The effect of altitude change on anemia treatment response in hemodialysis patients

New Approaches to Diabetic Nephropathy from Bed to Bench

Diabetic nephropathy (DN) is the main cause of end-stage kidney disease (ESKD). DN-related ESKD has the worst prognosis for survival compared with other causes. Due to the complex mechanisms of DN and the heterogeneous presentations, unmet needs exist for the renal outcome of diabetes mellitus. Clinical evidence for treating DN is rather solid. For example, the first Kidney Disease: Improving Global Outcomes (KDIGO) guideline was published in October 2020: KDIGO Clinical Practice Guideline for Diabetes Management in Chronic Kidney Disease. In December of 2020, the International Society of Nephrology published 60 (+1) breakthrough discoveries in nephrology. Among these breakthroughs, four important ones after 1980 were recognized, including glomerular hyperfiltration theory, renal protection by renin-angiotensin system inhibition, hypoxia-inducible factor, and sodium-glucose cotransporter 2 inhibitors. Here, we present a review on the pivotal and new mechanisms of DN from the implications of clinical studies and medications.

What are optimum target levels of hemoglobin in older adults?

AIM

The aim of this study is to identify optimum target levels of hemoglobin (Hgb) in older males and females according to cognitive performance, mood state, nutrition intake, balance-walking functions, muscle strength and performance in daily life activities.

METHOD

A total of 1942 geriatric patients who had undergone comprehensive geriatric assessment were evaluated. The patient's demographic characteristics, comorbid diseases, number of drugs, cognitive performance, mood and nutritional states, basic and instrumental daily living activity indexes were obtained from hospital files. Hgb levels were analyzed on the same day. Receiver Operating Characteristic analysis was used to detect the optimum level of Hgb according to the best performance of geriatric assessment parameters.

RESULTS

1095 participants took part of who 71.9% were female and the mean age was 76.92 ± 7.38 years (65-103 years). There was a significant negative correlation between age, number of drugs used, Geriatric Depression Scale-15, Timed Up and Go test and Hgb in both sexes while a significant positive correlation was found between Barthel and Lawton activities of daily living, Tinetti test, Mini Nutritional Assessment, Mini-Mental State Examination and Hgb (p < 0.05). The optimum Hgb levels were ≥ 13.0 for females and ≥ 13.9 in males.

CONCLUSION

Findings from the present study in relation to Hgb and key geriatric evaluation parameters suggests that the optimum level of Hgb for older females and males is higher than the level of Hgb in current definitions. Data from this study suggest that the optimum value of the Hgb level is 13.0 for females and 13.9 for males.

Prolyl-hydroxylase inhibitors for the treatment of anemia in chronic kidney disease

PURPOSE OF REVIEW

Prolyl-hydroxylase inhibitors are a novel class of orally administered drugs that are under development for the treatment of anemia in patients with chronic kidney disease. This review discusses the biology of these drugs and their target - hypoxia-inducible factor and potential advantages and disadvantages of these therapies. Finally, we will discuss current trials in patients with both chronic kidney disease and end-stage renal disease.

RECENT FINDINGS

Recent smaller studies have found that prolyl-hydroxylase are as effective as erythropoietin in treating anemia of chronic kidney disease. We do not yet know if they have the same cardiovascular and cancer-related risk profile and these questions will be answered by large phase III trials that are ongoing.

SUMMARY

Although prolyl hydroxylase inhibitors have much potential, questions remain regarding their efficacy and safety. Should these concerns prove to be unfounded, the treatment of anemia in chronic kidney disease will likely be transformed over the next decade.

