Diagnosis and management of atherosclerotic cardiovascular disease in chronic kidney disease: a review

Patients with chronic kidney disease (CKD) have a high prevalence of atherosclerotic cardiovascular disease, likely reflecting the presence of traditional risk factors. A greater distinguishing feature of atherosclerotic cardiovascular disease in CKD is the severity of the disease, which is reflective of an increase in inflammatory mediators and vascular calcification secondary to hyperparathyroidism of renal origin that are unique to patients with CKD. Additional components of atherosclerotic cardiovascular disease that are prominent in patients with CKD include microvascular disease and myocardial fibrosis. Therapeutic interventions that minimize cardiovascular events related to atherosclerotic cardiovascular disease in patients with CKD, as determined by well-designed clinical trials, are limited to statins. Data are lacking regarding other available therapeutic measures primarily due to exclusion of patients with CKD from major trials studying cardiovascular disease. Data from well-designed randomized controlled trials are needed to guide clinicians who care for this high-risk population in the management of atherosclerotic cardiovascular disease to improve clinical outcomes.

Is nephrology specialty at risk?

Interest in nephrology as a career choice has been steadily waning among internal medicine residents. This decline is reflected in a significant increment in unfilled fellowship training spots for several years. Interventional nephrology can help to reinvigorate an interest in nephrology as a whole.

Transient Hypocalcemia in a Dialysis Patient With Paget's disease and Presumed Renal Cell Carcinoma

A 68-year-old man with end-stage renal disease was hospitalized because of radicular pain and weakness in the left arm and hand. Sonography and computed tomography had recently shown a large right renal mass. On admission, magnetic resonance imaging demonstrated vertebral metastases with epidural extension, and radiotherapy was directed to the spine and kidney. Hypocalcemia was first noted on the fourth hospital day. A second computed tomography scan showed bleeding into and around the kidney, and arterial embolization was required to halt the bleeding. Hypocalcemia persisted for at least 27 days at values between 6.0 and 7.7 mg/dL and was consistently associated with ionized calcium concentrations less than or equal to 4.44 mg/dL. After an unrevealing search for a recognized cause, we attributed hypocalcemia to persistent sequestration of calcium in the right retroperitoneum. Exogenous supplementation eventually restored the concentration to normal. In the absence of renal and intestinal loss, hypocalcemia reflects abnormal flux of calcium from the extracellular compartment into tissue. Our patient's repository appears to have been a necrotic and hemorrhagic cancer. Tumor-induced sequestration of calcium should be included in the differential diagnosis of hypocalcemia.

Hyperglycemia and Acute Kidney Injury During the Perioperative Period

Hyperglycemia and acute kidney injury (AKI) are frequently observed during the perioperative period. Substantial evidence indicates that hyperglycemia increases the prevalence of AKI as a surgical complication. Patients who develop hyperglycemia and AKI during the perioperative period are at significantly elevated risk for poor outcomes such as major adverse cardiac events and all-cause mortality. Early observational and interventional trials demonstrated that the use of intensive insulin therapy to achieve strict glycemic control resulted in remarkable reductions of AKI in surgical populations. However, more recent interventional trials and meta-analyses have produced contradictory evidence questioning the renal benefits of strict glycemic control. Although the exact mechanisms through which hyperglycemia increases the risk of AKI have not been elucidated, multiple pathophysiologic pathways have been proposed. Hypoglycemia and glycemic variability may also play a significant role in the development of AKI. In this literature review, the complex relationship between hyperglycemia and AKI as well as its impact on clinical outcomes during the perioperative period is explored.

In silico ordinary differential equation/partial differential equation hemodialysis model estimates methadone removal during dialysis

Background

There is a need to have a model to study methadone’s losses during hemodialysis to provide informed methadone dose recommendations for the practitioner.

Aim

To build a one-dimensional (1-D), hollow-fiber geometry, ordinary differential equation (ODE) and partial differential equation (PDE) countercurrent hemodialyzer model (ODE/PDE model).

