Better microvascular function on long-term treatment with lisinopril than with nifedipine in renal transplant recipients

An observational study of microcirculation in dialysis patients and kidney transplant recipients

BACKGROUND

Microcirculatory dysfunction contributes to acute and chronic kidney diseases. To the best of our knowledge, no study has compared differences in microcirculation among healthy volunteers, dialysis patients and kidney transplant recipients.

MATERIALS AND METHODS

Sublingual microcirculation was examined using sidestream dark field imaging and was compared among 90 healthy volunteers, 40 dialysis patients and 40 kidney transplant recipients. The gender effect on microcirculation and the correlations among the microcirculation parameters, age, body mass index, heart rate and blood pressure were analysed.

RESULTS

Total small vessel density, perfused small vessel density and the proportion of perfused small vessels were lower in the dialysis patients than in the healthy volunteers and kidney transplant recipients [total small vessel density; healthy volunteers vs. dialysis patients vs. kidney transplant recipients, 25·2 (2·3) vs. 22·8 (2·6) vs. 24·2 (2·9) mm/mm² , P < 0·001]. Systolic blood pressure showed a weak negative correlation with the microvascular flow index scores in the healthy volunteers. By contrast, systolic blood pressure, diastolic blood pressure and mean arterial pressure showed weak positive correlations with proportion of perfused small vessels and the microvascular flow index scores in the dialysis patients.

CONCLUSIONS

Microcirculatory dysfunction is noted in dialysis patients, and this alteration is ameliorated in KT recipients. The positive correlation between blood pressure and microcirculation in dialysis patients suggests that additional studies should investigate the optimal goal of blood pressure management for dialysis patients.

Management of Hypertension in Solid-Organ Transplantation

Posttransplant hypertension is a major risk factor for cardiovascular disease and chronic renal allograft dysfunction. A significant number of transplant recipients suffer from posttransplant hypertension in part because of corticosteroid and calcineurin inhibitor use. Although the optimal blood pressure range and the antihypertensive agents of choice in the transplant population have not been determined, the guidelines for blood pressure control in the general population can be extrapolated to the transplant population. The choice of an antihypertensive regimen should be tailored on the basis of the individual patient's risk factors and comorbidities.

Antihypertensive treatment for kidney transplant recipients

BACKGROUND

In some nontransplant populations, effects of different antihypertensive drug classes vary. Relative effects in kidney transplant recipients are uncertain.

OBJECTIVES

To assess comparative effects of different classes of antihypertensive agents in kidney transplant recipients.

SEARCH STRATEGY

MEDLINE, EMBASE, the Cochrane Central Register of Controlled Trials, conference proceedings and reference lists of identified studies were searched.

SELECTION CRITERIA

Randomised controlled trials of any antihypertensive agent applied to kidney transplant recipients for at least two weeks were included.

DATA COLLECTION AND ANALYSIS

Data was extracted by two investigators independently. Study quality, transplant outcomes and other patient centred outcomes were assessed using random effects meta-analysis. Risk ratios (RR) for dichotomous outcomes and mean difference (MD) for continuous outcomes, both with 95% confidence intervals (CI) were calculated. Stratified analyses and meta-regression were used to investigate heterogeneity.

MAIN RESULTS

We identified 60 studies, enrolling 3802 recipients. Twenty-nine studies (2262 participants) compared calcium channel blockers (CCB) to placebo/no treatment, 10 studies (445 participants) compared angiotensin converting enzyme inhibitors (ACEi) to placebo/no treatment and seven studies (405 participants) compared CCB to ACEi. CCB compared to placebo/no treatment (plus additional agents in either arm as required) reduced graft loss (RR 0.75, 95% CI 0.57 to 0.99) and improved glomerular filtration rate (GFR), (MD, 4.45 mL/min, 95% CI 2.22 to 6.68). Data on ACEi versus placebo/no treatment were inconclusive for GFR (MD -8.07 mL/min, 95% CI -18.57 to 2.43), and variable for graft loss, precluding meta-analysis. In direct comparison with CCB, ACEi decreased GFR (MD -11.48 mL/min, 95% CI -5.75 to -7.21), proteinuria (MD -0.28 g/24 h, 95% CI -0.47 to -0.10), haemoglobin (MD -12.96 g/L, 95% CI -5.72 to -10.21) and increased hyperkalaemia (RR 3.74, 95% CI 1.89 to 7.43). Graft loss data were inconclusive (RR 7.37, 95% CI 0.39 to 140.35). Other drug comparisons were compared in small numbers of participants and studies.

