Treatment and prevention of hyperkalemia in end-stage renal disease

Potassium homeostasis and therapeutic intervention with sodium zirconium cyclosilicate: A model-informed drug development case study

Potassium (K+ ) is the main intracellular cation in the body. Elevated K+ levels (hyperkalemia) increase the risk of life-threatening arrhythmias and sudden cardiac death. However, the details of K+ homeostasis and the effects of orally administered K+ binders, such as sodium zirconium cyclosilicate (SZC), on K+ redistribution and excretion in patients remain incompletely understood. We built a fit-for-purpose systems pharmacology model to describe K+ homeostasis in hyperkalemic subjects and capture serum K+ (sK+ ) dynamics in response to acute and chronic administration of SZC. The resulting model describes K+ distribution in the gastrointestinal (GI) tract, blood, and extracellular and intracellular spaces of tissue, renal clearance of K+ , and K+ -SZC binding and excretion in the GI tract. The model, which was fit to time-course sK+ data for individual patients from two clinical trials, accounts for bolus delivery of K+ in meals and oral doses of SZC. The virtual population of patients derived from fitting the model to these trials was then modified to predict the SZC dose-response and inform clinical trial design in two new applications: emergency lowering of sK+ in severe hyperkalemia and prevention of hyperkalemia between dialysis sessions in patients with end-stage chronic kidney disease. In both cases, the model provided novel and useful insight that was borne out by the now completed clinical trials, providing a concrete case study of fit-for-purpose, model-informed drug development after initial approval of a drug.

Clinical phenotypes and prognosis of IgG4-related diseases accompanied by deteriorated kidney function: a retrospective study

INTRODUCTION

IgG4-related disease (IgG4-RD) is a multiorgan autoimmune disorder that causes irreversible injury. Deteriorated kidney functions are common but easily ignored complications associated with IgG4-RD. Yet the clinical manifestations and prognosis of this specific entity have not been fully illustrated.

METHOD

Three hundred fifty patients with IgG4-RD were retrospectively enrolled and divided into 119 IgG4-RD with chronic kidney disease (IgG4-RD CKD+) and 231 IgG4-RD without CKD (IgG4-RD CKD-). Demographic clinical and laboratory characteristics and survival of two cohorts were compared using restricted cubic splines, logistic and Cox regression, and Kaplan-Meier analysis. A nomogram was generated for calculating the probability of CKD in IgG4-RD.

RESULTS

The spectrum of organ involvement was different between IgG4-RD CKD+ and CKD- cohorts (p<0.001). Lung (26.89%) and retroperitoneum (18.49%) involvement were more common in the IgG4-RD CKD+ cohort. Increased serum potassium and phosphorus, reduced calcium levels, and hypocomplementemia (all p<0.05) were observed in IgG4-RD CKD+. Restricted cubic splines revealed a U-shaped plot regarding associations between serum potassium and CKD. Kaplan-Meier analysis demonstrated significantly lower long-term survival rates in IgG4-RD patients with kidney function at CKD stages 4-5. Cox regression revealed declined kidney functions (G4 HR 6.537 (95% CI: 1.134-37.675)) associated with increased all-cause mortality in IgG4-RD patients. A nomogram was constructed to predict CKD in IgG4-RD promptly with a discrimination (C-index) of 0.846.

CONCLUSIONS

CKD in IgG4-RD was associated with poor outcomes and electrolyte disturbances. Patients with IgG4-RD should be aware of possible deterioration in kidney function. The nomogram proposed would help to identify the subtle possibility of CKD in IgG4-RD. Key points • IgG4-related diseases with deteriorated kidney function have specific clinical and laboratory characteristics. • It is crucial to recognize and address the negative impact of deteriorating kidney function in IgG4-related diseases to prevent further harm. • The nomogram proposed would help to identify subtle kidney involvement by evaluating the possibility of CKD in IgG4-related diseases.

The Effects of Ouabain and Potassium on Peritoneal Fluid and Solute Transport Characteristics

Background

We reported anomalous transport characteristics of potassium during experimental peritoneal dialysis in rats and suggested that mechanisms of peritoneal potassium transport could be other than simple passive transport. Intracellular transport of potassium in cultured human mesothelial cells was reported to be regulated by three different pathways, such as channels blocked by ouabain, channels blocked by furosemide, and other.

Objective

To investigate the effect of ouabain on peritoneal potassium and water transport characteristics.

Methods

A single 4-hour peritoneal dwell was performed in 28 5prague-Dawley rats. To minimize the diffusive transport of potassium, 4.5 mmol/L of KCI was added into conventional dialysis solution with 3.86% glucose [acidic peritoneal dialysis solution (APD)]. To evaluate the effect of the pH of dialysis solution on the transport of potassium and water, 4 mmol/L of NaOH was added into the potassium -containing study solutions [neutral peritoneal dialysis solution (NPD)]. To evaluate the effect of a potassium channel blocker on peritoneal potassium transport ATPase sensitive Na+-K+-transport inhibitor, ouabain (10–5 mmol/L) was added to dialysis solutions immediately before the dwell study in eight rats with APD (APD-O) and six rats with NPD (NPD-O). Ouabain was not added in eight and six rats with APD and NPD (APD-C and NPD-C, respectively). They were used as control. Infusion volume was 30 mL. The intraperitoneal volume (V D) was estimated by using a volume marker dilution method with corrections for the elimination of volume marker, radioiodinated human serum albumin (RI5A), from the peritoneal cavity (KE). The diffusive mass transport coefficient (KBD) and sieving coefficient (5) were estimated using the modified Babb-Randerson-Farrell model.

Results

VD was significantly higher (p < 0.05 from 90 min to 240 min) and KE (0.027 ± 0.018 mL/min for APD-O, 0.026 ± 0.017 mL/min for NPD-O, and 0.030 ± 0.022 mL/min for NPD-C, vs 0.058 ± 0.030 mL/min for APD-C, p < 0.05 for each) significantly lower during dialysis with APD -O, NPD -O, and NPD-C than with APD-C. The intraperitoneal glucose expressed as a percentage of the initial amount was significantly higher with APD-O, NPD-C, and NPD-Q than with APD-C (p < 0.05 from 90 min to 240 min). KBD for sodium was higher during dialysis with ouabain than without ouabain, while KBD for urea, glucose, and potassium, and 5 for urea, glucose, sodium, and potassium did not differ between the four groups.

