Association between Low Serum Bicarbonate Concentrations and Cardiovascular Disease in Patients in the End-Stage of Renal Disease

Renoprotective strategies

Kidney disease remains a condition with an increasing incidence, high morbidity and mortality associated with cardiovascular events. The incidence of end-stage renal disease is expected to increase. Despite of the technical improvement, dialysis never achieved a full clearance of the blood dialysis. Therefore, the demand for new renoprotective measures has never been greater. Here, we report new strategies for preventing renal damage.

Pathophysiological concepts and screening of cardiovascular disease in dialysis patients

Dialysis patients experience 10-20 times higher cardiovascular mortality than the general population. The high burden of both conventional and nontraditional risk factors attributable to loss of renal function can explain higher rates of cardiovascular disease (CVD) morbidity and death among dialysis patients. As renal function declines, uremic toxins accumulate in the blood and disrupt cell function, causing cardiovascular damage. Hemodialysis patients have many cardiovascular complications, including sudden cardiac death. Peritoneal dialysis puts dialysis patients with end-stage renal disease at increased risk of CVD complications and emergency hospitalization. The current standard of care in this population is based on observational data, which has a high potential for bias due to the paucity of dedicated randomized clinical trials. Furthermore, guidelines lack specific guidelines for these patients, often inferring them from non-dialysis patient trials. A crucial step in the prevention and treatment of CVD would be to gain better knowledge of the influence of these predisposing risk factors. This review highlights the current evidence regarding the influence of advanced chronic disease on the cardiovascular system in patients undergoing renal dialysis.

Variety of Cardiac Events in Hospitalized Chronic Kidney Disease Patients

Objective This study assessed the variety and frequency of various cardiovascular events in different stages of chronic kidney disease (CKD) patients who were hospitalized due to different causes. Methods This prospective cross-sectional observational analysis was conducted at the Department of Nephrology in The Kidney Centre Post Graduate Training Institute Karachi on all adult CKD (of all stages with or without dialysis) patients, who developed cardiovascular events during their hospital admission either in ward or ICU due to any cause between August 2020 and February 2021. Total of 765 patients got admitted in the given time period and among them, 290 patients developed various cardiovascular events. Baseline data, co-morbidities, clinical features, drug history and management were determined. Results There were a total of 290 patients in our study in which 154 (53.1%) were male and 136(46.9%) were female. Mean age was 57 ± 15.5. Our majority of patients were end-stage renal disease and on maintenance hemodialysis (n=119, 41%) while the most prevalent co-morbid condition was hypertension (n=227, 78.3%) followed by diabetes mellitus (n=204, 70.4%). The most frequent cardiovascular events in CKD patients was the atrial fibrillation 101(34.8%) while 37(12.8%) patients suffered ST-elevation myocardial infarction and supraventricular tachycardia. Patients who had high potassium levels (>5.2) most frequently suffered from atrial fibrillation (n=16, 28.1%) as compared to other cardiovascular events. Conclusion Patients with CKD are at increased risk of having several cardiovascular events. Numerous risk factors involved in the pathogenesis. Among the diverse causes, fluctuations in serum levels of various electrolytes are important causes as certain electrolytes disbalance can trigger various life-threatening cardiac arrhythmias.

Relationship between serum total carbon dioxide concentration and bicarbonate concentration in patients undergoing hemodialysis

Background

Few studies have investigated the relationship between serum total carbon dioxide (CO₂) concentration and bicarbonate ion (HCO₃^-) concentration in patients undergoing hemodialysis. We determined the agreement and discrepancy between serum total CO₂ and HCO₃^- concentrations and the diagnostic accuracy of serum total CO₂ for the prediction of low (HCO₃^- < 24 mEq/L) and high (HCO₃^- ≥ 24 mEq/L) bicarbonate concentrations in hemodialysis patients.

Methods

One hundred forty-nine arteriovenous blood samples from 84 hemodialysis patients were studied. Multiple linear regression analysis was used to determine factors correlated with HCO₃^- concentration. Diagnostic accuracy of serum total CO₂ was evaluated using receiver operating characteristic curve analysis and a 2 × 2 table. Agreement between serum total CO₂ and HCO₃^- concentrations was assessed using Bland-Altman analysis.

Results

Serum total CO₂ concentration was closely correlated with HCO₃^- concentration (β = 0.858, P < 0.001). Area under the curve of serum total CO₂ for the identification of low and high bicarbonate concentrations was 0.989. Use of serum total CO₂ to predict low and high bicarbonate concentrations had a sensitivity of 100%, specificity of 50.0%, positive predictive value of 96.5%, negative predictive value of 100%, and accuracy of 96.6%. Bland-Altman analysis showed moderate agreement between serum total CO₂ and HCO₃^- concentrations. Discrepancies between HCO₃^- and serum total CO₂ concentrations (serum total CO₂ - HCO₃^- ≤ -1) were observed in 89 samples.