AUTHORS' CONCLUSIONS

These data suggest that CCB may be preferred as first line agents for hypertensive kidney transplant recipients. ACEi have some detrimental effects in kidney transplant recipients. More high quality studies reporting patient centred outcomes are required.

Calcineurin inhibitor effects on glucose metabolism and endothelial function following renal transplantation

BACKGROUND

Calcineurin inhibitors (CNI) are involved in the development of post-transplant diabetes mellitus (PTDM). Changes in insulin secretion and sensitivity contribute to the development of PTDM and are associated with endothelial function.

METHODS

In a pre-defined substudy of a previously published randomized trial in renal transplant recipients we compared the effect of CNI treatment (n = 23) with complete CNI-avoidance (n = 21) on insulin secretion and sensitivity (oral glucose tolerance test) as well as endothelial function (laser Doppler flowmetry), 10 wk and 12 months following transplantation.

RESULTS

Insulin sensitivity differed 10 wk post-transplant and was significantly better after 12 months in patients never treated with CNI drugs [0.091 (0.050) vs. 0.083 (0.036) micromol/kg/min/pmol/L, p = 0.043]. Insulin secretion tended to be higher in CNI treated patients at both time points (p = 0.068). Endothelial function was not significantly different at week 10 [540 (205) vs. 227 (565) arbitary units x minutes, p = 0.35] or month 12 [510 (620) vs. 243 (242), p = 0.33].

CONCLUSIONS

Findings in the present study indicate that long-term CNI treatment negatively affects glucose metabolism and this may contribute to the increased risk for premature cardiovascular disease in CNI treated renal transplant recipients. Further studies to elucidate this hypothesis are, however, needed.

Association between insulin resistance and endothelial dysfunction in renal transplant recipients

BACKGROUND

Endothelial dysfunction is a common finding in renal transplant recipients (RTR) and is related to impaired local regulation of vasodilative and vasoconstrictive substances, such as nitric monoxide (NO) and endothelin-1 (ET-1). In non-transplanted patients, an association between impaired endothelial function and insulin resistance has been shown. Whether such an association also exists in RTR is unknown.

OBJECTIVE

The aim of the present study was to examine whether insulin resistance is associated with endothelial dysfunction in RTR.

MATERIAL AND METHODS

A total of 47 RTR in a stable phase six yr post-transplant were included in the statistical analysis. The immunosuppressive therapy was based on cyclosporine and prednisolone. Non-invasive assessment of endothelial function was performed with laser Doppler flowmetry of the forearm skin vasculature after local acetylcholine stimulation. Oral glucose tolerance tests comprising both glucose and insulin measurements were used to calculate insulin sensitivity (IS) indices. NO, ET-1 and von Willebrand factor were measured in fasting plasma samples.

RESULTS

Normal glucose tolerance was found in 31 RTR. In these subjects, both IS (r(2) = 0.164, p = 0.044) and plasma NO (r(2) = 0.326, p = 0.002) were significantly correlated with endothelial function. Patients with glucose intolerance (n = 16) had higher plasma ET-1 and lower NO levels, but the association between IS and endothelial function was not significant in these subjects. In the total patient cohort, IS and endothelial function tended to be correlated (p = 0.127).

CONCLUSIONS

Endothelial dysfunction is significantly associated with insulin resistance in normoglycemic RTR but explains a rather small part of the variation. In glucose-intolerant recipients, IS appears to be more critically dependent on other factors not revealed in the present study.

Predictors of health-related quality of life in hypertensive recipients following renal transplantation

BACKGROUND

Health-related quality of life (HRQoL) improves after renal transplantation. However, it is unclear which variables are the strongest determinants of HRQoL following renal transplantation. In this study, we wanted to assess whether antihypertensive medication, donor type, human leukocyte antigen (HLA)-compatibility or other variables could predict HRQoL 6-12 months after transplantation.

