Posttransplant Acidosis and Associated Disorders of Mineral Metabolism in Patients With a Renal Graft

Efficacy and safety of oral sodium bicarbonate in kidney-transplant recipients and non-transplant patients with chronic kidney disease: a systematic review and meta-analysis

Introduction

We investigated the efficacy and safety of oral sodium bicarbonate in kidney-transplant recipients and non-transplant patients with chronic kidney disease (CKD), which are currently unclear.

Methods

PubMed, Cochrane Library, Embase, and Web of Science were searched for randomized controlled trials investigating the efficacy and safety of sodium bicarbonate versus placebo or standard treatment in kidney-transplant and non-transplant patients with CKD.

Results

Sixteen studies of kidney-transplant recipients (two studies, 280 patients) and non-transplant patients with CKD (14 studies, 1,380 patients) were included. With non-transplant patients, sodium bicarbonate slowed kidney-function declines (standardized mean difference [SMD]: 0.49, 95% confidence interval [CI]: 0.14-0.85, p = 0.006) within ≥12 months (SMD: 0.75 [95% CI: 0.12-1.38], p = 0.02), baseline-serum bicarbonate <22 mmol/L (SMD: 0.41 [95% CI: 0.19-0.64], p = 0.0004) and increased serum-bicarbonate levels (mean difference [MD]: 2.35 [95% CI: 1.40-3.30], p < 0.00001). In kidney-transplant recipients, sodium bicarbonate did not preserve graft function (SMD: -0.07 [95% CI: -0.30-0.16], p = 0.56) but increased blood pH levels (MD: 0.02 [95% CI: 0.00-0.04], p = 0.02). No significant adverse events occurred in the kidney-transplant or non-transplant patients (risk ratio [RR]: 0.89, [95% CI: 0.47-1.67], p = 0.72; and RR 1.30 [95% CI: 0.84-2.00], p = 0.24, respectively). However, oral sodium bicarbonate correlated with increased diastolic pressure and worsened hypertension and edema (MD: 2.21 [95% CI: 0.67-3.75], p = 0.005; RR: 1.44 [95% CI: 1.11-1.88], p = 0.007; and RR: 1.28 [95% CI: 1.00-1.63], p = 0.05, respectively).

Discussion

Oral sodium bicarbonate may slow kidney-function decline in non-transplant patients with CKD taking sodium bicarbonate supplementation for ≥12 months or a baseline serum bicarbonate level of <22 mmol/L, without preserving graft function in kidney-transplant recipients. Sodium bicarbonate may increase diastolic pressure, and elevate a higher incidence of worsening hypertension and edema.

Systematic Review Registration

https://www.crd.york.ac.uk/prospero/, identifier CRD42023413929.

Metabolic acidosis in chronic kidney disease: mere consequence or also culprit?

Metabolic acidosis is a frequent complication in non-transplant chronic kidney disease (CKD) and after kidney transplantation. It occurs when net endogenous acid production exceeds net acid excretion. While nephron loss with reduced ammoniagenesis is the main cause of acid retention in non-transplant CKD patients, additional pathophysiological mechanisms are likely inflicted in kidney transplant recipients. Functional tubular damage by calcineurin inhibitors seems to play a key role causing renal tubular acidosis. Notably, experimental and clinical studies over the past decades have provided evidence that metabolic acidosis may not only be a consequence of CKD but also a driver of disease. In metabolic acidosis, activation of hormonal systems and the complement system resulting in fibrosis have been described. Further studies of changes in renal metabolism will likely contribute to a deeper understanding of the pathophysiology of metabolic acidosis in CKD. While alkali supplementation in case of reduced serum bicarbonate < 22 mmol/l has been endorsed by CKD guidelines for many years to slow renal functional decline, among other considerations, beneficial effects and thresholds for treatment have lately been under intense debate. This review article discusses this topic in light of the most recent results of trials assessing the efficacy of dietary and pharmacological interventions in CKD and kidney transplant patients.

Current Status of Mineral and Bone Disorders in Transplant Recipients

Most patients with end-stage kidney disease undergoing kidney transplantation are affected by the chronic kidney disease-mineral and bone disorder. This entity encompasses laboratory abnormalities, calcification of soft tissues, and the bone abnormalities of renal osteodystrophy that together result in an increased risk of fracture, cardiovascular events, and mortality. Although many biochemical disturbances associated with end-stage kidney disease improve in the first year after transplantation, hyperparathyroidism commonly persists, and residual changes of renal osteodystrophy are slow to resolve. When superimposed on common, traditional risk factors, post-transplant glucocorticoid treatment, the possibility of tubular disturbances and post-transplant chronic kidney disease, rates of incident fracture remain high. This review examines hormonal and biochemical changes before and after kidney transplantation, fracture risk assessment tools and imaging modalities, a staged approach to management and concerns associated with antiresorptive and anabolic therapies. A multidisciplinary approach is proposed as the best means to improve patient-level outcomes.

Metabolic acidosis post kidney transplantation

Metabolic acidosis, a common complication in patients with chronic kidney disease (CKD), results in a multitude of deleterious effects. Though the restoration of kidney function following transplantation is generally accompanied by a correction of metabolic acidosis, a subset of transplant recipients remains afflicted by this ailment and its subsequent morbidities. The vulnerability of kidney allografts to metabolic acidosis can be attributed to reasons similar to pathogenesis of acidosis in non-transplant CKD, and to transplant specific causes, including donor related, recipient related, immune mediated factors, and immunosuppressive medications. Correction of metabolic acidosis in kidney transplantation either with alkali therapy or through dietary manipulations may have potential benefits and the results of such clinical trials are eagerly awaited. This review summarizes the published evidence on the pathogenesis and clinical consequences of chronic metabolic acidosis in kidney transplant recipients.

Increased intrarenal post-glomerular blood flow is a key condition for the development of calcineurin inhibitor-induced renal tubular acidosis in kidney transplant recipients

BACKGROUND

Hyperchloremic metabolic acidosis (HCMA) from renal tubular acidosis (RTA) is common in kidney transplant (KT) recipients. Calcineurin inhibitors (CNIs) are a potential cause of RTA, and whether HCMA is a determinant of poor graft prognosis is controversial.

METHODS

The subjects were living-donor KT recipients (LDKTRs, n = 47) and matched donors (n = 43). All cases of rejection, extrarenal causes, and respiratory disorders were excluded. HCMA was defined as having a [Na+] - [Cl-] value of ≤ 34 or starting alkalization. We determined the potential causes of HCMA in LDKTRs at 3 months (m) and 1 year (y) post-KT. We examined renal hemodynamic parameters in 26 LDKTRs at 1 y post-KT: namely, glomerular filtration rate (GFR), renal plasma flow (RPF), filtration fraction (FF; GFR/RPF) and pre-/post-glomerular vascular resistance (pre-/postVR).