Conclusions

The physiologic potassium concentration in neutral dialysis solutions and the use of ouabain decreased the intraperitoneal fluid absorption. The diffusive transport coefficient and sieving coefficient for potassium did not differ, while the diffusive transport coefficient for sodium increased during use of ouabain.

The Effect of Dialysate Acidity on Peritoneal Solute Transport in the Rat

Objective

To investigate the possible effect of unphysiologically low pH in dialysis fluid on peritoneal transport.

Design

A 4-hour single-cycle experimental session of peritoneal dialysis was performed in six 5prague-Dawley rats using Dianeal 3.86% solution modified by adding 5 mmol/L of sodium hydroxide, neutral pH solution (NpH5) (pH 7.4). The intraperitoneal volume (V D) and peritoneal bulkfluid reabsorption (aa) were calculated using a marker, 1311–labeled human serum albumin (RI5A). The diffusive mass transport coefficient (KBD) as well as sieving coefficient (5) for glucose, urea, sodium, and potassium were calculated using the Babb-Randerson-Farrell model. The same study was performed in seven rats using Dianeal 3.86% solution, acidic pH solution (ApH5) (pH 5.7) to provide control values.

Results

The dialysate pH was stable with NpH5; 45 min after the infusion of ApH5 it increased rapidly and reached the physiological value 7.4. Dialysate volume and KBD values for sodium and potassium with NpH5 were significantly higher than with ApH5, while the KBD values for glucose and urea did not differ between the two solutions. 5 values for sodium and urea did not differ between the two solutions, while the values for glucose and potassium with NpH5 were significantly higher and lower, respectively, than the values with ApH5 (0.92±1.04 vs 0.04±0.63 and 0.56±060 vs 1.15±0.39, p < 0.05). The absorption of glucose from the dialysis solution expressed as a percentage of the initial amount of dialysate glucose was significantly lower with NpH5 than with ApH5 at 30 min (17.3±1.7% vs 29.7±2.0%, p < 0.05).

Conclusion

We conclude that the peritoneal transport of fluid and small solutes might to some extent be influenced by the acidity of the dialysis solution. The vasodilatory effect of acidic dialysis solution might be the most important mechanism for these differences. However, a larger KBD value and a lower 5 value for potassium and higher 5 values for glucose during dialysis with the neutral dialysis solution may indicate that transport mechanisms other than simple passive transport are involved in peritoneal transport for glucose and electrolytes.

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.

RAS Inhibitor Is Not Associated With Cardiovascular Benefits in Patients Undergoing Hemodialysis in Japan

Definitive evidence of whether renin angiotensin system (RAS) inhibition is beneficial on cardiovascular events (CVE) among patients undergoing hemodialysis (HD) is lacking. The objective of this study was to investigate the association of RAS inhibitor usage with CVEs in patients enrolled in the Dialysis Outcomes Practice Pattern Study in Japan (J-DOPPS). Association of RAS inhibitor prescription with outcomes including all-cause death, death caused by CVE, and hospitalization due to cardiac failure was investigated by using a multivariable Cox proportional hazards model. Of the 3848 patients enrolled, 1784 (45%) patients were treated by RAS inhibitors. After adjusting for potential cofounders by Cox proportional hazards models, we found a statistically insignificant but positive association of RAS inhibitor usage with death caused by CVE (HR: 1.46, 95%CI: 0.96-2.23, P = 0.08). Similar results were observed in the association of RAS inhibitor with all-cause death, hospitalization due to cardiac failure, and hospitalization due to CV disease (HR for all-cause death: 1.24, 95%CI: 0.84-1.48, P = 0.28, HR for hospitalization due to cardiac failure: 1.24, 95%CI: 0.84-1.81, P = 0.28, and HR for hospitalization due to CV disease: 1.20, 95%CI: 0.95-1.51, P = 0.13). Sensitivity analyses using propensity scores gave similar results. RAS inhibition did not show favorable association with CVEs suggesting that RAS inhibition alone was insufficient to reduce the risk of CV complications in patients undergoing HD. Some strategies in addition to RAS inhibition may be needed to protect against CVEs in this population.

Pharmacodynamics and pharmacokinetics of sodium zirconium cyclosilicate [ZS-9] in the treatment of hyperkalemia

INTRODUCTION

Hyperkalemia is a common electrolyte disorder that arises from dysfunctional homeostatic mechanisms or as a consequence of decreased renal function. Sodium zirconium cyclosilicate (ZS-9) is a potential new therapy for hyperkalemia in both acute and chronic settings.

AREAS COVERED

Here we discuss mechanisms of potassium homeostasis and preclinical and clinical studies that present pharmacokinetics/pharmacodynamics, efficacy and safety profiles of ZS-9.

EXPERT OPINION

ZS-9 has a unique mechanism of action consisting of thermodynamically favorable sequestration of potassium ions, enabling rapid trapping and removal of excess potassium. The potassium lowering action of ZS-9 is predictable and rapid, leading to significant reduction of serum potassium within 1 hour of administration by irreversibly eliminating excess potassium rather than acting via intracellular translocation. Its safety profile, including gastrointestinal events, has been generally similar to that of placebo, with the exception of infrequent but manageable events of peripheral edema and transient hypokalemia. ZS-9 has demonstrated potential for enabling renin-angiotensin-aldosterone system inhibitors in mid-term studies, with long-term studies ongoing.

