The role of autonomic neuropathy in the genesis of intradialytic hypotension

Management of diabetes mellitus in dialysis patients: Obstacles and challenges

BACKGROUND AND AIMS

Diabetic kidney disease (DKD) is a major health issue that is associated with an increased risk of morbidity and mortality. The treatment of DKD is challenging given changes in blood glucose homeostasis, unclear accuracy of glucose metrics, and altered kinetics of the blood glucose-lowering medications. There is uncertainty surrounding the optimal glycemic target in this population although recent epidemiologic data suggest that HbA1c ranges of 6-8%, as well as 7-9%, are associated with increased survival rates among diabetic dialysis patients. Furthermore, the treatment of diabetes in patients maintained on dialysis is challenging, and many blood glucose-lowering medications are renally metabolized and excreted hence requiring dose adjustment or avoidance in dialysis patients.

METHOD

ology: PubMed, Google Scholar, and Medline were searched for all literature discussing the management of diabetes in dialysis patients.

RESULTS

The literature was discussed under many subheadings providing the latest evidence in the treatment of diabetes in dialysis patients.

CONCLUSION

The management of diabetes in dialysis is very complex requiring a multi-disciplinary team involving endocrinologists and nephrologists to achieve targets and reduce morbidity and mortality.

Cardiovascular autonomic nervous system dysfunction in chronic kidney disease and end-stage kidney disease: disruption of the complementary forces

PURPOSE OF REVIEW

Several nontraditional risk factors have been the focus of research in an attempt to understand the disproportionately high cardiovascular morbidity and mortality in chronic kidney disease (CKD) and end-stage kidney disease (ESKD) populations. One such category of risk factors is cardiovascular autonomic dysfunction. Its true prevalence in the CKD/ESKD population is unknown but existing evidence suggests it is common. Due to lack of standardized diagnostic and treatment options, this condition remains undiagnosed and untreated in many patients. In this review, we discuss current evidence pointing toward the role of autonomic nervous system (ANS) dysfunction in CKD, building off of crucial historical evidence and thereby highlighting the areas in need for future research interest.

RECENT FINDINGS

There are several key mediators and pathways leading to cardiovascular autonomic dysfunction in CKD and ESKD. We review studies exploring the mechanisms involved and discuss the current measurement tools and indices to evaluate the ANS and their pitfalls. There is a strong line of evidence establishing the temporal sequence of worsening autonomic function and kidney function and vice versa. Evidence linking ANS dysfunction and arrhythmia, sudden cardiac death, intradialytic hypotension, heart failure and hypertension are discussed.

SUMMARY

There is a need for early recognition and referral of CKD and ESKD patients suspected of cardiovascular ANS dysfunction to prevent the downstream effects described in this review.There are many unknowns in this area and a clear need for further research.

Hemodialysis immediately after cardiac catheterization is a risk factor for intradialytic hypotension

Many hemodialysis clinicians have noticed that patients frequently develop intradialytic hypotension (IDH) immediately after cardiac catheterization (CC). However, precise data about the incidence of IDH immediately after CC are scarce. This study involved a single-center, retrospective, cross-sectional design. We reviewed the medical records of all HD patients who underwent CC between January 2009 and March 2012 at Hiroshima Prefectural Hospital. IDH was defined as a fall of systolic blood pressure of more than 20 mm Hg or a fall of mean blood pressure of more than 10 mm Hg, with symptoms according to the K/DOQI criteria. Data on a total of 112 patients were obtained: 64 patients commenced HD immediately after CC (IA group) and 48 patients underwent HD on the day after CC (ND group). The overall incidence of IDH was 34% (38/112). The incidence of IDH was significantly higher in the IA group than in the ND group (27/64, 42% vs. 11/48, 23%; P < 0.05). Multivariate logistic regression analysis showed that IA (odds ratio, 5.39; 95% confidence interval, 1.76 to 16.49; P < 0.01), coronary stenosis (odds ratio, 4.16; 95% confidence interval, 1.49 to 11.64; P < 0.05) were independently associated with IDH. This study revealed that HD immediately after CC is associated with a higher incidence of IDH. Clinicians should consider that HD following CC be scheduled for the next day, especially in patients with coronary stenosis.

Absolute blood volume in hemodialysis patients: why is it relevant, and how to measure it?