RESULTS

The HCMA incidence in the 3-m post-KT LDKTR group was higher than that of the donors (51.0% vs. 6.9%, p<0.001, adjusted odds ratio: 6.7-15.7). Among adjusted factors, the most dominant HCMA contributor was low hemoglobin concentration (Hb ≤12 g/dL). Compared to non-HCMA cases, HCMA patients had low FF and low post-VR (p = 0.008, 0.003, respectively) suggesting increased intrarenal post-glomerular blood flow. The high pathological score of alternative arteriolar hyalinosis (aah) ≥2 was a significant HCMA risk. The tacrolimus trough level was not high in HCMA but was significantly high in HCMA in the low post-VR setting (p = 0.002).

CONCLUSION

Among LDKTRs, low hemoglobin level is an important contributor to the manifestation of HCMA in the induction period, and increased intrarenal post-glomerular blood flow is a key condition for the development of CNI-induced RTA. This article is protected by copyright. All rights reserved.

Fludrocortisone Is an Effective Treatment for Hyperkalaemic Metabolic Acidosis in Kidney Transplant Recipients on Tacrolimus: A Case Series

BACKGROUND

Hyperkalaemia with metabolic acidosis is common but under-reported following kidney transplantation. Calcineurin inhibitors, such as tacrolimus, are widely used in the management of transplant patients and are associated with the development of hyperkalaemia. We report on 10 renal transplant patients, treated with fludrocortisone, following identification of hyperkalaemic metabolic acidosis.

RESULTS

All 10 patients were male aged (mean ± SD) 53.0 ± 13.2 years; 7 were Caucasian and 3 South Asian. Before and after fludrocortisone administration, respective (mean ± SD) serum potassium was 6.1 ± 0.4 mmol/L and 5.3 ± 0.3 mmol/L (p = 0.0002); serum bicarbonate 18.5 ± 1.6 mmol/L and 20.5 ± 2.3 mmol/L (p = 0.002); serum sodium 135 ± 4.6 mmol/L and 137 ± 2.2 mmol/L (p = 0.0728); serum creatinine 181 ± 61 μmol/L and 168 ± 64 μmol/L (p = 0.1318); eGFR 42 ± 18 mL/min and 46 ± 18 mL/min (p = 0.0303); blood tacrolimus 10.1 ± 2.9 ng/mL and 10.4 ± 1.4 ng/mL (p = 0.7975); and blood pressure 129 ± 15/79 ± 25 mm Hg and 126 ± 24/75 ± 7 mm Hg. Pre-fludrocortisone, there were 7 episodes of serum potassium ≥6.5 mEq/L, with 4 patients requiring admission for the treatment of hyperkalaemia. Following fludrocortisone, no patients had hyperkalaemia requiring inpatient management.

CONCLUSIONS

Treatment of hyperkalaemic metabolic acidosis in transplant patients on tacrolimus with low-dose fludrocortisone resulted in rapid correction of hyperkalaemia and acidosis without significant effects on blood pressure or serum sodium. Fludrocortisone can be an effective short-term option for the treatment of hyperkalaemic metabolic acidosis in kidney transplant recipients on tacrolimus; however, patient selection remains important in order to reduce to risk of potential adverse effects.

Incidence of hyperkalemic RTA in pediatric post-renal transplant patients and the role of fludrocortisone

BACKGROUND

One of the most common forms of post-transplant tubulopathy is hyperkalemic (RTA). The true incidence of hyperkalemic RTA in pediatric patients has not yet been studied. (CNIs) remain mostly blamed. Most cases are managed with sodium bicarbonate and potassium binding resins. Few studies have addressed the role of fludrocortisone in managing such patients. This study aimed to assess the efficacy and safety of fludrocortisone in the treatment of post-transplant hyperkalemic RTA.

METHOD

This is a retrospective cohort study of all pediatric (aged ≤16 years) post-kidney transplant patients who were followed up in KFSH-D, Saudi Arabia from January 2015 until September 2019. A total of 136 pediatric post-renal transplant patients were reviewed, of these, 39 patients who were commenced on fludrocortisone post-transplant treatment and were followed up for at least 6 months after fludrocortisone initiation were included in this study.

RESULTS

The incidence of hyperkalemic RTA in our center was 60.6%. The medication requirements decreased significantly after fludrocortisone initiation. The median sodium bicarbonate dose decreased from 1.2 mEq/kg/day (range, 0.0-4.7) prior to fludrocortisone treatment to 0.0 mEq/kg/day (range, 0.0-4.3) at 6-month follow-up (p < .001). Similarly, the median (SPS) dose decreased from 1.2 g/kg/day (range, 0.0-4.0) before fludrocortisone treatment to 0.0 g/kg/day (range, 0.0-3.6) (p < .001) at 6-month follow-up. The initial mean potassium level 5.17 mmol/L ± 0.61SD dropped to 4.60 mmol/L ± 0.46SD at 6-month follow-up (p < .001). The initial mean serum bicarbonate level 22.31 mmol/L ± 3.67SD increased to 24.5 mmol/L ± 2.8SD at 6-month follow-up (p < .01). No effect on systolic and diastolic blood pressure was observed during follow-up.

CONCLUSION

Hyperkalemic RTA incidence was high in our cohort. Fludrocortisone is safe and effective drug in the treatment of post-kidney transplant hyperkalemic RTA.

Metabolic acidosis in the initial 6 months after renal transplantation: A prospective study

BACKGROUND

There is limited information about the incidence of metabolic acidosis (MA) after renal transplantation. This single centre prospective study aimed to delineate the incidence and risk factors of MA in the first 6 months after renal transplantation (RTX).

DESIGN, SETTING, PARTICIPANTS AND MEASUREMENTS

Patients who underwent RTX between November 2018 and July 2020 were monitored with weekly measurement of serum bicarbonate level for 6 months and those who were diagnosed with MA were evaluated further to characterize the type of MA.