Methodology

We conducted a cross-sectional study in silico that evaluated eleven hemodialysis patients. Patients received a ceiling dose of methadone hydrochloride 30 mg/day. Outcome measures included: the total amount of methadone removed during dialysis; methadone’s overall intradialytic mass transfer rate coefficient, k_m; and, methadone’s removal rate, j_ME. Each metric was measured at dialysate flow rates of 250 mL/min and 800 mL/min.

Results

The ODE/PDE model revealed a significant increase in the change of methadone’s mass transfer with increased dialysate flow rate, %Δk_m=18.56, P=0.02, N=11. The total amount of methadone mass transferred across the dialyzer membrane with high dialysate flow rate significantly increased (0.042±0.016 versus 0.052±0.019 mg/kg, P=0.02, N=11). This was accompanied by a small significant increase in methadone’s mass transfer rate (0.113±0.002 versus 0.014±0.002 mg/kg/h, P=0.02, N=11). The ODE/PDE model accurately predicted methadone’s removal during dialysis. The absolute value of the prediction errors for methadone’s extraction and throughput were less than 2%.

Conclusion

ODE/PDE modeling of methadone’s hemodialysis is a new approach to study methadone’s removal, in particular, and opioid removal, in general, in patients with end-stage renal disease on hemodialysis. ODE/PDE modeling accurately quantified the fundamental phenomena of methadone’s mass transfer during hemodialysis. This methodology may lead to development of optimally designed intradialytic opioid treatment protocols, and allow dynamic monitoring of outflow plasma opioid concentrations for model predictive control during dialysis in humans.

Role of T-regulatory cells in the response to hepatitis B vaccine in hemodialysis patients

Human disease elicits a complex array of biological processes that results in long-term protective immunological memory to infectious agents. Chronic kidney disease is known to impair induction of sustained immunological memory to hepatitis B vaccine (HBVax) antigens. We asked the question: Does end-stage renal disease promote changes in subtypes of regulatory T (Treg) cells that correlate with diminished amnestic response to HBVax antigen compared to healthy controls? The study design and setting was a prospective observational cohort at a veterans affairs medical center. End-stage renal disease patients on hemodialysis (HD) were compared with individuals with self-reported normal kidney function. All subjects received HBVax. Peripheral blood was sampled for assessment for Treg cells pre and post vaccination. CD4+ FOXP3 Treg numbers were similar between HD and healthy subjects during a 14-day time period post vaccination. HD subjcts had lower anti-HBSag antibody than CON (control) subjects (330 ± 108.7 vs. 663.1 ± 129.7 IU/mL; P = 0.063). Hemodialysis subjects with resting Tregs higher than the median value in our cohort demonstrated a significantly lower change in HBsAB at 30 days post booster vaccination (P = 0.030). No such relationship was found for the activated Treg subset among HD subjects, or either subset among CON subsets. In our limited comparison study of 11 HD and 8 CON subjects, Treg subsets did not differ between the two groups; but differences in the suppressive Treg numbers in the HD group could explain the altered antibody response to HBVax and is worthy of further study.

Effect of extended-release niacin on cardiovascular events and kidney function in chronic kidney disease: a post hoc analysis of the AIM-HIGH trial

