Control of serum potassium during fasting in patients with end-stage renal disease

Consensus recommendations on fasting during Ramadan for patients with kidney disease: review of available evidence and a call for action (RaK Initiative)

Ramadan fasting (RF) involves abstaining from food and drink during daylight hours; it is obligatory for all healthy Muslims from the age of puberty. Although sick individuals are exempt from fasting, many will fast anyway. This article explores the impact of RF on individuals with kidney diseases through a comprehensive review of existing literature and consensus recommendations. This study was conducted by a multidisciplinary panel of experts.The recommendations aim to provide a structured approach to assess and manage fasting during Ramadan for patients with kidney diseases, empowering both healthcare providers and patients to make informed decisions while considering their unique circumstances.

The effects of Ramadan fasting on clinical and biochemical markers among hemodialysis patients: A prospective cohort study

Background

Ramadan fasting is compulsory for all healthy adult Muslims. Although sick people are exempted from Ramadan fasting, some patients such as hemodialysis patients prefer to fast during Ramadan. The effect of Ramadan fasting on clinical outcomes and biochemical markers among hemodialysis patients is not clear. The aim of this study was to examine the effects of daily Ramadan fasting and partial Ramadan fasting on key biochemical and clinical markers among hemodialysis patients as compared to hemodialysis patients who chose not to fast during Ramadan.

Methods

A prospective cohort study of 269 end stage renal disease patients were recruited from the hemodialysis unit in An-Najah National University Hospital, Nablus, Palestine. The participants were divided into three cohorts based on their plans for fasting during Ramadan in May 2018; Ramadan fasting group (RFG), Ramadan partial fasting group (RPFG) and Ramadan not-fasting group (RNFG). Key clinical and biochemical markers were measured before, during and after Ramadan.

Results

After adjustment for diabetic and hypertension status and other sociodemographic variables, RFG had higher mean inter-dialytic weight gain (IDWG) by 0.62 kg than RNFG (95% confidence interval (CI) 0.26, 0.99). RPFG also had slight increase in mean IDWG than RNFG by 0.35 kg (95% CI 0.11, 0.60). Additionally, RFG and RPFG had significant increase in mean serum potassium as compared to RNFG. Diabetes was independently associated with increased IDWG by 0.48 kg (0.25, 0.72). Diabetes and hypertension were associated with some independent changes in biochemical markers, but these were clinically negligible.

Conclusion

Our findings suggest that Ramadan fasting (fully or partially) is tolerable by hemodialysis patients and is not associated with important clinical complications. However, these patients should be made aware of the potential risk of fluid overload and hyperkalemia, if they decide to fast during Ramadan. Thus, they should be closely monitored and instructed to adhere to their dietary and fluid intake allowances. Further prospective cohort studies with comprehensive dietary measures and information on adverse clinical outcomes may provide more evidence about the tolerability and safety of Ramadan fasting by hemodialysis patients.

Microfluidic DNA-based potassium nanosensors for improved dialysis treatment

BACKGROUND

Patients with end-stage renal disease (ESRD) have failed kidney function, and often must be treated with hemodialysis to extend the patient's life by artificially removing excess fluid and toxins from the blood. However, life-threatening treatment complications can occur because hemodialysis protocols are adjusted infrequently, as opposed to the kidneys which filter blood continuously. Infrequent blood tests, about once per month on average, are used to adjust hemodialysis protocols and as a result, patients can experience electrolyte imbalances, which can contribute to premature patient deaths from treatment complications, such as sudden cardiac death. Since hemodialysis can lead to blood loss, drawing additional blood for tests to assess the patient's kidney function and blood markers is limited. However, sampling multiple drops of blood per session using a microfluidic device has the potential to reduce not only the amount of blood drawn and avoid unnecessary venipuncture, but also reduce costs by limiting medical complications of hemodialysis and provide a more comprehensive assessment of the patient's health status in real time.

RESULT

We present preliminary proof-of-concept results of a microfluidic device which uses DNA-based fluorescence nanosensors to measure potassium concentration in a flowing solution. In a matter of minutes, the flowing potassium solution reduced the fluorescence intensity of the nanosensors to a steady-state value.

