Bruno C. Silva

Hemodynamic Behavior During Hemodialysis: Effects of Dialysate Concentrations of Bicarbonate and Potassium

Background/Aims: Ultrafiltration that occurs during hemodialysis (HD) promotes profound alterations in a relatively short period of time. The dialysate content of bicarbonate (DBic) and potassium (DK) may have impact over intradialytic hemodynamics, which goes beyond ultrafiltration, and its impact was evaluated in a prospective cohort. Methods: 30 patients under HD were submitted to hemodynamic assessment (HA) at the beginning and at the end of HD sessions, through a non-invasive method. Serum minus dialysate potassium concentration was expressed as K-Gap. Cardiac index (CI) and peripheral arterial resistance (PAR) variation (post-HD minus pre-HD) were expressed as ΔCI and ΔPAR. Dialysate content of sodium and calcium were expressed as DNa and DCa, respectively. Results: Mean DNa, DK and DBic were, respectively, 136.4 ± 1.1, 2.1 ± 0.6 and 38.2 ± 2.1 mEq/L. In 15 patients, DCa was >1.5 mmol/L and in the other 15 patients ≤ 1.5 mmol/L. The K-Gap ranged from 1.4 to 5.1 mEq/l (median 3.0 mEq/L). There was a reduction in post-HD CI and systolic blood pressure (ΔCI = -0.72l/min/m2 and -11.3±15.1mmHg, respectively, p<0.001 for both). Conversely, PAR increased (ΔPAR = 272dyn.s/cm5, p<0.001). Lower post-HD CI was was associated to higher DBic (p=0.0013) and lower K-Gap (p=0.026). In multivariate analysis, ΔCI was dependent on DBic and K-Gap, whereas ΔPAR was dependent on dialysate calcium during HD. Conclusion: We confirmed that Na and Ca dialysate content exerts and important role on hemodynamic during HD. In addition, our findings pointed out that higher dialysate concentrations of bicarbonate and potassium promote lower cardiac performance at the end of hemodialysis session.

Impact of Compression Stockings vs. Continuous Positive Airway Pressure on Overnight Fluid Shift and Obstructive Sleep Apnea among Patients on Hemodialysis

Introduction Obstructive sleep apnea (OSA) is common in edematous states, notably in hemodialysis patients. In this population, overnight fluid shift can play an important role on the pathogenesis of OSA. The effect of compression stockings (CS) and continuous positive airway pressure (CPAP) on fluid shift is barely known. We compared the effects of CS and CPAP on fluid dynamics in a sample of patients with OSA in hemodialysis, through a randomized crossover study. Methods Each participant performed polysomnography (PSG) at baseline, during CPAP titration, and after 1 week of wearing CS. Neck circumference (NC) and segmental bioelectrical impedance were done before and after PSG. Results Fourteen patients were studied (53 ± 9 years; 57% men; body mass index 29.7 ± 6.8 kg/m2). Apnea–hypopnea index (AHI) decreased from 20.8 (14.2; 39.6) at baseline to 7.9 (2.8; 25.4) during CPAP titration and to 16.7 (3.5; 28.9) events/h after wearing CS (CPAP vs. baseline, p = 0.004; CS vs. baseline, p = 0.017; and CPAP vs. CS, p = 0.017). Nocturnal intracellular trunk water was higher after wearing CS in comparison to baseline and CPAP (p = 0.03). CS reduced the fluid accumulated in lower limbs during the day, although not significantly. Overnight fluid shift at baseline, CPAP, and CS was −183 ± 72, −343 ± 220, and −290 ± 213 ml, respectively (p = 0.006). Overnight NC increased at baseline (0.7 ± 0.4 cm), decreased after CPAP (−1.0 ± 0.4 cm), and while wearing CS (−0.4 ± 0.8 cm) (CPAP vs. baseline, p < 0.0001; CS vs. baseline, p = 0.001; CPAP vs. CS, p = 0.01). Conclusion CS reduced AHI by avoiding fluid retention in the legs, favoring accumulation of water in the intracellular component of the trunk, thus avoiding fluid shift to reach the neck. CPAP improved OSA by exerting local pressure on upper airway, with no impact on fluid redistribution. CPAP performed significantly better than CS for both reduction of AHI and overnight reduction of NC. Complementary studies are needed to elucidate the mechanisms by which CPAP and CS reduce NC.

