Admission serum potassium concentration and long-term mortality in patients with acute myocardial infarction: results from the MONICA/KORA myocardial infarction registry

Potassium levels and the risk of all-cause and cardiovascular mortality among patients with cardiovascular diseases: a meta-analysis of cohort studies

BACKGROUND

Abnormal blood potassium levels are associated with an increased risk of cardiometabolic diseases and mortality in the general population; however, evidence regarding the association between dyskalemia and mortality among patients with cardiovascular disease (CVD) remains inconclusive. This study aimed to evaluate the association of potassium levels with all-cause and cardiovascular mortality among patients with CVD.

METHODS

PubMed, Embase, Web of Science, and Cochrane Library databases were searched up to August 2023 to identify relevant cohort studies among patients with CVD, such as myocardial infarction, stroke, and heart failure. Abnormal potassium levels were considered as hypokalemia or hyperkalemia. The primary outcomes were all-cause mortality based on follow-up length (including in-hospital, short-term and long-term mortality) and cardiovascular mortality. The methodological quality of included studies was assessed by using the Newcastle-Ottawa Scale. The pooled relative risks (RRs) and 95% confidence intervals (CIs) were calculated using random-effects models. Restricted cubic splines were applied to explore the dose-response relationship.

RESULTS

Thirty-one cohort studies involving 227,645 participants with an average age of 68.3 years were included in the meta-analysis, all of which achieved moderate to high quality. Hyperkalemia was significantly associated with an approximately 3.0-fold increased risk of all-cause in-hospital mortality (RR:2.78,95CI%:1.92,4.03), 1.8-fold of all-cause short-term mortality (RR:1.80, 95CI%:1.44,2.27), 1.3-fold of all-cause long-term mortality (RR:1.33, 95CI%:1.19,1.48) and 1.2-fold of cardiovascular mortality (RR:1.19, 95CI%:1.04,1.36). Similar positive associations were also observed between hypokalemia and risk of all-cause mortality and cardiovascular mortality. The RRs of all-cause in-hospital, short-term, long-term mortality and cardiovascular mortality with hyperkalemia were attenuated to 2.21 (95CI%:1.60,3.06), 1.46(95CI%:1.25,1.71), 1.23 (95CI%:1.09,1.39) and 1.13 (95CI%:1.00,1.27) when treating hypokalemia together with normokalemia as the reference group. A U-shaped association was observed between potassium levels and mortality, with the lowest risk at around 4.2 mmol/L.

CONCLUSIONS

Both hypokalemia and hyperkalemia were positively associated with the risk of mortality in patients with CVD. Our results support the importance of potassium homeostasis for improving the CVD management.

REGISTRATION

PROSPERO, CRD42022324337.

Why hemolysis detection should be an integral part of any near-patient blood gas analysis

Blood gas analysis at or near the patient’s bedside is a common practice in acute medicine and plays a crucial role in the diagnosis and management of patient’s respiratory status, metabolites, electrolytes, co-oximetry and acid–base balance. Pre-analytical quality aspects of the specimens are getting more and more attention, including the presence of potential interferences. Central laboratories have implemented technologies to detect interferences such as hemolysis, lipidemia or hyperbilirubinemia in blood samples to ensure the highest possible quality in results provided to routine care. However, systematic detection for interference due to hemolysis is currently not in place for blood gas analysis at the point-of-care (POC). To apply hemolysis detection solutions at the central laboratory, but not at the POC for blood gas analysis, is a clear contradiction when novel hemolysis detecting technologies are available. The introduction of a system that systematically detects hemolysis in connection to POC blood gas analysis would be imperative to patient safety and costs associated with potential clinical malpractice (leading to wrong, missing and/or delayed treatment) and would also ensure better compliance to CLSI guidelines and ISO standards, and be beneficial for patient and staff.