METHODS

The study was a follow up of 124 patients recruited to a single center, randomized, double-blind clinical trial, comparing the effects of lisinopril and nifedipine in hypertensive renal transplant recipients. HRQoL was assessed with the Short Form 36 (SF-36) questionnaire. Bivariate and multiple linear regression analysis were used to assess the relationship between potential predictors and the physical component summary (PCS) and mental component summary (MCS) scales of the SF-36.

RESULTS

Average scores 6-12 months after transplantation did not differ between patients randomized to lisinopril or nifedipine, or between cadaveric and living donor recipients on any of the eight SF-36 scales, or the two summary scales. In multivariate analyses, recipient age (p = 0.01) and cold ischemia time >14.5 h (p = 0.04) were independent predictors of the PCS score. Recipient age (p = 0.05), 2-4 HLA-AB mismatches (p = 0.05) and donor age (p = 0.03) were independent predictors of the MCS score.

CONCLUSIONS

There was no evidence of differences in HRQoL according to lisinopril or nifedipine, or living vs. cadaveric donor transplantation. HRQoL was significantly reduced with longer cold ischemia time and more than one HLA-AB mismatches, after adjusting for age. These donor kidneys related issues need confirmation.

Successful renal transplantation decreases aortic stiffness and increases vascular reactivity in dialysis patients

BACKGROUND

Patients with end-stage renal disease on dialysis have among the highest cardiovascular event rates documented. Abnormal nitric oxide (NO)-dependent endothelial reactivity and increased arterial stiffness are commonly described in hemodialysis (HD) patients. Measures of aortic stiffness--aortic pulse wave velocity (PWV) and augmentation index (AGI)--have been shown to be powerful predictors of survival on hemodialysis. It is not known how these parameters interfere with successful renal transplantation.

METHODS

PWV and aortic AGI (difference between the first and second systolic peak on the aortic pressure waveform divided by the pulse wave height) were determined from contour analysis of arterial waveforms recorded by applanation tonometry using a SphygmoCor device in 41 HD patients (20 men; age, 41.8 years) and in a control group of 20 patients with essential hypertension (HTA) (10 men; age, 43.6 years). Twenty of the HD patients (10 men; age, 39.7 years) received live-related renal transplants (RTx) and were restudied (3 months after RTx, normal serum creatinine). NO-dependent and NO-independent vascular reactivity were assessed by changes in AGI after challenges with inhaled salbutamol (SAL) and sublingual nitroglycerin (NTG), respectively.

RESULTS

AGI values were significantly lower in RTx patients compared with subjects on hemodialysis (15.9 +/- 13.9% vs. 27.9 +/- 11.9%, P<0.05), but similar to essential HTA controls (16.5 +/- 17%). Serial AGI measurements showed that successful renal transplantation is associated with a decrease in AGI in all cases, from a mean of 25.1 +/- 7.8% while on dialysis to 15.9 +/- 7.0% 3 months after transplantation (P<0.0001). The responsiveness to both endothelium-dependent stimuli (inhaled SAL) and endothelium-independent stimuli (sublingual NTG) was greater in transplant patients than in hemodialysis patients (SAL-induced decrease in AGI -82.3 +/- 65.7% vs. 45 +/- 72.3%, P<0.01; and NTG-induced decrease in AGI 197 +/- 108 vs. -129.0 +/- 215.5%, P<0.01). PWV values in dialysis patients (7.19 +/- 1.88 m/sec) were significantly higher than those measured in essential HTA patients (6.34 +/- 1.32 m/sec, P<0.05) with normal renal function (despite similar blood pressure levels). PWV after RTx was 6.59 +/- 1.62 m/sec, significantly different from pretransplantation (dialysis) values (P<0.05 for comparison) but similar to the control group of essential HTA patients.

CONCLUSIONS

Renal transplantation is associated with marked improvements in vascular structure and function to a profile comparable to essential HTA patients.

