Adrenergic modulation of extrarenal potassium disposal

New strategies for the treatment of hyperkalemia

Renin-angiotensin-aldosterone system inhibitors (RAASi) and mineralocorticoid receptor antagonists (MRAs) are key drugs in the management of patients with cardiovascular diseases (CVD), particularly those with hypertension, diabetes, chronic kidney disease and heart failure (HF), given their demonstrated effectiveness in reducing the risk of both surrogate and hard endpoints. Despite their positive impact on the outcome, patients with RAASi and MRAs are particularly vulnerable to hyperkalaemia, with approximately 50 % of these individuals experiencing two or more recurrences annually. The common practice of reducing the dose or discontinuing the treatment with RAASi and MRAs in conditions of hyperkalaemia results in suboptimal management of these patients, with a potential impact on their mortality and morbidity risk. Recent guidelines from cardiovascular and renal international societies increasingly recognize the need for alternative strategies to manage the risk of hyperkalaemia, allowing the continuation of RAASi and MRA therapies. In this review, we summarise the new potential options available to manage hyperkalaemia in patients with CVD and the recommendations of the most recent guidelines on the topic.

Re-Thinking Hyperkalaemia Management in Chronic Kidney Disease-Beyond Food Tables and Nutrition Myths: An Evidence-Based Practice Review

Potassium dysregulation can be life-threatening. Dietary potassium modification is a management strategy for hyperkalaemia. However, a 2017 review for clinical guidelines found no trials evaluating dietary restriction for managing hyperkalaemia in chronic kidney disease (CKD). Evidence regarding dietary hyperkalaemia management was reviewed and practice recommendations disseminated. A literature search using terms for potassium, hyperkalaemia, and CKD was undertaken from 2018 to October 2022. Researchers extracted data, discussed findings, and formulated practice recommendations. A consumer resource, a clinician education webinar, and workplace education sessions were developed. Eighteen studies were included. Observational studies found no association between dietary and serum potassium in CKD populations. In two studies, 40-60 mmol increases in dietary/supplemental potassium increased serum potassium by 0.2-0.4 mmol/L. No studies examined lowering dietary potassium as a therapeutic treatment for hyperkalaemia. Healthy dietary patterns were associated with improved outcomes and may predict lower serum potassium, as dietary co-factors may support potassium shifts intracellularly, and increase excretion through the bowel. The resource recommended limiting potassium additives, large servings of meat and milk, and including high-fibre foods: wholegrains, fruits, and vegetables. In seven months, the resource received > 3300 views and the webinar > 290 views. This review highlights the need for prompt review of consumer resources, hospital diets, and health professionals' knowledge.

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.

Serum potassium changes during hypothermia and rewarming: a case series and hypothesis on the mechanism

Introduction

Hypokalemia is known to occur in association with therapeutically induced hypothermia and is usually managed by the administration of potassium (K+).

Methods

We reviewed data from 74 patients who underwent a therapeutic hypothermia protocol at our medical institution.

Results

In four patients in whom data on serum K+ and temperature were available, a strong positive correlation between serum K+ and body temperature was found. Based on the close positive relationship between serum K+ and total body temperature, we hypothesize that serum K+ decreases during hypothermia owing to decreased activity of temperature-dependent K+ exit channels that under normal conditions are sufficiently active to match cellular K+ intake via sodium/K+/adenosine triphosphatase. Upon rewarming, reactivation of these channels results in a rapid increase in serum K+ as a result of K+ exit down its concentration gradient.

Conclusion

Administration of K+ during hypothermia should be done cautiously and avoided during rewarming to avoid potentially life-threatening hyperkalemia. K+ exit via temperature-dependent K+ channels provides a logical explanation for the rebound hyperkalemia. K+ exit channels may play a bigger role than previously appreciated in the regulation of serum K+ during normal and pathophysiological conditions.

Acute hyperkalemia in adults

Hyperkalemia is a common, life-threatening medical situation in chronic renal disease patients in the emergency department (ED). Since hyperkalemia does not present with any specific symptom, it is difficult to diagnose clinically. Hyperkalemia causes broad and dramatic medical presentations including cardiac arrhythmia and sudden death. Hyperkalemia is generally determined through serum measurement in the laboratory. Treatment includes precautions to stabilize cardiac membranes, shift potassium from the extracellular to the intracellular, and increase potassium excretion. The present article discusses the management of hyperkalemia in the ED in the light of current evidence.

Potassium disorders in pediatric emergency department: Clinical spectrum and management

INTRODUCTION

Potassium abnormalities are frequent in intensive care but their incidence in the emergency department is unknown.

AIM

We describe the spectrum of potassium abnormalities in our tertiary-level pediatric emergency department.

METHODS

Retrospective case-control study of all the patients admitted to a single-center tertiary emergency department over a 2.5-year period. We compared patients with hypokalemia (<3.0mEq/L) and patients with hyperkalemia (>6.0mEq/L) against a normal randomized population recruited on a 3:1 ratio with potassium levels between 3.5 and 5mEq/L.