The effects of transdermal insulin treatment of streptozotocin-induced diabetic rats on kidney function and renal expression of glucose transporters

The tight glycemic control required to attenuate chronic complications in type 1 diabetes mellitus requires multiple daily injections of bolus insulin which cause hyperinsulinemic edema and hypertension due to Na(+) retention. Reports indicate that pectin insulin (PI)-containing dermal patches sustain controlled insulin release into the bloodstream of streptozotocin (STZ)-induced diabetic rats. This study investigated whether PI dermal patches can improve the impaired renal function in diabetes. PI patches were prepared by dissolving pectin/insulin in deionized water and solidified with CaCl(2). Short-term (five weeks) effects of thrice daily treatments with PI patches on renal function and urinary glucose outputs were assessed in diabetic animals. Blood and kidney samples were collected after five weeks for measurements of selected biochemical parameters. Blood was also collected for insulin measurement 6 h following treatments. The low plasma insulin concentrations exhibited by STZ-induced diabetic rats were elevated by the application of insulin-containing dermal patches to levels comparable with control non-diabetic rats. Untreated STZ-induced diabetic rats exhibited elevated urinary glucose, K(+) outputs and depressed urinary Na(+) outputs throughout the 5-week period. Treatment with PI dermal patches increased urinary Na(+) output and reduced urine flow, urinary glucose and K(+) excretion rates in weeks 4 and 5. PI dermal patches increased GFR of diabetic rats with concomitant reduction of plasma creatinine concentrations. Transdermal insulin treatment also decreased the renal expressions of GLUT1 and SGLT1 of STZ-induced diabetic rats. We conclude that PI dermal patches deliver physiologically relevant amounts of insulin that can improve kidney function in diabetes.

Potassium abnormalities in a pediatric intensive care unit: frequency and severity

BACKGROUND

Potassium abnormalities are common in critically ill patients. We describe the spectrum of potassium abnormalities in our tertiary-level pediatric intensive care unit (PICU).

METHODS

Retrospective observational cohort of all the patients admitted to a single-center tertiary PICU over a 1-year period. Medical records and laboratory results were obtained through a central electronic data repository.

RESULTS

A total of 512 patients had a potassium measurement. Of a total of 4484 potassium measurements, one-third had abnormal values. Hypokalemia affected 40% of the admissions. Mild hypokalemia (3-3.4 mmol/L) affected 24% of the admissions. Moderate or severe hypokalemia (K <3.0 mmol/L) affected 16% of the admissions. Hyperkalemia affected 29% of the admissions. Mild hyperkalemia (5.1-6.0 mmol/L) affected 17% of the admissions. Moderate or severe hyperkalemia (>6.0 mmol/L) affected 12%. Hemolysis affected 2% of all the samples and 24% of hyperkalemic values. On univariate analysis, severity of hypokalemia was associated with mortality (odds ratio 2.2, P = .003).

CONCLUSIONS

Mild potassium abnormalities are common in the PICU. Repeating hemolyzed hyperkalemic samples may be beneficial. Guidance in monitoring frequencies of potassium abnormalities in pediatric critical care is needed.

Bullous skin reaction seen after extravasation of calcium gluconate

Intravenous (IV) calcium is usually given to temporarily treat the effects of hyperkalaemia on muscle and heart. When extravasation of a calcium gluconate infusion occurs, there may be rapid and marked swelling and erythema, with signs of soft-tissue necrosis or infection, and ensuing extensive local calcification, called calcinosis cutis. We report a 26-year-old woman who was hospitalized for exacerbation of acute intermittent porphyria. She had a history of hypertension and chronic renal failure. On the second day of her hospitalization, she developed hyperpotassaemia (6.7 mEq/L potassium; normal range 3.5-5 mEq/L). She was given an IV infusion of 10 mL calcium gluconate into the left dorsal pedal vein. Bullous skin reactions occurred in the infusion area nearly 2 h after administration. The patient's leg was elevated and the lesions cleaned with 0.9% saline. By day 9 of hospitalization, the lesions had markedly regressed. Several drugs have been associated with dermoepidermal blistering as an adverse drug reaction, but there is only one existing report in the literature about this side-effect associated with calcium gluconate. Clinicians should be alert to the possibility of bullous skin reactions, which may be a predictor of extravasation and necrosis, when treating patients with IV calcium gluconate.

The frequency of hyperkalemia and its significance in chronic kidney disease

BACKGROUND

Hyperkalemia is a potential threat to patient safety in chronic kidney disease (CKD). This study determined the incidence of hyperkalemia in CKD and whether it is associated with excess mortality.

METHODS

This retrospective analysis of a national cohort comprised 2 103 422 records from 245 808 veterans with at least 1 hospitalization and at least 1 inpatient or outpatient serum potassium record during the fiscal year 2005. Chronic kidney disease and treatment with angiotensin-converting enzyme inhibitors and/or angiotensin II receptor blockers (blockers of the renin-angiotensin-aldosterone system [RAAS]) were the key predictors of hyperkalemia. Death within 1 day of a hyperkalemic event was the principal outcome.

RESULTS

Of the 66 259 hyperkalemic events (3.2% of records), more occurred as inpatient events (n = 34 937 [52.7%]) than as outpatient events (n = 31 322 [47.3%]). The adjusted rate of hyperkalemia was higher in patients with CKD than in those without CKD among individuals treated with RAAS blockers (7.67 vs 2.30 per 100 patient-months; P < .001) and those without RAAS blocker treatment (8.22 vs 1.77 per 100 patient-months; P < .001). The adjusted odds ratio (OR) of death with a moderate (potassium, >or=5.5 and <6.0 mEq/L [to convert to mmol/L, multiply by 1.0]) and severe (potassium, >or=6.0 mEq/L) hyperkalemic event was highest with no CKD (OR, 10.32 and 31.64, respectively) vs stage 3 (OR, 5.35 and 19.52, respectively), stage 4 (OR, 5.73 and 11.56, respectively), or stage 5 (OR, 2.31 and 8.02, respectively) CKD, with all P < .001 vs normokalemia and no CKD.

CONCLUSIONS

The risk of hyperkalemia is increased with CKD, and its occurrence increases the odds of mortality within 1 day of the event. These findings underscore the importance of this metabolic disturbance as a threat to patient safety in CKD.

Therapeutic efficacy of renin—angiotensin blockade in patients receiving dialysis

Observational data in dialysis patients has indicated an increased cardiovascular mortality. One pathophysiological cause of this cardiovascular mortality in these patients is volume overload. In addition, an inappropriately activated renin—angiotensin system (RAS) has been proposed as another possible mechanism for the increased cardiovascular mortality. With these possible causes in mind, blockade of the RAS with an angiotensin-converting enzyme (ACE) inhibitor or an angiotensin receptor blocker (ARB) have both emerged as means of preventing cardiovascular events in this population. This review focuses on clinical evidence of the beneficial effects of ACE inhibitors and ARBs in dialysis patients with regard to the improvement of cardiovascular events as well as blood pressure control and maintenance of dialysis therapy.

