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. 2025 Aug 26;33(1):144.
doi: 10.1186/s13049-025-01454-8.

The association between arrival potassium and 30-day survival following resuscitation from out-of-hospital cardiac arrest: a retrospective cohort study

Christina Byrne  1 , Maria Lukacs Krogager  2 , Kristian Kragholm  2 , Manan Pareek  3   4 , Grimur Høgnason Mohr  4   5 , Kristian Bundgaard Ringgren  2 , Mads Wissenberg  3   4 , Signe Riddersholm  2 , Martin Wolder  2 , Fredrik Folke  4 , Gunnar Gislason  4 , Lars Køber  3 , Christian Hassager  3 , Jesper Kjærgaard  3 , Christopher B Fordyce  6 , Christian Torp-Pedersen  7 , Gregory Y H Lip  8 , Carlo A Barcella  3   4
Affiliations

The association between arrival potassium and 30-day survival following resuscitation from out-of-hospital cardiac arrest: a retrospective cohort study

Christina Byrne et al. Scand J Trauma Resusc Emerg Med. .

Abstract

Background: It is unknown whether there is an association between initial serum potassium level and short-term survival in out-of-hospital cardiac arrest (OHCA) survivors. The aim of this study was to describe potential associations between first recorded potassium level and 30-day survival in patients surviving OHCA.

Methods: We identified 4,894 patients who had return of spontaneous circulation (ROSC) at hospital arrival, and a registered post-OHCA serum-potassium value, using Danish nationwide registry data from 2001-2019. Potassium values were divided into seven predefined levels: < 2.5, 2.5-2.9, 3.0-3.4, 3.5-4.6, 4.7-5.5, 5.5-6.0, > 6.0 mmol/L. Thirty-day survival was estimated using a multivariable Cox regression (reference normokalemia 3.5-4.6 mmol/L). The multivariable model included age, sex, Charlson comorbidity index (including chronic kidney disease), witnessed status, performance of bystander cardiopulmonary resuscitation (CPR) and first registered heart rhythm.

Results: Over the 30-day follow-up period, survival rates in the seven strata were as follows: 25 (51.0%), 119 (53.6%), 512 (65.4%), 1,631 (57.9%), 220 (32.7%), 34 (22.8%), and 46 (22.7%), respectively. Thirty-day survival was significantly lower for all groups with hyperkalemia compared with normokalemia: 4.7-5.5 mmol/L: (average risk ratio (RR): 0.72, 95% confidence interval (95% CI): 0.66-0.78); 5.5-6.0 mmol/L: (average RR: 0.60, 95% CI: 0.47-0.73); > 6.0 mmol/L: (average RR: 0.56, 95% CI: 0.46-0.66). Survival did not differ significantly in patients with hypokalemia compared with normokalemia.

Conclusions: In OHCA survivors, hyperkalemia was associated with reduced 30-day survival compared with normokalemia, independent of age, sex, comorbidity burden and pre-hospital OHCA-characteristics. Conversely, hypokalemia was not associated with reduced 30-day survival.

Keywords: Out-of-hospital cardiac arrest survivors; Potassium; Survival.

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Conflict of interest statement

Declarations. Ethics approval and consent to participate: The study was approved by the Danish Data Protection Agency. Registry-based studies does not require ethical approval by The Danish National Committee on Health Research Ethics. Consent for publication: Not applicable. Competing interests: The authors declare no competing interests.

Figures

Fig. 1
Fig. 1
Selection of the study population. OHCA out-of-hospital cardiac arrest. ROSC return of spontaneous circulation
Fig. 2
Fig. 2
Log-rank test of the survival probability among the different potassium intervals (n = 4,894)
Fig. 3
Fig. 3
Standardized 30-day survival probability and average risk ratio in OHCA-patients stratified by potassium intervals. Reference interval represented by the interval K+: 3.5–4.6 mmol/l. * The models included age, sex, Charlson score, witnessed status, performance of bystander cardiopulmonary resuscitation, and first registered heart rhythm
Fig. 4
Fig. 4
Restricted cubic splines showing the adjusted hazard ratios for 30-day survival as a function of potassium concentration. Knots at the 25th, 50th and 75th percentiles of potassium. Model adjusted for age, sex, Charlson score, witnessed status, performance of bystander cardiopulmonary resuscitation, and first registered heart rhythm
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