RESULTS

Between January 1, 2013 and August 31, 2016 we admitted 108,209 patients to our emergency department. A total of 9342 blood samples were tested and the following potassium measurements were found: 60 cases of hypokalemia (2.8±0.2mEq/L) and 55 cases of hyperkalemia (6.4±0.6mEq/L). In total, 200 patients with normokalemia were recruited (4.1±0.3mEq/L). The main causes of the disorders were non-specific: lower respiratory tract infection (23%) and fracture (15%) for hypokalemia, lower respiratory tract (21.8%) and ear-nose-throat infections (20.0%) for hyperkalemia. Patients with hyperkalemia had an elevated creatinine level (0.72±1.6 vs. 0.40±0.16mg/dL, P<0.0001) with lower bicarbonate (19.4±3.8 vs. 21.8±2.8mmol/L, P=0.0001) and higher phosphorus levels (1.95±0.6 vs. 1.42±0.27mg/dL, P=0.0001). Patients with hypokalemia had an elevated creatinine level (0.66±0.71 vs. 0.40±0.16mg/dL, P<0.0001) and a lower phosphorus level (1.12±0.31 vs. 1.42±0.27mg/dL, P=0.0001). We did not observe significant differences in pH, PCO2, base excess and lactate, or in the mean duration of hospitalization in general wards and pediatric intensive care units according to the PIM and PRISM scores.

DISCUSSION

Dyskalemia is rare in emergency department patients: 0.64% for hypokalemia and 0.58% for hyperkalemia. This condition could be explained by a degree of renal failure due to transient volume disturbance. The main mechanism is dehydration due to digestive losses, polypnea in young patients, and poor intake. In the case of hypokalemia, poor intake and digestive losses could be the main explanation. These disorders resolve easily with feeding or perfusion and do not impair development.

CONCLUSION

Dyskalemia is rare in emergency department patients and is easily resolved with feeding or perfusion. A plausible etiological mechanism is a transient volume disturbance. Dyskalemia is not predictive of poor development in the emergency pediatric population.

Serum Potassium Is Associated with Cognitive Decline in Patients with Lewy Body Dementia

BACKGROUND

Epidemiological studies link serum potassium (K+) to cognitive performance, but whether cognitive prognosis in dementia is related to K+ levels is unknown.

OBJECTIVE

To determine if K+ levels predict cognitive prognosis in dementia and if this varies according to diagnosis or neuropathological findings.

METHODS

This longitudinal cohort study recruited 183 patients with mild Alzheimer's disease or Lewy body dementia (LBD). Serum K+ and eGFR were measured at baseline and medications which could affect K+ registered. The Mini-Mental State Examination (MMSE) was measured annually over 5 years, and mortality registered. Association between K+ and √(30 -MMSE) was estimated overall, and according to diagnosis (joint model). Associations between MMSE-decline and K+ were assessed in two subgroups with neuropathological examination (linear regression) or repeated measurements of K+ over 3 years (mixed model).

RESULTS

Serum K+ at baseline was associated with more errors on MMSE over time (Estimate 0.18, p = 0.003), more so in LBD (p = 0.048). The overall association and LBD interaction were only significant in the 122 patients not using K+ relevant medication. Repeated K+ measures indicated that the association with MMSE errors over time was due to a between-person effect (p < 0.05, n = 57). The association between the annual MMSE decline was stronger in patients with autopsy confirmed LBD and more α-synuclein pathology (all: p < 0.05, n = 41).

CONCLUSION

Higher serum K+ predicts poorer cognitive prognosis in demented patients not using medications which affect K+, likely a between-person effect seen mainly in LBD.

Hyperkalaemia: aetiology, epidemiology, and clinical significance

Disturbances in the potassium homeostasis are common among patients with heart failure (HF) and negatively affect clinical outcome. Patients with HF have a higher prevalence of common risk factors related to hyperkalaemia, including diabetes mellitus, hypertension, and chronic kidney disease. Furthermore, the use of renin-angiotensin-aldosterone system (RAAS) inhibitors, is an important risk factor for developing hyperkalaemia. The association between hyperkalaemia and mortality is not unequivocal, depends on the study type (trial vs. real-world setting) and is often confounded. More importantly, hyperkalaemia is an important cause of discontinuation or failure to uptitrate to guideline recommended dosages of RAAS inhibitors, which in turn may negatively impact clinical outcomes. The goal of this review is to discuss the epidemiology, aetiology, and clinical consequences of potassium disturbances in HF.

New developments in the pharmacotherapeutic management of heart failure in elderly patients: concerns and considerations

INTRODUCTION

Heart failure (HF) remains a major public health problem worldwide, affecting approximately 23 million patients, and is predominantly a disease of the elderly population. Elderly patients mostly suffer from HF with preserved ejection fraction (HFpEF), which often presents with multiple co-morbidities and they require multiple medical treatments. This, together with the heterogeneous phenotype of HFpEF, makes it a difficult syndrome to diagnose and treat. Areas covered: Although HF is most abundant in the elderly, this group is still underrepresented in clinical trials, which results in the lack of evidence-based medical regimens. The current review has focused on new potential therapies for this poorly studied population. The focus will be on several classes of drugs currently recommended or might be expected soon. These will include sacubitril/valsartan (former LCZ696), Omecamtiv mecarbil, Vericiguat, Ivabradine, mineralocorticoid receptor antagonists (MRAs) and potassium binders. Expert opinion: We discuss promising new treatments and hypothesize that personalized approaches will be needed to treat elderly patients optimally. Medical doctors should not only focus on HF therapy, but comorbidities and polypharmacy should also influence therapeutic decision making. Furthermore, the importance of quality of life as a management endpoint should not be underestimated in the frail elderly.