Fluvastatin reduces atherogenic lipids without any effect on native endothelial function early after kidney transplantation

BACKGROUND

Cardiovascular risk is greatly increased in renal transplant recipients. 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor (statin) therapy may reduce cardiovascular risk by improving both dyslipidemia and endothelial function. We therefore performed this study to assess the effect of fluvastatin on endothelial function in renal transplant recipients.

METHODS

This randomized, placebo-controlled, double-blind designed study investigated the effect of fluvastatin on endothelial function. Thirty-seven recipients received fluvastatin 40 mg/d and 35 received placebo during the first 12 wk following transplantation. All patients initially received cyclosporin A, prednisolone and azathioprine. At the end of treatment, endothelial function was assessed in the forearm skin microvasculature by laser Doppler flowmetry following acetylcholine stimulation. Samples were taken for measurements of serum lipids and vasoactive markers.

RESULTS

There were no differences in endothelial function between fluvastatin recipients and controls, AUCACh was 656 +/- 479 and 627 +/- 518 AU min, respectively (fluv vs. control, p > 0.65). In the placebo limb, total cholesterol and LDL cholesterol increased 22 +/- 12% and 22 +/- 18%, respectively in the first 12 wk following transplantation. The respective values were 18 +/- 13% (p = 0.010) and 34 +/- 19% (p = 0.0013) lower at 12 wk in the fluvastatin treated patients. Plasma ET-1, BigET-1 and urinary excretion of cGMP were not significantly different between treatment groups (p > 0.55).

CONCLUSION

Although fluvastatin 40 mg/d significantly lowers cholesterol it does not affect endothelial function the first 3 months after renal transplantation. The lack of effect on endothelial function is consistent with a lack of effect on vasoactive substances.

Calcium channel blockers as the treatment of choice for hypertension in renal transplant recipients: fact or fiction

Posttransplantation hypertension has been identified as an independent risk factor for chronic allograft dysfunction and loss. Based on available morbidity and mortality data, posttransplantation hypertension must be identified and managed appropriately. During the past decade, calcium channel blockers have been recommended by some as the antihypertensive agents of choice in this population, because it was theorized that their vasodilatory effects would counteract the vasoconstrictive effects of the calcineurin inhibitors. With increasing data becoming available, reexamining the use of traditional antihypertensive agents, including diuretics and beta-blockers, or the newer agents, angiotensin-converting enzyme (ACE) inhibitors and angiotensin II receptor blockers, may be beneficial. Transplant clinicians must choose antihypertensive agents that will provide their patients with maximum benefit, from both a renal and a cardiovascular perspective. Beta-blockers, diuretics, and ACE inhibitors have all demonstrated significant benefit on morbidity and mortality in patients with cardiovascular disease. Calcium channel blockers have been shown to possess the ability to counteract cyclosporine-induced nephrotoxicity. When compared with beta-blockers, diuretics, and ACE inhibitors, however, the relative risk of cardiovascular events is increased with calcium channel blockers. With the long-term benefits of calcium channel blockers on the kidney unknown and a negative cardiovascular profile, these agents are best reserved as adjunctive therapy to beta-blockers, diuretics, and ACE inhibitors.

Update on calcium antagonists and the kidney

PURPOSE OF REVIEW

The treatment of hypertension has been proven to reduce cardiovascular and renal risk. The role of long-acting calcium channel antagonists in the management of hypertension has been confused in the past because of a lack of controlled clinical trials on people with hypertension and in subpopulations including those with diabetes and renal disease. The year 2002 saw the publication of the results of the Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial, the largest ever prospective drug-treatment trial, which involved 33 357 people with hypertension and included a calcium-antagonist group of 9048 individuals. Major publications on blood pressure control in people with kidney disease include the African American Study of Kidney Disease and Hypertension, and publications on people with diabetes include the results of the normotensive arm of the Appropriate Blood Pressure Control in Diabetes trial.