New options for the anemia of chronic kidney disease

Anemia is a common complication of chronic kidney disease. Use of erythropoiesis-stimulating agents (ESA) has been a mainstay of treatment since 1990. A series of large trials demonstrated that ESAs have serious safety problems, including increasing cardiovascular and thrombotic events, and death. Analyses suggest high pharmacologic doses of ESAs, rather than the highly achieved hemoglobin, may mediate harm. Hypoxia-inducible factor (HIF) activators stimulate endogenous erythropoietin production and enhance iron availability. In early clinical trials, these oral agents appear to be capable of replacing ESA therapy and minimizing the need for i.v. iron therapy for chronic kidney disease–related anemia, while having other potentially advantageous actions. Large phase 3 trials are underway with several HIF activators. This commentary reviews trends in anemia management, the safety issues related to our present therapies, the role of HIF in regulating erythropoiesis, and the diverse actions of HIF activators.

The effect of altitude on erythropoiesis-stimulating agent dose, hemoglobin level, and mortality in hemodialysis patients

Residence at higher altitude has been associated with improved anemia parameters and lower mortality rates among end-stage renal disease (ESRD) patients. However, these associations were observed prior to the 2011 shift in erythropoiesis-stimulating agent (ESA) dosing. To determine the impact of altitude on contemporary ESRD patients, a retrospective observational analysis was conducted in which patients were ascribed to one of four altitude categories as of 1 Jan 2012 and outcomes were assessed during 2012. Associations between altitude category and outcomes were estimated using generalized linear mixed models, adjusted for covariates that differed at baseline. Patients at higher altitude were less likely to receive ESA treatment, and dose was 723 U/treatment (95 % confidence interval [CI]: 544, 834) lower in the highest altitude category compared to the lowest category. The proportion of patients using IV iron decreased with increasing altitude category. Patients in the highest two categories had greater mean hemoglobin values (+0.15 and +0.23 g/dL) than the lowest. Mortality was lower for patients in the highest altitude category compared to those in the lowest (incidence rate ratio 0.73; 95 % CI: 0.63, 0.88), although their rate of missed dialysis treatments was slightly higher. This study confirms that, in the context of current anemia management practices, high altitude is associated with higher hemoglobin and lower mortality, despite lower utilization of ESA and IV iron.

Mimicking hypoxia to treat anemia: HIF-stabilizer BAY 85-3934 (Molidustat) stimulates erythropoietin production without hypertensive effects

Oxygen sensing by hypoxia-inducible factor prolyl hydroxylases (HIF-PHs) is the dominant regulatory mechanism of erythropoietin (EPO) expression. In chronic kidney disease (CKD), impaired EPO expression causes anemia, which can be treated by supplementation with recombinant human EPO (rhEPO). However, treatment can result in rhEPO levels greatly exceeding the normal physiological range for endogenous EPO, and there is evidence that this contributes to hypertension in patients with CKD. Mimicking hypoxia by inhibiting HIF-PHs, thereby stabilizing HIF, is a novel treatment concept for restoring endogenous EPO production. HIF stabilization by oral administration of the HIF-PH inhibitor BAY 85-3934 (molidustat) resulted in dose-dependent production of EPO in healthy Wistar rats and cynomolgus monkeys. In repeat oral dosing of BAY 85-3934, hemoglobin levels were increased compared with animals that received vehicle, while endogenous EPO remained within the normal physiological range. BAY 85-3934 therapy was also effective in the treatment of renal anemia in rats with impaired kidney function and, unlike treatment with rhEPO, resulted in normalization of hypertensive blood pressure in a rat model of CKD. Notably, unlike treatment with the antihypertensive enalapril, the blood pressure normalization was achieved without a compensatory activation of the renin–angiotensin system. Thus, BAY 85-3934 may provide an approach to the treatment of anemia in patients with CKD, without the increased risk of adverse cardiovascular effects seen for patients treated with rhEPO. Clinical studies are ongoing to investigate the effects of BAY 85-3934 therapy in patients with renal anemia.

Childhood anemia at high altitude: risk factors for poor outcomes in severe pneumonia

BACKGROUND

Pneumonia is the leading cause of mortality in young children globally, and factors that affect tissue delivery of oxygen may affect outcomes of pneumonia. We studied whether altitude and anemia influence disease severity and outcomes in young children with World Health Organization-defined severe pneumonia.