CONCLUSIONS

These proof-of-concept results demonstrate the ability of our DNA-based nanosensors to measure potassium concentration in a microfluidic device. The long-term goal is to integrate this technology with a device to measure potassium and eventually other blood contents multiple times throughout a hemodialysis session, enabling protocol adjustment similar to a healthy kidney.

Vegetable-Based Diets for Chronic Kidney Disease? It Is Time to Reconsider

Traditional dietary recommendations to renal patients limited the intake of fruits and vegetables because of their high potassium content. However, this paradigm is rapidly changing due to the multiple benefits derived from a fundamentally vegetarian diet such as, improvement in gut dysbiosis, reducing the number of pathobionts and protein-fermenting species leading to a decreased production of the most harmful uremic toxins, while the high fiber content of these diets enhances intestinal motility and short-chain fatty acid production. Metabolic acidosis in chronic kidney disease (CKD) is aggravated by the high consumption of meat and refined cereals, increasing the dietary acid load, while the intake of fruit and vegetables is able to neutralize the acidosis and its deleterious consequences. Phosphorus absorption and bioavailability is also lower in a vegetarian diet, reducing hyperphosphatemia, a known cause of cardiovascular mortality in CKD. The richness of multiple plants in magnesium and vitamin K avoids their deficiency, which is common in these patients. These beneficial effects, together with the reduction of inflammation and oxidative stress observed with these diets, may explain the reduction in renal patients' complications and mortality, and may slow CKD progression. Finally, although hyperkalemia is the main concern of these diets, the use of adequate cooking techniques can minimize the amount absorbed.

Usefulness of urinary parameters in advanced chronic kidney disease

This review discusses the diagnostic value of urinary parameters in the setting of advanced chronic kidney disease and we present the key concepts that summarise the suggestions of the manuscript.

URINARY VOLUME

The amount of fluid intake may be a non-established risk factor for CKD. For these patients, a urinary output ≥2-3 l/day is a reasonable proposal. This recommendation is not applicable to patients with cardiorenal syndrome or fluid overload risk. NA: This determination is very useful to monitor salt intake. Reducing urinary Na<120 mEq/day (≅salt intake≤5-6g) is a reasonable objective.

URINARY UREA NITROGEN (UUN)

This parameter is useful to estimate protein intake (Maroni BJ equation). A protein intake between 48-72g (0.8-0.9g/kg/day according to weight) is equivalent to UUN 7-10g/day approximately.

ACID LOAD AND POTASSIUM

Acid load reduction may be an additional strategy in the nutritional management of this population. It may be estimated indirectly from a diet survey or by measuring the elimination of UUN and K_ur. The limits of this recommendation have not been established, but we propose a cautious and prudent diet of fruit and vegetables.

PHOSPHORUS

There is a significant positive correlation between phosphorus and protein, both in dietary records and urine elimination. Based on this information, we suggest a urinary P excretion<800mg/day or<600mg/day for patients with GFR<25ml/min or<15ml/min, respectively.

CONCLUSION

Urinary parameters provide sensitive and useful knowledge for clinical practice, provide information about the dietary habits of patients and the adherence to our recommendations.

Effects of Ramadan fasting on moderate to severe chronic kidney disease. A prospective observational study

Objectives:

To examin the effect of Ramadan fasting on worsening of renal function (WRF).

Method:

This was a single-arm prospective observational study including 65 patients with stage 3 or higher chronic kidney disease (CKD). By definition, WRF was considered to have occurred when serum creatinine levels increased by 0.3 mg/dL (26.5 µmol/l) from baseline during or within 3 months after Ramadan. The study was conducted in the Nephrology Clinic of King Khalid University Hospital, Riyadh, Kingdom of Saudi Arabia during the month of Ramadan 1436 AH (Hijiri), which corresponded to June 18-July 17, 2015.

Results:

This study included 65 adults with a mean age of 53 years. Overall, 33% of patients developed WRF. In the multivariate analysis, more advanced CKD stage, higher baseline systolic blood pressure and younger age were independently associated with WRF. Underlying cause of CKD, use of diuretics, use of renin angiotensin blockers, gender, and smoking status were not associated with WRF.

