Hypertension after kidney transplantation: a pathophysiologic approach

A Statistical Prediction Model for Survival After Kidney Transplantation from Deceased Donors

Background

In an environment of limited kidney donation resources, patient recovery and survival after kidney transplantation (KT) are highly important. We used pre-operative data of kidney recipients to build a statistical model for predicting survivability after kidney transplantation.

Material/Methods

A dataset was constructed from a pool of patients who received a first KT in our hospital. For allogeneic transplantation, all donated kidneys were collected from deceased donors. Logistic regression analysis was used to change continuous variables into dichotomous ones through the creation of appropriate cut-off values. A regression model based on the least absolute shrinkage and selection operator (LASSO) algorithm was used for dimensionality reduction, feature selection, and survivability prediction. We used receiver operating characteristic (ROC) analysis, calibration, and decision curve analysis (DCA) to evaluate the performance and clinical impact of the proposed model. Finally, a 10-fold cross-validation scheme was implemented to verify the model robustness.

Results

We identified 22 potential variables from which 30 features were selected as survivability predictors. The model established based on the LASSO regression algorithm had shown discrimination with an area under curve (AUC) value of 0.690 (95% confidence interval: 0.557–0.823) and good calibration result. DCA demonstrated clinical applicability of the prognostic model when the intervention progressed to the possibility threshold of 2%. An average AUC value of 0.691 was obtained on the validation data.

Conclusions

Our results suggest that the proposed model can predict the mortality risk for patients after kidney transplants and could help kidney specialists choose kidney recipients with better prognosis.

Salt-sensitive hypertension in chronic kidney disease: distal tubular mechanisms

Chronic kidney disease (CKD) causes salt-sensitive hypertension that is often resistant to treatment and contributes to the progression of kidney injury and cardiovascular disease. A better understanding of the mechanisms contributing to salt-sensitive hypertension in CKD is essential to improve these outcomes. This review critically explores these mechanisms by focusing on how CKD affects distal nephron Na+ reabsorption. CKD causes glomerulotubular imbalance with reduced proximal Na+ reabsorption and increased distal Na+ delivery and reabsorption. Aldosterone secretion further contributes to distal Na+ reabsorption in CKD and is not only mediated by renin and K+ but also by metabolic acidosis, endothelin-1, and vasopressin. CKD also activates the intrarenal renin-angiotensin system, generating intratubular angiotensin II to promote distal Na+ reabsorption. High dietary Na+ intake in CKD contributes to Na+ retention by aldosterone-independent activation of the mineralocorticoid receptor mediated through Rac1. High dietary Na+ also produces an inflammatory response mediated by T helper 17 cells and cytokines increasing distal Na+ transport. CKD is often accompanied by proteinuria, which contains plasmin capable of activating the epithelial Na+ channel. Thus, CKD causes both local and systemic changes that together promote distal nephron Na+ reabsorption and salt-sensitive hypertension. Future studies should address remaining knowledge gaps, including the relative contribution of each mechanism, the influence of sex, differences between stages and etiologies of CKD, and the clinical relevance of experimentally identified mechanisms. Several pathways offer opportunities for intervention, including with dietary Na+ reduction, distal diuretics, renin-angiotensin system inhibitors, mineralocorticoid receptor antagonists, and K+ or H+ binders.

mTOR–mLST8 interaction: hot spot identification through quantum biochemistry calculations

Quantum calculation of mTOR–mLST8 interaction.

"Smartphone Medication Adherence Saves Kidneys" for Kidney Transplantation Recipients: Protocol for a Randomized Controlled Trial

Background

Kidney transplant recipients’ poor medication adherence and poor control of comorbidities, particularly hypertension, are risk factors for graft rejection, graft loss, and death. Few randomized controlled trials (RCTs) have been successful in improving sustained medication adherence and blood pressure control among kidney transplantation recipients. We provide rationale for an RCT evaluating a mobile health medical self-management system for kidney transplantation recipients called Smartphone Medication Adherence Saves Kidneys (SMASK).

