Evaluation of Hypokalemia

Disorders of Potassium

Abnormalities in serum potassium are commonly encountered in patients presenting to the emergency department. A variety of acute and chronic causes can lead to life-threatening illness in both hyperkalemia and hypokalemia. Here we summarize the relevant causes, risks, and treatment options for these frequently encountered disorders.

Potassium homeostasis - Physiology and pharmacology in a clinical context

Membrane voltage controls the function of excitable cells and is mainly a consequence of the ratio between the extra- and intracellular potassium concentration. Potassium homeostasis is safeguarded by balancing the extra-/intracellular distribution and systemic elimination of potassium to the dietary potassium intake. These processes adjust the plasma potassium concentration between 3.5 and 4.5 mmol/L. Several genetic and acquired diseases but also pharmacological interventions cause dyskalemias that are associated with increased morbidity and mortality. The thresholds at which serum K+ not only associates but also causes increased mortality are hotly debated. We discuss physiologic, pathophysiologic, and pharmacologic aspects of potassium regulation and provide informative case vignettes. Our aim is to help clinicians, epidemiologists, and pharmacologists to understand the complexity of the potassium homeostasis in health and disease and to initiate appropriate treatment strategies in dyskalemic patients.

Systematically Treating the Extra Sweet Pediatric Patient, Without Inadvertently Giving Them a Big Head

Treating pediatric patients with diabetic ketoacidosis (DKA) during transport can be complex and multifactorial. Cerebral edema is a frequent occurrence in pediatric patients with DKA; however, the signs often occur in a subtle manner. Overzealous correction of their blood glucose may result in cerebral edema as well as a cascade of electrolyte abnormalities. Pediatric patients with diabetes mellitus are prone to developing DKA. Serious complications from DKA in pediatrics often present acutely and rapidly.

An electrolyte flip flop - a patient with chronic hyperkalemic acidosis presenting with severe hypokalemic alkalosis

A 76-year-old man was evaluated in our emergency department (ED) for right toe swelling and pain. His initial ED workup revealed volume overload, uncontrolled hypertension, slow atrial fibrillation, refractory hypokalemia, mixed metabolic alkalosis and respiratory acidosis, with a normal plasma pH, and hypernatremia. His medical chart revealed long standing hyperkalemia and metabolic acidosis, related to his diabetic kidney disease. We hypothesized that a short course of daily SPS ingestion (Sodium Polystyrene Sulfonate, "Kayexalate") was the sole etiology for the compound electrolyte abnormalities and the electrolyte "flip flop". SPS ingestion can cause hypokalemia by excessive potassium binding in the gut. SPS exchanging potassium for sodium caused excessive sodium retention leading to hypernatremia, hypertension and volume overload. Volume overload worsened his chronic obstructive sleep apnea and yielded respiratory acidosis. Finally hypokalemia by itself was the main trigger for generation and maintenance of metabolic alkalosis. Urinary electrolytes, and renin and aldosterone levels taken at the ED ruled out primary aldosteronism and renal potassium and hydrogen loss. The patient's potassium was replenished by both PO and IV routes. He was treated for his volume overload and hypertension with furosemide. Spironolactone and amiloride, potassium sparing diuretics, were cautiously given only during his hypokalemic phase. His plasma sodium and potassium levels, blood pressure and volume status gradually improved. "Kayexalate" effect should be suspected in a patient presenting with unexplained hypokalemia and alkalosis, accompanied by volume overload rather than volume depletion, developing shortly after SPS ingestion. ED doctors should specifically ask CKD or ESRD patients on SPS, as it otherwise can skip the medication reconciliation process.

Subtyping hospitalized patients with hypokalemia by machine learning consensus clustering and associated mortality risks

Background

Hospitalized patients with hypokalemia are heterogeneous and cluster analysis, an unsupervised machine learning methodology, may discover more precise and specific homogeneous groups within this population of interest. Our study aimed to cluster patients with hypokalemia at hospital admission using an unsupervised machine learning approach and assess the mortality risk among these distinct clusters.

Methods

We performed consensus clustering analysis based on demographic information, principal diagnoses, comorbidities and laboratory data among 4763 hospitalized adult patients with admission serum potassium ≤3.5 mEq/L. We calculated the standardized mean difference of each variable and used the cutoff of ±0.3 to identify each cluster's key features. We assessed the association of the hypokalemia cluster with hospital and 1-year mortality.

Results

Consensus cluster analysis identified three distinct clusters that best represented patients’ baseline characteristics. Cluster 1 had 1150 (32%) patients, cluster 2 had 1344 (28%) patients and cluster 3 had 1909 (40%) patients. Based on the standardized difference, patients in cluster 1 were younger, had less comorbidity burden but higher estimated glomerular filtration rate (eGFR) and higher hemoglobin; patients in cluster 2 were older, more likely to be admitted for cardiovascular disease and had higher serum sodium and chloride levels but lower eGFR, serum bicarbonate, strong ion difference (SID) and hemoglobin, while patients in cluster 3 were older, had a greater comorbidity burden, higher serum bicarbonate and SID but lower serum sodium, chloride and eGFR. Compared with cluster 1, cluster 2 had both higher hospital and 1-year mortality, whereas cluster 3 had higher 1-year mortality but comparable hospital mortality.

Conclusion

Our study demonstrated the use of consensus clustering analysis in the heterogeneous cohort of hospitalized hypokalemic patients to characterize their patterns of baseline clinical and laboratory data into three clinically distinct clusters with different mortality risks.

Potassium and the kidney: a reciprocal relationship with clinical relevance

By controlling urinary potassium excretion, the kidneys play a key role in maintaining whole-body potassium homeostasis. Conversely, low urinary potassium excretion (as a proxy for insufficient dietary intake) is increasingly recognized as a risk factor for the progression of kidney disease. Thus, there is a reciprocal relationship between potassium and the kidney: the kidney regulates potassium balance but potassium also affects kidney function. This review explores this relationship by discussing new insights into kidney potassium handling derived from recently characterized tubulopathies and studies on sexual dimorphism. These insights reveal a central but non-exclusive role for the distal convoluted tubule in sensing potassium and subsequently modifying the activity of the sodium-chloride cotransporter. This is another example of reciprocity: activation of the sodium-chloride cotransporter not only reduces distal sodium delivery and therefore potassium secretion but also increases salt sensitivity. This mechanism helps explain the well-known relationship between dietary potassium and blood pressure. Remarkably, in children, blood pressure is related to dietary potassium but not sodium intake. To explore how potassium deficiency can cause kidney injury, we review the mechanisms of hypokalemic nephropathy and discuss if these mechanisms may explain the association between low dietary potassium intake and adverse kidney outcomes. We discuss if potassium should be repleted in patients with kidney disease and what role dietary potassium plays in the risk of hyperkalemia. Supported by data and physiology, we reach the conclusion that we should view potassium not only as a potentially dangerous cation but also as a companion in the battle against kidney disease.