of Science:
- Neurology
- Cardiology
- Nephrology
Background:
- Hypokalemia (low plasma potassium) is a known electrolyte imbalance.
- Its prevalence and impact in acute stroke patients are not fully understood.
- Comparison with other cardiovascular conditions is needed.
Purpose of the Study:
- To determine the prevalence of hypokalemia in stroke patients.
- To compare hypokalemia rates in stroke patients versus myocardial infarction and hypertension patients.
- To investigate the association between plasma potassium levels and stroke outcomes.
Main Methods:
- Observational study including 421 stroke patients, 150 myocardial infarction patients, and 161 hypertension patients.
- Plasma electrolytes measured within 2 hours of admission for stroke and cardiac patients; clinic for hypertensive patients.
- Stroke severity, blood pressure, and 24-hour urine electrolytes were recorded. Patient outcomes assessed at 3 months.
Main Results:
- Hypokalemia was significantly more frequent in stroke patients (20%) compared to myocardial infarction (10%) and hypertension (8%) patients (P < .001).
- This difference persisted even when excluding patients on diuretics.
- Lower admission plasma potassium levels were independently associated with an increased risk of death post-stroke (HR 1.73).
Conclusions:
- Hypokalemia is a common finding in patients following a stroke.
- Low potassium levels post-stroke are associated with poorer patient outcomes, including increased mortality.
Objectives:
To determine (1) the prevalence of hypokalemia (plasma potassium < or = 3.4 mmol/L) in a group of stroke patients in comparison with age- and sex-matched groups of patients having sustained a myocardial infarction or having mild hypertension and (2) the association between plasma potassium concentration and stroke outcome.
Design:
Observational study.
Participants:
A total of 421 consecutive stroke patients admitted to a teaching hospital, 150 consecutive patients 50 years or older with myocardial infarction admitted to the hospitals Coronary Care Unit, and 161 out-patients 60 years or older with borderline and established hypertension.
Measurements:
All stroke and cardiac patients had plasma urea and electrolytes estimated within 2 hours of hospital admission; in the hypertensive group blood samples were taken in clinic. Stroke patients had blood pressure, stroke severity (Barthel score) and smoking status recorded. A sub-group of 61 stroke patients and all 79 hypertensive patients not taking antihypertensive medication had 24-hour urine electrolyte excretion measured. Outcome (independent, dependent, or dead) at 3 months post-stroke was established in 349 patients.
Results:
Hypokalemia occurred more frequently in stroke patients than in patients with myocardial infarction (84 (20%) vs 15 (10%), P = .008) or patients with hypertension (84 (20%) vs 13 (8%), P < .001), even when patients taking diuretics were excluded from analysis (56 (19%) vs 12 (9%) of cardiac group, P = .014 and 56 (19%) vs 4 (5%) of hypertensive group, P = .005, respectively). 24-hour urine excretion of potassium and the potassium:creatinine ratio was lower in stroke patients than in hypertensive patients (41 +/- 21 vs 62 +/- 25 mmol/24 hour, P = .001, 5.5 +/- 2.2 vs 7.4 +/- 2.6 mmol/24 hour, P = .001, respectively). On survival analysis, a lower plasma potassium on admission to hospital was associated with an increased chance of death, independent of age, stroke severity, history of hypertension, blood pressure level, or smoking history (hazard ratio 1.73 (95% CI: 1.03-2.9) for a 1 mmol/L lower plasma potassium concentration).
Conclusions:
Hypokalemia post stroke is common and may be associated with a poor outcome.