Objective

Our objective is to determine whether SMASK is efficacious in improving medication adherence and sustaining blood pressure control among kidney transplantation recipients with uncontrolled hypertension and poor medication adherence compared to an enhanced standard care.

Methods

This two-arm, 6-month, phase II single-site efficacy RCT will involve 80 kidney transplantation recipients. Participants will be randomly assigned to the SMASK intervention arm or control arm. SMASK includes multilevel components: automated reminders from an electronic medication tray; tailored text messages and motivational feedback, guided by the self-determination theory; and automated summary reports for providers. Evaluations will be conducted preintervention, at 3 and 6 months, and posttrial at 12 months. Specific aims are to test the hypotheses that compared to standard care, the SMASK cohort will demonstrate significantly improved changes at 3, 6, and 12 months in the primary outcome variables medication adherence (proportion with electronic monitor-derived score >0.90) and blood pressure control (proportion meeting and sustaining adherence to the Kidney Disease Improving Global Outcomes [KDIGO] guidelines for blood pressure control); the secondary outcome variables provider adherence to KDIGO guidelines, measured by timing of medication changes and changes in self-determination theory constructs; and the exploratory outcome variables estimated glomerular filtration rate, variability in calcineurin inhibitor trough levels, and proportion of patients meeting and sustaining the 24-hour ambulatory blood pressure below 130/80 mm Hg. After the 6-month evaluation, interviews with a random sample of SMASK subjects (n=20) and health care providers (n=3-5) will assess user reactions including acceptability, usability, and aids/barriers to sustainability. Data from the RCT and interviews will be triangulated to further refine and optimize SMASK and prepare for a multisite effectiveness RCT.

Results

The SMASK project received funding from National Institute of Diabetes and Digestive and Kidney Diseases in June 2016, obtained institutional review board approval in April 2016, and began data collection in July 2016. As of July 2018, we completed enrollment with a total of 80 participants.

Conclusions

This study will provide data regarding the efficacy of SMASK to improve medication adherence and blood pressure control in a cohort of hypertensive kidney transplant recipients. An efficacious SMASK intervention will pave the way for a larger, multicenter, effectiveness RCT powered sufficiently to evaluate clinical events in a real-world setting and with the potential to demonstrate improved outcomes at lower cost than standard care.

International Registered Report Identifier (IRRID)

DERR1-10.2196/13351

Sustainability of improvements in medication adherence through a mobile health intervention

Context-Very few patient-centered, theory-guided programs for medication adherence and blood pressure control have been conducted in kidney transplant recipients. Objective-To evaluate preliminary indications of sustainability of improved blood pressure in kidney transplant recipients 12 months after completion of a 3-month randomized controlled trial of a mobile health pilot program to improve blood pressure and medication adherence. Participants and Design-A total of 18 of the 19 trial participants were contacted and all consented to inclusion in the retrospective analysis of their medical records showing their clinic-recorded systolic blood pressures at 3, 6, and 12 months following participation in the 3-month trial of a medical regimen self-management intervention. Results-A significant group difference in systolic blood pressure was observed longitudinally, indicating that the intervention group, as compared with the standard-care group, exhibited lower clinic-measured systolic blood pressures at the 12-month posttrial follow-up visit (P= .01). At 12-month follow-up, success in establishing and sustaining control of systolic blood pressure (<131 mm Hg) was greater in the intervention group (50%) than in the control group (11%). Conclusion-Patients in the intervention group continued to exhibit lower systolic blood pressure than did patients in the control group 12 months after the trial ended, suggesting that the intervention may have a durable impact on blood pressure control that most likely reflects sustained medication adherence. These findings will aid in the development of an adequately powered randomized controlled trial to address the sustainable impact of the intervention program on medication adherence and blood pressure control.

Hypertension in kidney transplantation is associated with an early renal nerve sprouting

Background. Normalization of arterial pressure occurs in just a few patients with hypertensive chronic kidney disease undergoing kidney transplantation. Hypertension in kidney transplant recipients may be related to multiple factors. We aimed to assess whether hypertension in kidney-transplanted patients may be linked to reinnervation of renal arteries of the transplanted kidney.