Intradialytic hypotension (IDH) is the most common complication during hemodialysis and is associated with significant morbidity. It occurs as a consequence of a reduction in blood volume during ultrafiltration. Today, devices for monitoring relative blood volume (i.e. the intradialytic blood volume as a fraction of the blood volume at the start of the dialysis treatment) are routinely available and have been used to analyze the relationship between changes in relative blood volume and the occurrence of IDH in an attempt to derive critical thresholds that, when observed, would help avoid hypotensive episodes during the treatment. However, the results have been unsatisfactory in many patients. Here we illustrate the importance of absolute blood volume in hemodialysis patients, summarize the acute physiologic mechanisms involved in the preservation of adequate circulation during ultrafiltration, and outline why hemodialysis patients are often particularly vulnerable to reductions in blood volume. We then discuss the shortcomings of relative blood volume measurements, make a case for the superiority of absolute blood volume measurements, and introduce the reader to a mathematical concept that allows relative blood volume devices to be used for the estimation of absolute blood volume. Finally, we discuss the implications of absolute blood volume beyond IDH and propose a paradigm shift in the approach to dry weight attainment.

Neurologic manifestations of acute and chronic renal disease

Acute and chronic renal disease is prevalent in hospitalized and ambulatory patient populations. Most patients with acute or chronic renal disease exhibit some degree of neurologic dysfunction affecting the CNS, peripheral nervous system, or both. Neurologic manifestations may be a direct consequence of the uremic state or a consequence of renal replacement therapy. Early recognition of common central and peripheral nervous system dysfunction as it relates to renal disease may provide opportunities for therapeutic intervention and improved outcomes. This review will summarize the most frequently encountered manifestations of acute and chronic renal disease, organized with respect to their occurrence as a direct consequence of advanced renal dysfunction or renal replacement therapy.

Korean red ginseng improves blood pressure stability in patients with intradialytic hypotension

Introduction. Intradialytic hypotension (IDH) is a common complication during hemodialysis which may increase mortality risks. Low dose of Korean red ginseng (KRG) has been reported to increase blood pressure. Whether KRG can improve hemodynamic stability during hemodialysis has not been examined. Methods. The 8-week study consisted of two phases: observation phase and active treatment phase. According to prehemodialysis blood pressure (BP), 38 patients with IDH were divided into group A (BP ≥ 140/90 mmHg, n = 18) and group B (BP < 140/90 mmHg, n = 20). Patients were instructed to chew 3.5 gm KRG slices at each hemodialysis session during the 4-week treatment phase. Blood pressure changes, number of sessions disturbed by symptomatic IDH, plasma levels of vasoconstrictors, blood biochemistry, and adverse effects were recorded. Results. KRG significantly reduced the degree of blood pressure drop during hemodialysis (P < 0.05) and the frequency of symptomatic IDH (P < 0.05). More activation of vasoconstrictors (endothelin-1 and angiotensin II) during hemodialysis was found. The postdialytic levels of endothelin-1 and angiotensin II increased significantly (P < 0.01). Conclusion. Chewing KRG renders IDH patients better resistance to acute BP reduction during hemodialysis via activation of vasoconstrictors. Our results suggest that KRG could be an adjuvant treatment for IDH.

Cardiovascular risk in diabetic end-stage renal disease patients

Diabetes mellitus is the leading cause of end-stage renal disease (ESRD), accounting for 54% of all incident cases according to the US Renal Data System. These patients suffer an extremely high mortality rate due to the very high incidence of cardiovascular disease. A significant proportion of these patients already has established cardiovascular disease at the time of initiation of dialysis treatment. More importantly, as these patients develop progressive kidney dysfunction, they are not only subjected to traditional Framingham risk factors, but, more importantly, to a whole host of "kidney disease-related risk factors" that further accelerate the progression of cardiovascular disease and thus contribute to adverse cardiovascular outcomes. The present article provides an updated view on the multitude of traditional Framingham risk factors and kidney disease-related risk factors that diabetic ESRD patients are subjected to. A better understanding of the different cardiovascular risk factors will be fundamental to institute early detection programs, as well as to provide aggressive cardiovascular management of these patients.

