A double-blind evaluation of sodium gradient hemodialysis

In a double-blind, crossover trial, 7 chronic hemodialysis patients underwent three 4-week treatment periods. During one period, dialysate contained 135 mEq/l sodium. During another period, dialysate contained 143 mEq/l sodium. During the remaining period, we used "sodium gradient' dialysate, the sodium concentration of which was decreased from 160 to 133 mEq/l during each 4-hour dialysis session. Ultrafiltration was performed at a constant rate to achieve a predetermined post-dialysis weight. Interdialytic weight gain, thirst, blood pressure control, and incidence of side effects were monitored. There was a significant difference in interdialytic weight gain for the 3 treatments (p = 0.005). Interdialytic weight gain using 135 mEq/l sodium dialysate (2.2 +/- 0.9 kg, mean +/- SD) was significantly less than that using either 143 mEq/l sodium dialysate (2.6 +/- 0.8 kg) or sodium gradient dialysate (2.8 +/- 0.7 kg). Self-reported thirst tended to be less severe with 135 mEq/l sodium dialysate than with 143 mEq/l sodium dialysate or with sodium gradient dialysate, but changes in thirst were not statistically significant (p = 0.13). The incidence of intradialytic hypotensive episodes was comparable with the 3 levels of dialysate sodium. The results suggest that the described sodium gradient method does not prevent the increased interdialytic weight gain and thirst seen with other forms of high-sodium dialysis, and probably does not reduce the incidence of side effects.     

Effects of high sodium dialysate during maintenance hemodialysis

The effects of high sodium 144 mmol/l (mEq/l) dialysate were studied in normotensive, hypertensive and anephric chronic hemodialysis patients. Comparisons of blood pressures, weights and side effects associated with the hemodialysis procedure were made between two 6-month periods using dialysate sodium concentration of 133 mmol/l (mEq/l), followed by a high dialysate sodium of 144 mmol/l (mEq/l), each patient acting as his own control. No difference was found in the frequency of cramps or 'disequilibrium' side effects (nausea, vomiting, headache, restlessness). High sodium dialysate is beneficial for normotensive and anephric patients in reducing dialysis-induced hypotension and was not associated with any deleterious effects on long-term blood pressure control. In hypertensive patients, the benefit is less clear, and hypertension may increase.     

High and low sodium acetate haemodialysis and ultrafiltration

CA levels, PRA, PAC responses to low and high sodium dialysates in haemodialysed patients were investigated. Increased levels of dopamine (DA), adrenaline (A) and noradrenaline (NA) were found during dialysis and ultrafiltration with high sodium dialysate (148 mEq/l), and significantly higher PRA with low sodium dialysate (131 mEq/l). PAC slightly but significantly decreased during dialysis with low sodium dialysate and significantly increased during ultrafiltration. The present results suggest that sodium dialysate concentration has a significant influence on the function of the autonomic system, PRA and PAC in haemodialysed patients.     

Comparison of point-of-care versus central laboratory measurement of electrolyte concentrations on calculations of the anion gap and the strong ion difference

BACKGROUND: Clinicians calculate the anion gap (AG) and the strong ion difference (SID) to make acid-base diagnoses. The technology used is assumed to have limited impact. The authors hypothesized that different measurement technologies markedly affect AG and SID values. METHODS: SID and AG were calculated using values from the point-of-care blood gas and electrolyte analyzer and the central hospital laboratory automated blood biochemistry analyzer. Simultaneously measured plasma sodium, potassium, and chloride concentrations were also compared. RESULTS: Mean values for central laboratory and point-of-care plasma sodium concentration were significantly different (140.4 +/- 5.6 vs. 138.3 +/- 5.9 mm; P < 0.0001), as were those for plasma chloride concentration (102.4 +/- 6.5 vs. 103.4 +/- 6.0 mm; P < 0.0001) but not potassium. Mean AG values calculated with the two different measurement techniques differed significantly (17.6 +/- 6.2 mEq/l for central laboratory vs. 14.5 +/- 6.0 mEq/l for point-of-care blood gas analyzer; P < 0.0001). Using the Stewart-Figge methodology, SID values also differed significantly (43.7 +/- 4.8 vs. 40.7 +/- 5.6 mEq/l; P < 0.0001), with mean difference of 3.1 mEq/l (95% limits of agreement, -3.4, 9.5 mEq/l). For 83 patients (27.6%), differences in AG values were as high as 5 mEq/l or more, and for 46% of patients whose AG value was outside the reference range with one technology, a value within normal limits was recorded with the other. CONCLUSIONS: Results with two different measurement technologies differed significantly for plasma sodium and chloride concentrations. These differences significantly affected the calculated AG and SID values and might lead clinicians to different assessments of acid-base and electrolyte status.     