RECENT FINDINGS

The main finding, from the studies reported in the last year, is that blood pressure control can be achieved using one or more of the first-line agents, including diuretics, calcium antagonists and angiotensin-converting enzyme inhibitors. On the basis of the Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial, diuretics make clinical and economic sense as initial therapy for those with hypertension. Calcium antagonists are well tolerated and effective and should be considered as the initial drug therapy when diuretics are not tolerated or when multiple drug therapy is indicated. Angiotensin-converting enzyme inhibitors should be used in people with nephropathy, and, in these patients, will nearly always need to be part of multiple drug therapy to achieve blood pressure control. When blood pressure control can be achieved in largely non-nephropathic populations, there is further evidence that the drug class used as initial therapy may not be important. One of the main themes coming from the literature in the last year is that renal function is increasingly being recognized as an important outcome measure and marker of cardiovascular risk.

SUMMARY

The focus in blood pressure management must now be on identifying those with hypertension and bringing their blood pressure to target. For the majority of those with hypertension and renal disease, multiple drug therapy will be required, and, to achieve blood pressure targets, calcium antagonists are an appropriate part of this regimen. Particular attention is needed for nephropathic patients because of their higher risk of progression and the need for combination therapy; this group is likely to be the focus of future research and publications.

Five preventable causes of kidney graft loss in the 1990s: a single-center analysis

BACKGROUND

Despite improvements in immunosuppressive protocols and patient care, kidney allografts continue to fail. We studied causes of graft loss for primary kidney transplants in the 1990s to determine major causes and potential interventions.

METHODS

Causes of graft loss were reviewed for 1467 primary kidney transplants done at our institution between January 1, 1990, and December 31, 1999. Graft loss for that entire population was studied and then the causes of loss selectively examined at <1 year, 1 to 5 years, and>5 years post-transplant. Finally, causes of loss in the 1990s versus the 1980s were compared.

RESULTS

Five major causes of graft loss were noted in the 1990s: thrombosis, acute rejection (either alone or combined with delayed graft function or infection), chronic rejection, death with function, and noncompliance. In the first year post-transplant, thrombosis (25%) and death with function (41%) were the major causes of graft loss. After the first year, chronic rejection and death with function predominated. For recipients dying with graft function, cardiovascular disease was the major cause of death.

CONCLUSIONS

This study identified the five major causes of kidney graft loss in the 1990s. Different interventions are required to decrease loss from each of these causes. Future research needs to be directed at such interventions.

Atorvastatin improves endothelial function in renal-transplant recipients

BACKGROUND

Hyperlipidaemia and endothelial dysfunction are common features in cyclosporin A (CsA)-treated renal transplant recipients. Endothelial dysfunction may contribute to the risk of premature atherosclerosis and cardiovascular death in these patients. A beneficial effect of statin therapy beyond cholesterol lowering may be an improvement of endothelial function. The present study was designed to assess the effect of atorvastatin on serum lipids and endothelial function in CsA treated renal transplant recipients.

METHODS

This pilot study was an open trial of 4 weeks atorvastatin (10 mg per day) treatment in renal transplant recipients (n=22). All patients received a CsA- and prednisolone-based immunosuppressive regimen. Endothelial function was assessed in the forearm skin microvasculature by acetylcholine stimulation and laser Doppler flowmetry, before and after atorvastatin treatment. Serum lipids, plasma endothelin-1 (ET-1), nitric oxide (NO), and von Willebrand factor (vWF) were also measured.

RESULTS

Both total and LDL cholesterol were significantly reduced by 26.8 +/- 8.4 and 41.5 +/- 11.0% respectively, after 4 weeks of treatment. Endothelial function was significantly improved during atorvastatin treatment, area under the flux versus time curve (AUC)(ACh) was 538 +/- 362 AU x min before and 682 +/- 276 AU x min after treatment (P=0.042). Plasma NO levels also showed a borderline significant increase from 49 +/- 30 to 57 +/- 37 micromol/l during the treatment period (P=0.051), though plasma ET-1 (0.37+/-0.08 vs 0.37+/-0.12 fmol/ml) and vW (196+/-57 vs 197+/-37%) were unchanged.

CONCLUSION

Atorvastatin lowered serum cholesterol significantly and improved endothelial function in renal transplant recipients after 4 weeks of treatment. Plasma NO levels were increased during atorvastatin treatment, indicating a possible endothelial protective effect through an "endothelial-NO pathway".