Transient Left Bundle Branch Block due to Severe Hyperkalemia

Hyperkalemia is a potentially life-threatening electrolyte imbalance that can lead to sudden death from cardiac arrhythmias and asystole. We present a case of transient left bundle branch block pattern on an electrocardiogram (ECG) secondary to hyperkalemia in a patient with history of end-stage renal disease. A 52-year-old man presented to the emergency room (ER) with chief complaints of weakness and lethargy after missing his regularly scheduled session of hemodialysis. A 12-lead ECG in the ER showed sinus tachycardia at 118 beats/min, wide QRS complexes, peaked T waves and left bundle branch block-like pattern. The initial basic metabolic panel revealed a serum potassium level of 8.8 mEq/L. Subsequently, the patient underwent emergent hemodialysis. Serum chemistry after hemodialysis showed improvement in serum potassium to 4.3 mEq/L. Repeat ECG performed after correcting potassium showed dissolution of left bundle branch block finding.

Electrolytes and Fluid Management in Hemodialysis and Peritoneal Dialysis

The kidney is a complex and vital organ, regulating the electrolyte and fluid status of the human body. As hemodialysis (HD) and peritoneal dialysis (PD) are forms of renal replacement therapy and not an actual kidney, they do not possess the same physiologic regulation of both fluid and electrolytes. Precise regulation of fluid and electrolytes in the HD and PD population remains a constant challenge. In this review, fluid status of both HD and PD will be examined, as well as sodium, potassium, phosphorous, and calcium. Each electrolyte will be analyzed by its physiological significance, the complications that arise when a proper balance cannot be maintained, and methods to correct these imbalances. An overview of the fluid compartments and volume of distribution within the body will be discussed. Ultrafiltration, a modality used in both forms of renal replacement therapy, will be defined, along with its impact on fluid status. Fluid assessment will be addressed, along with proper maintenance of fluid homeostasis. By having an understanding of the pathophysiology behind the fluid and electrolyte abnormalities that occur in end-stage renal disease, one can direct proper management with medications, diet, and alterations in dialysis to provide patients with the most optimal form of renal replacement therapy available.

Sodium Zirconium Cyclosilicate (ZS-9): A Novel Agent for the Treatment of Hyperkalemia

Hyperkalemia is a potentially life-threatening electrolyte abnormality that may be caused by select medications, underlying organ dysfunction, or alterations in potassium homeostasis. Treatment for this condition has remained largely unchanged since the release of sodium polystyrene sulfonate (SPS) in 1958. Despite its widespread use, the safety and efficacy of SPS remains controversial. Two novel potassium-binding resins have emerged in recent years. Patiromer was the first of these to receive U.S. Food and Drug Administration approval for the treatment of hyperkalemia in October 2015. A second potassium-binding resin, a zirconium cyclosilicate currently known as ZS-9, may provide yet another alternative to the archetypal treatment with SPS. ZS-9 is an orally administered nonabsorbed inorganic compound that selectively binds potassium ions in vivo. Two phase III multicenter, randomized, placebo-controlled, double-blind trials have evaluated ZS-9 for the treatment of acute hyperkalemia. In this review, we discuss the pharmacology, clinical efficacy, safety, and potential place in therapy of ZS-9 for the enhanced elimination of potassium in the setting of hyperkalemia.

Hyperkalemia: Disorders of Internal and External Potassium Balance

The serum potassium level is normally preserved de spite changes in potassium intake and output (the exter nal potassium balance) and changes in its distribution in the body (the internal potassium balance). External potassium homeostasis depends primarily on renal ex cretion of the daily exogenous potassium burden. Inter nal homeostasis depends on the extrarenal regulation of potassium. Skeletal muscle and liver are the dominant sites of that regulation. The two chief regulators of inter nal balance are insulin and catecholamines, the latter acting through β-adrenergic receptors. Acid-base bal ance and the cellular potassium content are other important regulators of internal balance. The major disorders of external balance are renal failure, hypo reninemic hypoaldosteronism, interstitial nephritis, and a variety of drugs that impair renal potassium excretion. The major disorders of internal balance are diabetes mellitus, acidosis, medications, and release of endoge nous potassium during vigorous exercise, traumatic muscle injury, or tumor lysis chemotherapy. These dis orders frequently result in troublesome elevations of serum potassium in the intensive care setting. Their re view in this article includes a thorough discussion of the evaluation and proper management of the hyperkalemic patient.

Possible Metoprolol-Induced Hyperkalemia

Hyperkalemia can be a life-threatening event due to the risk of potentially fatal arrhythmias. Hyperkalemia has been reported in 1.3% (serum potassium greater than 6.0 mEq/mL) to 10% (greater than 5.3 mEq/mL) of patients. Hyperkalemia secondary to beta-adrenergic receptor blockade can occur in 1% to 5% of patients and is more likely to occur in non-cardio-selective beta-blockers versus cardio-selective beta-blockers. This case report describes hyperkalemia in a 72-year-old female with diabetes and underlying chronic renal failure receiving metoprolol. Chronically, potassium balance is maintained by the kidney. In acute situations, such as a larger than normal potassium load, both the kidney and the body's cells react to maintain normal potassium levels. Generally, hyperkalemia occurs secondary to 3 mechanisms: excessive potassium intake, disturbed cellular uptake of potassium, or impaired renal excretion of potassium. Beta-blockers, when used in patients with comorbidities such as renal dysfunction or insulin insufficiency, can potentially cause hyperkalemia. As demonstrated in this case report, hyperkalemia can occur in patients treated with cardio-selective beta-blockers with concurrent risk factors. Health care professionals need to be aware of this potentially life-threatening event to effectively prevent occurrences of beta-blocker-induced hyperkalemia.