Conclusion:

In patients with stage 3 or higher CKD, Ramadan fasting during the summer months was associated with worsening of renal function. Clinicians need to warn CKD patients against Ramadan fasting.

Changes in biochemical, hemodynamic, and dialysis adherence parameters in hemodialysis patients during Ramadan

This paper aimed to study the effect of Ramadan fasting on biochemical and clinical parameters and compliance for dialysis. A prospective multicenter observational cross-sectional study comparing fasting with a non-fasting stable adult hemodialysis patients for demographic and biochemical parameters, compliance with dialysis, inter-dialytic weight gain, pre- and post-blood pressure, and frequency of intradialytic hypotensive episodes was carried out. Six hundred thirty-five patients, of whom 64.1% fasted, were studied. The fasters were younger (53.3 ± 16.2 vs. 58.4 ± 16.1 years; P = 0.001) but had similar duration on dialysis (P = 0.35). More fasters worked (22.0% vs. 14.6%; P = 0.001) and missed dialysis sessions during Ramadan. No differences were noted between groups in sex, diabetic status, or dialysis shift or day. There were no differences in the pre- and post-dialysis blood pressure; serum potassium, albumin or weight gain; diabetic status; sex; and dialysis shift time or days. However, serum phosphorous was significantly higher in the fasting group (2.78 ± 1.8 vs. 2.45 ± 1.6 mmol/L; P = 0.045). There were no intragroup differences in any of the parameters studied when comparing the findings during Ramadan with those in the month before Ramadan. Fasters were significantly younger and more likely to be working, to miss dialysis sessions, and to have higher serum phosphorous levels. No other differences were observed.

Potassium balance in dialysis patients

The advent of dialytic therapy has enabled nephrologists to provide life-saving therapy, but potassium balance continues to be an ever present challenge in the ESRD population. Although a small percent of patients are chronically hypokalemic, hyperkalemia is by far the most common abnormality in dialysis patients. It is associated with increased all-cause mortality, cardiovascular mortality, and arrhythmogenic death. Although alterations of the dialysis bath may decrease predialysis potassium, potassium baths <2 mEq/l are associated with a higher risk of sudden cardiac death. Studies show that patients are aware of the risks of hyperkalemia, but adherence to a low potassium diet is suboptimal. ACEI, ARBs, and spironolactone may cause slight increases in potassium even in anuric patients, requiring increased surveillance. Fludrocortisone and potassium binders have not been proven to be beneficial in lowering interdialytic potassium levels. Frequent hemodialysis may be a viable option, and studies of prophylactic placement of implantable cardioverter/defibrillators are underway.

The intuitive case for β-blockers in patients with ESRD

Sudden cardiac death (SCD) is common in dialysis patients accounting for up to 25% of all-cause mortality. Unlike in the general population, occlusive coronary artery disease is implicated in a minority of these deaths. Activation of the sympathetic nervous system is prevalent in the dialysis population and may underlie this high rate of SCD. β-blockers reduce SCD in the general population and, given their mode of action, β-blockers would seem to be an ideal class of agents to prevent SCD in dialysis patients. In this review, we will explore the etiology of SCD in dialysis patients and discuss the evidence supporting the use of β-blockers in patients with ESRD. We will also examine potential impediments to the use β-blocker in the dialysis population and outline directions for future trials in this area.

Abnormalities of serum potassium concentration in dialysis-associated hyperglycemia and their correction with insulin: review of published reports

The main difference between dialysis-associated hyperglycemia (DH) and diabetic ketoacidosis (DKA) or nonketotic hyperglycemia (NKH) occurring in patients with preserved renal function is the absence of osmotic diuresis in DH, which eliminates the need for large fluid and solute (including potassium) replacement. We analyzed published reports of serum potassium (K(+)) abnormalities and their treatment in DH. Hyperkalemia was often present at presentation of DH with higher frequency and severity than in hyperglycemic syndromes in patients with preserved renal function. The frequency and severity of hyperkalemia were higher in DH episodes with DKA than those with NKH in both hemodialysis and peritoneal dialysis. For DKA, the frequency and severity of hyperkalemia were similar in hemodialysis and peritoneal dialysis. For NKH, hyperkalemia was more severe and frequent in hemodialysis than in peritoneal dialysis. Insulin infusion corrected the hyperkalemia of DH in most cases. Additional measures for the management of hyperkalemia or modest potassium infusions for hypokalemia were needed in a few DH episodes. The predictors of the decrease in serum K(+) during treatment of DH with insulin included the starting serum K(+) level, the decreases in serum values of glucose concentration and tonicity, and the increase in serum total carbon dioxide level. DH represents a risk factor for hyperkalemia. Insulin infusion is the only treatment for hyperkalemia usually required.