RESULTS

One hundred and twenty-five patients were included in the study, 89 (71.2%) of whom developed MA. Seventy-two patients developed MA in the first month, 11 during the 2-3 months and 6 between 4 and 6 months after transplantation. Of the 89 patients, 55(61.8%) had type 1 renal tubular acidosis (T1RTA), 27 (30.3%) had type 2 RTA (T2RTA) and 7 (7.9%) type 4 RTA (T4RTA). Two patient who had T1RTA, subsequently developed high anion gap MA following severe graft rejection. On stepwise multivariate regression analysis, serum creatinine at time of diagnosis of MA [OR (95% CI): 12.02 (1.79 to 80.59), p = .01] and high tacrolimus C0 levels [OR (95% CI): 2.43 (1.0 to 5.90), p = .049], were independent risk factors for MA.

CONCLUSION

There is a high incidence of MA in the initial 6 months post-transplant with serum creatinine and high tacrolimus C0 levels being independent risk factors.

Acidosis and alkali therapy in patients with kidney transplant is associated with transcriptional changes and altered abundance of genes involved in cell metabolism and acid-base balance

BACKGROUND

Metabolic acidosis occurs frequently in patients with kidney transplant and is associated with higher risk for and accelerated loss of graft function. To date, it is not known whether alkali therapy in these patients improves kidney function and whether acidosis and its therapy is associated with altered expression of proteins involved in renal acid-base metabolism.

METHODS

We collected retrospectively kidney biopsies from 22 patients. Of these patients, 9 had no acidosis, 9 had metabolic acidosis (plasma HCO3- < 22 mmol/l), and 4 had acidosis and received alkali therapy. We performed transcriptome analysis and immunohistochemistry for proteins involved in renal acid-base handling.

RESULTS

We found the expression of 40 transcripts significantly changed between kidneys from non-acidotic and acidotic patients. These genes are mostly involved in proximal tubule amino acid and lipid metabolism and energy homeostasis. Three transcripts were fully recovered by alkali therapy: the Kir4.2 K+-channel, an important regulator of proximal tubule HCO3--metabolism and transport, ACADSB and SHMT1, genes involved in beta-oxidation and methionine metabolism. Immunohistochemistry showed reduced staining for the proximal tubule NBCe1 HCO3- transporter in kidneys from acidotic patients that recovered with alkali therapy. In addition, the HCO3-exchanger pendrin was affected by acidosis and alkali therapy.

CONCLUSIONS

Metabolic acidosis in kidney transplant recipients is associated with alterations in the renal transcriptome that are partly restored by alkali therapy. Acid-base transport proteins mostly from proximal tubule were also affected by acidosis and alkali therapy suggesting that the downregulation of critical players contributes to metabolic acidosis in these patients.

Novel approaches to management of hyperkalaemia in kidney transplantation

PURPOSE OF REVIEW

Medications used frequently after kidney transplantation, including calcineurin inhibitors, angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, beta blockers and antimicrobials, are considered the leading culprit for posttransplant hyperkalaemia in recipients with a well functioning allograft. Other risk factors include comorbidities such as diabetes, hypertension and heart failure; and consumption of a potassium-enriched diet. We review the mechanisms for hyperkalaemia following kidney transplantation that are addressed using nonpharmacological and pharmacological interventions. We also discuss emerging therapeutic approaches for the management of recurrent hyperkalaemia in solid organ transplantation, including newer potassium binding therapies.

RECENT FINDINGS

Patiromer and sodium zirconium cyclosilicate are emerging potassium binders approved for the treatment of hyperkalaemia. Patiromer is a polymer that exchanges potassium for calcium ions. In contrast, sodium zirconium cyclosilicate is a nonpolymer compound that exchanges potassium for sodium and hydrogen ions. Both agents are efficacious in the treatment of chronic or recurrent hyperkalaemia and may result in fewer gastrointestinal side effects than older potassium binders such as sodium polystyrene sulfonate and calcium polystyrene sulfonate. Large-scale clinical studies have not been performed in kidney transplant patients. Patiromer may increase serum concentrations of tacrolimus, but not cyclosporine. Sodium zirconium cyclosilicate does not appear to compromise tacrolimus pharmacokinetics, although it may have a higher sodium burden.

SUMMARY

Patiromer and sodium zirconium cyclosilicate may be well tolerated options to treat asymptomatic hyperkalaemia and have the potential to ease potassium dietary restrictions in kidney transplant patients by maintaining a plant-dominant, heart-healthy diet. Their efficacy, better tolerability and comparable cost with respect to previously available potassium binders make them an attractive therapeutic option in chronic hyperkalaemia following kidney transplantation.

The Effects of Immunosuppressive Treatment during Pregnancy on the Levels of Potassium, Iron, Chromium, Zinc, Aluminum, Sodium and Molybdenum in Hard Tissues of Female Rats and Their Offspring

The ideal immunosuppressive regimen should provide for excellent immunosuppression with no side effects. Yet, current immunosuppressive therapy regimens commonly used in clinical applications fail to meet this criterion. One of the complications caused by immunosuppressive drugs is mineralization disorders in hard tissues. In this study, we evaluated the effects of three immunosuppressive therapies used after transplantation on the levels of potassium, iron, chromium, zinc, aluminum, sodium and molybdenum in the bones and teeth of female rats and their offspring. The study was conducted on 32 female Wistar rats, subjected to immunosuppressive regimens (cyclosporine A, mycophenolate mofetil and prednisone; tacrolimus, mycophenolate mofetil and prednisone; and cyclosporine A, everolimus and prednisone). The hard tissues of rats were analyzed using inductively coupled plasma optical emission spectrometry (ICP-OES, ICAP 7400 Duo, Thermo Scientific) equipped with a concentric nebulizer and a cyclonic spray chamber. All the immunosuppressive regimens included in the study affected the concentrations of the studied minerals in hard tissues of female rats and their offspring. The therapy based on cyclosporine A, everolimus and prednisone led to a decline in the levels of iron in bone, zinc in teeth, and molybdenum in the bone and teeth of mothers, while in the offspring, it caused a decline of bone potassium, with a decrease in iron and increase of molybdenum in teeth. Moreover, the regimen caused an increase in aluminum and chromium in the teeth and aluminum in the bones of the offspring, and consequently, it seems to be the therapy with the most negative impact on the mineral metabolism in hard tissues.

Causes and Consequences of Metabolic Acidosis in Patients after Kidney Transplantation

BACKGROUND

Metabolic acidosis (MA) is a common complication in kidney transplantation (KTx). It is more prevalent in KTx than in CKD, and it occurs at higher glomerular filtration rates. The pathophysiologic understanding of MA in KTx and its clinical impact has been highlighted by few recent studies. However, no guidelines exist yet for the treatment of MA after KTx.