METHODS

We analyzed data from the SPEAR (Severe Pneumonia Evaluation Antimicrobial Research) study, a World Health Organization- and USAID-sponsored multinational randomized controlled trial of antibiotics for severe pneumonia among children aged 2 to 59 months in resource-poor settings. The trial enrolled 958 children in 8 sites at varying elevations, classified as high (≥ 2000 m) or low (<2000 m) altitude. We compared illness severity and assessed the effect of anemia on treatment outcome at high and low altitudes, adjusting for potential confounders and study site.

RESULTS

Children at high altitudes had significantly lower oxygen saturation on presentation, more cyanosis, lower systolic blood pressure, and higher hemoglobin. After adjusting for potential confounders, anemia predicted treatment failure in children living at high altitude (relative risk: 4.07; 95% confidence interval: 2.60-6.38) but not at low altitude (relative risk: 1.12; 95% confidence interval: 0.96-1.30). Children at high altitude took longer to reach normoxemia than did children at lower altitudes (5.25 vs 0.75 days; P < .0001).

CONCLUSIONS

Children at high altitude present with more severe disease, and children with anemia at high altitude are at greater risk of poor outcome when being treated for severe pneumonia. Given the high global prevalence of anemia among young children, prevention and treatment of anemia should be a priority in children living at high altitude and could improve outcomes of pneumonia.

Cardiovascular and renal effects of chronic exposure to high altitude

Over 140 million people live at high altitude, defined as living at an altitude of 2400 m or more above sea level. Subjects living under these conditions are continuously living under hypoxic conditions and, depending on the population, various adaptations have developed. Interestingly, subjects living chronically at high altitude appear to have a decreased frequency of obesity, diabetes and coronary artery disease. However, these benefits on health are balanced by the frequent development of systemic and pulmonary hypertension. Recently, it has been recognized that subjects living at high altitude are at risk for developing high-altitude renal syndrome (HARS), which is a syndrome consisting of polycythemia, hyperuricemia, systemic hypertension and microalbuminuria, but with preserved glomerular filtration rate. More studies should be performed to characterize the mechanisms and etiology of HARS; as such studies may be of benefit not only to the high-altitude population, but also to better understanding of the renal consequences of acute and chronic hypoxia.

Altitude and the risk of cardiovascular events in incident US dialysis patients

BACKGROUND

Altitude is associated with all-cause mortality in US dialysis patients, but its association with cardiovascular outcomes has not been assessed. We hypothesized that higher altitude would be associated with lower rates of cardiovascular events due to an altered physiological response of dialysis patients to altitude induced hypoxia.

METHODS

We studied 984,265 patients who initiated dialysis from 1995 to 2006. Patients were stratified by the mean elevation of their residential zip codes and were followed from the start of dialysis to the occurrence of several validated cardiovascular endpoints: myocardial infarction, stroke, cardiovascular death and a composite of these end points. Incidence rate ratios across altitude strata were estimated using proportional hazards regression.

RESULTS

All outcomes occurred less frequently among patients living at higher altitude compared with patients living at or near sea level, and the association appeared monotonic for all outcomes except for stroke, which was most incident in the 250-1999 ft group. Compared with otherwise similar patients residing at or near sea level, patients living at ≥ 6000 ft had 31% [95% confidence interval (CI): 21-41%] lower rates of myocardial infarction, 27% (95% CI: 15-37%) lower rates of stroke and 19% (95% CI: 14-24%) lower rates of cardiovascular death. Additional adjustment for biometric information did not materially change these findings. Effect modification between race and altitude was only consistently significant for Native Americans. Altitude did not significantly alter the rates of non-cardiovascular death.

CONCLUSION

We conclude that dialysis patients at higher altitude experience lower rates of cardiovascular events compared to otherwise similar patients at lower altitude.