Abnormalities of serum potassium concentration in dialysis-associated hyperglycemia and their correction with insulin: review of published reports

The main difference between dialysis-associated hyperglycemia (DH) and diabetic ketoacidosis (DKA) or nonketotic hyperglycemia (NKH) occurring in patients with preserved renal function is the absence of osmotic diuresis in DH, which eliminates the need for large fluid and solute (including potassium) replacement. We analyzed published reports of serum potassium (K(+)) abnormalities and their treatment in DH. Hyperkalemia was often present at presentation of DH with higher frequency and severity than in hyperglycemic syndromes in patients with preserved renal function. The frequency and severity of hyperkalemia were higher in DH episodes with DKA than those with NKH in both hemodialysis and peritoneal dialysis. For DKA, the frequency and severity of hyperkalemia were similar in hemodialysis and peritoneal dialysis. For NKH, hyperkalemia was more severe and frequent in hemodialysis than in peritoneal dialysis. Insulin infusion corrected the hyperkalemia of DH in most cases. Additional measures for the management of hyperkalemia or modest potassium infusions for hypokalemia were needed in a few DH episodes. The predictors of the decrease in serum K(+) during treatment of DH with insulin included the starting serum K(+) level, the decreases in serum values of glucose concentration and tonicity, and the increase in serum total carbon dioxide level. DH represents a risk factor for hyperkalemia. Insulin infusion is the only treatment for hyperkalemia usually required.

Management of hyperkalemia in dialysis patients

Hyperkalemia is common in patients with end-stage renal disease, and may result in serious electrocardiographic abnormalities. Dialysis is the definitive treatment of hyperkalemia in these patients. Intravenous calcium is used to stabilize the myocardium. Intravenous insulin and nebulized albuterol lower serum potassium acutely, by shifting it into the cells. Despite their widespread use, neither intravenous bicarbonate nor cation exchange resins are effective in lowering serum potassium acutely. Prevention of hyperkalemia currently rests largely upon dietary compliance and avoidance of medications that may promote hyperkalemia. Prolonged fasting may provoke hyperkalemia, which can be prevented by administration of intravenous dextrose.

Effect of Oral Glucose Administration on Serum Potassium Concentration in Hemodialysis Patients

BACKGROUND

Extrarenal potassium disposal is particularly critical in patients with end-stage renal disease. Exogenous insulin stimulates this disposal by enhancing potassium uptake into cells in hemodialysis (HD) patients and healthy subjects. However, the effect of physiological levels of endogenous insulin on this disposal in these patients or healthy subjects is unknown.

METHODS

Effects of an oral glucose tolerance test (37.5, 75, and 150 g) on serum potassium levels were determined in 13 HD patients and 7 healthy controls. Serum potassium and insulin levels and plasma aldosterone and epinephrine levels were measured before and after glucose loads.

RESULTS

In HD patients and controls, serum insulin levels increased to a similar magnitude in parallel with increased serum glucose levels, but serum potassium levels decreased significantly only in HD patients. In HD patients, plasma aldosterone or epinephrine levels were not changed significantly after a glucose load. In HD patients, the decrease in serum potassium levels was dependent on the increase in serum insulin levels and was more prominent when 150 g of glucose was administered. In HD patients, the decrease in serum potassium levels correlated negatively (r = -0.45; P < 0.001) with the increase in serum insulin levels, and maximal decrease in serum potassium levels correlated negatively (r = -0.54; P < 0.001) with maximal increase in serum insulin levels.

CONCLUSION

Endogenous production of physiological concentrations of insulin in response to exogenous glucose administration decreases serum potassium levels only in HD patients, independently of plasma aldosterone and epinephrine levels.