Management of yellow oleander poisoning

BACKGROUND

Poisoning due to deliberate self-harm with the seeds of yellow oleander (Thevetia peruviana) results in significant morbidity and mortality each year in South Asia. Yellow oleander seeds contain highly toxic cardiac glycosides including thevetins A and B and neriifolin. A wide variety of bradyarrhythmias and tachyarrhythmias occur following ingestion. Important epidemiological and clinical differences exist between poisoning due to yellow oleander and digoxin; yellow oleander poisoning is commonly seen in younger patients without preexisting illness or comorbidity. Assessment and initial management. Initial assessment and management is similar to other poisonings. No definite criteria are available for risk stratification. Continuous ECG monitoring for at least 24 h is necessary to detect arrhythmias; longer monitoring is appropriate in patients with severe poisoning. Supportive care. Correction of dehydration with normal saline is necessary, and antiemetics are used to control severe vomiting. Electrolytes. Hypokalemia worsens toxicity due to digitalis glycosides, and hyperkalemia is life-threatening. Both must be corrected. Hyperkalemia is due to extracellular shift of potassium rather than an increase in total body potassium and is best treated with insulin-dextrose infusion. Intravenous calcium increases the risk of cardiac arrhythmias and is not recommended in treating hyperkalemia. Oral or rectal administration of sodium polystyrene sulfonate resin may result in hypokalemia when used together with digoxin-specific antibody fragments. Unlike digoxin toxicity, serum magnesium concentrations are less likely to be affected in yellow oleander poisoning. The effect of magnesium concentrations on toxicity and outcome is not known. Hypomagnesaemia should be corrected as it can worsen cardiac glycoside toxicity. Gastric decontamination. The place of emesis induction and gastric lavage has not been investigated, although they are used in practice. Gastric decontamination by the use of single dose and multiple doses of activated charcoal has been evaluated in two randomized controlled trials, with contradictory results. Methodological differences (severity of poisoning in recruited patients, duration of treatment, compliance) between the two trials, together with differences in mortality rates in control groups, have led to much controversy. No firm recommendation for or against the use of multiple doses of activated charcoal can be made at present, and further studies are needed. Single-dose activated charcoal is probably beneficial. Activated charcoal is clearly safe. Arrhythmia management. Bradyarrhythmias are commonly managed with atropine, isoprenaline, and temporary cardiac pacing in severe cases, although without trial evidence of survival benefit, or adequate evaluation of possible risks. Accelerating the heart rate with atropine or beta-adrenergic agents theoretically increases the risk of tachyarrhythmias, and it has been claimed that atropine increases tachyarrhythmic deaths. Further studies are required. Tachyarrhythmias have a poor prognosis and are more difficult to treat. Lidocaine is the preferred antiarrhythmic; the role of intravenous magnesium is uncertain. Digoxin-specific antibody fragments. Digoxin-specific antibody fragments are effective in reverting life-threatening cardiac arrhythmias; prospective observational studies show a beneficial effect on mortality. High cost and lack of availability limit the widespread use of digoxin-specific antibody fragments in developing countries.

CONCLUSIONS

Digoxin-specific antibody fragments remain the only proven therapy for yellow oleander poisoning. Further studies are needed to determine the place of activated charcoal, the benefits or risks of atropine and isoprenaline, the place and choice of antiarrhythmics, and the effect of intravenous magnesium in yellow oleander poisoning.

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.

Safety of perioperative hemodialysis and continuous hemodiafiltration for dialysis patients with cardiac surgery

OBJECTIVE

We have routinely used postoperative continuous hemodiafiltration (CHDF) combined with intraoperative hemodialysis (IHD) for dialysis patients undergoing open-heart surgery. This perioperative management could avoid any limitation of potassium concentration in the cardioplegic solution, strict restriction of fluid administration, or blood transfusion.

METHODS

To evaluate the safety of this strategy, 22 dialysis patients who underwent open-heart surgery (Dialysis Group) were retrospectively compared with 30 patients with normal renal function selected from the same time period with rigorously matched clinical characteristics such as age, gender, and operative procedures (Matched Group).

RESULTS

No significant difference was found in the operative variables such as the operative procedures, cardiopulmonary bypass time, and aortic cross-clamp time in both groups. There were two deaths (9.1%) in the Dialysis Group compared with Matched Group (0%). In the Dialysis Group, the levels of serum potassium and creatinine were well controlled in the perioperative period with a mean duration of IHD and CHDF of 243.7 +/- 60.6 min and 2.7 +/- 1.1 days, respectively. In particular, no significant difference between intraoperative and postoperative levels of serum potassium was observed in the Dialysis Group (P = 0.09), whereas there was a significant increase in the Matched Group (P = 0.004). Mean volume administered for the first 24 h after surgery was not different from the Matched Group. There were no vascular access-related complications in the Dialysis Group.

CONCLUSIONS

Postoperative CHDF combined with IHD can provide a similar management protocol for dialysis patients compared to patients with normal renal function.

Characteristics of sudden death in hemodialysis patients

Hemodialysis (HD) is an intermittent procedure during which large fluid and electrolyte shifts occur. We hypothesized that sudden death occurrences in HD patients are related to the timing of HD, and that they occur more frequently in the 12 h period starting with dialysis and in the 12 h period at the end of the dialysis-free weekend interval. In a retrospective study, 228 patient deaths were screened to determine if they met the criteria for sudden death. Information was obtained from clinic charts, dialysis center records, and interview of witnesses of the death event. There were 80 HD patients who met the criteria for sudden death. A bimodal distribution of death occurrences was present, with a 1.7-fold increased death risk occurring in the 12 h period starting with the dialysis procedure and a threefold increased risk of death in the 12 h before HD at the end of the weekend interval (P=0.011). Patients with sudden death had a high prevalence of congestive heart failure and coronary artery disease. Only 40% of patients experiencing sudden death were receiving beta-blockers, and the prior monthly serum potassium value was less than 4 mEq/l in 25%. Sudden death is temporally related to the HD procedure. Every other day HD could be beneficial in preventing sudden death. Careful attention to the usage of beta-blockers and to the maintenance of normal serum potassium values is indicated in HD patients at risk for sudden death.

