Hemodialysis patients with less extracellular water overload and smaller cardiac atrial chamber sizes are at greater risk of a fall in blood pressure during dialysis

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.

Changes in total and segmental extracellular and intracellular volumes with hypotension during hemodialysis measured with bioimpedance spectroscopy

BACKGROUND

Bioelectrical impedance analysis (BIA) devices have been advocated to guide volume management in hemodialysis (HD) patients. We hypothesized that understanding the dynamics of fluid shifts in different body segments may provide additional insight on preventive measures to reduce the risk of intradialytic hypotension.

METHODS

A prospective observational study was conducted among 42 HD patients at risk of hypotension who were admitted as emergencies inpatient.

RESULTS

A total of 191 BIA measurements were made during the 42 HD sessions, and hypotension occurred during 52 measurements (27%). The extracellular water (ECW) to intracellular water ratio (EIR) was measured in different body segments and declined significantly only in the non-access arm with increasing HD session duration (β = -0.04; 95% confidence interval (CI): -0.05 to -0.03, p < 0.01). There was no significant association between EIR and hypotension with respect to the different body segments. Only pre-HD N-terminal-pro b-type natriuretic peptide was significantly associated with hypotension (β = 0.20, 95% CI: 0.04 to 0.89, p = 0.04). There was no association between relative blood volume monitoring change and EIR.

CONCLUSION

In summary, we found that segmental BIA during HD was unable to detect or predict hypotension during dialysis. Although BIA is able to provide information about ECW and guide clinical assessment of volume in HD patients prior to dialysis, our findings did not suggest the use of serial measurements of changes in EIR in different body segments during HD provided sufficient information to predict intradialytic hypotension. Similarly, changes in EIR did not provide information on changes in plasma volume that could potentially trigger interventions to prevent or reduce intra-dialytic hypotension.

Diastolic blood pressure is associated with brain atrophy in hemodialysis patients: A single center case-control study

Brain atrophy (BA) is often found in neuroimaging of hemodialysis patients, representing parenchymal cerebral damage. Likely contributing factors to BA are age, chronic hypertension, diabetes mellitus and other cardiovascular risk factors of atherosclerosis that are also common among hemodialysis patients. BA may also occur due to focal ischemia and hypoperfusion during hemodialysis. However, data on optimal blood pressure (BP) in these patients are limited. The goal of this study was to determine whether the prevalence and severity of BA would be higher among hemodialysis patients with lower BP. A blinded neuroradiologist graded BA of all hemodialysis patients who underwent brain non-contrast computerized tomography (CT) from 2015 to 2017 in our institution. Age- and sex-matched patients with normal kidney function who underwent brain CT during the same period and technique served as the control group. A total of 280 patients were included in this retrospective study, with average BP of 140/70 mmHg among hemodialysis patients and 142/75 mmHg in the control group. BA was more common in dialysis patients and its severity increased with age and traditional cardiovascular risk factors. We observed a significant negative correlation between diastolic BP (DBP) at dialysis initiation and BA. Average DBP decreased with increasing severity of BA. These findings were observed in both hemodialysis and non-CKD patients. BA was associated with lower DBP, which may induce cerebral hypoperfusion and ischemia. This finding should discourage over-treatment of hypertension among hemodialysis patients.

Changes in extracellular water with hemodialysis and fall in systolic blood pressure

Introduction:

Intra-dialytic hypotension (IDH) remains the most common complication with outpatient hemodialysis (HD) sessions. As fluid is removed during HD, there is contraction of the extracellular volume (ECW). We wished to determine whether the fall in ECW was associated with a fall in systolic blood pressure (SBP).

Methods:

We retrospectively reviewed the records of adult dialysis outpatients attending for their midweek sessions who had corresponding pre- and post-HD bioimpedance measurements of ECW.