Serum Potassium Handling at Pre- and Posthemodialysis in Patients with End-Stage Renal Disease

The current study simultaneously measured serum and red blood cell (RBC) K+ as well as plasma pH, bicarbonate, serum insulin, and aldosterone at pre-, end-, and at 5, 11, and 19 hours posthemodialysis in 25 patients with end-stage renal disease and evaluated the factors influencing serum K+ levels during those periods. Our patients were studied under their current dietary conditions. At end-dialysis, serum K+ levels decreased, but RBC K+ levels were not changed. At this time point, the decrease in serum K+ levels was exclusively caused by removal of K+ by dialysis. At 5 hours postdialysis, serum K+ rapidly increased, whereas RBC K+ decreased. The 5 hour postdialysis serum K+ increase negatively correlated with the decrease in serum insulin levels. At 11 hours postdialysis, serum K+ slowly but significantly increased, and RBC K+ increased to those levels at pre- and end-dialysis. At 19 hours postdialysis, serum K+ further increased, but RBC K+ remained stable. From 5 to 19 hours postdialysis, the increase in serum K+ was independent of changes in plasma pH, bicarbonate, insulin, and aldosterone but was associated with both the predialysis serum K+ levels and the magnitude of the decrease in serum K+ at end-dialysis.

Absence of adverse outcomes in hyperkalemic patients undergoing vascular access surgery

PURPOSE

The decision to cancel vascular access surgery because of hyperkalemia requires knowledge of the risks vs benefits. This study sought to identify and characterize cases where surgery had been performed in patients with uncorrected hyperkalemia.

METHODS

One thousand four hundred and seventy-two consecutive cases of vascular access surgery at an academic medical centre between 1995 and 2000 by a single surgeon were analyzed retrospectively.

RESULTS

Eight cases had clear documentation that the case proceeded with hyperkalemia. Anesthesia techniques were one general anesthetic, one regional block, five monitored anesthesia care (MAC), and one local infiltration only. Mean potassium was 6.9 mmol x L(-1) (range 6.1-8.0). In this series of selected asymptomatic hyperkalemic patients undergoing low risk surgery, no adverse results occurred.

CONCLUSION

While this review of eight cases (only one receiving general anesthesia) cannot be used to prove the safety of proceeding to surgery with uncorrected hyperkalemia, it does suggest that asymptomatic hyperkalemia may not be an absolute contraindication to vascular access surgery.

Treating interdialytic hyperkalemia with fludrocortisone

Hyperkalemia is a frequent and dangerous problem in dialysis patients. Many factors contribute to potentially life-threatening potassium elevation and most remedies used to treat hyperkalemia are handicapped by the consequences of the separate pools of intra- and extracellular potassium. Besides the kidney, the colon has the ability to excrete potassium, which can help lower total body potassium. Several prior authors have addressed the colon's ability to up-regulate potassium secretion, including the effect of aldosterone on fecal potassium content. Potentially dangerous intradialytic maneuvers to lower potassium levels may be avoidable with the use of the mineralocorticoid agonist fludrocortisone.

Renin-angiotensin system blockade and the risk of hyperkalemia in chronic hemodialysis patients

BACKGROUND

Blockade of the renin-angiotensin system by angiotensin-converting enzyme (ACE) inhibitors or angiotensin receptor blockers can cause hyperkalemia in patients with chronic renal insufficiency who are not on dialysis, but the risk of hyperkalemia in hemodialysis patients is unknown.

SUBJECTS AND METHODS

We conducted a prospective study of 251 adult hemodialysis patients to determine if renin-angiotensin system blockade was associated with hyperkalemia, defined as a predialysis serum potassium concentration of 5.5 mmol/L or higher. Medication use was determined by chart review and patient interview. Predialysis serum potassium concentration was measured monthly.

RESULTS

There were 367 episodes of hyperkalemia during 1877 person-months of follow-up. After adjustment for potential confounding variables and for clustering of episodes by patient, use of an ACE inhibitor or an angiotensin receptor blocker was associated with a significantly higher risk of hyperkalemia (odds ratio [OR] = 2.2; 95% confidence interval [CI]: 1.4 to 3.4). The increased risk of hyperkalemia with renin-angiotensin system blockade was seen in anuric dialysis patients (OR = 2.3; 95% CI: 1.3 to 4.2), as well as those with residual renal function (OR = 2.1; 95% CI: 1.0 to 4.1).

