Evaluation of Causes of Hyperkalemia in Systemic Lupus Erythematosus Patients: Retrospective Single-Center Experience

Abstract

Hyperkalemia is a major electrolyte disturbance with potentially life-threatening consequences. Varying prevalence and causes of hyperkalemia have been reported for study populations. Primary risk factors include renal insufficiency, diabetes mellitus (DM) and use of certain medication such as angiotensin converting enzyme (ACE) inhibitors. So far, causes of hyperkalemia in systemic lupus erythematosus (SLE) have not been investigated. Our aim here is to elaborate the causes underlying hyperkalemia and to determine the prevalence of hyperkalemic Type 4 renal tubular acidosis (RTA) in SLE patients. Among the patients followed up at the Department of Rheumatology due to SLE between January 2010 and February 2020, those with a potassium level of ≥5.5 mEq/L (hyperkalemia) were identified. For hyperkalemia patients, patient charts and digital record system were retrospectively searched for clinical and laboratory findings. Those with a non-SLE diagnosis and without hyperkalemia were excluded. Causes of hyperkalemia were classified as renal failure/insufficiency [acute kidney injury, chronic kidney disease (CKD)], medication, hormonal reasons (Addison’s disease, Type 4 RTA), pseudo-hemolysis, and others. Hyperkalemia was identified in 35 SLE patients, who were 40.1±16.9 years old, on average, and 85.7% of them were female. In 57.1% of the patients (n=20) lupus nephritis was identified. The most common type of renal involvement was Class IV lupus nephritis, at a rate of 68.7% (11/16). At the time of hyperkalemia diagnosis, mean duration of SLE disease was 5.2±5.52 years and mean SLE disease activation index (SLEDAI) was 19.8±13.4. Mean potassium level was 6.6 ±1.08 mEq/L. Metabolic acidosis was detected in 40% of the patients. The most common cause of hyperkalemia was renal failure/disease in 45.7% (n=16), followed by use of medication in 25.7%. In two (5%) patients hyperkalemia was attributed to Type 4 RTA. When patient subsets were compared by their causes of hyperkalemia for clinical and laboratory parameters, subset of renal failure/disease has a higher level of creatinine (p≤0.001), but there was no difference in other parameters. In line with its occurrence in general population, hyperkalemia in SLE most often occurs due to renal failure/disease. In addition, Type 4 RTA is an important reason for hyperkalemia. SLE patients presenting with hyperkalemia should also be queried for hyperkalemic Type 4 RTA, once the common causes for hyperkalemia are ruled out or in the event of persistent hyperkalemia.