The management of diabetic neuropathy in CKD

A 64-year-old male with a 15-year history of poorly controlled type 2 diabetes and a 10-year history of hypertension and hyperlipidemia had developed multiple diabetes-related complications within the last 5 years. He first developed albuminuria 5 years ago, and over the next several years experienced fairly rapid decline in kidney function, with eGFR of 55 mL/min/1.73m2 noted 2 years ago. He was diagnosed with proliferative retinopathy 5 years ago and underwent laser photocoagulation. Four years ago, he noted symptoms of peripheral neuropathy manifested as shooting pain and numbness with loss of light touch, thermal and vibratory sensation in a stocking distribution. Last year he developed a non-healing ulcer on the plantar aspect of his left foot which was complicated with gangrene and resulted in a below-the-knee amputation of the left leg one year ago. He now reports a new onset of weakness, lightheadedness and dizziness on standing that affects his daily activities. He reports lancinating pain in his right lower extremity, worse in the evening. Medications include: neutral protamine Hagedorn insulin twice daily and regular insulin on a sliding scale, metoprolol 50 mg/d, lisinopril 40 mg/d, atorvastatin 80 mg/d, furosemide 40 mg/d and aspirin 81 mg/d. Blood pressure is 127/69 mm Hg with a pulse rate of 96 bpm while supine and 94/50 mmHg with a pulse rate of 102 bpm while standing. Strength is normal but with a complete loss of all sensory modalities to the knee in his remaining limb and up to the wrists in both upper extremities, and he is areflexic. Today's laboratory evaluations show a serum creatinine of 2.8 mg/dl, an estimated GFR (eGFR) of 24 ml/min/1.73m2, a hemoglobin A1c (HbA1c) of 7.9 % and 2.1 g of urine protein per gram of creatinine. What would be the most appropriate management for this patient?

Neuromuscular disease in the dialysis patient: an update for the nephrologist

Neuromuscular disease is an extremely common complication of end-stage kidney disease (ESKD), manifesting in almost all dialysis patients, and leading to weakness, reduced exercise capacity, and disability. Recent studies have suggested that hyperkalemia may underlie the development of neuropathy. As such, maintenance of serum K(+) within normal limits between periods of dialysis in ESKD patients manifesting early neuropathic symptoms may reduce neuropathy development and progression. For patients with more severe neuropathic syndromes, increased dialysis frequency or a switch to high-flux dialysis may prevent further deterioration, while ultimately, renal transplantation is required to improve and restore nerve function. Exercise training programs are beneficial for ESKD patients with muscle weakness due to neuropathy or myopathy, and are capable of improving exercise tolerance and quality of life. Specific treatments have recently been evaluated for symptoms of autonomic neuropathy, including sildenafil for impotence and midodrine for intra-dialytic hypotension, and have been shown to be effective and well tolerated. Other important management strategies for neuropathy include attention to foot care to prevent callus and ulceration, vitamin supplementation, and erythropoietin. Treatment with membrane-stabilizing agents, such as amitryptiline and gabapentin, are highly effective in patients with painful neuropathy.

Autonomic neuropathy in hemodialysis patients: questionnaires versus clinical tests

AIM

Uremic neuropathy (UN) is a typical complication of long-term dialysis therapy and may manifest as distal, symmetric, and both senso-motoric and autonomic nerve dysfunction. Its clinical picture is highly variable and it is not known how the symptoms of UN reported by chronic dialysis patients correspond to positive results of clinical tests for autonomic dysfunction. The objective of this study was to compare the prevalence of self-reported symptoms of autonomic neuropathy (AN) revealed in patient questionnaires with the prevalence of findings from objective clinical tests.

METHODS

The study group included 45 patients (26 males, 19 females), mean age 60 +/- 15.5 years, on chronic hemodialysis for 7.8 +/- 2.6 years. In all subjects, blood pressure (BPci) and heart rate (HRci) variability indexes (calculated as BP and HR during Ewing and Clarke' tests divided by HR and BP at rest) were measured using the Finapres which records beat-to-beat blood pressure and heart rate. Additionally, patients completed seven-question questionnaires which assessed the presence of most typical AN symptoms. The control group comprised 12 healthy subjects (age 52 +/- 19.5 years).