CONCLUSION

The use of ACE inhibitors or angiotensin receptor blockers is independently associated with an increased risk of developing hyperkalemia in chronic hemodialysis patients. The serum potassium concentration should be closely monitored when these medications are prescribed for hemodialysis patients.

Insulin and mineralocorticoids influence on extrarenal potassium metabolism in chronic hemodialysis patients

Insulin-mineral corticoids effects on extrarenal K+ metabolism in dialysis patients. During the inter-dialytic interval in dialyzed patients, hydrogen and potassium ions are regulated by extrarenal mechanisms. We studied the hormonal and acidotic effects on the extrarenal potassium metabolism, in selected, anuric and stable, hemodialysis patients. Fifteen patients, were grouped according to the mean mid-week pre-dialysis K+ over the past 12 months: > 6.0 mEq/L (G1, n=5), = 5.1-6.0 mEq/L (G2, n=5), < or = 5.0 mEq/L (G3, n=5). After a mid-week hemodialysis session and 12 h fasting, they received 1 g/Kg glucose p.os (A). Insulin, aldosterone, renin, pH, HCO3-, glucose, body weight, blood pressure and heart rate were measured before and 60' after the meal. We recorded the same parameters, except insulin, in 15 patients, similarly grouped, before hemodialysis (T0) and on 3 consecutive off dialysis days (T1-T3); G1 received fluorohydrocortisone (FHC) 0.1 mg-0.3 mg/day, according to body weight and G3 spironolactone (SLT) 200 mg per day. G2 were controls (B). (A) A significant rise in glycemia (81 +/- 23 to 157 +/- 52 mg/dL, P<0.001) and insulin (11.8 +/- 6.2 to 46.8 +/- 19.5 microU/mL, P<0.001), with a drop in K+ (5.1 +/- 0.6 to 4.8 +/- 0.7 mEq/L, P=0.001) and aldosterone (453 +/- 373 to 383 +/- 364 pg/mL, P<0.01), were noted at T60 vs. T0, in all groups. Insulin levels correlated negatively (r=-0.54, P<0.04) to serum K+ at T60, in all patients. (B) No major pH, HCO3 and aldosterone changes were observed in the 3 groups. Despite that, K+ dropped in G1 by FHC (6.7 +/- 0.9 to 5.9 +/- 0.6 mEq/L, P<0.05), rose in G3 by SLT (4.4 +/- 0.4 to 5.4 +/- 0.3 mEq/L, P<0.05) and remained unchanged in controls (5.8 +/- 0.2 to 5.8 +/- 0.6 mEq/L), (T0 vs T3 pre-dialysis values). Glucose significantly lowered K+ by promoting adequate insulin secretion. Drugs affecting aldosterone action significantly influenced potassium metabolism. Acid-base balance was not important in K+ handling in steady state anuric dialysis patients.

Hyperkalemia in dialysis patients

Serious hyperkalemia is common in patients with end-stage renal disease (ESRD) and accounts for considerable morbidity and death. Mechanisms of extrarenal disposal of potassium (gastrointestinal excretion and cellular uptake) play a crucial role in the defense against hyperkalemia in this population. In this article we review extrarenal potassium homeostasis and its alteration in patients with ESRD. We pay particular attention to the factors that influence the movement of potassium across cell membranes. With that background we discuss the emergency treatment of hyperkalemia in patients with ESRD. We conclude with a review of strategies to reduce the risk of hyperkalemia in this population of patients.

Hypokalemia and hyperkalemia

This article discusses the causes and nature of hypokalemia and hyperkalemia. Diagnosis, testing, drug administration, and general management are outlined in detail.

Glucose modulation of the disposal of an acute potassium load in patients with end-stage renal disease

PURPOSE

Extrarenal potassium disposal plays an important role in the tolerance of an acute potassium load and is particularly critical in patients with renal failure. Insulin is known to stimulate this disposal by enhancing potassium uptake into the cells. Since dietary potassium is generally ingested in combination with carbohydrates, the predictable stimulation of endogenous insulin release may blunt the expected increase in plasma potassium. The goal of the current study was to evaluate the effect of oral glucose on the disposition of an acute oral potassium load in hemodialysis patients and in normal controls.