Result:

We reviewed 736 patients, median age 67 (54–76) years, 62.8% male, 45.7% diabetic with a median dialysis vintage of 24.4 (9.2–56.8) months. The percentage fall in ECW (ECW%) was associated with post-dialysis systolic blood pressure (SBP) (r = −0.14, p < 0.001). Patients with SBP falls of >20 mmHg had a greater fall in ECW% compared to patients with stable SBP 7.6 (4.6–10.1) vs 6.0 (4.0–8.5), p < 0.001). Patients with greater dialyzer urea clearance had greater fall in ECW% (r = 0.19, p < 0.001). In a logistic model an increased fall in ECW% was associated with weight loss (odds ratio (OR) 1.88, 95% confidence limits (CL) 1.62–2.176, p < 0.001), and session duration (OR 1.45 (CL 1.05–1.99), p = 0.024), and negatively with hemodiafiltration compared to hemodialysis (OR 0.37 (0.19–0.74) p = 0.005 and dialysate sodium to plasma gradient (OR 0.95 (CL 0.90–0.99), p = 0.021).

Conclusion:

We observed an association between the reduction in ECW and SBP with dialysis. Our results would advocate monitoring ECW changes during dialysis and developing biofeedback devices to control ultrafiltration and dialysate sodium to reduce the risk of IDH.

Patient-reported symptoms during dialysis: the effect of pre-dialysis extracellular water and change in extracellular water post-dialysis

Background

Quality of life for haemodialysis (HD) patients may be affected by symptoms during dialysis treatments, and patient groups have highlighted the need to improve post-dialysis fatigue and dialysis-related symptoms. As changes in extracellular water (ECW) may lead to cramps and other symptoms, we wished to determine whether there was an association between ECW and intra-dialytic symptoms.

Methods

We reviewed the hospital records of HD patients who completed a self-reported intra-dialytic symptom questionnaire, using a visual analogue scale, who had contemporaneous pre- and postdialysis bioimpedance ECW measurements adjusted to height (aECW).

Results

We studied dialysis sessions of 506 patients, 314 (62.1%) male, 226 (44.7%) diabetic, mean age 64.6 ± 15.7 years, weight 69.9 ± 17.4 kg, and duration of dialysis treatment 26 (9.6–60.1) months. We divided patients into three groups according to pre-dialysis aECW, and total dialysis symptom scores were greater for those in the lower tertile (25 (10–41) vs middle 18 (8.5–34) vs upper 20 (7–31), p < 0.05). Only feeling cold, dizziness, and low blood pressure were statistically different between the three pre-dialysis aECW groups, and there was no difference in post-dialysis recovery times.

We analysed the effect of the fall in aECW pre-to post-dialysis. Patients in the group with the greatest fall in aECW did not report more intra-dialytic symptoms or longer recovery times.

Conclusion

We found that patients starting dialysis with lower relative ECW were more likely to report intra-dialytic symptoms than those with greater amounts of fluid to remove, and most commonly reported symptoms were associated with intra-vascular volume depletion.

Does Pulse Wave Velocity Increase Over Time in Hemodialysis Patients?

OBJECTIVES

Arterial stiffness, measured by pulse wave velocity (PWV), is reported to be increased in hemodialysis (HD) patients and increases cardiovascular mortality. Previous studies have reported an association between extracellular water (ECW) and PWV. We wished to review whether PWV increases over time and whether this is associated with ECW.

METHODS

We reviewed repeat aortic PWV measurements using an oscillograph method along with corresponding ECW measured by multifrequency bioimpedance in HD patients a minimum of 5 years apart.

RESULTS

Twenty-four patients (16 [66.7%] male and 11 [45.8%] diabetic, mean age 61.7 ± 15.2 years) had PWV and ECW initially measured after 46 (26-124) months of HD and then after 112 (97-202) months. Overall, there was no change in PWV or ECW (9.4 ± 2.2 vs. 8.1 ± 2.5 cm/s; 14.7 ± 2.5 vs. 15.2 ± 2.9 L, respectively), whereas the ECW/total body water ratio increased (0.399 ± 0.015 vs. 0.408 ± 0.021, p < 0.05). We found no association between changes in PWV and ECW (r = -0.05, p = 0.84), whereas there was an association with the change in peri-dialytic systolic blood pressure (SBP) (r = 0.59, p = 0.007).

CONCLUSION

In our small observational study, there was no overall change in PWV, after 5 years of HD, with PWV increasing in 50% and falling in 50%. Changes in PWV were not associated with changes in ECW but were associated with changes in peri-dialytic SBP. Our study demonstrates that PWV does not increase in all HD patients with time, and interventional studies are required to determine whether targeted blood pressure control reduces PWV in HD patients.