Conclusion

Serum total CO₂ concentration is closely correlated with HCO₃^- concentration in hemodialysis patients. However, there is a non-negligible discrepancy between serum total CO₂ and HCO₃^- concentrations.

Changing the paradigm of bicarbonate (HCO3−) hemodialysis prescription in Portugal: a 24-month prospective study

Background

Metabolic acidosis is common in hemodialysis (HD) patients. The KDOQI guidelines therapeutic goal is pre-dialysis HCO3− ≥ 22 mmol/L. The aim of the study was to evaluate an individualized HCO3− hemodialysis prescription as a preventing factor of metabolic changes.

Methods

Twenty-four-month prospective study of patients on online high-flux hemodiafiltration. Every 3 months, HCO3− blood levels were analyzed and hemodialysis HCO3− was changed using the following rules:

Data collected comprised demographic information, renal disease etiology, comorbidities, HD treatment information, and lab results. Statistical analysis was performed using SPSS.

Results

Thirty-one patients were enrolled and completed the follow-up period. At baseline, average serum pH was 7.38 ± 0.06, serum HCO3− 25.92 ± 1.82 mmol/L, and every patient had a 32 mmol/L dialytic HCO3− prescription. At time point 9, average serum HCO3− was 23.87 ± 1.93 mmol/L and 58% of the patients had a dialytic HCO3− prescription of 28 mmol/L. Serum HCO3− differed with statistical significance during time and approached the reference serum HCO3− (23 mmol/L) that we have defined as ideal. Through time, the HCO3− prescription deviated more from the 32 mmol/L initial prescription that was defined as standard.

Conclusions

Our findings suggest that the standard HCO3− prescription of 32 mmol/L should be rethought, as an individualized HCO3− prescription could be beneficial for the patient.

Metabolic and volume status evaluation of hemodialysis patients with and without residual renal function in the long interdialytic interval

Introduction:

It is unclear whether residual renal function (RRF) in dialysis patients can attenuate the metabolic impact of the long 68-hour interdialytic interval, in which water, acid, and electrolyte accumulation occurs.

Objective:

to evaluate serum electrolyte levels, water balance, and acid-base status in dialytic patients with and without RRF over the long interdialytic interval (LII).

Methodology:

this was a single-center, cross-sectional, and analytical study that compared patients with and without RRF, defined by diuresis above 200 mL in 24 hours. Patients were weighed and serum samples were collected for biochemical and gasometric analysis at the beginning and at the end of the LII.

Results:

27 and 24 patients with and without RRF were evaluated, respectively. Patients without RRF had a higher increase in serum potassium during the LII (2.67 x 1.14 mEq/L, p < 0.001), reaching higher values at the end of the study (6.8 x 5.72 mEq/L, p < 0.001) and lower pH value at the beginning of the interval (7.40 x 7.43, p = 0.018). More patients with serum bicarbonate < 18 mEq/L (50 x 14.8%, p = 0.007) and mixed acid-base disorder (57.7 x 29.2%, p = 0.042), as well as greater interdialytic weight gain (14.67 x 8.87 mL/kg/h, p < 0.001) and lower natremia (137 x 139 mEq/L, p = 0.02) at the end of the interval. Calcemia and phosphatemia were not different between the groups.

Conclusion:

Patients with RRF had better control of serum potassium, sodium, acid-base status, and volemia throughout the LII.

Cardiovascular disease in dialysis patients

Cardiovascular disease (CVD) is a highly common complication and the first cause of death in patients with end-stage renal disease (ESRD) on haemodialysis (HD). In this population, mortality due to CVD is 20 times higher than in the general population and the majority of maintenance HD patients have CVD. This is likely due to ventricular hypertrophy as well as non-traditional risk factors, such as chronic volume overload, anaemia, inflammation, oxidative stress, chronic kidney disease–mineral bone disorder and other aspects of the ‘uraemic milieu’. Better understanding the impact of these numerous factors on CVD would be an important step for prevention and treatment. In this review we focus non-traditional CVD risk factors in HD patients.