Postoperative hyperkalemia

Hyperkalemia occurs frequently in hospitalized patients and is of particular concern for those who have undergone surgery, with postoperative care provided by clinicians of many disciplines. This review describes the normal physiology and how multiple perioperative factors can disrupt potassium homeostasis and lead to severe elevations in plasma potassium concentration. The pathophysiologic basis of diverse causes of hyperkalemia was used to broadly classify etiologies into those with altered potassium distribution (e.g. increased potassium release from cells or other transcellular shifts), reduced urinary excretion (e.g. reduced sodium delivery, volume depletion, and hypoaldosteronism), or an exogenous potassium load (e.g. blood transfusions). Surgical conditions of particular concern involve: rhabdomyolysis from malpositioning, trauma or medications; bariatric surgery; vascular procedures with tissue ischemia; acidosis; hypovolemia; and volume or blood product resuscitation. Certain acute conditions and chronic co-morbidities present particular risk. These include chronic kidney disease, diabetes mellitus, many outpatient preoperative medications (e.g. beta blockers, salt substitutes), and inpatient agents (e.g. succinylcholine, hyperosmolar volume expanders). Clinicians need to be aware of these pathophysiologic mechanisms for developing perioperative hyperkalemia as many of the risks can be minimized or avoided.

A complication to be aware of: hyperkalaemia following propranolol therapy for an infant with intestinal haemangiomatozis

Infantile haemangiomas, benign vascular tumours seen in 4-10% of infants are characterised by their spontaneous remission following a 3-9 month period of dynamic growth. Propranolol has been reported to be used as a successful treatment of severe symptomatic infantile haemangiomas. Hyperkalaemia has not been recognised as a serious effect of propranolol since recently. Here, we would like to portray a 2-year-old male patient with intestinal haemangiomatosis who presented with severe hyperkalaemia and was successfully managed with hydration, loop diuretics, potassium binding granules, inhaler β-2 agonists and insulin. To date, this is the first case of intestinal haemangiomatosis complicated with severe hyperkalaemia. Our case suggested the idea of close monitorisation of potassium levels as well as haemodynamic status at the initialisation of the propranolol treatment.

Life-threatening hyperkalemia in a patient with normal renal function

With media focus on benefits from reducing sodium intake, there is increased popularity of salt substitutes, typically potassium chloride. While viewed by the public as a healthy alternative to standard table salt, less appreciated is the severe risk with certain comorbidities and medications. We report the case of an elderly female with chronically high salt substitute intake, normal renal function, diabetes, hypertension treated with angiotensin-converting enzyme inhibitor and beta blockade, who developed life-threatening hyperkalemia after a minimally invasive outpatient procedure. We describe the pathophysiology of the disruption in potassium homeostasis and emphasize the importance of dietary history and educating high-risk patients to avoid salt substitutes.

Hyperkalemia complicating propranolol treatment of an infantile hemangioma

Propranolol treatment was recently reported to be successful for the management of severe infantile hemangioma. Known adverse effects of propranolol treatment include transient bradycardia, hypotension, hypoglycemia, and bronchospasm (in patients with underlying spastic respiratory illnesses), which led to a general recommendation to gradually increase propranolol dosage and closely monitor patients' hemodynamics at the onset of therapy. To date, no serious or unexpected adverse effects that required specific intervention have been reported. In this report, we describe the case of a 17-week-old female preterm infant who presented with a large, ulcerated, cutaneous-subcutaneous hemangioma of the right lateral thoracic wall, which we treated successfully with propranolol. A few days into therapy, a potentially life-threatening adverse effect, severe hyperkalemia, was observed and required treatment with loop diuretics, fluids, and nebulized salbutamol to normalize her serum potassium levels. This therapy could be gradually tapered and finally discontinued only after several weeks of propranolol treatment. Our case report indicates that, at least during the initial phase of the propranolol treatment of infantile hemangioma, close monitoring of serum electrolytes, besides the monitoring of hemodynamics and blood glucose, is necessary.

Electrolyte disturbances associated with commonly prescribed medications in the intensive care unit

Electrolyte imbalances are common in critically ill patients. Although multiple disease states typically encountered in the intensive care unit may be responsible for the development of electrolyte disorders, medications may contribute to these disturbances as well. Medications can interfere with the absorption of electrolytes, alter hormonal responses affecting homeostasis, as well as directly impact organ function responsible for maintaining electrolyte balance. The focus on this review is to identify commonly prescribed medications in the intensive care unit and potential electrolyte disturbances that may occur as a result of their use. This review will also discuss the postulated mechanisms associated with these drug-induced disorders. The specific drug-induced electrolyte disorders discussed in this review involve abnormalities in sodium, potassium, calcium, phosphate, and magnesium. Clinicians encountering electrolyte disturbances should be vigilant in monitoring the patient's medications as a potential etiology. Insight into these drug-induced disorders should allow the clinician to provide optimal medical management for the critically ill patient, thus improving overall healthcare outcomes.

Beta-blockers, trimethoprim-sulfamethoxazole, and the risk of hyperkalemia requiring hospitalization in the elderly: a nested case-control study

BACKGROUND AND OBJECTIVES

The simultaneous use of beta adrenergic receptor blockers (beta-blockers) and trimethoprim-sulfamethoxazole (TMP-SMX) may confer a high risk of hyperkalemia.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Two nested case-control studies were conducted to examine the association between hospitalization for hyperkalemia and the use of TMP-SMX in older patients receiving beta-blockers. Linked health administrative records from Ontario, Canada, were used to assemble a cohort of 299,749 beta-blockers users, aged 66 years or older and capture data regarding medication use and hospital admissions for hyperkalemia.