Conversion from temporary to tunneled catheters by nephrologists: report of a single-center experience

Background Nephrologists have increasingly participated in the conversion from temporary catheters (TC) to tunneled-cuffed catheters (TCCs) for hemodialysis. Objective To prospectively analyze the outcomes associated with TCC placement by nephrologists with expertise in such procedure, in different time periods at the same center. The impact of vancomycin or cefazolin as prophylactic antibiotics on the infection outcomes was also tested. Patients and methods Hemodialysis patients who presented to such procedure were divided into two cohorts: A (from 2004 to 2008) and B (from 2013 to 2015). Time from TC to TCC conversion, prophylactic antibiotics, and reasons for TCC removal were evaluated. Results One hundred and thirty patients were included in cohort A and 228 in cohort B. Sex, age, and follow-up time were similar between cohorts. Median time from TC to TCC conversion was longer in cohort A than in cohort B (14 [3; 30] vs 4 [1; 8] days, respectively; P⩽0.0001). Infection leading to catheter removal occurred in 26.4% vs 18.9% of procedures in cohorts A and B, respectively, and infection rate was 0.93 vs 0.73 infections per 1,000 catheter-days, respectively (P=0.092). Infection within 30 days from the procedure occurred in 1.4% of overall cohort. No differences were observed when comparing vancomycin and cefazolin as prophylactic antibiotics on 90-day infection-free TCC survival in a Kaplan–Meier model (log-rank = 0.188). TCC removal for low blood flow occurred in 8.9% of procedures. Conclusion Conversion of TC to TCC by nephrologists had overall infection, catheter patency, and complications similar to data reported in the literature. Vancomycin was not superior to cefazolin as a prophylactic antibiotic.

Fluid Redistribution in Sleep Apnea: Therapeutic Implications in Edematous States

Sleep apnea (SA), a condition associated with increased cardiovascular risk, has been traditionally associated with obesity and aging. However, in patients with fluid-retaining states, such as congestive heart failure and end-stage renal disease, both prevalence and severity of SA are increased. Recently, fluid shift has been recognized to play an important role in the pathophysiology of SA, since the fluid retained in the legs during the day shifts rostrally while recumbent, leading to edema of upper airways. Such simple physics, observed even in healthy individuals, has great impact in patients with fluid overload. Correction of the excess fluid volume has risen as a potential target therapy to improve SA, by attenuation of nocturnal fluid shift. Such strategy has gained special attention, since the standard treatment for SA, the positive airway pressure, has low compliance rates among its users and has failed to reduce cardiovascular outcomes. This review focuses on the pathophysiology of edema and fluid shift, and summarizes the most relevant findings of studies that investigated the impact of treating volume overload on SA. We aim to expand horizons in the treatment of SA by calling attention to a potentially reversible condition, which is commonly underestimated in clinical practice.

Relationship between chronic kidney disease and central sleep apnea: the importance of volume management