Chronic kidney disease (CKD) in patients is strongly associated with cardiovascular morbidity and mortality, and prevalent abnormal lipid metabolism. The AIM-HIGH trial examined the benefits of adding extended-release niacin (ERN) to simvastatin in patients with established coronary heart disease. Here we conducted a post hoc analysis of the AIM-HIGH trial examining whether participants derived cardiovascular or renal benefits when stratified by renal function. Of 3414 participants, 505 had stage 3 CKD at baseline. Among the CKD subset, demographics and cardiovascular disease (CVD) risk factors were well balanced in the ERN and placebo arms. Compared with placebo, CKD participants receiving ERN had a significant decrease in triglycerides by a median of 59.0 mg/dl, and high-density lipoprotein cholesterol significantly increased by a mean of 11.3 mg/dl over a mean follow-up of 3 years. CVD events were similar between CKD participants in both arms. However, all-cause mortality was significantly higher in the ERN group (hazard ratio of 1.73). Mean change in eGFR among ERN-treated CKD participants was not significantly different between study arms. Thus, among AIM-HIGH participants with CKD, the addition of ERN to simvastatin for secondary prevention of CVD improved triglyceride and high-density lipoprotein-cholesterol concentrations but did not improve cardiovascular outcomes or kidney function, and was associated with higher all-cause mortality.

Continued Eculizumab Therapy for Persistent Atypical Hemolytic Uremic Syndrome

Atypical hemolytic uremic syndrome (atypical HUS) is characterized by endothelial injury and microvascular thrombosis resulting in microangiopathic hemolytic anemia, thrombocytopenia, and ischemic injury to organs, especially the kidney. Activation of complements is involved in the pathogenesis of atypical HUS. Eculizumab, a neutralizing monoclonal antibody directed against complement C5, has shown salutary effects in patients with atypical HUS. In this report, we present a 23-year-old man with atypical HUSwho was treated with eculizumab. During the first four weeks of treatment, eculizumab failed to achieve a remission. Microangiopathic hemolytic anemia and thrombocytopenia persisted, while renal function deteriorated necessitating initiation of hemodialysis. Continuation of eculizumab therapy, however, led to marked improvement in hemolytic anemia, thrombocytopenia, and renal function. After 10 weeks of eculizumab therapy, hemodialysis was discontinued. At 5-month follow-up, serum creatinine was 1.1 mg/dL with continued eculizumab therapy every other week. In addition, platelet count was normal, while there was no evidence of hemolysis. We conclude that in patients with persistent atypical HUS continued treatment with eculizumab can be helpful in achieving remission.

Blood pressure recordings during hemodialysis access interventions: implications for acute management

A retrospective study evaluating the pattern of blood pressure and its related complications before, during, and after percutaneous hemodialysis interventions was performed in patients presenting with asymptomatic hypertension. Hemodialysis patients undergoing percutaneous interventions including tunneled hemodialysis catheter insertion, percutaneous balloon angioplasty and thrombectomy procedure, and stage II hypertension (systolic blood pressure ≥160 mmHg) were included in this analysis. Blood pressure medications were not used while midazolam and fentanyl were routinely administered. Patients were followed for up to 4 weeks to monitor any complications. The mean blood pressure before, during, and after the procedures were 185 ± 18/96 ± 14, 172 ± 22/92 ± 15, and 153 ± 25/87 ± 14, respectively. There was a statistically significant difference between the blood pressure readings before and after the procedure (before = 185 ± 18/96 ± 14, after = 153 ± 25/87 ± 14; p = 0.001). None of the patients had a stroke, myocardial infarction, or acute pulmonary edema before, during, or after the procedure or during the 4-week follow-up period. A significant reduction in blood pressure was observed after the procedure without the administration of any antihypertensive medication. These results suggest that the reduction in blood pressure observed after percutaneous dialysis access interventions (particularly in the presence of midazolam and fentanyl) may make it unnecessary to treat asymptomatic hypertension prior to these procedures.