RESULTS

Over the study period from 1994 to 2008, 189 patients in this cohort were hospitalized for hyperkalemia within 14 days of receiving a study antibiotic. Compared with amoxicillin, the use of TMP-SMX was associated with a substantially greater risk of hyperkalemia requiring hospital admission (adjusted odds ratio, 5.1; 95% confidence interval [CI], 2.8 to 9.4). No such risk was identified with ciprofloxacin, norfloxacin, or nitrofurantoin. When dosing was considered, the association was greater at higher doses of TMP-SMX. When the primary analysis was repeated in a cohort of non-beta-blocker users, the risk of hyperkalemia comparing TMP-SMX to amoxicillin was not significantly different from that found among beta-blocker users.

CONCLUSIONS

Although TMP-SMX is associated with an increased risk of hyperkalemia in older adults, these findings show no added risk when used in combination with beta-blockers.

Hypokalemia and outcomes in patients with chronic heart failure and chronic kidney disease: findings from propensity-matched studies

BACKGROUND

Little is known about the effects of hypokalemia on outcomes in patients with chronic heart failure (HF) and chronic kidney disease.

METHODS AND RESULTS

Of the 7788 patients with chronic HF in the Digitalis Investigation Group trial, 2793 had chronic kidney disease, defined as estimated glomerular filtration rate <60 mL/min per 1.73 m(2). Of these, 527 had hypokalemia (serum potassium <4 mEq/L; mild) and 2266 had normokalemia (4 to 4.9 mEq/L). Propensity scores for hypokalemia were used to assemble a balanced cohort of 522 pairs of patients with hypokalemia and normokalemia. All-cause mortality occurred in 48% and 36% of patients with hypokalemia and normokalemia, respectively, during 57 months of follow-up (matched hazard ratio when hypokalemia was compared with normokalemia, 1.56; 95% CI, 1.25 to 1.95; P<0.0001). Matched hazard ratios (95% CIs) for cardiovascular and HF mortalities and all-cause, cardiovascular, and HF hospitalizations were 1.65 (1.29 to 2.11; P<0.0001), 1.82 (1.28 to 2.57; P<0.0001), 1.16 (1.00 to 1.35; P=0.036), 1.27 (1.08 to 1.50; P=0.004), and 1.29 (1.05 to 1.58; P=0.014), respectively. Among 453 pairs of balanced patients with HF and chronic kidney disease, all-cause mortality occurred in 47% and 38% of patients with mild hypokalemia (3.5 to 3.9 mEq/L) and normokalemia, respectively (matched hazard ratio, 1.31; 95% CI, 1.03 to 1.66; P=0.027). Among 169 pairs of balanced patients with estimated glomerular filtration rate <45 mL/min per 1.73 m(2), all-cause mortality occurred in 57% and 47% of patients with hypokalemia (<4 mEq/L; mild) and normokalemia, respectively (matched hazard ratio, 1.53; 95% CI, 1.07 to 2.19; P=0.020).

CONCLUSIONS

In patients with HF and chronic kidney disease, hypokalemia (serum potassium <4 mEq/L) is common and associated with increased mortality and hospitalization.

Adrenergic control of Na+-K+-homoeostasis

Catecholamines induce hypokalaemia via stimulation of beta-adrenoceptors, primarily in skeletal muscle but also in other tissues. This is the result of increased active Na+-K+-transport, leading to a rise in the intracellular K+/Na+-ratio and hyperpolarisation in muscle cells. These effects are mediated by 3', 5'-cyclic adenosine monophosphate, can be detected down to physiological concentrations of adrenaline and noradrenaline, and are seen both in vitro and in vivo. Catecholamines released from the adrenal medulla as well as sympathetic nerve endings are of importance in clearing K+ from the extracellular water space during K+-loading or exercise. beta 2-adrenoceptor agonists can be used in the treatment of hyperkalaemia, and beta-adrenoceptor blockade may induce hyperkalaemia, in particular during exercise. The effects of catecholamines on the contractile performance of skeletal muscles are partly due to stimulation of the active electrogenic Na+-K+-transport across the sarcolemma.

The effect of adrenergic blockade on potassium concentrations in different conditions

A moderate increase in serum potassium concentrations has been observed in several controlled clinical trials with beta-blockers. This increase cannot be explained by the retention of potassium in the organism, and is probably caused by the redistribution of potassium from intracellular to extracellular compartments. beta-adrenergic mechanisms seem to be concerned in the extrarenal handling of the potassium-load in man, presumably by inducing an increased uptake of potassium in muscular cells and liver cells. These beta-adrenergic mechanisms are probably of the beta 2-type. In theory there are several conditions in which it is important to have a defence against hyperkalaemia from exogenous or endogenous sources for example, during heavy physical exercise, after a potassium-rich meal, or after traumatic tissue damage. Available data indicate that non-selective beta-blockade increases serum potassium concentrations during and after heavy exercise and during coronary bypass. The clinical implications of these findings are unknown.

Plasma potassium and phosphate concentrations--influence by adrenaline infusion, beta-blockade and physical exercise

Infusion of adrenaline into healthy male subjects reduced the plasma concentrations of both potassium and phosphate to a similar extent, in a dose-dependent manner, an effect which was prevented by the administration of propranolol. Ergometer bicycling until exhaustion, which caused marked accumulation of lactic acid in the blood and reduction of pH, induced great elevations of both plasma potassium and phosphate with close relationships between the raised plasma concentrations and the reduction in pH, also during beta-blockade. However, longer-term aerobic exercise, without acidosis, also caused some rise of the potassium and phosphate concentrations. During recovery from anaerobic, but not from aerobic, exercise there was a rapid decrease of the plasma potassium levels while the phosphate values normalized gradually together with pH. From measurements of the ion concentrations both in the femoral effluent of one leg, which carried out maximal isokinetic work, and in the opposite antecubital vein it could be calculated that there was for potassium, but not for phosphate, a post-exercise uptake both in the exercised muscle and in the entire organism, indicating the participation of systemic factors.