Arrhythmogenic Mechanisms in Hypokalaemia: Insights From Pre-clinical Models

Potassium is the predominant intracellular cation, with its extracellular concentrations maintained between 3. 5 and 5 mM. Among the different potassium disorders, hypokalaemia is a common clinical condition that increases the risk of life-threatening ventricular arrhythmias. This review aims to consolidate pre-clinical findings on the electrophysiological mechanisms underlying hypokalaemia-induced arrhythmogenicity. Both triggers and substrates are required for the induction and maintenance of ventricular arrhythmias. Triggered activity can arise from either early afterdepolarizations (EADs) or delayed afterdepolarizations (DADs). Action potential duration (APD) prolongation can predispose to EADs, whereas intracellular Ca²⁺ overload can cause both EADs and DADs. Substrates on the other hand can either be static or dynamic. Static substrates include action potential triangulation, non-uniform APD prolongation, abnormal transmural repolarization gradients, reduced conduction velocity (CV), shortened effective refractory period (ERP), reduced excitation wavelength (CV × ERP) and increased critical intervals for re-excitation (APD-ERP). In contrast, dynamic substrates comprise increased amplitude of APD alternans, steeper APD restitution gradients, transient reversal of transmural repolarization gradients and impaired depolarization-repolarization coupling. The following review article will summarize the molecular mechanisms that generate these electrophysiological abnormalities and subsequent arrhythmogenesis.

Serum potassium levels and mortality of patients with acute myocardial infarction: A systematic review and meta-analysis of cohort studies

BACKGROUND

The evidence of current epidemiological studies investigating the association between serum potassium levels and mortality of acute myocardial infarction (AMI) patients is controversial and inadequate.

DESIGN

Systematic review and meta-analysis.

METHODS

Two researchers independently searched the PubMed, EMBASE and Web of Science databases to identify observational studies published prior to 31 October 2017. Similarly, two researchers separately extracted data and any differences were resolved by discussion. Pooled relative risks and 95% confidence intervals (CIs) were computed with an inverse variance-weighted random-effects model. Heterogeneity among studies was assessed with the I² statistic.

RESULTS

Seven cohort studies were included for analysis. Compared with the reference group (3.5 to <4.0 mEq/L), the pooled relative risks of mortality were 1.15 (95% CI = 1.00-1.32), 1.09 (95% CI = 0.97-1.24), 1.42 (95% CI = 1.19-1.70) and 1.85 (95% CI = 1.39-2.47) for AMI patients with a potassium level of<3.5, 4.0 to <4.5, 4.5 to <5.0, and ≥5.0 mEq/L, respectively. For admission and post-admission potassium, although J-shaped associations were also indicated, non-significant results were observed for AMI patients with potassium levels of <3.5 mEq/L when compared with the reference group. Notably, in subgroup analyses of study characteristics, stratified by study quality, geographic location, type of outcome, number of cases, type of AMI, and adjustment for potential confounders, the findings were broadly consistent across strata.

CONCLUSIONS

These findings indicate that both lower (<3.5 mEq/L) and higher (≥4.5 mEq/L) serum potassium levels are associated with an increased risk of mortality of patients with AMI.

Serum Potassium Levels at Hospital Discharge and One-Year Mortality among Hospitalized Patients

Background and Objectives: The optimal range of serum potassium at hospital discharge is unclear. The aim of this study was to assess the relationship between discharge serum potassium levels and one-year mortality in hospitalized patients. Materials and Methods: All adult hospital survivors between 2011 and 2013 at a tertiary referral hospital, who had available admission and discharge serum potassium data, were enrolled. End-stage kidney disease patients were excluded. Discharge serum potassium was defined as the last serum potassium level measured within 48 h prior to hospital discharge and categorized into ≤2.9, 3.0–3.4, 3.5–3.9, 4.0–4.4, 4.5–4.9, 5.0–5.4 and ≥5.5 mEq/L. A Cox proportional hazards analysis was performed to assess the independent association between discharge serum potassium and one-year mortality after hospital discharge, using the discharge potassium range of 4.0–4.4 mEq/L as the reference group. Results: Of 57,874 eligible patients, with a mean discharge serum potassium of 4.1 ± 0.4 mEq/L, the estimated one-year mortality rate after discharge was 13.2%. A U-shaped association was observed between discharge serum potassium and one-year mortality, with the nadir mortality in the discharge serum potassium range of 4.0–4.4 mEq/L. After adjusting for clinical characteristics, including admission serum potassium, both discharge serum potassium ≤3.9 mEq/L and ≥4.5 mEq/L were significantly associated with increased one-year mortality, compared with the discharge serum potassium of 4.0–4.4 mEq/L. Stratified analysis based on admission serum potassium showed similar results, except that there was no increased risk of one-year mortality when discharge serum potassium was ≤3.9 mEq/L in patients with an admission serum potassium of ≥5.0 mEq/L. Conclusion: The association between discharge serum potassium and one-year mortality after hospital discharge had a U-shaped distribution and was independent of admission serum potassium. Favorable survival outcomes occurred when discharge serum potassium was strictly within the range of 4.0–4.4 mEq/L.