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.

Aldosterone-receptor antagonism and end-stage renal disease

Blockade of aldosterone effect with either spironolactone or eplerenone is an approach that is being used more frequently in the treatment of hypertension and congestive heart failure; however, sparse information exists pertaining to efficacy or side-effects of this line of treatment for patients with chronic kidney disease and/or end-stage renal disease (ESRD). Hyperkalemia is, by far, the most worrisome complication of therapy with either of these compounds and, not surprisingly, hinders their use in moderate-to-advanced renal failure. However, patients with anuric ESRD should theoretically not be at risk for hyperkalemia. To this end, pilot safety studies with aldosterone-receptor antagonists in ESRD patients have begun. These studies imply that spironolactone can be safely used in carefully selected and closely monitored patients. Eplerenone has not been studied in ESRD in a therapeutic or safety capacity. Additional studies are needed with these compounds in the ESRD population before their use can be considered safe.

Review Articles: Nondialytic Management of Hyperkalemia and Pulmonary Edema Among End-Stage Renal Disease Patients: An Evaluation of the Evidence

Congestive heart failure (CHF) and hyperkalemia are the two leading reasons for emergency dialysis among individuals with end-stage renal disease (ESRD). While hemodialysis provides definitive treatment of both hyperkalemia and volume overload among ESRD patients, for those who present outside of "regular dialysis hours," institution of dialysis may be delayed. Nondialytic management can be instituted immediately and should be the initial therapy in the management of hyperkalemia and CHF in these individuals. Current available evidence does not allow conclusions as to whether treatment with nondialytic strategies alone results in different outcomes than nondialytic strategies coupled with emergent hemodialysis. Therefore, whether or not nondialytic management alone is appropriate remains a matter of individual judgment that should be decided on a case-by-case basis.

Na+-K+ Pump Regulation and Skeletal Muscle Contractility

Clausen, Torben. Na+-K+ Pump Regulation and Skeletal Muscle Contractility. Physiol Rev 83: 1269-1324, 2003; 10.1152/physrev.00011.2003.—In skeletal muscle, excitation may cause loss of K+, increased extracellular K+ ([K+]o), intracellular Na+ ([Na+]i), and depolarization. Since these events interfere with excitability, the processes of excitation can be self-limiting. During work, therefore, the impending loss of excitability has to be counterbalanced by prompt restoration of Na+-K+ gradients. Since this is the major function of the Na+-K+ pumps, it is crucial that their activity and capacity are adequate. This is achieved in two ways: 1) by acute activation of the Na+-K+ pumps and 2) by long-term regulation of Na+-K+ pump content or capacity. 1) Depending on frequency of stimulation, excitation may activate up to all of the Na+-K+ pumps available within 10 s, causing up to 22-fold increase in Na+ efflux. Activation of the Na+-K+ pumps by hormones is slower and less pronounced. When muscles are inhibited by high [K+]o or low [Na+]o, acute hormone- or excitation-induced activation of the Na+-K+ pumps can restore excitability and contractile force in 10-20 min. Conversely, inhibition of the Na+-K+ pumps by ouabain leads to progressive loss of contractility and endurance. 2) Na+-K+ pump content is upregulated by training, thyroid hormones, insulin, glucocorticoids, and K+ overload. Downregulation is seen during immobilization, K+ deficiency, hypoxia, heart failure, hypothyroidism, starvation, diabetes, alcoholism, myotonic dystrophy, and McArdle disease. Reduced Na+-K+ pump content leads to loss of contractility and endurance, possibly contributing to the fatigue associated with several of these conditions. Increasing excitation-induced Na+ influx by augmenting the open-time or the content of Na+ channels reduces contractile endurance. Excitability and contractility depend on the ratio between passive Na+-K+ leaks and Na+-K+ pump activity, the passive leaks often playing a dominant role. The Na+-K+ pump is a central target for regulation of Na+-K+ distribution and excitability, essential for second-to-second ongoing maintenance of excitability during work.

Outcome and complications of intraoperative hemodialysis during cardiopulmonary bypass with potassium-rich cardioplegia

BACKGROUND

Potassium-rich cardioplegia has advantages over other cardioplegic solutions in preserving the myocardium during cardiopulmonary bypass, but it is avoided in patients with renal failure because of hyperkalemia.

METHODS

We first determined the ability of intraoperative hemodialysis (IHD) to remove potassium during cardiopulmonary bypass with potassium-rich cardioplegia in 9 patients by measuring potassium levels in all dialysate and urine. We then studied 24 patients with renal failure, grouped with the 9 previous patients, to assess safety, rebound hyperkalemia, and patient outcome with this technique.

RESULTS

In the first phase, 9 patients were administered 128 +/- 11 mmol of potassium in potassium-rich cardioplegia, and IHD removed 157 +/- 23 mmol. Urinary potassium excretion was only 10 +/- 3 mmol. Potassium removal occurred at a rate of 1.25 mmol/min with 0-mEq/L (mmol/L) potassium dialysate and a rate of 0.75 mmol/min with 3.0-mEq/L (mmol/L) potassium dialysate. In all 33 patients, successful initiation of cardiac rhythm occurred after cardiopulmonary bypass, and 5 patients had cardiac arrhythmias possibly from hypokalemia. In the next 24 hours, 5 dialysis-dependent patients developed hyperkalemia (potassium > 5.2 mEq/L [mmol/L]) requiring hemodialysis. Postoperative hemodialysis was delayed 2 to 3 days in the other patients. The overall death rate was 24% at 30 days.

CONCLUSION

IHD effectively and safely removes potassium administered during potassium-rich cardioplegia during cardiopulmonary bypass in patients with renal failure and prevents postoperative hyperkalemia in the majority of patients. Overall mortality in patients with acute and chronic renal failure undergoing cardiac surgery is high irrespective of control of potassium balance in these patients.

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.