Methods. We investigated renal arteries innervation from native and transplanted kidneys in three patients 5 months, 2 years and 11 years after transplantation, respectively. Four transplanted kidneys from non-hypertensive patients on immunosuppressive treatment without evidence of hypertensive arteriolar damage were used as controls.

Results. Evidence of nerve sprouting was observed as early as 5 months following transplantation, probably originated from ganglions of recipient patient located near the arterial anastomosis and was associated with mild hypertensive arteriolar damage. Regeneration of periadventitial nerves was already complete 2 years after transplantation. Nerve density tended to reach values observed in native kidney arteries and was associated with hypertension-related arteriolar lesions in transplanted kidneys. Control kidneys, albeit on an immunosuppressive regimen, presented only a modest regeneration of sympathetic nerves.

Conclusions. Our results suggest that the considerable increase in sympathetic nerves, as found in patients with severe arterial damage, may be correlated to hypertension rather than to immunosuppressive therapy, thus providing a morphological basis for hypertension recurrence despite renal denervation.

Understanding the Two Faces of Low-Salt Intake

Fierce debate has developed whether low-sodium intake, like high-sodium intake, could be associated with adverse outcome. The debate originates in earlier epidemiological studies associating high-sodium intake with high blood pressure and more recent studies demonstrating a higher cardiovascular event rate with both low- and high-sodium intake. This brings into question whether we entirely understand the consequences of high- and (very) low-sodium intake for the systemic hemodynamics, the kidney function, the vascular wall, the immune system, and the brain. Evolutionarily, sodium retention mechanisms in the context of low dietary sodium provided a survival advantage and are highly conserved, exemplified by the renin-angiotensin system. What is the potential for this sodium-retaining mechanism to cause harm? In this paper, we will consider current views on how a sodium load is handled, visiting aspects including the effect of sodium on the vessel wall, the sympathetic nervous system, the brain renin-angiotensin system, the skin as "third compartment" coupling to vascular endothelial growth factor C, and the kidneys. From these perspectives, several mechanisms can be envisioned whereby a low-sodium diet could potentially cause harm, including the renin-angiotensin system and the sympathetic nervous system. Altogether, the uncertainties preclude a unifying model or practical clinical guidance regarding the effects of a low-sodium diet for an individual. There is a very strong need for fundamental and translational studies to enhance the understanding of the potential adverse consequences of low-salt intake as an initial step to facilitate better clinical guidance.

Hypertension in the Kidney Transplant Recipient: Overview of Pathogenesis, Clinical Assessment, and Treatment

Cardiovascular disease is the leading cause of death in patients with chronic renal disease and the most common cause of death and allograft loss among kidney transplant recipients. Transplant patients often have multiple cardiovascular risk factors antedating transplantation. Among the most prominent is hypertension (HTN), which affects at least 90% of transplant patients. Uncontrolled HTN is an independent risk factor for allograft loss. The etiology of HTN in transplant recipients is complex and multifactorial, including the use of essential immunosuppressive medications. Post-transplant HTN management requires a systematic and individualized approach with nonpharmacologic and pharmacologic therapies. There is no single ideal agent or treatment algorithm. Patients should regularly monitor and record their blood pressure at home. Often, multiple antihypertensive drugs are needed to achieve a goal blood pressure of 120-140/70-90 mm Hg. As transplant recipients commonly must take 8 to 12 different medications daily, adherence must be continually encouraged and monitored. Special attention must be paid to potential drug side effects and drug interactions with immunosuppressive medications.

Chlorthalidone Versus Amlodipine for Hypertension in Kidney Transplant Recipients Treated With Tacrolimus: A Randomized Crossover Trial

BACKGROUND

Chlorthalidone is a very effective antihypertensive drug, but it has not been studied prospectively in kidney transplant recipients with hypertension. Recent data indicate that calcineurin inhibitors activate the thiazide-sensitive sodium chloride cotransporter, providing further rationale to test thiazides in this population.