Factors related to peripheral arterial disease in patients undergoing hemodialysis: the potential role of monocyte chemoattractant protein-1

Peripheral arterial disease (PAD) is substantially prevalent among patients in the end stage of renal disease (ESRD). We considered factors related to peripheral arterial disease in patients undergoing hemodialysis including the important role of monocyte chemoattractant protein-1 (MCP-1) serum concentrations. We studied 150 patients in on-line-predilution hemodiafiltration. Dialysis sufficiency was defined by Kt/V for urea. PAD was defined using clinical criteria, ankle-brachial index and Doppler ultrasound in the lower limbs. MCP-1 serum concentrations were measured using enzyme-linked immunoabsorbed assay (ΕLISA). We performed chi-square tests and logistic regression analysis to investigate risk factors for the prevalence of PAD in these patients including MCP-1 serum concentrations. The patients with manifested PAD had elevated MCP-1, higher BP, higher arterial stiffness markers, higher markers of malnutrition, uncontrolled metabolic acidosis, bone disease and lower obtained dialysis adequacy than the patients without PAD. The association between PAD manifestation and high MCP-1 was found significant (x² = 9.6, p = 0.001). The built logistic regression analysis showed that the high MCP-1 increased the risk for PAD 3.2 (95% C.I 1.3-8.2) folds after adjustment for confounders. PAD was also significantly associated with non-administration of vitamin D agents during dialysis (x² = 3.5, p = 0.04).Malnutrition, low-grade inflammation mainly defined by high MCP-1 serum concentrations, metabolic acidosis and bone disease were included in significant predictors for peripheral arterial disease in patients undergoing hemodiafiltration. The obtained dialysis sufficiency and the therapy during dialysis sessions seem to play an additional role in the demonstration of peripheral vascular disease in these patients.

The Association between Intradialytic Hypertension and Metabolic Disorders in End Stage Renal Disease

Background

Intradialytic hypertension was associated with a high mortality risk. We examined the relationship between intradialytic hypertension and metabolic disorders in hemodialysis treatment patients.

Methods

We studied 76 patients in online hemodiafiltration. Dialysis adequacy was defined by Kt/V for urea. Normalized protein catabolic rate (nPCR), as a marker of protein intake, was calculated. Sodium removal was determined as percent sodium removal. Metabolic acidosis was determined by serum bicarbonate less than 22 mmol/L. Interdialytic urine volume more than 100 ml was recorded. Intradialytic hypertension was defined by an increase in systolic blood pressure equal to 10 mmHg from pre- to posthemodialysis. Arterial stiffness was assessed as carotid-femoral pulse wave velocity (c-fPWV) and carotid augmentation index (AIx). Chi-square tests and logistic regression analysis were applied for intradialytic hypertension prediction.

Results

Patients with intradialytic hypertension were older and had significantly lower hemoglobin, nPCR, urine output, and serum bicarbonate and significantly higher c-fPWV, though similar Kt/V for urea, than patients without intradialytic hypertension. They also had increased sodium removal and pulse pressure related to less urine output. Serum bicarbonate was inversely associated with c-fPWV (r = -0.377, p = 0.001). Chi-square test showed significant association between intradialytic hypertension and serum bicarbonate < 22 mmol/L (x² = 5.6, p = 0.01), which was supported by an adjusted model.

Conclusion

The intradialytic hypertension was significantly associated with metabolic disorders including malnutrition/inflammation and uncontrolled metabolic acidosis in hemodialysis treatment patients. Severe metabolic acidosis may reflect sodium imbalance and hemodynamic instability of these patients resulting in volume overload and increased vascular resistance.

The Association between Intradialytic Hypertension and Metabolic Disorders in End Stage Renal Disease

BACKGROUND

Intradialytic hypertension was associated with a high mortality risk. We examined the relationship between intradialytic hypertension and metabolic disorders in hemodialysis treatment patients.

METHODS

We studied 76 patients in online hemodiafiltration. Dialysis adequacy was defined by Kt/V for urea. Normalized protein catabolic rate (nPCR), as a marker of protein intake, was calculated. Sodium removal was determined as percent sodium removal. Metabolic acidosis was determined by serum bicarbonate less than 22 mmol/L. Interdialytic urine volume more than 100 ml was recorded. Intradialytic hypertension was defined by an increase in systolic blood pressure equal to 10 mmHg from pre- to posthemodialysis. Arterial stiffness was assessed as carotid-femoral pulse wave velocity (c-fPWV) and carotid augmentation index (AIx). Chi-square tests and logistic regression analysis were applied for intradialytic hypertension prediction.

RESULTS

Patients with intradialytic hypertension were older and had significantly lower hemoglobin, nPCR, urine output, and serum bicarbonate and significantly higher c-fPWV, though similar Kt/V for urea, than patients without intradialytic hypertension. They also had increased sodium removal and pulse pressure related to less urine output. Serum bicarbonate was inversely associated with c-fPWV (r = -0.377, p = 0.001). Chi-square test showed significant association between intradialytic hypertension and serum bicarbonate < 22 mmol/L (x² = 5.6, p = 0.01), which was supported by an adjusted model.

CONCLUSION

The intradialytic hypertension was significantly associated with metabolic disorders including malnutrition/inflammation and uncontrolled metabolic acidosis in hemodialysis treatment patients. Severe metabolic acidosis may reflect sodium imbalance and hemodynamic instability of these patients resulting in volume overload and increased vascular resistance.