The heart and potassium: a banana republic

Hypoglycaemia and Cardiovascular Disease Risk in Patients with Diabetes

Hypoglycaemia represents an important side effect of insulin therapy and insulin secretagogues. It can occur in both type 1 and type 2 diabetes mellitus patients. Also, some associations between hypoglycaemia and cardiovascular (CV) risk have been reported. Several mechanisms may be involved, including the sympathoadrenal system, hypokalaemia, endothelial dysfunction, coagulation, platelets, inflammation, atherothrombosis and impaired autonomic cardiac reflexes. This narrative review discusses the associations of hypoglycaemia with CV diseases, including coronary heart disease (CHD), cardiac arrhythmias, stroke, carotid disease and peripheral artery disease (PAD), as well as with dementia. Severe hypoglycaemia has been related to CHD, CV and all-cause mortality. Furthermore, there is evidence supporting an association between hypoglycaemia and cardiac arrhythmias, potentially predisposing to sudden death. The data linking hypoglycaemia with stroke, carotid disease and PAD is limited. Several factors may affect the hypoglycaemia-CV relationships, such as the definition of hypoglycaemia, patient characteristics, co-morbidities (including chronic kidney disease) and antidiabetic drug therapy. However, the association between hypoglycaemia and dementia is bilateral. Both the disorders are more common in the elderly; thus, glycaemic goals should be carefully selected in older patients. Further research is needed to elucidate the impact of hypoglycaemia on CV disease.

Plasma potassium ranges associated with mortality across stages of chronic kidney disease: the Stockholm CREAtinine Measurements (SCREAM) project

Background

Small-scale studies suggest that hyperkalaemia is a less threatening condition in chronic kidney disease (CKD), arguing adaptation/tolerance to potassium (K⁺) retention. This study formally evaluates this hypothesis by estimating the distribution of plasma K⁺ and its association with mortality across CKD stages.

Methods

This observational study included all patients undergoing plasma K⁺ testing in Stockholm during 2006–11. We randomly selected one K⁺ measurement per patient and constructed a cross-sectional cohort with mortality follow-up. Covariates included demographics, comorbidities, medications and estimated glomerular filtration rate (eGFR). We estimated K⁺ distribution and defined K⁺ ranges associated with 90-, 180- and 365-day mortality.

Results

Included were 831 760 participants, of which 70 403 (8.5%) had CKD G3 (eGFR <60–30 mL/min) and 8594 (1.1%) had CKD G4–G5 (eGFR <30 mL/min). About 66 317 deaths occurred within a year. Adjusted plasma K⁺ increased across worse CKD stages: from median 3.98 (95% confidence interval 3.49–4.59) for eGFR >90 to 4.43 (3.22–5.65) mmol/L for eGFR ≤15 mL/min/1.73 m². The association between K⁺ and mortality was U-shaped, but it flattened at lower eGFR strata and shifted upwards. For instance, the range where the 90-day mortality risk increased by no more than 100% was 3.45–4.94 mmol/L in eGFR >60 mL/min, but was 3.36–5.18  in G3 and 3.26–5.53 mmol/L in G4–G5. In conclusion, CKD stage modifies K⁺ distribution and the ranges that predict mortality in the community.

Conclusion

Although this study supports the view that hyperkalaemia is better tolerated with worse CKD, it challenges the current use of a single optimal K⁺ range for all patients.