STUDY DESIGN

Randomized noninferiority crossover trial (noninferiority margin, -2.8mmHg).

SETTING & PARTICIPANTS

Hypertensive kidney transplant recipients using tacrolimus (median duration, 2.4 years after transplantation; mean estimated glomerular filtration rate, 63±27 [SD] mL/min/1.73m²; mean systolic blood pressure [SBP], 151±12mmHg).

INTERVENTION

Amlodipine (5-10mg) and chlorthalidone (12.5-25mg) for 8 weeks (separated by 2-week washout).

OUTCOMES

Average daytime (9 am to 9 pm) ambulatory SBP.

MEASUREMENTS

Blood pressure and laboratory parameters.

RESULTS

88 patients underwent ambulatory blood pressure monitoring, of whom 49 (56%) with average daytime SBP>140mmHg were enrolled. 41 patients completed the study. Amlodipine and chlorthalidone both reduced ambulatory SBP after 8 weeks (mean changes of 150±12 to 137±12 [SD] vs 151±12 to 141±13mmHg; effect size, -4.2 [95% CI, -7.3 to 1.1] mmHg). Despite these similar blood pressure responses, chlorthalidone reduced proteinuria by 30% (effect size, -65 [95% CI, -108 to -35] mg/g) and also reduced physician-assessed peripheral edema (22% to 10%; P<0.05 for both). In contrast, chlorthalidone temporarily reduced kidney function and increased both serum uric acid and glycated hemoglobin levels.

LIMITATIONS

Open-label design, short follow-up, per-protocol analysis.

CONCLUSIONS

Chlorthalidone is an antihypertensive drug equally effective as amlodipine after kidney transplantation.

Unique Considerations When Managing Hypertension in the Transplant Patient

For the select fortunate recipients of organ transplants, transplantation affords the rare opportunity for a new life. Given the scarcity of organs for transplantation, it is imperative that the health of transplant recipients be optimized in order to fully benefit from this gift of life. Unfortunately, hypertension is highly prevalent in the transplant population and it is considered a major cardiovascular risk factor contributing to mortality and morbidity in this population. In this chapter, we expound on the epidemiology, unique pathophysiology, evaluation, and management of hypertension as it pertains to the solid organ transplant recipient. In addition, a brief commentary is made on the subject of hypertension following living kidney donation, and practical aspects of management of hypertension in the solid organ recipient are summarized at the end of the chapter.

The Short-Term Impact of Dietary Counseling on Sodium Intake and Blood Pressure in Renal Allograft Recipients

Background:

Sodium retention causes posttransplant hypertension, and sodium restriction is recommended in kidney allograft recipients. However, there have been few studies on the impact of dietary counseling on sodium intake and blood pressure (BP) in this population.

Objective:

To determine the effect of dietary counseling on sodium intake and consequent BP control in kidney allograft recipients.

Design, Setting, and Participants:

A prospective single-arm study to determine the effect of dietary counseling on sodium intake. Enrolled were renal allograft recipients with sodium intake >100 mEq/d, BP >130/80, antihypertensive use, or body mass index >25 kg/m2. Of 53 renal transplant recipients who met the criteria, 48 participated in the present study. Sodium intake was estimated based on 24-hour urinary sodium excretion before and after 3 sessions of dietary counseling by a board-certified dietitian.

Results:

Sodium intake was significantly decreased after dietary counseling (158.7 vs 129.6 mEq/d; P = .005). Systolic BP was significantly decreased from 124 mm Hg (interquartile range: 122-134) before counseling to 121 mm Hg (interquartile range: 117-128) after counseling ( P < .001). The number of patients with systolic BP >130 mm Hg was decreased by 30% (n = 19-13; P = .07). Among 34 patients on antihypertensive medications, 8 (23.5%) ceased or reduced their drugs due to improvement in BP, whereas 2 increased or changed the drugs due to poor control of BP.

Conclusion:

Dietary counseling showed a short-term efficacy of reducing sodium intake and clinically relevant BP improvement in renal allograft recipients.