SUMMARY

MA in KTx seems to share pathophysiologic mechanisms with CKD, such as impaired ammoniagenesis. Additional kidney transplant-specific factors seem to alter not only the prevalence but also the phenotype of MA, which typically shows features of renal tubular acidosis. There is evidence that calcineurin inhibitors, immunological factors, process of donation, donor characteristics, and diet may contribute to MA occurrence. According to several mainly observational studies, MA seems to play a role in disturbed bone metabolism, cardiovascular morbidity, declining graft function, and mortality. A better understanding of the pathophysiology and evidence from randomized controlled trials, in particular, are needed to clarify the role of MA and the potential benefit of alkali treatment in KTx. Alkali therapy might not only be beneficial but also cost effective and safe. Key Messages: MA seems to be associated with several negative outcomes in KTx. A deeper understanding of the pathophysiology and clinical consequences of MA in KTx is crucial. Clinical trials will have to determine the potential benefits of alkali therapy.

Is Metabolic Acidosis a Novel Risk Factor for a Long-Term Graft Survival in Patients after Kidney Transplantation?

BACKGROUND

Results of both experimental and clinical studies suggest that metabolic acidosis (MA) contributes to the progression of chronic kidney disease (CKD) and mortality in CKD patients. It is unknown whether the same relationship exists in kidney transplantation (KTx) patients. The aim of this observational study was to examine this relationship between MA and both mortality and renal outcomes in patients after KTx.

METHODS

Four hundred eighty-six (290 male; 196 female) patients aged 48 ± 12 years, at least 1 year after KTx, were analyzed. Blood HCO3- was measured, and patients were then observed over 3 years. MA was defined as the blood HCO3- concentration <22 mmol/L. The end points of survival analysis were death and initiation of dialysis therapy. In patients who did not reach the above-mentioned end points, the difference between final (after 3 years of follow-up) and initial estimated glomerular filtration rate (eGFR) was calculated.

RESULTS

MA was initially diagnosed in 57 (12%) patients after KTx. Three-year patient survival was 89.5% in the MA group and 97.4% in the non-MA group (p = 0.001). Three-year graft survival was 73.7% for patients with MA and 93.0% for patients without MA (p < 0.001). In patients with MA who did not reach study end points, blood bicarbonate concentration at baseline correlated positively with a change in eGFR (R = 0.48, p = 0.002, n = 36). Such a correlation was not found in patients without MA (n = 388).

CONCLUSIONS

(1) MA significantly increases the risk of mortality in patients after KTx. (2) The intensity of MA may be associated with progression of transplanted kidney dysfunction in KTx patients.

Association of blood bicarbonate and pH with mineral metabolism disturbance and outcome after kidney transplantation

In kidney transplant recipients (KTRs), scarce evidence has associated low blood bicarbonate levels with mineral metabolic disturbance and reduced allograft survival. However, the contribution of the blood pH to these observations remains unassessed. Equally, little is known about the influence of the blood provenance (arteriovenous fistula vs peripheral vein) on bicarbonate values. We analyzed blood gas parameters in a single-center cohort of 1260 stable KTRs, 3 months after transplantation. Inspection of pO₂ distribution allowed the unambiguous identification of the arterial (N = 914) or venous (N = 346) origin of the samples. In patients with arterial blood samples, 435 (46%) had bicarbonate levels below 22 mmol/L. Among them, 196 (40%) were acidemic (blood pH <7.38). In multivariate analysis, low arterial blood pH was associated with increased blood ionized calcium and phosphate and reduced fibroblast growth factor 23 and calcitriol, but not with outcome. In contrast, low bicarbonate concentration predicted allograft loss independently of measured glomerular filtration rate and other potential confounders (hazard ratio [HR] 1.70; 95% confidence interval [CI] 1.04-2.80). In KTRs, reduced arterial blood bicarbonate levels predict outcome while acidemia is associated with altered mineral metabolism.

Relationship of Serum Bicarbonate Levels with 1-Year Graft Function in Kidney Transplant Recipients in Switzerland

BACKGROUND

Metabolic acidosis (MA) is common in kidney transplant recipients (KTRs). Several studies have shown that MA is involved in the progression of chronic kidney disease. However, it is unclear if there is also a relationship between serum bicarbonate and graft function after kidney transplantation (KTx). We hypothesized that low serum bicarbonate is associated with a lower estimated glomerular filtration rate (eGFR) 1 year after KTx.

METHODS

We performed a post hoc analysis of a single-center, open-label randomized trial in 90 KTRs and investigated the relationship of serum bicarbonate and graft function in the first year after KTx.

RESULTS

Prevalence of MA was high after KTx (63%) and decreased to 28% after 1 year. Bicarbonate (20.6 ± 3.0 to 22.7 ± 2.7 mmol/L) increased in the first year after transplantation whereas eGFR (53.4 ± 15.8 to 56.9 ± 18.5 mL/min/1.73 m2) did not change significantly. Higher serum bicarbonate (p = 0.029) was associated with higher eGFR in the first year after KTx.

CONCLUSION

Prevalence of MA is high in KTRs. In the first year after KTx, serum bicarbonate was positively correlated with eGFR, suggesting a potential role of MA in kidney graft function.

Effect of Sodium Bicarbonate in Kidney Transplant Recipients With Chronic Metabolic Acidosis

Background

Metabolic acidosis (MA) is a common complication after kidney transplantation and regarded to increase mortality, graft failure, and bone fractures. Here, we conducted a retrospective cohort study to analyze the effect of sodium bicarbonate on those events.

Methods

All kidney transplant recipients of the German health insurance Allgemeine Ortskrankenkasse (AOK) were selected, who received their transplantation between 2007 and 2015. Three groups were formed: (1) control group (no acidosis, n = 3602), (2) acidosis group (encoded acidosis, n = 370), and (3) treatment group (encoded therapy, n = 769). The study endpoints were mortality, death-censored graft failure, and bone fractures.

Results

The prevalence of MA in the first year after transplantation was 46.2%. The 5-year patient and graft survival were 89.8% and 89.3% in the control group, 90% and 90.8% in the acidosis group, and 87.5% and 81.6% in the treatment group, respectively. The rate of bone fractures did not differ between the groups. Neither log-rank tests nor multivariable Cox regression analyses could detect a negative impact of MA on mortality (hazard ratio [HR] 0.94; confidence interval [CI] 0.67-1.30), graft failure (HR1.18; CI 0.82-1.72), or the incidence of bone fractures (HR1.19; CI 0.92-1.55). Treatment with sodium bicarbonate was associated with an increased risk of graft failure (HR1.52; CI 1.03-2.25), whereas mortality (HR0.86; CI 0.59-1.26) and the incidence of bone fractures (HR1.16; CI 0.86-1.56) were not altered.