Comparative effects of carvedilol and lercanidipine on ultrafiltration and solute transport in CAPD patients

BACKGROUND

Peritonitis, the type of buffer used in the dialysate, continue ambulatory peritoneal dialysis (CAPD) of greater than two years duration, increased exposure to dialysate glucose, diabetes mellitus, and the use of beta blockers may contribute to impaired ultrafiltration.

OBJECTIVES

The aim of the present study is to compare the effects of a calcium-channel blocker and a beta-blocker on the peritoneal transport and clearance.

METHODS

We studied 48 patients with ESRD on chronic peritoneal dialysis, included 27 females and 19 males with mean age 42.6 +/- 16.4 years. Two patients were excluded from the study due to peritonitis. Patients were treated either with carvedilol or lercanidipine. In all patients; peritoneal equilibration test (PET), ultrafiltration (UF), Kt/V ratio, creatinine clearance (CrCl), systolic blood pressure, diastolic blood pressure, serum BUN, creatinine, glucose, sodium, potassium, albumin, cholesterol, and triglyceride values were obtained before and after 8 weeks from the start of the drug treatment.

RESULTS

Lercanidipine and carvedilol showed a good antihypertensive effect in CAPD patients. Both drugs had a good tolerability profile and showed no effect on plasma lipids. There were no differences in terms of PET, ultrafiltration, Kt/V ratio, CrCl, systolic blood pressure, diastolic blood pressure, serum BUN, creatinine, glucose, sodium, and potassium values between both patient groups. After antihypertensive treatment, neither group showed a difference in the above-mentioned parameters (p > 0.05) except potassium, which was significantly higher in the carvedilol group (p < 0.05).

CONCLUSIONS

In CAPD patients. short-term usage of carvedilol has no effect on ultrafiltration and solute transport like lercanidipine. Both drugs showed a good antihypertensive effect.

[Hyperkalemia induced by atenolol]

We report a 53-year-old woman with hyperkaliemia secondary to treatment with atenolol. The diagnosis of atenolol induced hyperkaliemia was obtained after excluding other causes of hyperkaliemia and normalization of potassium serum level following the discontinuation of this medication without any other modification (treatment or diet). Furthermore, when atenolol was again introduced, serum potassium level increased and normalized when atenol was definitively discontinued. The mechanism of hyperkaliemia we suspected is probably a reduction of potassium intracellular transfer.

Hyperkalemia risk and treatment of heart failure

This article briefly reviews the participation of the kidney in heart failure and the renal consequences of the treatment, with special emphasis on the risk for hyperkalemia and its management in daily clinical practice.

A propensity-matched study of low serum potassium and mortality in older adults with chronic heart failure

OBJECTIVE

Most HF patients are older adults, yet the associations of low serum potassium and outcomes in these patients are unknown. We studied the effect of low serum potassium in a propensity-matched population of elderly HF patients.

METHODS

Of the 7788 patients in the Digitalis Investigation Group trial, 4036 were >or=65 years. Of these, 3598 had data on baseline serum potassium and 324 with potassium >or=5 mEq/L were excluded. Remaining patients were categorized into low (<4 mEq/L; n=590) and normal (4-4.9 mEq/L; n=2684) potassium groups. Propensity scores for low-potassium, calculated for each patient, were used to match 561 low-potassium and 1670 normal-potassium patients. Association of low potassium and outcomes were assessed using matched Cox regression analyses.

RESULTS

Patients had a mean (+/-SD) age of 72 (+/-6) years, 29% were women and 12% were non-whites. Of the 561 low-potassium patients, 500 had low-normal (3.5-3.9 mEq/L) potassium. All-cause mortality occurred in 37% (rate, 1338/10,000 person-years) normal-potassium and 43% (rate, 1594/10,000 person-years) low-potassium patients (hazard ratio {HR} for low-potassium, 1.22; 95% confidence interval {CI}, 1.04-1.44; p=0.014). Low-normal (3.5-3.9 mEq/L) potassium levels had a similar association with mortality (HR, 1.19, 95% CI, 1.00-1.41, p=0.049). Low (HR, 1.10; 95% CI, 0.96-1.25; p=0.175) or low-normal (HR=1.09, 95% CI=0.95-1.25, p=0.229) serum potassium levels were not associated with all-cause hospitalization.

CONCLUSIONS

In a propensity-matched population of elderly ambulatory chronic HF patients, well-balanced in all measured baseline covariates, low and low-normal serum potassium were associated with increased mortality but had no association with hospitalization.

Cardiac arrests associated with hyperkalemia during red blood cell transfusion: a case series

BACKGROUND

Transfusion-associated hyperkalemic cardiac arrest is a serious complication of rapid red blood cell (RBC) administration. We examined the clinical scenarios and outcomes of patients who developed hyperkalemia and cardiac arrest during rapid RBC transfusion.

METHODS

We retrospectively reviewed the Mayo Clinic Anesthesia Database between November 1, 1988, and December 31, 2006, for all patients who developed intraoperative transfusion-associated hyperkalemic cardiac arrest.