Skeletal muscle regulates extracellular potassium

Maintaining extracellular fluid (ECF) K(+) concentration ([K(+)]) within a narrow range is accomplished by the concerted responses of the kidney, which matches K(+) excretion to K(+) intake, and skeletal muscle, the main intracellular fluid (ICF) store of K(+), which can rapidly buffer ECF [K(+)]. In both systems, homologous P-type ATPase isoforms are key effectors of this homeostasis. During dietary K(+) deprivation, these P-type ATPases are regulated in opposite directions: increased abundance of the H,K-ATPase "colonic" isoform in the renal collecting duct drives active K(+) conservation while decreased abundance of the plasma membrane Na,K-ATPase alpha(2)-isoform leads to the specific shift of K(+) from muscle ICF to ECF. The skeletal muscle response is isoform and muscle specific: alpha(2) and beta(2), not alpha(1) and beta(1), levels are depressed, and fast glycolytic muscles lose >90% alpha(2), whereas slow oxidative muscles lose ~50%; however, both muscle types have the same fall in cellular [K(+)]. To understand the physiological impact, we developed the "K(+) clamp" to assess insulin-stimulated cellular K(+) uptake in vivo in the conscious rat by measuring the exogenous K(+) infusion rate needed to maintain constant plasma [K(+)] during insulin infusion. Using the K(+) clamp, we established that K(+) deprivation leads to near-complete insulin resistance of cellular K(+) uptake and that this insulin resistance can occur before any decrease in plasma [K(+)] or muscle Na(+) pump expression. These studies establish the advantage of combining molecular analyses of P-type ATPase expression with in vivo analyses of cellular K(+) uptake and excretion to determine mechanisms in models of disrupted K(+) homeostasis.

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.

Salbutamol metered-dose inhaler with spacer for hyperkalemia: how fast? How safe?

OBJECTIVE

To determine the efficacy of inhaled salbutamol (rapidly delivered, using a metered-dose inhaler with a spacer device [MDI-S]) in lowering the serum potassium levels in patients with hyperkalemia.

DESIGN

A randomized, double-blind, placebo-controlled trial.

PATIENTS

Seventeen chronic renal failure patients referred to the Nephrology Unit between October 1, 1997 and March 31, 1998 for hemodialysis were randomized.

INTERVENTION AND RESULTS

Group 1 received salbutamol followed by a placebo. Group 2 received a placebo followed by salbutamol. Each patient inhaled 1,200 microg salbutamol or a placebo through an MDI-S within 2 min. Blood samples were obtained repeatedly before inhalation and after 1, 3, 5, 10, and 60 min. The pulse rate and blood pressure were repeatedly measured. Insulin levels were examined in a subset of patients (n = 10) before, and 1 and 5 min following inhalation. Salbutamol's known side effects, palpitation, tachycardia tremor, and headache, were recorded. Potassium levels rose after 1 min following the completion of treatment and then decreased steadily thereafter. A rise of > or = 0.1 mEq/L was seen in 10 of 17 patients (59%) during the treatment period and there was no change (0%) seen during the placebo period (p < 0.0001). Within 3 min after inhalation of salbutamol, potassium levels declined as a function of time. Potassium levels in those patients taking the placebo did not change as a function of time (p < 0.001). The difference between the placebo and the salbutamol-treated periods reached significance after 5 min (p < 0.05). The serum glucose levels rose following inhalation of salbutamol, with a significant rise after 3 min. The heart rate rose significantly within the first 5 min following inhalation. Serum insulin levels remained unchanged 1 min after inhalation; however, after 5 min, a significant elevation was detected.

CONCLUSION

Salbutamol inhalation of 1,200 microg, using an MDI-S, has a relatively rapid onset of action that induces a consistent reduction in serum potassium levels, starting 3 to 5 min following delivery. Unexpectedly, a paradoxical elevation was detected in serum potassium levels in the first minutes following inhalation. This effect, although minor (0.15 mEq/L above baseline), may cast some doubt on the role of salbutamol inhalation as the first treatment for excessive hyperkalemia.

Potassium

In a logical, stepwise approach to patients presenting with hypokalaemia or hyperkalaemia the clinician must first recognise circumstances in which the dyskalaemia represents a clinical emergency because therapy then takes precedence over diagnosis. If a dyskalaemia has been present for a long time, there is an abnormal renal handling of K+. The next step to analyse is the rate of excretion of K+ and, if necessary, its two components (urine flow rate and K+ concentration in the cortical collecting duct [CCD]) analysed independently. If the K+ concentration in the CCD is not in the expected range, its basis should be defined at the ion-channel level in the CCD from clinical information that can be used to deduce the relative rates of reabsorption of Na+ and Cl- in the CCD. This analysis provides the basis for diagnosis and may indicate where non-emergency therapy should then be directed.

Ritodrine- and terbutaline-induced hypokalemia in preterm labor: mechanisms and consequences

The effects of ritodrine and terbutaline on potassium homeostasis, renal function, and cardiac rhythm were assessed in women treated with these drugs for preterm labor. Timed blood and urine samples were obtained for two hours before and during six hours of intravenous ritodrine (N = 5) and terbutaline (N = 5) administered in pharmacologically equivalent doses. No differences were found in any parameters affecting potassium homeostasis or renal function between these drugs. A decrease in mean plasma potassium of 0.9 mEq/liter occurred after 30 minutes of drug infusion (4.2 +/- 0.1 to 3.3 +/- 0.1 mEq/liter, P < 0.005) before any significant changes in plasma glucose (75.0 +/- 4.7 to 93.7 +/- 6.1 mg/dl, P = NS) or plasma insulin (12.4 +/- 6.0 to 28.4 +/- 5.1 mU/ml, P = NS). The mean plasma potassium after four hours of drug infusion was 2.5 +/- 0.1 mEq/liter. Plasma insulin rose to a level known to induce cellular potassium uptake (39.2 +/- 7.7 mU/ml) after 60 minutes of drug therapy and remained at this level for four hours. Hyperlactatemia occurred at four hours (4.7 +/- 0.8 mmol/liter) and the plasma lactate/pyruvate ratio increased in a 10:1 ratio. Both drugs significantly reduced glomerular filtration rate, sodium, potassium, and chloride excretion and urinary flow rate. Changes in acid-base homeostasis, plasma aldosterone, or renal potassium excretion did not contribute to ritodrine-or terbutaline-induced hypokalemia. In 83 women with preterm labor randomly assigned to ritodrine (N = 42) or terbutaline (N = 41), the maximum decrease in plasma potassium occurred after six hours of drug infusion. During Holter monitoring, 3 of 14 women treated with ritodrine or terbutaline developed symptomatic cardiac arrhythmias at the lowest plasma potassium while no women treated with saline and morphine (N = 12) developed cardiac arrhythmias (P = 0.14). We conclude that ritodrine and terbutaline induce profound hypokalemia by stimulating cellular potassium uptake and both drugs cause significant renal sodium and fluid retention and cardiac arrhythmias. Careful monitoring of electrolytes, fluid balance, and cardiac rhythm should occur during tocolytic therapy with ritodrine or terbutaline.