RESULTS

The results from the questionnaires showed that falls of BP occurred in 73% of patients, itching of skin in 42%, constipation or diarrhea in 33%, filling of stomach in 25%, and decreased sweating in 17%. Altogether 85.9% of patients reported one or more subjective symptoms of neuropathy. In contrast, modified Ewing and Clarke's test revealed that only 17.7% of participants demonstrated overt pathologies. Neither blood pressure nor heart rate changeability indexes in patients and healthy subjects showed significant differences with the exception of intense inhalation and static effort.

CONCLUSIONS

Our results show much higher frequency of subjective symptoms of AN in chronic dialysis patients than objective symptoms detected with clinical tests.

Noninvasive Measurement of Cardiac Output in Hemodialysis Patients by Task Force Monitor: A Comparison with the Transonic System

Cardiovascular disease is the leading cause of morbidity and mortality in maintenance hemodialysis (MHD) patients. The Transonic (TRS; Transonic Systems, Ithaca, NY) device is frequently used for determination of cardiac output (CO) by an indicator dilution technique. The Task Force Monitor (TFM; CN Systems, Graz, Austria) has gained attention as noninvasive tool for continuous beat-to-beat assessment of cardiovascular variables, including CO by impedance cardiography. Despite its use in cardiology and intensive care settings, the TFM has yet not been validated in dialysis patients. This study compares CO measurements in 12 MHD patients by TFM and TRS. Bland-Altman and regression analysis were used. CO was measured simultaneously by TRS and TFM. Average CO was 5.4 L/min by TRS and 5.0 L/min by TFM, respectively. Bland-Altman analysis revealed no significant systematic differences between the two methods (mean difference: 0.4 L/min; SD: 0.6; p > 0.05). Linear regression analysis showed significant correlation between both techniques (r = 0.802, p = 0.002). The SD of mean individual CO values was 1.1 L/min with TRS and 0.8 L/min with TFM, respectively.CO measured by TFM and TRS does not differ significantly, thus making the TFM an attractive noninvasive tool for the continuous beat-to-beat assessment of CO in MHD patients.

Uremic neuropathy: clinical features and new pathophysiological insights

Neuropathy is a common complication of end-stage kidney disease (ESKD), typically presenting as a distal symmetrical process with greater lower-limb than upper-limb involvement. The condition is of insidious onset, progressing over months. and has been estimated to be present in 60%-100% of patients on dialysis. Neuropathy generally only develops at glomerular filtration rates of less than 12 ml/min. The most frequent clinical features reflect large-fiber involvement, with paresthesias, reduction in deep tendon reflexes, impaired vibration sense, muscle wasting, and weakness. Nerve conduction studies demonstrate findings consistent with a generalized neuropathy of the axonal type. Patients may also develop autonomic features, with postural hypotension, impaired sweating, diarrhea, constipation, or impotence. The development of uremic neuropathy has been related previously to the retention of neurotoxic molecules in the middle molecular range, although this hypothesis lacked formal proof. Studies utilizing novel axonal excitability techniques have recently shed further light on the pathophysiology of this condition. Nerves of uremic patients have been shown to exist in a chronically depolarized state prior to dialysis, with subsequent improvement and normalization of resting membrane potential after dialysis. The degree of depolarization correlates with serum K(+), suggesting that chronic hyperkalemic depolarization plays an important role in the development of nerve dysfunction in ESKD. These recent findings suggest that maintenance of serum K(+) within normal limits between periods of dialysis, rather than simple avoidance of hyperkalemia, is likely to reduce the incidence and severity of uremic neuropathy.