RESULTS

We identified 16 patients with transfusion-associated hyperkalemic cardiac arrest, 11 adult and 5 pediatric. The majority of patients underwent three types of surgery: cancer, major vascular, and trauma. The mean serum potassium concentration measured during cardiac arrest was 7.2 +/- 1.4 mEq/L (range, 5.9-9.2 mEq/L). The number of RBC units administered before cardiac arrest ranged between 1 (in a 2.7 kg neonate) and 54. Nearly all patients were acidotic, hyperglycemic, hypocalcemic, and hypothermic at the time of arrest. Fourteen (87.5%) patients received RBC via central venous access. Commercial rapid infusion devices (pumps) were used in 8 of 11 (72.7%) of the adult patients, but RBC units were rapidly administered (pressure bags, syringe pumped) in all remaining patients. Mean resuscitation duration was 32 min (range, 2-127 min). The in-hospital survival rate was 12.5%.

CONCLUSION

The pathogenesis of transfusion-associated hyperkalemic cardiac arrest is multifactorial and potassium increase from RBC administration is complicated by low cardiac output, acidosis, hyperglycemia, hypocalcemia, and hypothermia. Large transfusion of banked RBCs and conditions associated with massive hemorrhage should raise awareness of the potential for hyperkalemia and trigger preventative measures.

Potassium Chloride Supplementation Alone May Not Improve Hypokalemia in Thyrotoxic Hypokalemic Periodic Paralysis

This article reports a 29-year-old man who came to the Emergency Department because of sudden onset of bilateral lower extremity weakness and inability to walk after intake of a high carbohydrate meal and alcohol. He was found to have severe hypokalemia, with K(+) level at 1.7 mmol/L. However, after administration of potassium chloride (KCl), 10 mEq/h intravenous (i.v.) drip for 4 h, follow-up serum potassium was even lower at 1.5 mmol/L and the patient complained of persistent weakness. Twenty mg of propranolol, a non-selective beta-blocker, was given orally and a dramatic improvement of muscle power to grade 5 was noted after 30 min of administration. On the fifth day after discharge, he had another episode of bilateral lower extremity weakness after ingesting a mouthful of alcohol. Muscle power recovered completely after i.v. drip of KCl, 20 mEq. Laboratory data revealed an underlying primary hyperthyroidism for which he was given anti-thyroid agents and beta-blockers.

A role for epinephrine in post-traumatic hypokalemia

We have previously described a high incidence of admission hypokalemia in trauma patients at our institution. We subsequently performed a prospective study of 112 trauma patients to examine the possible etiologies of post-traumatic hypokalemia. Trauma patients >or=5 years old were evaluated within 6 h of injury with a variety of studies including catecholamines, cortisol, and insulin levels, with studies repeated 24 to 36 h after admission. No potassium replacement was given during this time. Demographic factors such as age, types of injury, and severity of injuries were collected. We found that the mean age of those with post-traumatic hypokalemia (<or=3.5 mEq/L) was significantly younger (29 vs. 37 years old; P = 0.004) and epinephrine levels were significantly higher (863 vs. 406 pg/mL; P = 0.01) when compared with normokalemic patients on admission. At 24 to 36 h, the hypokalemia group compared with the normokalemic patients showed a significant rise in the mean potassium levels (17.2% vs. 4.1%; P < 0.001), a significant fall in mean epinephrine levels (-86.6% vs. -81.4%; P < 0.001), and a significant rise in insulin levels (161% vs. 24%; P < 0.005). Finally, because our previous study had shown that post-traumatic hypokalemia was predictive of injury severity score, 4 trauma admission groups were compared with regard to potassium levels and injury severity score. Those trauma patients with both high injury severity and hypokalemia had significantly higher admission epinephrine levels (1222 vs. 290 pg/mL; P = 0.005), glucose levels (174 vs. 126 mg/dL; P = 0.001), and lower carbon dioxide levels (21.3 vs. 24.6 mEq/L; P < 0.03) than those trauma patients with less severe injury and normokalemia. We conclude that post-traumatic hypokalemia seems to be related to a rise in epinephrine levels, that this rise in epinephrine levels seems to be blunted in older patients, and that post-traumatic hypokalemia is rapidly reversible without specific therapy.

The influence of the AA 16 beta 2-adrenoceptor polymorphism on systemic and airway responses in asthma

BACKGROUND

The impact of the polymorphic amino acids 16 and 27 of the beta 2-adrenoceptor (beta 2-AR) on the susceptibility to bronchodilator tolerance remains unclear since clinical studies thus far have shown discordant results. Tolerance towards the effects of inhaled beta 2-AR agonists generally is more easily shown for systemic parameters than for airway effects and can be substantial. This study evaluates whether differences exist between position 16 homozygous genotyped asthmatics, in tolerance development towards airway responses and the systemic effect hypokalemia.

METHODS

Twenty patients were genotyped for amino acids 16 and 27 of the beta 2-AR gene. Time-effect curves for FEV1 and serum potassium concentration were constructed after s.c. administration of terbutaline after two-week treatment periods with either terbutaline inhalation or matching placebo in a double-blind, randomised and cross-over design. Statistical analysis was done by a repeated measures multivariate analysis on area under time-effect curve (AUC).

MAIN RESULTS

Pre-treatment with inhaled terbutaline did not influence the improvement in FEV1 in response to s.c. terbutaline and there were no significant differences between Arg-16 and Gly-16 individuals in this respect. Pre-treatment with inhaled terbutaline resulted in an overall increase of baseline plasma potassium before administration of s.c. terbutaline (3.78-3.95 mmol/L, p=0.034). However, this effect appeared to be solely confined to the Arg-16 homozygous individuals, leading to a statistically highly significant difference between the Arg-16 and Gly-16 subjects (p=0.005). However, there was no genotype related difference in the decrease in plasma potassium response to s.c. terbutaline relative to baseline.