PATIENTS AND METHODS

Eight hemodialysis patients and eight normal control subjects were studied after an overnight fast. Each subject received an oral load of potassium chloride elixir (0.25 mmol/kg). Plasma potassium was measured at baseline and at 30-minute intervals for 3 hours. On a separate study day, the subjects underwent the identical protocol, with the addition of 50 g of oral glucose to the potassium load to stimulate endogenous insulin release. The identical two experimental protocols were repeated in each subject during concomitant beta blockade with propranolol.

RESULTS

The maximal increase in plasma potassium after the potassium load was significantly greater in the hemodialysis patients than in the controls (0.93 +/- 0.08 versus 0.52 +/- 0.04 mmol/L, p < 0.001). Concomitant oral glucose markedly blunted the maximal rise in potassium levels in both experimental groups (0.40 +/- 0.09 and 0.22 +/- 0.07 mmol/L, respectively, p < 0.005 versus potassium alone). With concomitant beta blockade, the maximal increase in plasma potassium after the potassium load was significantly greater in the hemodialysis patients than in the controls (1.11 +/- 0.12 versus 0.72 +/- 0.09 mmol/L, p = 0.02). Concomitant oral glucose again markedly blunted the maximal increase in potassium in both experimental groups (0.72 +/- 0.09 and 0.39 +/- 0.06 mmol/L, respectively, p < 0.01 versus potassium alone). The potassium load in the absence of glucose did not produce changes in plasma insulin concentration in either experimental group. The potassium load in combination with oral glucose load produced more sustained hyperinsulinemia in the dialysis patients than in the control subjects.

CONCLUSIONS

Exogenous glucose, by stimulating endogenous secretion of insulin, enhances extrarenal disposal of a potassium load. This protective effect of exogenous glucose against hyperkalemia is independent of adrenergic stimulation. The beneficial effect of exogenous glucose defends against the development of severe hyperkalemia after dietary potassium ingestion, and is critically important in hemodialysis patients, due to their negligible renal potassium excretion.

Effect of insulin-plus-glucose infusion with or without epinephrine on fasting hyperkalemia

Extrarenal potassium disposal is an important defense against hyperkalemia in patients with end-stage renal disease. Both insulin and epinephrine are important modulators of this process. Hemodialysis patients are prone to developing hyperkalemia during fasting. We tested the hypothesis that the infusion of physiologic doses of insulin prevents fasting hyperkalemia in hemodialysis patients, both by a direct stimulation of extrarenal potassium disposal, as well as by augmenting the potassium-lowering effect of epinephrine. Ten stable, nondiabetic maintenance hemodialysis patients were studied prospectively in a Clinical Research Center. They were fasted for 18 hours, followed by an acute infusion of epinephrine at 0.01 microgram/kg/min, in the absence or presence of prior beta-blockade with propranolol. Serial measurements of plasma potassium, insulin and glucose were obtained. The patients were restudied under the same experimental protocols, while receiving a continuous infusion of insulin with dextrose. The plasma potassium increased by 0.58 +/- 0.13 mmol/liter (P = 0.002) after 18 hours of fasting. Administration of insulin with dextrose at a dose that doubled the plasma insulin levels within the physiologic range (9.3 +/- 1.1 vs. 20.2 +/- 2.3 mU/liter, P < 0.002), completely prevented the rise in plasma potassium (+0.06 +/- 0.13 mmol/liter, P = 0.64). Epinephrine did not significantly change the plasma potassium during fasting alone (+0.05 +/- 0.09 mmol/liter, P = 0.59), whereas it lowered the potassium significantly (-0.16 +/- 0.04 mmol/liter, P = 0.003) when the subjects were receiving insulin with glucose.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic modulation of extrarenal potassium disposal in men with end-stage renal disease

