The effects of angiotensin converting enzyme inhibitors on potassium homeostasis in dialysis patients with and without residual renal function

Hyperkalemia in chronic peritoneal dialysis patients

Background. Chronic peritoneal dialysis (PD) patients often develop hypokalemia but less commonly hyperkalemia.

Methods. We explored incidence and mechanisms of hyperkalemia in 779 serum samples from 33 patients on PD for 1 − 59 months. Normal serum potassium concentration was defined as 3.5 − 5.1 meq/l.

Results. Mean monthly serum potassium concentrations were normal (except for 1 month), but we observed hypokalemia (<3.5 meq/l) in 5% and hyperkalemia (>5.1 meq/l) in 14% of 779 serum samples. Incidence of hyperkalemia did not change over time on PD: Year 1 (15%), Year 2 (11%), Year 3 (19%), Years 4–5 (22%). Hyperkalemia was mostly modest but occasionally extreme [5.2–5.4 meq/l (55%), 5.5–5.7 meq/l (21%), 5.8–6.0 meq/l (10%), >6.0 meq/l (14%)]. Of 31 patients (2 excluded due to brief PD time), 39% displayed hyperkalemia only, 23% displayed hypokalemia only, and the remainder (38%) displayed both or neither. Comparing hypokalemia-only with hyperkalemia-only patients, we found no difference in potassium chloride therapy, medications interrupting the renin-angiotensin system, small-molecule transport status, and renal urea clearance. We compared biochemical parameters from the hypokalemic and hyperkalemic serum samples and observed lower bicarbonate concentrations, higher creatinine concentrations, and higher urea nitrogen concentrations in the hyperkalemic samples (p < 0.001 for each), without difference in glucose concentrations.

Conclusion. We observed hyperkalemia 3 times as frequently as hypokalemia in our PD population. High-potassium diet, PD noncompliance, increased muscle mass, potassium shifts, and/or the daytime period without PD might contribute to hyperkalemia.

Framing Cause-Effect Relationship of Acute Coronary Syndrome in Patients with Chronic Kidney Disease

The main causes of death in patients with chronic kidney disease (CKD) are of cardiovascular nature. The interaction between traditional cardiovascular risk factors (CVRF) and non-traditional risk factors (RF) triggers various complex pathophysiological mechanisms that will lead to accelerated atherosclerosis in the context of decreased renal function. In terms of mortality, CKD should be considered equivalent to ischemic coronary artery disease (CAD) and properly monitored. Vascular calcification, endothelial dysfunction, oxidative stress, anemia, and inflammatory syndrome represents the main uremic RF triggered by accumulation of the uremic toxins in CKD subjects. Proteinuria that appears due to kidney function decline may initiate an inflammatory status and alteration of the coagulation-fibrinolysis systems, favorizing acute coronary syndromes (ACS) occurrence. All these factors represent potential targets for future therapy that may improve CKD patient's survival and prevention of CV events. Once installed, the CAD in CKD population is associated with negative outcome and increased mortality rate, that is the reason why discovering the complex pathophysiological connections between the two conditions and a proper control of the uremic RF are crucial and may represent the solutions for influencing the prognostic. Exclusion of CKD subjects from the important trials dealing with ACS and improper use of the therapeutical options because of the declined kidney functioned are issues that need to be surpassed. New ongoing trials with CKD subjects and platelets reactivity studies offers new perspectives for a better clinical approach and the expected results will clarify many aspects.

Hypertension Drug Therapy

Hypertension is still the number one global killer. No matter what causes are, lowering blood pressure can significantly reduce cardiovascular complications, cardiovascular death, and total death. Unfortunately, some hypertensive individuals simply do not know having hypertension. Some knew it but either not being treated or treated but blood pressure does not achieve goal. The reasons for inadequate control of blood pressure are many. One important reason is that we are not very familiar with antihypertensive agents and less attention has been paid to comorbidities, complications as well as the hypertension-modified target organ damage in patients with hypertension. The right antihypertensive drug was not given to the right hypertensive patients at right time. This reviewer studied comprehensively the literature, hopefully that the review will help improve antihypertensive drug selection and antihypertensive therapy.