Conclusions

MA is common after kidney transplantation but not associated with an increased frequency of death, graft failure, or bone fractures. Conversely, sodium bicarbonate therapy increased the incidence of graft failure.

Post-Renal Transplant Metabolic Acidosis: A Neglected Entity

Metabolic acidosis is a prevalent yet overlooked entity among renal transplant recipients (RTRs) and incurs adverse effects on graft function. Although graft dysfunction and calcineurin inhibitor usage have been linked with renal tubular acidosis (RTA), there is no Indian data on prevalence or risk factors of post-transplant acidosis. A cross-sectional study was conducted on 106 adult RTRs, with a transplant duration of >6 months and an estimated glomerular filtration rate (GFR) >40 ml/min/1.73 m². Acidosis was diagnosed on basis of plasma bicarbonate and arterial pH. Serum and urine electrolytes with anion gap were determined to diagnose and type RTA. Acidosis was diagnosed in 44 of 106 patients (41.5%) with 23 (52.27%) having severe acidosis. Type I RTA was the most common subtype (52.5%) followed by type IV (30.9%) and type II RTA (7.5%). The correlation between estimated glomerular filtration rate and acidosis was minimally linear (r = 0.1088), with multivariate analysis revealing previous acute rejection episodes, current serum tacrolimus levels, cotrimoxazole usage and intake of animal proteins to be independent risk factors. The serum albumin levels were low in the acidosis group and showed linear correlation with bicarbonate levels (r = 0.298). There is a high prevalence of metabolic acidosis in RTRs with type I RTA being most common subtype. Screening of RTRs on a regular basis is a feasible approach for early diagnosis and intervention. However, prospective studies are needed to demonstrate the effect of acidosis on graft survival and benefit of bicarbonate therapy in RTRs.

Hyperchloremic metabolic acidosis in the kidney transplant patient

Hyperchloremic metabolic acidosis of renal origin results from a defect in renal tubular acidification mechanism, and this tubular dysfunction can consist of an altered tubular proton secretion or bicarbonate reabsorption capability. Studies have documented that all forms of renal tubular acidosis (RTA), type I to IV, are documented in kidney transplant patients. Among RTA pathophysiologic mechanisms have been described the renal mass reduction, hyperkalemia, hyperparathyroidism, graft rejection, immunologic diseases, and some drugs such as renin-angiotensin-aldosterone blockers, and calcineurin inhibitors. RTA can lead to serious complications as is the case of muscle protein catabolism, muscle protein synthesis inhibition, renal osteodystrophy, renal damage progression, and anemia promotion. RTA should be treated by suppressing its etiologic factor (if it is possible), avoiding hyperkalemia, and/or supplying bicarbonate or a precursor (citrate). In conclusion: Hyperchloremic metabolic acidosis of renal origin is a relatively frequent complication in kidney transplantation patients, which can be harmful, and should be adequately treated in order to avoid its renal and systemic adverse effects.

Electrolytes disturbances after kidney transplantation

Objectives: Water and electrolytes disturbances often occur in renal transplant recipients. The objective is to describe the pathophysiology and the treatment of the most prevalent abnormalities. Methods: We screened PubMed for the following words in various combination: kidney transplantation and (disturbances or abnormalities) of (electrolytes or sodium or potassium or phosphate or calcium or acid-base). Results: We found abnormalities in all major electrolytes, as a consequence of tubular dysfunction caused by both rejection episodes and toxic effects of calcineurin inhibitors (CNIs; cyclosporine or tacrolimus). The renal tubular acidosis found in kidney transplant recipients is characterized by a normal anion gap and normal or high serum chloride levels. The incidence of hyperkalemia is 5-40% of patients treated with CNIs. The majority of kidney transplant recipients develop hypomagnesemia within the first weeks and months. Both cyclosporine and tacrolimus do induce hypomagnesemia by several mechanisms. Severe magnesium depletion may include clinical manifestations such as confusion, muscle weakness, tremor, dysphagia, tetany and convulsions. The immediate posttransplant period (first 3 months) is often accompanied by a decline in serum phosphate. Phosphate substitution is needed when serum levels fall below 0.5 mmol/l, or in patients with clinical symptoms and serum levels between 0.5 and 1.0 mmol/l. Hypercalcemia is also a common disorder in the chronic posttransplant phase, and is most often due to persistent hyperparathyroidism. Conclusions: Patients with kidney transplants display electrolytes abnormalities more frequently than non-transplanted patients with the same levels of renal function. A good knowledge of their physiopathology and treatment is important in the care of those patients.

Metabolic Acidosis 1 Year Following Kidney Transplantation and Subsequent Cardiovascular Events and Mortality: An Observational Cohort Study

RATIONALE & OBJECTIVE

Recent studies suggest that metabolic acidosis is associated with mortality and graft failure in kidney transplant recipients. However, it is unknown whether serum bicarbonate (measured as total carbon dioxide [tCO₂] in serum) levels predict cardiovascular events (CVEs) following kidney transplantation.

STUDY DESIGN

Observational cohort study.

SETTINGS & PARTICIPANTS

Single-center study of 2,128 kidney transplant recipients free of CVEs during the first 13.5 months following transplantation.

PREDICTOR

tCO₂ level at 1 year posttransplantation.

OUTCOMES

Ischemic, arrhythmic, and heart failure CVEs and death from any cause.

ANALYTICAL APPROACH

Independent associations were assessed using multivariable proportional hazards regression models. Restricted cubic spline Poisson models were used to explore nonlinear associations. Linear spline proportional hazards models were used to assess associations at different tCO₂ levels.

RESULTS

The prevalence of metabolic acidosis defined as tCO₂ level < 24 mEq/L was 38.8% (n=826). There were 384 recipients with a CVE and 610 deaths during a median follow-up of 4.0 years. CVEs included 241 ischemic, 137 arrhythmic, and 150 heart failure events. tCO₂ level < 20 mEq/L was associated with increased risk for CVEs (adjusted HR [aHR], 2.00; 95% CI, 1.29-3.10) compared to the reference category of tCO₂ level of 24.0 to 25.9 mEq/L. This association was primarily due to ischemic CVEs (aHR, 2.28; 95% CI, 1.34-3.90). For every 1 mEq/L lower tCO₂ level for those with tCO₂ < 24 mEq/L, risks for all CVEs and ischemic events were 17% and 15% higher, respectively (aHR for all CVEs of 0.83 [95% CI, 0.74-0.94] and aHR for ischemic CVEs of 0.85 [95% CI, 0.74-0.99]). Notably, tCO₂ level < 20 mEq/L, compared to tCO₂ level of 24.0 to 25.9 mEq/L, was independently associated with all-cause mortality (aHR, 1.43; 95% CI, 1.02-2.02). For every 1-mEq/L lower tCO₂ level for those with tCO₂ < 24 mEq/L, there was 17% higher risk for death (aHR, 0.83; 95% CI, 0.75-0.92).