In normal subjects, beta-adrenergic stimulation lowers the serum potassium, whereas alpha-stimulation raises it. Epinephrine, a mixed alpha and beta agonist, acutely lowers the blood potassium in normal subjects, but not in patients with end-stage renal disease. This study was designed to determine whether the resistance to the hypokalemic effect of epinephrine in dialysis patients is due to a blunted beta-adrenergic response, or to an augmented alpha-adrenergic response. The infusion of epinephrine at low doses (0.01 microgram/kg/min) produced a significant increase in serum potassium in hemodialysis patients (+0.21 +/- 0.07 mmol/liter, P less than 0.05), as compared to a nonsignificant decrease (-0.06 +/- 0.04 mmol/liter) in normal subjects. Epinephrine at high physiologic doses (0.04 microgram/kg/min) failed to significantly change the serum potassium in the dialysis patients (-0.10 +/- 0.14 mmol/liter), but substantially lowered serum potassium in the controls (-0.64 +/- 0.10 mmol/liter, P less than 0.001). There was no significant correlation (r = 0.03) between the baseline serum potassium concentration and the magnitude of change during epinephrine infusion. Epinephrine infusion (0.04 microgram/kg/min) during beta-blockade with propranolol produced a greater rise in serum potassium in the dialysis patients as compared to the controls (+0.69 +/- 0.11 vs. +0.32 +/- 0.11 mmol/liter, P less than 0.05). Epinephrine infusion (0.01 microgram/kg/min) during alpha-blockade with phentolamine resulted in similar changes in serum potassium in dialysis patients and in normal control (-0.10 +/- 0.12 vs. -0.10 +/- 0.06 mmol/liter). Moreover, phentolamine reversed the increase in serum potassium observed in dialysis patients during the infusion of epinephrine following beta-blockade.(ABSTRACT TRUNCATED AT 250 WORDS)

Extrarenal potassium tolerance in chronic renal failure: implications for the treatment of acute hyperkalemia

The role of extrarenal potassium homeostasis is well recognized as a major mechanism for the acute defense against the development of hyperkalemia. The purpose of this report is to examine whether or not the various mechanisms of extrarenal potassium regulation are intact in patients with end-stage renal disease (ESRD). The available data suggest that with the development of ESRD and the uremic syndrome there is impaired extrarenal potassium metabolism that is related to a defect in the Na,K-adenosine triphosphatase (ATPase). The responsiveness of uremic patients to the various effector systems that regulate extrarenal potassium handling is discussed. Insulin is well positioned to play an important role in the regulation of plasma potassium concentration in patients with impaired renal function. The role of basal insulin may be even more important than previously appreciated, since somatostatin infusion causes a much greater increase in the fasting plasma potassium in rats with renal failure than in controls. Furthermore, stimulation of endogenous insulin by oral glucose results in a greater intracellular translocation of potassium in uremic rats than in controls. Under at least two common physiologic circumstances, feeding and vigorous exercise, endogenous catecholamines might also act to defend against acute increments in extracellular potassium concentration. However, it is important to appreciate that the response to beta 2-adrenoreceptor-mediated internal potassium disposal is heterogeneous as judged by the variable responses to epinephrine infusion. Based on the evidence presented in this report, a regimen for the treatment of life-threatening hyperkalemia is outlined. Interpretation of the available data demonstrate that bicarbonate should not be relied on as the sole initial treatment for severe hyperkalemia, since the magnitude of the effect of bicarbonate on potassium is variable and may be delayed. The initial treatment for life-threatening hyperkalemia should always include insulin plus glucose, as the hypokalemic response to insulin is both prompt and predictable. Combined treatment with beta 2-agonists and insulin is also effective and may help prevent insulin-induced hypoglycemia.

A patient with hyperkalemia and metabolic acidosis

Uptake of potassium by extrarenal tissues, primarily muscle and liver, represents a major defense mechanism in the maintenance of normokalemia following an acute elevation in the serum potassium concentration. Insulin, epinephrine, and aldosterone all play major roles in maintaining the normal distribution of potassium between the intracellular and extracellular environment. In addition to hormonal regulation, changes in blood pH and tonicity also exert a strong influence on extrarenal potassium metabolism. Last, the serum potassium concentration per se directly influences its own cellular uptake and this transport mechanism appears to be inhibited by uremia.