Diabetes: changing the fate of diabetics in the dialysis unit

The prevalence of diabetes mellitus (DM) is very high worldwide. According to the World Health Organization in 2000 the worldwide prevalence of DM was 171,000,000. Diabetic nephropathy is a major vascular complication of DM. If DM is not treated early and adequately, many diabetic patients may reach end-stage renal disease (ESRD) secondary to advanced irreversible diabetic nephropathy. In many countries diabetic nephropathy has become the single most frequent cause of prevalent ESRD patients undergoing maintenance hemodialysis (MHD). In the early era of renal replacement therapy (RRT) by means of intermittent hemodialysis the prognosis of diabetic patients undergoing MHD was extremely poor and disappointing. While the prognosis of patients suffering from diabetic ESRD and maintained by chronic intermittent dialysis has greatly improved, the rehabilitation rate and survival of these patients continue to be worse than those of non-diabetic patients. A preexisting severely compromised cardiovascular condition, vascular access problems, diabetic foot disease, interdialytic weight gain, and intradialytic hypotension explain most of the less favorable outcome. Despite improved techniques and more aggressive medical therapy in recent years, a review of the fate of diabetics in dialysis units since 1972 reveals that these patients have had significant morbidity and mortality. We still have a long way to go in order to achieve more ideal outcomes for our patients. Most of the diabetic ESRD patients are still maintained by MHD, but they can choose other modalities of RRT such as chronic ambulatory peritoneal dialysis (CAPD), kidney and kidney plus pancreas transplantation. The results of different studies and national registries on the mortality and morbidity of ESRD patients being maintained on different modalities of dialysis are conflicting. It can be concluded that the two modalities of dialysis (CAPD and MHD) are almost comparable in terms of survival. The recent suggestions for nocturnal daily hemodialysis, short daily hemodialysis, and an integrative care approach for the management of diabetics with ESRD provides better promise for these patients.

Impedance Cardiography: A Potential Monitor for Hemodialysis

BACKGROUND

Impedance cardiography (ICG) technology has improved dramatically, and at least one device now can give a measurement of fluid status by using thoracic fluid content (TFC), along with cardiac output (CO) and cardiac index (CI). With a built-in sphygmomanometer cuff, it can also provide blood pressure (BP) and systemic vascular resistance index (SVRI). A currently available small portable ICG that provides reliable measures of fluid status could be an ideal noninvasive monitor for hemodialysis (HD), with the potential of helping avoid significant hemodynamic instability during HD.

METHODS

A case series of patients with chronic renal failure was studied while undergoing HD using ICG (BioZ, CardioDynamics, Int. Corp., San Diego, CA). Parameters recorded at 15-min intervals included TFC, CI, BP (systolic, diastolic, and mean arterial), SVRI, and heart rate. Using the Pearson method, the percentage changes in each of the parameters during the HD session were correlated to the amount of fluid removed (FR), normalized to body weight.

RESULTS

Forty-one patients were enrolled, but six patients were excluded due to incomplete data; therefore, 35 patients (13 men and 22 women) formed the basis of the analysis. The age range was 28 to 87 (mean 55.1 +/- 16.1) years. The amount of FR was 2.88 +/- 1.13 L (37.3 +/- 14.6 ml/kg). TFC decreased in all patients during the HD session (average reduction 12.7 +/- 8 kohms(-1)); whereas all other hemodynamic parameters showed both increases and decreases. The correlation of change in TFC with FR was moderate (r = 0.579, P = 0.0003); other hemodynamic parameters showed a poor correlation with FR. Neither the standard hemodynamic parameters nor the ICG device's special parameters were able to identify the five patients in this series who experienced significant hemodynamic instability or intradialytic hypotension.

CONCLUSION

TFC, measured easily and noninvasively using ICG, correlates with the amount of fluid removed during HD. In comparison with the other hemodynamic parameters measured, TFC changed most consistently with fluid removal. Whether or not serial TFC measurements in a given patient at different HD sessions can guide the extent of FR will require additional study. This compact, easily operated, and nonobtrusive ICG device with the capability for continuously providing the standard hemodynamic parameters plus CO, TFC, and standard limb lead electrocardiography could replace current monitoring systems.

Neurological complications in renal failure: a review

Neurological complications whether due to the uremic state or its treatment, contribute largely to the morbidity and mortality in patients with renal failure. Despite continuous therapeutic advances, many neurological complications of uremia, like uremic encephalopathy, atherosclerosis, neuropathy and myopathy fail to fully respond to dialysis. Moreover, dialytic therapy or kidney transplantation may even induce neurological complications. Dialysis can directly or indirectly be associated with dialysis dementia, dysequilibrium syndrome, aggravation of atherosclerosis, cerebrovascular accidents due to ultrafiltration-related arterial hypotension, hypertensive encephalopathy, Wernicke's encephalopathy, hemorrhagic stroke, subdural hematoma, osmotic myelinolysis, opportunistic infections, intracranial hypertension and mononeuropathy. Renal transplantation itself can give rise to acute femoral neuropathy, rejection encephalopathy and neuropathy in graft versus host disease. The use of immunosuppressive drugs after renal transplantation can cause encephalopathy, movement disorders, opportunistic infections, neoplasms, myopathy and progression of atherosclerosis. We address the clinical, pathophysiological and therapeutical aspects of both central and peripheral nervous system complications in uremia.