Dear editor: Nigam et al. [1] described the prevalence of central sleep apnea (CSA) in patients with chronic kidney disease (CKD) through a systematic review, in which they found an aggregate point prevalence of 9.6 % of CSA. Even though they have listed some limitations in this review, such as the small number of studies included, the heterogeneity regarding the definition of sleep-disordered breathing (SDB), and the characterization of central apneas and hypopneas, there are probably some other factors which might have underestimated CSA prevalence in this subgroup of patients. It is well recognized that CSA is more prevalent in edematous states, notably congestive heart failure (CHF). In such condition, the increased left filling pressure leads to pulmonary congestion, which causes stimulation of vagal receptors, with consequent augmentation of respiratory drive, lowering PaCO2 [2]. Nevertheless, not only volume overload and fluid shift but also other factors such as chemoreflex activation and upper airway collapsibility may guide the propensity for both CSA and OSA development [3]. In patients with CHF, factors such as male sex, hypocapnia, atrial fibrillation, and increasing age were already implicated in the pathogenesis of CSA. It is not clear whether such factors have the same impact on CSA in patients with CKD. Even so, the permanent volume overload state remains the most important cause of CSA in edematous states and volemic status is exactly our major concern regarding the findings of this review. Even though patients referred to renal replacement therapies (RRT) have all a unifying characteristic, which is (generally) a creatinine clearance lower than 10 ml/min/ 1.73 m, the similarities among them stop right there. There is a huge variability regarding baseline disease, age, performance status, cardiovascular disease, and residual diuresis. To this extent, there is a variety of hemodialysis (HD) and peritoneal dialysis (PD) modalities, which can be prescribed to CKD patients. The most commonly used—the conventional HD (which is performed on a thrice-week schedule) and the continuous ambulatory peritoneal dialysis (CAPD), in which a dialysate fluid is maintained within the peritoneal cavity throughout the 24-h period—are completely different methods. There are also variations in each modality, such as daily HD, long nocturnal HD, and automated peritoneal dialysis (APD). The choice among all these methods depends upon the clinical characteristics of the patient. Therefore, unlike CHF (which is characterized by chronic volume overload), patients under RRT are an extreme heterogeneous population regarding fluid status. Some patients might present normal diuresis, with no volume retention at all, while others behave as a seesaw: normovolemic after dialysis and hypervolemic during the inter-dialytic interval. Likewise, patients who are under daily dialysis might not exhibit such volemic fluctuations. Some studies have assessed SDB in patients under different RRT methods. In one of them, the conversion from conventional HD to long nocturnal hemodialysis, which is usually All authors certify that they have no affiliations with or involvement in any organization or entity with any financial interest (such as honoraria, educational grants, participation in speakers’ bureaus, membership, employment, consultancies, stock ownership, or other equity interest and expert testimony or patent-licensing arrangements), or non-financial interest (such as personal or professional relationships, affiliations, knowledge, or beliefs) in the subject matter or materials discussed in this manuscript.

Dialysate and Serum Potassium in Hemodialysis

To the Editor: Hung and Hakim described factors associated with sudden cardiac death in patients on hemodialysis therapy, using a sample case inwhich a patient had cardiac arrest in the second half of dialysis and basing the subsequent discussion on possible factors that could have contributed to this outcome.Given the article topic, the authors focus on potassium balance and note that normal or slightly elevated predialysis serum potassium levels and using a lower dialysate potassium concentration in patients with hyperkalemia have been associated with the greater likelihood of survival. Because the reported case had a normal predialysis potassium level and a fairly common dialysate potassium concentration (2 mEq/L), we wonder if overcorrection of acidosis may have contributed to cardiac arrest. A publication from DOPPS (Dialysis Outcomes and Practice Patterns Study) demonstrated that high dialysate bicarbonate concentration may increase mortality. In this regard, we recently described an association between higher dialysate bicarbonate concentration (.38 mEq/L) and greater decline in cardiac index during hemodialysis, independent of serum to dialysate potassium gradient and ultrafiltration rate. Guidelines focusing only on the target predialysis serum bicarbonate level of

High Dialysate Calcium Concentration May Cause More Sympathetic Stimulus During Hemodialysis

22 mEq/L potentially overlook the important role of myocardial depression during hemodialysis on cardiovascular events. This letter intends to both congratulate the authors for their excellent review and call attention to the fact that, although acidosis is deleterious, alkalemia may be similarly harmful. Which one may be a more substantial contributor to sudden cardiac death remains debatable.