LIMITATIONS

Single-center observational study.

CONCLUSIONS

Metabolic acidosis is an independent risk factor for ischemic CVEs after kidney transplantation. It is unknown whether correction of acidosis improves outcomes in these patients.

Electrolyte and Acid-Base Disorders in the Renal Transplant Recipient

Kidney transplantation is the current treatment of choice for patients with end-stage renal disease. Innovations in transplantation and immunosuppression regimens have greatly improved the renal allograft survival. Based on recently published data from the Scientific Registry of Transplant recipients, prevalence of kidney transplants is steadily rising in the United States. Over 210,000 kidney transplant recipients were alive with a functioning graft in mid-2016, which is nearly twice as many as in 2005. While successful renal transplantation corrects most of the electrolyte and mineral abnormalities seen in advanced renal failure, the abnormalities seen in the post-transplant period are surprisingly different from those seen in chronic kidney disease. Multiple factors contribute to the high prevalence of these abnormalities that include level of allograft function, use of immunosuppressive medications and metabolic changes in the post-transplant period. Electrolyte disturbances are common in patients after renal transplantation, and several studies have tried to determine the clinical significance of these disturbances. In this manuscript we review the key aspects of the most commonly found post-transplant electrolyte abnormalities. We focus on their epidemiology, pathophysiology, clinical manifestations, and available treatment approaches.

Mineral and Bone Disorders After Kidney Transplantation

The risk of mineral and bone disorders among patients with chronic kidney disease is substantially elevated, owing largely to alterations in calcium, phosphorus, vitamin D, parathyroid hormone, and fibroblast growth factor 23. The interwoven relationship among these minerals and hormones results in maladaptive responses that are differentially affected by the process of kidney transplantation. Interpretation of conventional labs, imaging, and other fracture risk assessment tools are not standardized in the post-transplant setting. Post-transplant bone disease is not uniformly improved and considerable variation exists in monitoring and treatment practices. A spectrum of abnormalities such as hypophosphatemia, hypercalcemia, hyperparathyroidism, osteomalacia, osteopenia, and osteoporosis are commonly encountered in the post-transplant period. Thus, reducing fracture risk and other bone-related complications requires recognition of these abnormalities along with the risk incurred by concomitant immunosuppression use. As kidney transplant recipients continue to age, the drivers of bone disease vary throughout the post-transplant period among persistent hyperparathyroidism, de novo hyperparathyroidism, and osteoporosis. The use of anti-resorptive therapies require understanding of different options and the clinical scenarios that warrant their use. With limited studies underscoring clinical events such as fractures, expert understanding of MBD physiology, and surrogate marker interpretation is needed to determine ideal and individualized therapy.

Preservation of kidney function in kidney transplant recipients by alkali therapy (Preserve-Transplant Study): rationale and study protocol

Background

Graft survival after kidney transplantation has significantly improved within the last decades but there is a substantial number of patients with declining transplant function and graft loss. Over the past years several studies have shown that metabolic acidosis plays an important role in the progression of Chronic Kidney Disease (CKD) and that alkalinizing therapies significantly delayed progression of CKD. Importantly, metabolic acidosis is highly prevalent in renal transplant patients and a recent retrospective study has shown that metabolic acidosis is associated with increased risk of graft loss and patient death in kidney transplant recipients. However, no prospective trial has been initiated yet to test the role of alkali treatment on renal allograft function.

Methods

The Preserve-Transplant Study is an investigator-initiated, prospective, patient-blinded, multi-center, randomized, controlled phase-IV trial with two parallel-groups comparing sodium bicarbonate to placebo. The primary objective is to test if alkali treatment will preserve kidney graft function and diminish the progression of CKD in renal transplant patients by assesing the change in eGFR over 2 years from baseline. Additionally we want to investigate the underlying pathomechanisms of nephrotoxicity of metabolic acidosis.

Discussion

This study has the potential to provide evidence that alkali treatment may slow or reduce the progression towards graft failure and significantly decrease the rate of end stage renal disease (ESRD), thus prolonging long-term graft survival. The implementation of alkali therapy into the drug regimen of kidney transplant recipients would have a favorable risk-benefit ratio since alkali supplements are routinely used in CKD patients and represent a well-tolerated, safe and cost-effective treatment.

Trial registration

ClinicalTrials.gov NCT03102996. Trial registration was completed on April 6, 2017.

Fifty shades of gray: Bone disease in renal transplantation

Kidney transplantation is the renal replacement therapy of choice for patients with end stage renal disease. Advances in technology, surgical techniques and pharmacotherapy have improved renal allograft survival. Increasingly, we are seeing long term side effects related to renal transplantation, bone disease being a major one amongst them. Renal transplant patients have a higher risk of fragility fractures even when compared to those who remain on dialysis. This is likely to be related to pre-existing underlying bone disease and the emergence of new metabolic bone problems post-transplant. Conditions such as persistent hyperparathyroidism and the use of certain immunosuppressive agents have a deleterious effect on the post renal transplant bone.

Remarkable advances in the field of metabolic bone research have been made in the last decade and newer imaging techniques, biomarkers and therapeutic options are now available for osteoporosis in the general population. Interest is being focused on attempting to extrapolate these new discoveries to the management of bone disease post renal transplant. This review will briefly describe the metabolic bone changes that occur after transplantation and will provide an update on the currently available investigative options and therapeutic strategies for the management of post renal transplant bone disease.

Metabolic acidosis in renal transplantation: neglected but of potential clinical relevance

Chronic metabolic acidosis (CMA) is a common complication of the more advanced stages of chronic kidney diseases (CKD), and is associated with morbidity and mortality of CKD patients and possibly with the progression of renal disease. Nevertheless, there is limited evidence or information on the prevalence, the potential causal factors, the clinical impact and the effects of correction of CMA in kidney transplant recipients. In this review, we briefly look at the more relevant, though scanty, studies which have, over time, addressed the above-mentioned points, with the hope that in the future the interest of transplant nephrologists and surgeons will grow towards this unreasonably neglected issue.