Radial artery harvest: a potential cause of arteriovenous access-associated hand ischemia

Hand ischemia has multiple causes. In this article, we report an additional factor that can induce hand ischemia in hemodialysis patients. A 64-year-old white man with coronary artery disease underwent a coronary artery bypass graft procedure using the left radial artery as the bypass graft. Several months later, a left extremity Gracz fistula was created for arteriovenous access. Ever since dialysis was performed via the fistula the patient has experienced a cold hand and pain during dialysis that was somewhat relieved by wearing a woolen glove while on dialysis. Absence of the radial artery in the context of an ipsilateral arteriovenous access was highlighted as a possible etiology. A complete arteriography to determine the presence of stenoses, distal arteriopathy, and true steal was recommended, but the patient refused to undergo any investigation or procedure and instead decided to continue wearing the glove during the treatment. A plan for close follow-up and possible interventions in the event of worsening pain/ulceration was agreed upon. Radial artery harvest can result in hand ischemia if an ipsilateral arteriovenous access is created. We suggest that the contralateral extremity should be considered if an arteriovenous access is required to minimize this risk of this phenomenon.

Renal replacement therapy in special situations: heart failure and neurological injury

The cardiorenal syndrome is a complicated and increasingly prevalent entity requiring a multidisciplinary approach. Renal replacement therapy (RRT) in the form of slow ultrafiltration (UF) demonstrates promise for the treatment of acutely decompensated heart failure. Despite the lack of evidence for decreased mortality, there is considerable short-term benefit in decreased rehospitalizations and a restoration of diuretic responsiveness. Given the potential for improvement in quality of life and cost if hospitalizations are minimized, slow UF should be considered in patients with repeated hospitalization for decompensated heart failure. Acute neurologic injury is a highly unstable state requiring strict adherence to evidence-based guidelines to achieve the best possible functional outcomes. With improved short-term survival, a greater burden of non-neurologic injury may hinder long-term functional recovery. Acute kidney injury is among such important considerations that can lead to worsened neurological injury. Careful application of continuous modalities of therapy, probably early in the course of illness to avoid intradialytic osmolar shifts and provide hemodynamic stability, will allow for unimpeded neurologic recovery. Newer evidence on dose and RRT modality on patients with acute and chronic brain injury will certainly add important knowledge to this field.

Renal kallikrein excretion and epigenetics in human acute kidney injury: expression, mechanisms and consequences

Background

Renal kallikrein (KLK1) synthesis and urinary excretion are reportedly diminished during AKI (acute kidney injury) in animal models, and provision of kallikrein abrogates renal injury in this setting, but data in human AKI is limited. Therefore we first examined KLK1 renal excretion in human AKI, and then probed potential endocrine and epigenetic mechanisms for its alterations.

Methods

KLK1 enzymatic activity excretion was evaluated in urine from patients with established or incipient AKI, versus healthy/non-hospital as well as ICU controls. Endocrine control of KLK1 excretion was then probed by catecholamine and aldosterone measurements in established AKI versus healthy controls. To examine epigenetic control of KLK1 synthesis, we tested blood and urine DNA for changes in promoter CpG methylation of the KLK1 gene, as well as LINE-1 elements, by bisulfite sequencing.

Results

Patients with early/incipient AKI displayed a modest reduction of KLK1 excretion, but unexpectedly, established AKI displayed substantially elevated urine KLK1 excretion, ~11-fold higher than healthy controls, and ~3-fold greater than ICU controls. We then probed potential mechanisms of the change. Established AKI patients had lower SBP, higher heart rate, and higher epinephrine excretion than healthy controls, though aldosterone excretion was not different. Promoter KLK1 CpG methylation was higher in blood than urine DNA, while KLK1 methylation in blood DNA was significantly higher in established AKI than healthy controls, though KLK1 methylation in urine tended to be higher in AKI, directionally consistent with earlier/incipient but not later/established changes in KLK1 excretion in AKI. On multivariate ANOVA, AKI displayed coordinate changes in KLK1 excretion and promoter methylation, though directionally opposite to expectation. Control (LINE-1 repetitive element) methylation in blood and urine DNA was similar between AKI and controls.

Conclusions

Unexpectedly, increased KLK1 excretion in AKI patients was found; this increase is likely to be due in part to increments in adrenergic tone during BP depression. Epigenetic changes at KLK1 may also play a role in early changes of KLK1 expression and thus AKI susceptibility or recovery.