Factors associated with subendocardial ischemia risk in patients on hemodialysis

Background/Aims: Acute activation of sympathetic activation during hemodialysis is essential to maintain blood pressure (BP), albeit long-term overactivity contributes to higher mortality. Low heart rate variability (HRV), a measure of autonomic nervous system activity, and abnormal ankle-brachial index (ABI) are associated with higher mortality in patients on hemodialysis. In this study, we assessed HRV and ABI pre and post dialysis in incident patients on hemodialysis using high (1.75mmol/l) and low (1.25mmol/l) dialysate calcium concentration (DCa). Methods: HRV was measured as the ratio between low frequency and high frequency power (LF/HF). Thirty patients (age 47±16 years, 67% men) were studied in two consecutive mid-week hemodialysis sessions. Results: Mean BP variation was positive with DCa 1.75 and negative with DCa 1.25 [4.0 (-6.0, 12.2 mmHg) vs. -3.2 (-9.8, 1.3 mmHg); p=0.050]. Reduction of ABI from pre to post HD was related to higher sympathetic activity (p=0.031). The increase in LF/HF ratio was higher with DCa 1.75 (58.3% vs. 41.7% in DCa 1.75 and 1.25, respectively, RR 2.8; p=0.026). Conclusion: Although higher DCa is associated with better hemodynamic tolerability during hemodialysis, this occurs at the expense of increased sympathetic activity. Higher sympathetic activity was associated with a decrease of ABI during hemodialysis.

Parathyroidectomized patients have impaired capacity of peripheral vascular constriction during hemodialysis

Introduction Bone metabolism disorder (BMD) and vascular dysfunction contribute to excess cardiovascular mortality observed in hemodialysis patients. Vascular dysfunction, a new marker of atherosclerosis, can play a role in this risk. Even though associated with higher mortality in the general population, such vascular evaluation in patients on hemodialysis has not been extensively studied. Methods In this cross-sectional study, hemodialysis patients were submitted to flow-mediated dilation, subendocardial viability ratio (SEVR) and ejection duration index assessment, in order to estimate the impact of BMD markers on vascular dysfunction. Results A matched cohort of patients with (n = 16) and without (n = 11) severe secondary hyperparathyroidism (SHPT) was studied. Additionally, time spent under severe SHPT was also evaluated. Patients with severe SHPT had lower SEVR and higher ejection duration index, indicating higher cardiovascular risk. Lower SEVR was also associated to diastolic blood pressure (r = 0.435, p = 0.049), serum 25-Vitamin-D levels (r = 0.479, p = 0.028) and to more time spent under severe secondary hyperparathyroidism (SHPT), defined as time from PTH > 500pg/ml until parathyroidectomy surgery or end of the study (r = -0.642, p = 0.027). In stepwise multiple regression analysis between SEVR and independent variables, lower SEVR was independently associated to lower serum 25-Vitamin-D levels (p = 0.005), female sex (p = 0.012) and more time spent under severe SHPT (p = 0.001) in a model adjusted for age, serum cholesterol, and blood pressure (adjusted r² = 0.545, p = 0.001). Conclusion Subendocardial perfusion was lower in patients with BMD, reflecting higher cardiovascular risk in this population. Whether early parathyroidectomy in the course of kidney disease could modify such results still deserves further investigation.

Obstructive Sleep Apnea, Hypertension, and Their Interaction on Arterial Stiffness and Heart Remodeling

Parathyroidectomy (PTx) seems to improve cardiovascular outcomes and reduce blood pressure levels. However, the effect of PTx on hemodynamic changes during hemodialysis (HD) is still overlooked. This was a prospective cohort design. Patients with end‐stage renal disease on maintenance HD were included. Diabetes and nonsinusal rhythm were exclusion criteria. History of PTx was recorded. Finometer monitor was used to access parameters immediately pre‐ and post‐HD sessions. Cardiac index (CI) variation (ΔCI) and peripheral arterial resistance variation (ΔPAR) were the variables of interest. Biochemical and echocardiographic data were also obtained. PTx patients (n = 11) were matched to non‐PTx patients (n = 20). ΔPAR was lower in PTx group in comparison with non‐PTx group (P = 0.039), which was independent of parathyroid hormone (PTH) levels. Multiple regression analysis showed that PTx, ΔCI, and dialysate calcium remained independently associated with PAR variation and even adjusted for ultrafiltration rate (adjusted r2 = 0.64). In conclusion, parathyroidectomized patients have impaired capacity of vasoconstriction in response to ultrafiltration, an effect independent of serum PTH levels. Further studies are needed to elucidate mechanisms explaining the interaction between PTx and systemic vascular tonus.