Hypoalbuminemia is an important risk factor of hypotension during hemodialysis

Ultrafiltration Tolerance: A Phenotype That We Need to Recognize

BACKGROUND

The evaluation and management of fluid balance are key challenges in critical care patients who require renal replacement therapies because cumulative fluid balance is an independent factor that increases morbidity and mortality in different clinical scenarios.

SUMMARY

One of the strategies when fluid overload is refractory to diuretics is extracorporeal fluid removal (i.e., net ultrafiltration [UFNET] during kidney replacement therapy). However, problems with UFNET without individualized assessment are cardiovascular events and intradialytic hypotension, events that contribute to decreasing organ perfusion and sympathetic stress. Therefore, we must consider and try to predict the best timing for the start of ultrafiltration and find the point where the patient is most tolerant to ultrafiltration, making a simile to the concept of fluid tolerance.

KEY MESSAGES

UFNET is a continuous and dynamic process, going through moments of tolerance and intolerance to ultrafiltration; as nephrologists, we must take the necessary measures to move through this period.

Why is Intradialytic Hypotension the Commonest Complication of Outpatient Dialysis Treatments?

Intradialytic hypotension (IDH) is the most frequent complication of hemodialysis (HD) treatments with a frequency of 10% to 12% for patients with chronic kidney disease attending for outpatient treatments and is associated with both temporary ischemic stress to vital organs, including the heart and brain, and increased patient mortality. Although there have been many different definitions of IDH over the years, an absolute nadir systolic blood pressure (SBP) has the strongest association with patient outcomes. The unifying pathophysiology is one of reduced effective blood volume, resulting in lower plasma tonicity, and if this cannot be adequately compensated for by activation of neurohumeral systems, then arteriolar tone and blood pressure fall. The risk factors for developing IDH are numerous, ranging from patient-related factors, including age and comorbidity with reduced cardiac reserve, to patient compliance with dietary and lifestyle advice, to reactions with the extracorporeal circuit and medications, choice of dialysate composition and temperature, setting of postdialysis target weight, ultrafiltration rate, and profiling. Advances in dialysis machine technology by providing real time estimates of the effective circulating volume and adjusting dialysate composition to maintain vascular tonicity are being developed, but currently require more sophisticated biofeedback loops to be clinically effective in preventing IDH. While awaiting advances in artificial intelligence, the clinician continues to rely on patient education to limit interdialytic weight gains, frequent assessment of the postdialysis target weight, adjusting dialysate composition and temperature, introducing convective therapies to increase thermal losses, and altering dialysis session duration and frequency to reduce ultrafiltration rate requirements.

Hemodynamic Instability during Acute Kidney Injury and Acute Renal Replacement Therapy: Pathophysiology and Clinical Implications

Hemodynamic instability associated with acute renal replacement therapy (aRRT, HIRRT) and/or with acute kidney injury (AKI) is frequently observed in the intensive care unit; it affects patients' renal recovery, and negatively impacts short- and long-term mortality. A thorough understanding of mechanisms underlying HIRRT and AKI-related hemodynamic instability may allow the physician in adopting adequate strategies to prevent their occurrence and reduce their negative consequences. The aim of this review is to summarize the main alterations occurring in patients with AKI and/or requiring aRRT of those homeostatic mechanisms which regulate hemodynamics and oxygen delivery. In particular, a pathophysiological approach has been used to describe the maladaptive interactions between cardiac output and systemic vascular resistance occurring in these patients and leading to hemodynamic instability. Finally, the potential positive effects of aRRT on these pathophysiological mechanisms and on restoring hemodynamic stability have been described.