Hypertension in the Pediatric Intensive Care Unit

Hypertension in the pediatric intensive care unit (PICU) is common and it contributes to the overall morbidity and mortality. Patients may present with hypertensive emergencies or hypertension can manifest itself later in PICU course. Although hypertension can be seen in most patients during hospitalization, patients with some specific diseases and conditions are more prone to hypertension. Hypertension should be recognized promptly and treated accordingly. Different pathophysiologic mechanisms can be responsible for the hypertension and management differs based on the underlying etiology. Any patient with a hypertensive emergency must be admitted to PICU, and treatment and diagnostic workup should be initiated immediately.

Hypertension, living kidney donors, and transplantation: where are we today?

Hypertension is a prevalent problem in kidney transplant recipients that is known to be a "traditional" risk factor for atherosclerotic cardiovascular disease leading to premature allograft failure and death. Donor, peritransplant, and recipient factors affect hypertension risk. Blood pressure control after transplantation is inversely associated with glomerular filtration rate (GFR). Calcineurin inhibitors, the most commonly used class of immunosuppressives, cause endothelial dysfunction, increase vascular tone, and sodium retention via the renin-angiotensin-aldosterone system resulting in systemic hypertension. Steroid withdrawal seems to have little impact on blood pressure control. Newer agents like belatacept appear to be associated with less hypertension. Transplant renal artery stenosis is an important, potentially treatable cause of hypertension. Dihydropyridine calcium channel blockers mitigate calcineurin inhibitor nephrotoxicity and may be associated with improved estimated GFR. Angiotensin-converting enzyme inhibitors and angiotensin receptor blockers are not recommended in the first 3 to 6 months given their effects on reduced estimated GFR, anemia, and hyperkalemia. The use of ß-blockers may be associated with improved patient survival, even for patients without cardiovascular disease. Living donation may increase blood pressure by 5 mm Hg or more. Some transplant centers accept Caucasian living donors with well-controlled hypertension on a single agent if they agree to close follow-up.

Assessment and management of hypertension in transplant patients

Hypertension in renal transplant recipients is common and ranges from 50% to 80% in adult recipients and from 47% to 82% in pediatric recipients. Cardiovascular morbidity and mortality and shortened allograft survival are important consequences of inadequate control of hypertension. In this review, we examine the epidemiology, pathophysiology, and management considerations of post-transplant hypertension. Donor and recipient factors, acute and chronic allograft injury, and immunosuppressive medications may each explain some of the pathophysiology of post-transplant hypertension. As observed in other patient cohorts, renal artery stenosis and adrenal causes of hypertension may be important contributing factors. Notably, BP treatment goals for renal transplant recipients remain an enigma because there are no adequate randomized controlled trials to support a benefit from targeting lower BP levels on graft and patient survival. The potential for drug-drug interactions and altered pharmacokinetics and pharmacodynamics of the different antihypertensive medications need to be carefully considered. To date, no specific antihypertensive medications have been shown to be more effective than others at improving either patient or graft survival. Identifying the underlying pathophysiology and subsequent individualization of treatment goals are important for improving long-term patient and graft outcomes in these patients.

Calcineurin inhibitors and hypertension: a role for pharmacogenetics?

Hypertension is a common side effect of calcineurin inhibitors (CNIs), which are drugs used to prevent rejection after transplantation. Hypertension after kidney transplantation has been associated with earlier graft failure and higher cardiovascular mortality in the recipient. Recent data indicate that enzymes and transporters involved in CNI pharmacokinetics and pharmacodynamics, including CYP3A5, ABCB1, WNK4 and SPAK, are also associated with salt-sensitive hypertension. These insights raise the question whether polymorphisms in the genes encoding these proteins increase the risk of CNI-induced hypertension. Predicting who is at risk for CNI-induced hypertension may be useful for when selecting specific interventions, including dietary salt restriction, thiazide diuretics or a CNI-free immunosuppressive regimen. This review aims to explore the pharmacogenetics of CNI-induced hypertension, highlighting the knowns and unknowns.