Effect of bicarbonate administration on plasma potassium in dialysis patients: interactions with insulin and albuterol

Acute treatment of hyperkalemia in patients with end-stage renal disease requires temporizing measures to shift potassium rapidly from the extracellular to the intracellular fluid compartments until hemodialysis can be initiated. Whereas insulin and albuterol are effective in lowering plasma potassium acutely, bicarbonate by itself is not. Bicarbonate administration may, however, potentiate the effects of insulin and albuterol on plasma potassium. Using a prospective cross-over design, we investigated the acute effects of (1) isotonic bicarbonate, (2) isotonic saline, (3) insulin + bicarbonate, (4) insulin + saline, (5) albuterol + bicarbonate, and (6) albuterol + saline on plasma potassium as well as blood bicarbonate and pH in nondiabetic hemodialysis patients. After obtaining a baseline blood sample, the subjects received one of the six treatment protocols, with plasma potassium measured every 15 minutes over 1 hour. Neither isotonic bicarbonate nor isotonic saline decreased plasma potassium significantly (-0.03 +/- 0.06 mmol/L v -0.01 +/- 0.10 mmol/L at 60 minutes; P = 0.60). Intravenous insulin decreased plasma potassium by a similar degree when given in conjunction with bicarbonate or saline (-0.81 +/- 0.05 mmol/L v -0.85 +/- 0.06 mmol/L at 60 minutes; P = 0.65). Likewise, nebulized albuterol decreased plasma potassium by a similar degree when given with bicarbonate or saline (-0.71 +/- 0.16 mmol/L v -0.53 +/- 0.15 mmol/L at 60 minutes; P = 0.18). The three protocols that included bicarbonate administration resulted in significant increases in blood bicarbonate (P < 0.005) and pH (P < 0.01), whereas the three protocols that included saline did not affect blood bicarbonate or pH. These observations suggest that bicarbonate administration does not potentiate the potassium-lowering effects of insulin or albuterol in hemodialysis patients.

Effective treatment of acute hyperkalaemia in childhood by short-term infusion of salbutamol

Hyperkalaemia is a life-threatening emergency and infusion of glucose with insulin has so far been regarded as the standard treatment of choice. Recently the beta-2 stimulatory drug salbutamol has been shown to be an effective agent to treat hyperkalaemia by inducing a shift of potassium into the intracellular compartment. We treated 15 children aged 0.1-14 (mean 5.2) years suffering from acute hyperkalaemia (mean level 6.6 +/- 0.54, range 5.9-7.7 mmol/l) with a single infusion of salbutamol (5 micrograms/kg over 15 min). Serum potassium concentrations decreased significantly within 30 min to levels of 5.74 +/- 0.53 and 4.92 +/- 0.53 mmol/l after 120 min (P < 0.001, respectively). No side-effects occurred other than a light increase in heart rate in 3 patients.

CONCLUSION

A single intravenous infusion of salbutamol at a dose of 5 micrograms/kg is a highly effective treatment for hyperkalaemia with minimal clinical side-effects. The effect lasts for at least 120 min and may reverse hyperkalaemia in some patients without further interventions so that salbutamol seems justified as the first choice treatment for this condition in childhood.

Effect of albuterol treatment on subsequent dialytic potassium removal

End-stage renal disease patients presenting with severe hyperkalemia are frequently treated with albuterol to lower their plasma potassium acutely, until emergent hemodialysis can be initiated. Such treatment stimulates potassium shifts from the extracellular to the intracellular fluid compartments. The resulting reduction of potassium concentration gradient between the blood and dialysate may potentially attenuate the efficacy of potassium removal during the ensuing hemodialysis treatment. To evaluate the effect of prior albuterol treatment on dialytic potassium removal, seven chronic hemodialysis patients were studied prospectively on two separate occasions. In one study the patients received 20 mg nebulized albuterol 30 minutes before dialysis; in the control study, albuterol treatment was omitted. Plasma potassium decreased 30 minutes after albuterol treatment (-0.84 +/- 0.06 mmol/L; P < 0.001) and remained unchanged in the corresponding period of the control experiment. Plasma potassium decreased during dialysis in both experimental protocols, but was significantly lower throughout dialysis in the albuterol study, as compared with the control study. Cumulative dialytic potassium removal was significantly lower following albuterol pretreatment compared with the control experiment (29.0 +/- 5.7 mmol v 49.6 +/- 7.0 mmol; P < 0.001). These observations suggest that acute albuterol therapy in patients with end-stage renal disease may substantially decrease potassium removal in the ensuing hemodialysis session. This may lead to rebound hyperkalemia several hours after the dialysis treatment.

Treatment of hyperkalemia in children with intravenous salbutamol

The aim of this study is to investigate the efficacy and safety of intravenous salbutamol in hyperkalemia. Fourteen children with chronic renal failure, three with acute renal failure and hyperkalemia were treated by intravenous infusions of 4 micrograms/kg salbutamol. Reductions in the mean plasma potassium (K+) concentrations obtained at 40 to 120 min after therapy were statistically significant when compared with the mean plasma K+ concentration at the beginning of therapy (P < 0.01).

