Potassium Levels and In-Hospital Cardiac Arrest: A Matched Case-Control Study

Hyperkalemia and hypokalemia are common in admitted patients and recognized as a reversible cause of cardiac arrest. How the risk of in-hospital cardiac arrest changes relative to the severity of hyperkalemia and hypokalemia remains uncertain. The objective of this study was to estimate the association between pre-cardiac arrest hyperkalemia and hypokalemia and in-hospital cardiac arrest and outcomes after in-hospital cardiac arrest.

Registry-based matched case-control study.

Hospitalized patients in Denmark from 2017 to 2021.

Cases were adults with in-hospital cardiac arrest identified through the Danish in-hospital cardiac arrest Registry. These were matched with controls on age, sex, and length and time of admission. The index time was defined for cases as their time of cardiac arrest. A corresponding index time was assigned to matched controls.

None.

The exposure was potassium levels within 24 hours of the index time. Outcomes were in-hospital cardiac arrest and return of spontaneous circulation, 30-day survival, and 1-year survival in those with cardiac arrest. A total of 6,658 cases and 49,906 controls were included. Severe hyperkalemia (K + > 6.5) and hypokalemia (K + < 2.5) were associated with 2.03 (95% CI, 1.28-3.23) and 2.65 (95% CI, 1.61-4.38) times the odds of in-hospital cardiac arrest compared with normokalemia, respectively. Increasing severity of hyperkalemia was associated with decreased odds of return of spontaneous circulation, 30-day survival, and 1-year survival after in-hospital cardiac arrest. There was no clear association between hypokalemia and these outcomes.

Hyperkalemia was associated with an increased risk of in-hospital cardiac arrest and with worse outcomes after cardiac arrest. Hypokalemia was associated with an increased risk of in-hospital cardiac arrest but was not associated with outcomes after cardiac arrest.