Bioimpedance-defined overhydration predicts survival in end stage kidney failure (ESKF): systematic review and subgroup meta-analysis

Both overhydration and comorbidity predict mortality in end-stage kidney failure (ESKF) but it is not clear whether these are independent of one another. We undertook a systematic review of studies reporting outcomes in adult dialysis patients in which comorbidity and overhydration, quantified by whole body bioimpedance (BI), were reported. PubMed, EMBASE, PsychInfo and the Cochrane trial database were searched (1990-2017). Independent reviewers appraised studies including methodological quality (assessed using QUIPS). Primary outcome was mortality, with secondary outcomes including hospitalisation and cardiovascular events. Of 4028 citations identified, 46 matched inclusion criteria (42 cohorts; 60790 patients; 8187 deaths; 95% haemodialysis/5% peritoneal dialysis). BI measures included phase angle/BI vector (41%), overhydration index (39%) and extra:intracellular water ratio (20%). 38 of 42 cohorts had multivariable survival analyses (MVSA) adjusting for age (92%), gender (66%), diabetes (63%), albumin (58%), inflammation (CRP/IL6-37%), non-BI nutritional markers (24%) and echocardiographic data (8%). BI-defined overhydration (BI-OH) independently predicted mortality in 32 observational cohorts. Meta-analysis revealed overhydration >15% (HR 2.28, 95% CI 1.56-3.34, P < 0.001) and a 1-degree decrease in phase angle (HR 1.74, 95% CI 1.37-2.21, P < 0.001) predicted mortality. BI-OH predicts mortality in dialysis patients independent of the influence of comorbidity.

A brief review of intradialytic hypotension with a focus on survival

Intradialytic hypotension (IDH), a common complication of ultrafiltration during hemodialysis therapy, is associated with high mortality and morbidity. IDH, defined as a nadir systolic blood pressure of less than 90 mm Hg on more than 30% of treatments, is a relevant definition and is correlated with mortality. Risk factors for IDH include patient demographics, anti-hypertensive medication use, larger interdialytic weight gain, and dialysis prescription features as dialysate sodium, high ultrafiltration rate, and dialysate temperature. A high frequency of IDH events carries a substantial death risk. An ultrafiltration rate >10 mL/h/kg, and even more so >13 mL/h/kg, is highly predictive of cardiovascular and all-cause mortality. Evidence suggests that IDH causes acute reversible segmental myocardial hypoperfusion and contractile dysfunction (myocardial stunning), which can result in long-term loss of myocardial contractility, leading to premature death. IDH also has negative end-organ effects on the brain and gut, contributing to mortality through stroke, and endotoxin translocation with associated inflammation and protein-energy wasting. Given strong association of IDH and dialysis mortality, a paradigm shift to its approach is urgently needed. Randomized controlled trials are required to prospectively test drugs and monitoring devices which may reduce IDH.

Hypoalbuminemia in hemodialyzed end stage renal disease patients: risk factors and relationships--a 2 year single center study

Background

Malnutrition affects 1/3 of hemodialysis patients and associates with a higher risk of morbidity and mortality. Serum albumin is a marker of nutrition and inflammation, and predicts mortality, particularly when <3.8 g/dL. This study was performed to identify risk factors for hypoalbuminemia (<3.8 g/dL) and the particular temporal relationship and strength of association between protein intake (nPCR) and serum albumin when confounding variables are taken into account.

Methods

Demographic, clinical, and dialysis-related data of 57 ESRD patients on hemodialysis over 24 months in 6 temporal segments were analyzed with serum albumin as a continuous, and categorical outcome (with 3.8 g/dl as cut-off) variable , against 13 potential independent variables [4 demographic factors, 3 nutrition-related, and 5 morbidity-related parameters, and % urea reduction ratio (URR)]. The temporal relationships between albumin and nPCR were analyzed for the concurrent & 3 subsequent months in each temporal segment.

Results

The impact of nPCR on serum albumin (p < 0.05) was significant but with no discernible temporal relationship. Advancing age, longer vintage, female gender, diabetes mellitus, nPCR, serum phosphate and ferritin had significant correlation with albumin <3.8 g/dl (p < 0.05). Serum phosphate levels correlated positively, and fever, bacteremia, hospital stay and weight loss negatively, with mean serum albumin but did not negate the effect of nPCR. Regression analysis showed that mean albumin associated with nPCR, fever, hospital stay, bacteremia, dialysis vintage, age, sex, and diabetes mellitus; and that an albumin level of <3.8 g/dl associated with age, female sex, diabetes, lower nPCR, and higher ferritin.

Conclusion

Suggested target albumin levels were not met in elderly, female, and diabetic patients. The association of nPCR with albumin was not nullified by confounding demographic or morbidity-related factors. nPCR had no demonstrable temporal relationship with albumin.