Long-term clinical practice experience with cinacalcet for treatment of hypercalcemic hyperparathyroidism after kidney transplantation

Within this prospective, open-label, self-controlled study, we evaluated the long-term effects of the calcimimetic cinacalcet on calcium and phosphate homeostasis in 44 kidney transplant recipients (KTRs) with hypercalcemic hyperparathyroidism by comparing biochemical parameters of mineral metabolism between pre- and posttreatment periods. Results are described as mean differences (95% CIs) between pre- and posttreatment medians that summarize all repeated measurements of a parameter of interest between the date of initial hypercalcemia and cinacalcet initiation (median of 1.6 (IQR: 0.6-3.8) years) and up to four years after treatment start, respectively. Cinacalcet was initiated after 1.8 (0.8-4.7) years posttransplant and maintained for 6.2 (3.9-7.6) years. It significantly decreased total serum calcium (-0.30 (-0.34 to -0.26) mmol/L, P < 0.001) and parathyroid hormone levels (-79 (-103 to -55) pg/mL, P < 0.001). Serum levels of inorganic phosphate (Pi) and renal tubular reabsorption of phosphate to glomerular filtration rate (TmP/GFR) increased simultaneously (Pi: 0.19 (0.15-0.23) mmol/L, P < 0.001, TmP/GFR: 0.20 (0.16-0.23) mmol/L, P < 0.001). In summary, cinacalcet effectively controlled hypercalcemic hyperparathyroidism in KTRs in the long-term and increased low Pi levels without causing hyperphosphatemia, pointing towards a novel indication for the use of cinacalcet in KTRs.

Urinary sulfur metabolites associate with a favorable cardiovascular risk profile and survival benefit in renal transplant recipients

In post-transplant conditions, sulfur may be protective by intermediate conversion to hydrogen sulfide and thiosulfate. However, sulfate, the end product of sulfur-containing amino acids (SAAs), contributes to metabolic acid load and may adversely influence acid-base homeostasis. We investigated the association of urinary sulfur metabolites with cardiometabolic parameters in renal transplant recipients (RTRs) and analyzed their predictive capacity for mortality. We studied urinary sulfate and thiosulfate excretion in 24-hour urine samples from 707 RTRs at a median 5.4 years (interquartile range, 1.9 to 12.2) after transplantation as well as from 110 controls. Diet was assessed for SAA content and various risk factors were measured. Urinary sulfate was similar, whereas thiosulfate was higher in RTRs versus controls. SAA intake was lower in RTRs compared with controls and correlated with sulfate but not thiosulfate excretion. Sulfate beneficially associated with eGFR, net acid excretion, systolic BP, high-sensitivity C-reactive protein, N-terminal probrain natriuretic peptide, and proteinuria (all P≤0.01). Thiosulfate beneficially associated with eGFR, serum acidity, high-sensitivity C-reactive protein, and N-terminal probrain natriuretic peptide (all P≤0.001). During a median 27 months (interquartile range, 22-36) of follow-up, 47 RTRs died. After adjustment for age, sex, and eGFR, hazard ratios for mortality were 0.87 (95% confidence interval, 0.82 to 0.92; P<0.001) for urinary sulfate and 0.60 (95% confidence interval, 0.41 to 0.59; P=0.01) for thiosulfate. Thus, despite the association of urinary sulfate with metabolic acid load, urinary sulfate and thiosulfate beneficially associated with survival in RTRs, possibly by influencing cardiovascular parameters. Intervention studies with exogenous sulfur are warranted to elucidate mechanisms underlying these promising associations in RTRs.

Dietary acid load and metabolic acidosis in renal transplant recipients

BACKGROUND AND OBJECTIVES

Acidosis is prevalent among renal transplant recipients (RTRs) and adversely affects cardiometabolic processes. Factors contributing to acidosis are graft dysfunction and immunosuppressive drugs. Little is known about the potential influence of diet on acidosis in RTRs. This study examined the association of metabolic acid load with acidosis and with cardiovascular risk factors in RTRs and aimed to identify dietary factors associated with acidosis. DESIGN, PARTICIPANTS, SETTING, & MEASUREMENTS: 707 RTRs were included. Metabolic acid load was assessed by measuring 24-hour urinary net acid excretion (NAE; i.e., titratable acid + ammonium - bicarbonate). Acidosis was defined as serum [HCO(3)(-)] < 24 mmol/L. BP and insulin resistance, reflected by hemoglobin A1c, were among cardiovascular risk factors. Diet was assessed with food-frequency questionnaires. Linear regression analysis was applied to investigate association between NAE and acidosis and between dietary factors and acidosis.

RESULTS

Mean age ± SD was 53 ± 13 years; 57% of patients were male. Acidosis was present in 31% of RTRs. NAE was associated with acidosis (serum HCO(3)(-): β=-0.61; serum pH: β=-0.010; both P<0.001). Patients with high intake of animal protein (i.e., from meat, cheese, and fish) and low intake of fruits and vegetables had significantly lower serum HCO(3)(-) and serum pH. No associations were observed between NAE and cardiovascular risk factors, such as hypertension and insulin resistance.

CONCLUSIONS

In addition to conventional factors contributing to acidosis, diet might influence acid-base homeostasis in RTRs. Higher intake of fruits and vegetables and lower animal protein intake is associated with less acidosis in RTRs.

Correction of metabolic acidosis with potassium citrate in renal transplant patients and its effect on bone quality

BACKGROUND

Acidosis and transplantation are associated with increased risk of bone disturbances. This study aimed to assess bone morphology and metabolism in acidotic patients with a renal graft, and to ameliorate bone characteristics by restoration of acid/base homeostasis with potassium citrate.

METHODS

This was a 12-month controlled, randomized, interventional trial that included 30 renal transplant patients with metabolic acidosis (S-[HCO(3)(-)] <24 mmol/L) undergoing treatment with either potassium citrate to maintain S-[HCO(3)(-)] >24 mmol/L, or potassium chloride (control group). Iliac crest bone biopsies and dual-energy X-ray absorptiometry were performed at baseline and after 12 months of treatment. Bone biopsies were analyzed by in vitro micro-computed tomography and histomorphometry, including tetracycline double labeling. Serum biomarkers of bone turnover were measured at baseline and study end. Twenty-three healthy participants with normal kidney function comprised the reference group.

RESULTS

Administration of potassium citrate resulted in persisting normalization of S-[HCO(3)(-)] versus potassium chloride. At 12 months, bone surface, connectivity density, cortical thickness, and cortical porosity were better preserved with potassium citrate than with potassium chloride, respectively. Serological biomarkers and bone tetracycline labeling indicate higher bone turnover with potassium citrate versus potassium chloride. In contrast, no relevant changes in bone mineral density were detected by dual-energy X-ray absorptiometry.