CONCLUSION

In patients carrying the Arg-16 genotype the development of hypokalemia by s.c. terbutaline is attenuated after pre-treatment with inhaled terbutaline, be it on the basis of higher baseline values.

A survey of local anaesthetic use among general dental practitioners in the UK attending postgraduate courses on pain control

OBJECTIVE

The aim of this study was to identify which local anaesthetic solutions were used by general dental practitioners in the United Kingdom and to determine selection criteria. In addition, differences in anaesthetic choice between recent graduates (< or = 5 years) and more experienced practitioners were investigated.

MATERIAL AND METHODS

Five hundred and six general dental practitioners attending postgraduate courses on pain control in dentistry completed a questionnaire. Participants were asked to indicate year and place of qualification, anaesthetic solutions available in their surgeries and criteria used in the choice of anaesthetic. In addition, the respondents were asked to indicate choice of local anaesthetic in a number of common medical conditions. Questionnaires were distributed and collected immediately prior to the start of the course presentation and participants were not asked to indicate whether the selection decisions were teaching, experience or evidence based. Data were analysed by using the Chi-square test.

RESULTS

Lidocaine with epinephrine was the most widely available solution among this group of practitioners (94%), the second most common solution was prilocaine with felypressin (74%). The majority of practitioners had two or more solutions available. Practitioners who qualified within the last five years (14%) were more likely to have articaine available, the most recently introduced local anaesthetic into the UK (p = 0.04, one degree of freedom). Common medical conditions lead to a modification in anaesthetic selection: the use of prilocaine/felypressin increases in the majority of circumstances, although it is avoided in pregnant females by recent graduates.

CONCLUSIONS

Lidocaine/epinephrine continues to be the most common anaesthetic solution used by this group of UK general practitioners. The primary criterion for selection of an anaesthetic agent was perceived efficacy. Prilocaine/felypressin is commonly selected as an alternative solution in the presence of common medical conditions.

The efficiency of potassium removal during bicarbonate hemodialysis

Patients on chronic hemodialysis often portray high serum [K+]. Although dietary excesses are evident in many cases, in others, the cause of hyperkalemia cannot be identified. In such cases, hyperkalemia could result from decreased potassium removal during dialysis. This situation could occur if alkalinization of body fluids during dialysis would drive potassium into the cell, thus decreasing the potassium gradient across the dialysis membrane. In 35 chronic hemodialysis patients, we compared two dialysis sessions performed 7 days apart. Bicarbonate or acetate as dialysate buffers were randomly assigned for the first dialysis. The buffer was switched for the second dialysis. Serum [K+], [HCO3-], and pH were measured in samples drawn before dialysis; 60, 120, 180, and 240 min into dialysis; and 60 and 90 min after dialysis. The potassium removed was measured in the dialysate. During the first 2 hr, serum [K+] decreased equally with both types of dialysates but declined more during the last 2 hr with bicarbonate dialysis. After dialysis, the serum [K+] rebounded higher with bicarbonate bringing the serum [K+] up to par with acetate. The lower serum [K+] through the second half of bicarbonate dialysis did not impair potassium removal (295.9 +/- 9.6 mmol with bicarbonate and 299.0 +/- 14.4 mmol with acetate). The measured serum K+ concentrations correlated with serum [HCO3-] and blood pH during bicarbonate dialysis but not during acetate dialysis. Alkalinization induced by bicarbonate administration may cause redistribution of K during bicarbonate dialysis but this does not impair its removal. The more marked lowering of potassium during bicarbonate dialysis occurs late in dialysis, when exchange is negligible because of a low gradient.

Subcutaneous Terbutaline Use in CKD to Reduce Potassium Concentrations

BACKGROUND

Acute hyperkalemia is a frequent and potentially life-threatening medical problem in patients on maintenance hemodialysis therapy. beta-Adrenergic receptor (betaAR) stimulation causes potassium cellular influx and a decline in plasma potassium concentrations. Therefore, betaAR agonists are used in the treatment of patients with hyperkalemia. The goal of this study is to evaluate the utility of weight-based subcutaneous terbutaline dosing to reduce plasma potassium concentrations in a group of subjects with chronic kidney disease (CKD) requiring hemodialysis.

METHODS

Fourteen subjects with CKD receiving long-term hemodialysis were administered terbutaline, 7 microg/kg, subcutaneously. Heart rate measurements and blood samples for potassium concentration determinations were made serially for 420 minutes. Effects of terbutaline on heart rate and potassium responses were determined in each subject.

RESULTS

Terbutaline significantly reduced plasma potassium concentrations and significantly increased heart rates during the time course of the study (P < 0.001, repeated-measures analysis of variance). Mean reduction in peak potassium concentration (-1.31 +/- 0.5 [SD] mEq/L) and increase in peak heart rate (25.8 +/- 10.5 beats/min) were significantly different from baseline (P < 0.001, baseline versus peak for both responses). No subject reported significant adverse effects.

CONCLUSION

Administration of subcutaneous terbutaline obviates the need for intravenous access and should be considered as an alternative to nebulized or inhaled beta-agonists to treat acute hyperkalemia in patients with CKD. As with the use of any beta-adrenergic agonist, close cardiovascular monitoring is necessary to avoid or minimize toxicity during therapy.