Potassium homeostasis and its disturbances in children

Although only 2% of the body potassium is present in the extracellular space, its concentration is finely regulated by the internal balance, or distribution of potassium between the intracellular and extracellular compartments, and by the external balance, or difference between intake and output of potassium. Internal balance is modulated by a host of factors, including insulin, epinephrine, extracellular pH and plasma tonicity. Potassium output from the body is mainly determined by renal excretion. Renal secretion of potassium takes place predominantly in the principal cells of late distal and cortical collecting tubules, by a process involving the accumulation of potassium in the cell by the activity of the basolateral Na+,K(+)-ATPase and its exit through luminal conductive channels. The factors regulating renal potassium secretion are potassium intake, rate of tubular fluid flow, distal sodium delivery, acid-base status and aldosterone. Hypokalaemia may result from a low potassium intake, excessive gastrointestinal, cutaneous or renal losses and altered body distribution. Aetiological diagnosis and therapy are best accomplished when the acid-base status is assessed at the same time. Before establishing the diagnosis of hyperkalaemia, spurious hyperkalaemia due to haemolysis or release of potassium from cells during clot retraction (pseudohyperkalaemia) should be ruled out. Hyperkalaemia may result from exogenous or endogenous loading, decreased renal output and altered body distribution. Acute hyperkalaemia represents an emergency situation which requires immediate therapy.

Effect of three laxatives and a cation exchange resin on fecal sodium and potassium excretion

BACKGROUND/AIMS

The treatment of hyperkalemia in patients with renal insufficiency often includes the ingestion of sorbitol and a cation exchange resin. Sorbitol alone may be used to remove sodium and water from overloaded patients. The efficacy of these regimens has never been compared with other laxative or laxative-resin combinations. The aim of the study was to compare the relative effect of three laxatives with different mechanisms of action, alone and in combination with resin, on fecal sodium and potassium excretion.

METHODS

Sodium, potassium, and water excretion in 12-hour stool collections were analyzed after various laxative-resin combinations in normal subjects.

RESULTS

Correctol (yellow phenolphthalein) (Schering Plough Health Care Products, Memphis, TN) was more effective than sorbitol or sodium sulfate in causing fecal sodium and potassium loss. Resin recovery in stool was much greater with phenolphthalein than with other laxatives, and more potassium was excreted in stool with phenolphthalein-resin than with phenolphthalein alone or other laxative-resin combinations. Sorbitol caused more undesirable gastrointestinal symptoms than did sodium sulfate or phenolphthalein.

CONCLUSIONS

In normal people, phenolphthalein (1) is preferable to other laxatives in causing fecal sodium and potassium excretion, (2) hastens resin transit through the intestine compared with other laxatives, and (3) produces greater fecal potassium excretion when combined with resin than phenolphthalein alone or other laxative-resin combinations.

Supplemented low-protein diet and once-weekly hemodialysis

The aim of this study was to evaluate the feasibility and the nutritional and depurative adequacy of the integrated diet dialysis program. The integrated diet dialysis program consists of a low-protein diet (0.4 g/kg ideal body weight/d), supplemented with essential amino acids or a mixture of essential amino acids and chetoanalogues, and once-weekly hemodialysis, tailored to maintain predialytic blood urea nitrogen levels lower than 90 mg/dL. Sixty-nine of 84 recruited patients with a mean age of 62.9 +/- (SD) 11.1 years and a baseline glomerular filtration rate of 2.54 +/- 0.94 mL/min entered the experimental phase; 15 dropped out, eight because of poor diet compliance. At 12-month follow-up, patient and technique survival were, respectively, 89% and 56%. The laboratory, anthropometric, and instrumental parameters of 28 patients with a follow-up of more than 12 months were also evaluated using repeated measures ANOVA. Mean predialytic blood urea nitrogen values were not significantly different (82 +/- 21 mg/dL v 93 +/- 26 mg/dL at baseline and after 12-month follow-up, respectively); total weekly KT/V from residual renal function plus dialysis (1.64 +/- 0.32 v 1.70 +/- 0.29; P = NS) and dialytic index according to Babb and Scribner (1.35 +/- 0.31 v 1.21 +/- 0.33) were stable. No problems were found as far as acid-base, calcium phosphate, water-electrolyte metabolism and blood pressure control are concerned. Body weight, fat free mass, fat, plasma proteins, albumin, and C3 and C4 complement factors were stable. Creatinine production (sum of metabolized plus excreted creatinine) decreased (14.3 +/- 3.2 mg/kg/d v 13.4 +/- 2.6 mg/kg/d; P < 0.05). Transferrin decreased but not significantly (221 +/- 46 mg/dL v 204 +/- 42 mg/dL; P < 0.09). Distal motor conduction velocity from the posterior tibial nerve did not improve during the study (37.8 +/- 4.9 m/s v 36.4 +/- 4.9 m/s), while distal motor conduction velocity from the median nerve worsened (50.8 +/- 4.3 m/s v 46.3 +/- 6.3 m/s; P < 0.05). In conclusion, even though the integrated diet dialysis program may be very important in the psychologically delicate phase between the conservative and the classical three-times-a-week hemodialysis programs, and may also solve some economic and dialytically related organizational problems, it arouses some concern as far as compliance and long-term nutritional and depurative adequacy are concerned. It should therefore be limited to highly motivated patients in centers with well-trained staff or where dialysis facilities are lacking.

Hypokalemic effects of intravenous infusion or nebulization of salbutamol in patients with chronic renal failure: comparative study

To examine and compare the efficacy and safety of different routes of administration of salbutamol in treating hyperkalemia, 15 patients with chronic renal failure (blood urea nitrogen > 80 mg/dL, serum creatinine > 8.0 mg/dL) were enrolled to sequentially receive either intravenous infusion (0.5 mg) or nebulization (10 mg) of salbutamol. Five of these patients (33.3%) did not respond to the intravenous salbutamol and were excluded from the study. Both treatments significantly decreased plasma potassium in 10 patients and the decrease was sustained for at least 3 hours. After infusion, the maximal reduction in plasma potassium levels was 0.92 +/- 0.10 mEq/L and occurred after 30 minutes. On the other hand, the maximal reduction in plasma potassium after nebulization (0.85 +/- 0.13 mEq/L) was similar to that after infusion, but it occurred after 90 minutes. Insulin and blood glucose increased, whereas blood pH, PCO2, sodium, osmolality, and blood pressure did not change after either treatment. Heart rate increased significantly after both treatments, but less after nebulization than after infusion. It is concluded that both infusion and nebulization are simple, effective, and safe therapeutic modalities for the treatment of hyperkalemia in patients with chronic renal failure. Infusion should be used in patients requiring a rapid decrease in plasma potassium; nebulization, on the other hand, should be used in patients with coronary artery diseases.