CONCLUSIONS

Treatment with potassium citrate in renal transplant patients is efficient and well tolerated for correction of metabolic acidosis and may be associated with improvement in bone quality. This study is limited by the heterogeneity of the investigated population with regard to age, sex, and transplant vintage.

Clinical impact of hypercalcemia in kidney transplant

Hypercalcemia (HC) has been variably reported in kidney transplanted (KTx) recipients (5–15%). Calcium levels peak around the 3rd month after KTx and thereafter slightly reduce and stabilize. Though many factors have been claimed to induce HC after KTx, the persistence of posttransplant hyperparathyroidism (PT-HPT) of moderate-severe degree is universally considered the first causal factor. Though not proven, there are experimental and clinical suggestions that HC can adversely affect either the graft (nephrocalcinosis) and other organs or systems (vascular calcifications, erythrocytosis, pancreatitis, etc.). However, there is no conclusive evidence that correction of serum calcium levels might avoid the occurrence of these claimed clinical effects of HC. The best way to reduce the occurrence of HC after KTx is to treat as best we can the secondary hyperparathyroidism (SHP) during the uraemic stages. The indication to Parathyroidectomy (PTX), either before or after KTx, in order to prevent or to treat, respectively, HC after KTx, is still a matter of debate which has been revived by the availability of the calcimimetic cinacalcet for the treatment of PT-HPT. However, we still need to better clarify many points as regards the potential adverse effects related to either PTX or cinacalcet use in this clinical set, and we are waiting for the results of future randomized controlled trials to achieve some more definite conclusions on this topic.

Pharmacologically-induced metabolic acidosis: a review

Metabolic acidosis may occasionally develop in the course of treatment with drugs used in everyday clinical practice, as well as with the exposure to certain chemicals. Drug-induced metabolic acidosis, although usually mild, may well be life-threatening, as in cases of lactic acidosis complicating antiretroviral therapy or treatment with biguanides. Therefore, a detailed medical history, with special attention to the recent use of culprit medications, is essential in patients with acid-base derangements. Effective clinical management can be handled through awareness of the adverse effect of certain pharmaceutical compounds on the acid-base status. In this review, we evaluate relevant literature with regard to metabolic acidosis associated with specific drug treatment, and discuss the clinical setting and underlying pathophysiological mechanisms. These mechanisms involve renal inability to excrete the dietary H+ load (including types I and IV renal tubular acidoses), metabolic acidosis owing to increased H+ load (including lactic acidosis, ketoacidosis, ingestion of various substances, administration of hyperalimentation solutions and massive rhabdomyolysis) and metabolic acidosis due to HCO3- loss (including gastrointestinal loss and type II renal tubular acidosis). Determinations of arterial blood gases, the serum anion gap and, in some circumstances, the serum osmolar gap are helpful in delineating the pathogenesis of the acid-base disorder. In all cases of drug-related metabolic acidosis, discontinuation of the culprit medications and avoidance of readministration is advised.

KDIGO clinical practice guideline for the care of kidney transplant recipients

The 2009 Kidney Disease: Improving Global Outcomes (KDIGO) clinical practice guideline on the monitoring, management, and treatment of kidney transplant recipients is intended to assist the practitioner caring for adults and children after kidney transplantation. The guideline development process followed an evidence-based approach, and management recommendations are based on systematic reviews of relevant treatment trials. Critical appraisal of the quality of the evidence and the strength of recommendations followed the Grades of Recommendation Assessment, Development, and Evaluation (GRADE) approach. The guideline makes recommendations for immunosuppression, graft monitoring, as well as prevention and treatment of infection, cardiovascular disease, malignancy, and other complications that are common in kidney transplant recipients, including hematological and bone disorders. Limitations of the evidence, especially on the lack of definitive clinical outcome trials, are discussed and suggestions are provided for future research.

KDIGO clinical practice guideline for the diagnosis, evaluation, prevention, and treatment of Chronic Kidney Disease-Mineral and Bone Disorder (CKD-MBD)

The 2009 Kidney Disease: Improving Global Outcomes (KDIGO) clinical practice guideline on the management of chronic kidney disease-mineral and bone disorder (CKD-MBD) is intended to assist the practitioner caring for adults and children with CKD stages 3-5, on chronic dialysis therapy, or with a kidney transplant. The guideline contains recommendations on evaluation and treatment for abnormalities of CKD-MBD. This disease concept of CKD-MBD is based on a prior KDIGO consensus conference. Tests considered are those that relate to the detection and monitoring of laboratory, bone, and cardiovascular abnormalities. Treatments considered are interventions to treat hyperphosphatemia, hyperparathyroidism, and bone disease in patients with CKD stages 3-5D and 1-5T. The guideline development process followed an evidence based approach and treatment recommendations are based on systematic reviews of relevant treatment trials. Recommendations for testing used evidence based on diagnostic accuracy or risk prediction and linked it indirectly with how this would be expected to achieve better outcomes for patients through better detection, evaluation or treatment of disease. Critical appraisal of the quality of the evidence and the strength of recommendations followed the GRADE approach. An ungraded statement was provided when a question did not lend itself to systematic literature review. Limitations of the evidence, especially the lack of definitive clinical outcome trials, are discussed and suggestions are provided for future research.

Electrolyte and Acid-base disturbances induced by clacineurin inhibitors

Nephrotoxicity is the most common and clinically significant adverse effect of calcineurin inhibitors. Cyclosporine and tacrolimus nephrotoxicity is manifested by both acute azotemia and chronic progressive renal disease and tubular zdysfunction. An elevation in the plasma potassium concentration due to reduced efficiency of urinary potassium excretion is common in cyclosporine-treated patients; it may be severe and potentially life-threatening with concurrent administration of an angiotensin converting enzyme inhibitor, which diminishes aldosterone release. Tubular injury induced by cyclosporine can also impair acid excretion. This may be presented as a hyperchloremic metabolic acidosis associated with decreased aldosterone activity and suppression of ammonium excretion by hyperkalemia. Some patients treated with cyclosporine develop hypophosphatemia due to urinary phosphate wasting. Renal magnesium wasting is also common presumably due to drug effects on magnesium reabsorption. Hypomagnesemia has also been implicated as a contributor to the nephrotoxicity associated with cyclosporine. Both cyclosporine and tacrolimus are associated with hypercalciuria. Attention must be paid to drug dose, side effects, and drug interactions to minimize toxicity and maximize efficacy.