Effects of Renin-Angiotensin-Aldosterone System Blockade in Patients with End-Stage Renal Disease

Blockers of the renin-angiotensin-aldosterone system (RAAS), such as angiotensin-converting enzyme inhibitors and angiotensin receptor blockers are routinely used in patients with chronic kidney disease because of their cardiovascular (CV) and renoprotective effects. However, there are no uniform recommendations about RAAS blockers for CV protection in the end-stage renal disease (ESRD) population other than the preferred drug class for blood pressure control. This uncertainty stems from the fact that patients with ESRD were generally excluded from randomized controlled trials evaluating the cardioprotective benefits of RAAS blockers. It is important to weigh the potential harms associated with the use of RAAS blockers, such as electrolyte disturbances and worsening anemia, with their role in protection of residual kidney function, alleviation of thirst and potential CV benefits. The objective of this review is to summarize the current knowledge about the use of RAAS blockers in patients with ESRD.

Pharmacological and non pharmacological strategies in the management of coronary artery disease and chronic kidney disease

Patients with advanced chronic kidney disease (CKD), including those treated with dialysis, are at high risk for the development of cardiovascular disease (CVD). CVD accounts for 45-50% of deaths among dialysis patients. Therapy of acute and chronic coronary heart disease (CHD) that is effective in the general population is frequently less effective in patients with advanced CKD. Drug therapy in such patients may require dose modification in some cases. Oral anti-platelet drugs are less effective in those with advanced CKD than in persons with normal or near normal renal function. The intravenous antiplatelet drugs eptifibatide and tirofiban both require dose reductions in patients with advanced CKD. Enoxaparin requires dose reduction in early stage CKD and is contraindicated in hemodialysis patients. Unfractionated heparin and warfarin maybe used without dose adjustment in CKD patients. Atenolol, acetbutolol and nadolol may require dose adjustments in CKD. Metoprolol and carvedilol do not. Calcium channel blockers and nitrates do not require dose adjustment, whereas ranolazine does. Angiotensin converting enzyme inhibitors and angiotensin receptor blockers may safely be used in CKD patients with close observation for hyperkalemia. The safety of spironolactone in such patients is questionable. Statins are less effective in reducing cardiovascular complication in CKD patients and their initiation is not recommended in dialysis patients. Coronary artery bypass grafting is associated with higher short-term mortality, but better long-term morbidity and mortality than percutaneous coronary interventions in patients with advanced CKD with non-ST segment ACS and chronic CHD.

Low dialysate potassium concentration: an overrated risk factor for cardiac arrhythmia?

Serum potassium concentrations rise with dietary potassium intake between dialysis sessions and are often at hyperkalemic levels by the next session. Conversely, potassium concentrations fall during each hemodialysis, and sometimes reach hypokalemic levels by the end. Low potassium dialysate, which rapidly decreases serum potassium and often brings it to hypokalemic levels, is almost universally considered a risk factor for life-threatening arrhythmias. While there is little doubt about the threat of lethal arrhythmias due to hyperkalemia, convincing evidence for the danger of low potassium dialysate and rapid or excess potassium removal has not been forthcoming. The original report of more frequent ventricular ectopy in early dialysis that was improved by reducing potassium removal has received very little confirmation from subsequent studies. Furthermore, the occurrence of ventricular ectopy during dialysis does not appear to predict mortality. Studies relating sudden deaths to low potassium dialysate are countered by studies with more thorough adjustment for markers of poor health. Dialysate potassium concentrations affect the excursions of serum potassium levels above or below the normal range, and have the potential to influence dialysis safety. Controlled studies of different dialysate potassium concentration and their effect on mortality and cardiac arrests have not been done. Until these results become available, I propose interim guidelines for the setting of dialysate potassium levels that may better balance risks and benefits.

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.

Sailing between Scylla and Charybdis: the high serum K-low dialysate K quandary

In HD patients, the optimal choice of dialysate K concentration is of paramount importance. Recent large observational studies have documented an association between low dialysate K concentration (< 2 or even <3 mEq/L) and a higher risk of sudden death. In this review, we first briefly discuss the available data concerning the link between hypokalemia and negative outcomes in non-CKD populations, especially after an acute myocardial infarction or in congestive heart failure. We next review the pathophysiology of the arrhythmogenic effect related to K fluxes during HD and discuss the dialytic strategies aiming at making potassium fall more gradual and thus at reducing the electrical disturbances triggered by the HD session. We conclude with practical recommendations regarding the optimal choice of K bath and the importance of more frequent monitoring of serum K in some clinical scenarios.