Optimal dialysis for the end-stage renal disease patient with cardiovascular disease

The increasing incidence and prevalence of end-stage renal disease (ESRD) that requires renal replacement therapy has placed a focus on the dialysis procedure itself with respect to its hemodynamic and cardiovascular complications. More than 50% of patients with ESRD will die of cardiovascular disease (CVD). A considerable contribution to cardiovascular events occurs with the dialysis procedure itself. This paper explores the intradialytic complications of hemodialysis as they relate to the cardiovascular system and highlights opportunities for research and improved quality of care.

Reverse epidemiology of conventional cardiovascular risk factors in patients with chronic heart failure

Traditional risk factors of a poor clinical outcome and mortality in the general population, including body mass index (BMI), serum cholesterol, and blood pressure (BP), are also found to relate to outcome in patients with chronic heart failure (CHF), but in an opposite direction. Obesity, hypercholesterolemia, and high values of BP have been demonstrated to be associated with greater survival among CHF patients. These findings are in contrast to the well-known associations of over-nutrition, hypercholesterolemia, and hypertension with a poor outcome in the general population. The association between traditional cardiovascular risk factors and an adverse clinical outcome in CHF patients is referred to as "reverse epidemiology." The mechanisms for this inverse association in CHF is not clear. There are other populations with a similar risk factor reversal phenomenon, including patients with end-stage renal disease receiving dialysis, those with advanced malignancies, and individuals with advanced age. Several possible causes are hypothesized: the time discrepancy of the competing risk factors may play a role; the presence of the "malnutrition-inflammation complex syndrome" in CHF patients may explain the existence of reverse epidemiology; and a decreased level of lipoprotein molecules may distort their endotoxin-scavenging role, predisposing CHF patients with a low serum cholesterol level to inflammatory consequences of endotoxemia. It is possible that new goals for such traditional risk factors as BMI, serum cholesterol, and BP should be developed for CHF. Reverse epidemiology of conventional cardiovascular risk factors is observed in CHF and may have a bearing on the management of these patients; thus, it deserves further investigation.

Reverse epidemiology of cardiovascular risk factors in maintenance dialysis patients

Conventional risk factors of cardiovascular disease and mortality in the general population such as body mass, serum cholesterol, and blood pressure are also found to relate to outcome in maintenance dialysis patients, but often in an opposite direction. Obesity, hypercholesterolemia, and hypertension appear to be protective features that are associated with a greater survival among dialysis patients. A similar protective role has been described for high serum creatinine and possibly homocysteine levels in end-stage renal disease (ESRD) patients. These findings are in contrast to the well-known association between over-nutrition and poor outcome in the general population. The association between under-nutrition and adverse cardiovascular outcome in dialysis patients, which stands in contrast to that seen in non-ESRD individuals, has been referred to as "reverse epidemiology." Publication bias may have handicapped or delayed additional reports with such paradoxical findings in ESRD patients. The etiology of this inverse association between conventional risk factors and clinical outcome in dialysis patients is not clear. Several possible causes are hypothesized. First, survival bias may play a role since only a small number of patients with chronic kidney disease (CKD) survive long enough to reach ESRD. Hence, the dialysis patients are probably a distinctively selected population out of CKD patients and may not represent the risk factor constellations of their CKD predecessors. Second, the time discrepancy between competitive risk factors may play a role. For example, the survival disadvantages of under-nutrition, which is frequently present in dialysis patients, may have a major impact on mortality in a shorter period of time, and this overwhelms the long-term negative effects of over-nutrition on survival. Third, the presence of the "malnutrition-inflammation complex syndrome" (MICS) in dialysis patients may also explain the existence of reverse epidemiology in dialysis patients. Both protein-energy malnutrition and inflammation or the combination of the two are much more common in dialysis patients than in the general population and many elements of MICS, such as low weight-for-height, hypocholesterolemia, or hypocreatininemia, are known risk factors of poor outcome in dialysis patients. The existence of reverse epidemiology may have a bearing on the management of dialysis patients. It is possible that new standards or goals for such traditional risk factors as body mass, serum cholesterol, and blood pressure should be considered for these individuals.