Hyperkalemia of angiotensin-converting enzyme inhibitors or angiotensin receptor blockers in hemodialysis: a meta-analysis

The safety of angiotensin-converting enzyme inhibitors (ACEIs) or angiotensin receptor blockers (ARBs) used in hemodialysis (HD) patients was evaluated. Medline, Embase, the Cochrane Library, some databases of clinical trial registries, grey literatures, other reference lists of eligible articles and review articles for the randomized clinical trials (RCTs) on comparison of ACEIs/ARBs or placebo in HD patients were retrieved. RCTs reporting the risk of hyperkalemia by using ACEIs/ARBs in HD patients were selected. Eight articles met the eligibility criteria and were subjected to meta-analysis by using the Cochrane Collaboration's RevMan 4.2 software package. The results showed that there was no significant difference in hyperkalemia in HD patients between ACEIs or ARBs group and control group (ACEIs vs. control: RD=0.03, 95% CI=-0.13-0.18, Z=0.34, P=0.73; ARBs vs. control: RD=-0.02, 95% CI=-0.07-0.03, Z=0.75, P=0.45). However, there was no significant difference in the serum potassium between ACEIs or ARBs group and control group in HD patients (ACEIs vs. control: WMD=0.10, 95% CI=0.06-0.15, Z=4.64, P<0.00001; ARBs vs. control: WMD=-0.24, 95% CI=-0.37-0.11, Z=3.58, P=0.0003). The use of ACEIs or ARBs could not cause an increased risk of hyperkalemia in HD patients, however the serum potassium could be increased with use of ACEIs in HD patients. Therefore the serum potassium concentration should still be closely monitored when ACEIs are taken during the maintenance HD.

The 2010 nephrology quiz and questionnaire: part 2

Presentation of the Nephrology Quiz and Questionnaire (NQQ) has become an annual "tradition" at the meetings of the American Society of Nephrology. It is a very popular session judged by consistently large attendance. Members of the audience test their knowledge and judgment on a series of case-oriented questions prepared and discussed by experts. They can also compare their answers in real time, using audience response devices, to those of program directors of nephrology training programs in the United States, acquired through an Internet-based questionnaire. As in the past, the topics covered were transplantation, fluid and electrolyte disorders, end-stage renal disease and dialysis, and glomerular disorders. Two challenging cases representing each of these categories along with single best answer questions were prepared by a panel of experts (Drs. Hricik, Palmer, Bargman, and Fervenza, respectively). The "correct" and "incorrect" answers then were briefly discussed, after the audience responses and the results of the questionnaire were displayed. The 2010 version of the NQQ was exceptionally challenging, and the audience, for the first time, gained a better overall correct answer score than the program directors, but the margin was small. Last month we presented the transplantation and fluid and the electrolyte cases; in this issue we present the remaining end-stage renal disease and dialysis and the glomerular disorder cases. These articles try to recapitulate the session and reproduce its educational value for a larger audience--that of the readers of the Clinical Journal of the American Society of Nephrology. Have fun.

Antihypertensive agents in hemodialysis patients: a current perspective

Hypertension affects most hemodialysis patients and is often poorly controlled. Adequate control of blood pressure is difficult with conventional hemodialysis alone but is important to improve cardiovascular outcomes. Nonpharmacologic interventions to improve blood pressure include educating patients about limiting sodium intake, ensuring adequate sodium solute removal during hemodialysis, and achieving target "dry weight." However, most patients require a number of antihypertensive medications to achieve an appropriate blood pressure. First-line antihypertensive agents include angiotensin converting enzyme inhibitors and angiotensin receptor blockers given their safety profile and demonstrated benefit on cardiovascular outcomes in clinical trials. beta-blockers and combined alpha- and beta-blockers should also be used in patients with cardiovascular disease or congestive heart failure and may improve outcomes in these populations. Calcium channel blockers and direct vasodilators are also effective for controlling blood pressure. Many blood pressure agents can be dosed once daily and should preferentially be administered at night to control nocturnal blood pressure and minimize intradialytic hypotension. In patients who are noncompliant with therapy, renally eliminated agents (such as lisinopril and atenolol) can be given thrice weekly following hemodialysis. Older antihypertensive agents which require thrice daily dosing ought to be avoided given the high pill burden with these regimens and the concern for noncompliance resulting in rebound hypertension. Newer antihypertensive agents, such as direct renin inhibitors, may provide alternative options to improve blood pressure but require testing for efficacy and safety in hemodialysis patients.