Studies on the sodium concentration of dialysate solution for continuous ambulatory peritoneal dialysis]

Overloaded sodium(Na) induces the expansion of extracellular volume in case with severe renal insufficiency. Accordingly, in patients undergoing CAPD, the Na balance via trans-peritoneum is the critical determinant of fluid state. This study was performed to clarify the trans-peritoneal Na kinetics in patients using standard dialysate (Na: 132mEq/1,2-1), and to explore the clinical effects of lower Na concentration solution. Peritoneal dialysis effluent obtained from 87 patients was analysed [1.5% dextrose dialysate (D): 33 bags, 2.5%D: 54 bags]. In terms of net-Na removal, no significant relation was found with serum Na level. Whereas, a significant positive relation was found with ultrafiltration (UF) volume (p < 0.01). Net-Na removal was 10.0 +/- 3.3mEq in 1.5%D and 30.2 +/- 1.8 mEq in 2.5%D (mean +/- SEM). On the other hand, ultra low sodium concentration dialysate (ULNaD, Na level: 98mEq/1, Osm:340mOsm/1, 2l) was effectively used for the purpose of increasing Na removal. Net-Na removal was 78.1 +/- 5. 6mEq after 4-hr dwelling (n = 18). ULNaD was applied to ten patients who showed signs of overhydration, using once a day consecutively instead of standard one. After 9 days (mean) in this regimen, signs of overhydration were disappeared. Significant reductions in their body weight and fall in blood pressure were found compared to the periods before commencement of ULNaD, showing remarkable increase in Na removal (p < 0.01, respectively). No significant changes were found in serum Na level or UF volume.(ABSTRACT TRUNCATED AT 250 WORDS)     

Acetate-Free Biofiltration: A Viable Alternative to Bicarbonate Dialysis

Eight patients were studied during four sessions of acetate-free biofiltration (AFBF). AFBF is a new dialysis technique with no base replacement agents in the dialysate and with the addition in postdilution mode of bicarbonate (HCO3) solution directly into the extracorporeal blood circuit. In this study the effects on acid-base balance of different infusions of sodium bicarbonate (NaHCO3) ranging from 751 to 1,002 mEq per session was evaluated. There were significant positive correlations between the HCO3 infused and net HCO3 gained (r = 0.776, p less than 0.0001) and between HCO3 infused and plasma intratreatment HCO3 changes (n = 0.562, p less than 0.001). Stepwise multiple linear regression analysis demonstrated that HCO3 infused and plasma predialysis HCO3 values played the major role in HCO3 balance in AFBF. The best correction of metabolic acidosis was obtained with the infusion of 900-1,000 mEq of HCO3. The use of substitution fluid with 145 mEq/L of Na concentration avoids the risk of a positive intratreatment Na balance.     

Calcium mass transfer in peritoneal dialysis patients using 2.5 mEq/l calcium dialysate.

Standard peritoneal dialysate has a relatively high calcium concentration of 3.5 mEq/l. Peritoneal dialysis patients thus gain calcium from the dialysate which contributes to the risk of hypercalcemia. Dialysate with 2.5 mEq/l calcium is now available. Theoretically, using dialysate with this calcium content, calcium transfer should be negative (from the patient into the dialysate) when the patient is hypercalcemic, and positive when the patient is normocalcemic or hypercalcemic. Thus, 2.5 mEq/l calcium dialysate may allow larger doses of calcium carbonate to be prescribed. We compared calcium mass transfer (CMT) in 17 stable peritoneal dialysis patients using 3.5 and 2.5 mEq/l calcium dialysate. A solution of 2.05 l, 1.5 g/dl dextrose was dwelled for 4 hours. Calcium was measured in the drained dialysate and serum (total and ionized). Mean CMT was 0.7 +/- 0.5 mEq/exchange using 3.5 mEq/l calcium dialysate and -0.9 +/- 0.9 mEq/exchange using 2.5 mEq/l calcium dialysate (p less than 0.0001). At the time of the CMT studies, the mean serum ionized calcium levels were identical for the two groups (2.6 mEq/l). CMT correlated inversely with serum total calcium, serum ionized calcium, and drained dialysate volume. During hypercalcemia calcium transfer was from the dialysate to the patient when 3.5 mEq/l calcium dialysate was used, but from the patient to the dialysate when 2.5 mEq/l calcium dialysate was used. We conclude that 2.5 mEq/l calcium dialysate is effective in removing calcium and will be helpful in preventing hypercalcemia when large doses of oral calcium compounds are prescribed as a phosphate binder.     

Comparison of Point-of-Care Versus Central Laboratory Measurement of Electrolyte Concentrations on Calculations of the Anion Gap and the Strong Ion Difference

Background: Clinicians calculate the anion gap (AG) and the strong ion difference (SID) to make acid-base diagnoses. The technology used is assumed to have limited impact. The authors hypothesized that different measurement technologies markedly affect AG and SID values.

Methods: SID and AG were calculated using values from the point-of-care blood gas and electrolyte analyzer and the central hospital laboratory automated blood biochemistry analyzer. Simultaneously measured plasma sodium, potassium, and chloride concentrations were also compared.

Results: Mean values for central laboratory and point-of-care plasma sodium concentration were significantly different (140.4 +/- 5.6 vs. 138.3 +/- 5.9 mm;P < 0.0001), as were those for plasma chloride concentration (102.4 +/- 6.5 vs. 103.4 +/- 6.0 mm;P < 0.0001) but not potassium. Mean AG values calculated with the two different measurement techniques differed significantly (17.6 +/- 6.2 mEq/l for central laboratory vs. 14.5 +/- 6.0 mEq/l for point-of-care blood gas analyzer;P < 0.0001). Using the Stewart-Figge methodology, SID values also differed significantly (43.7 +/- 4.8 vs. 40.7 +/- 5.6 mEq/l;P < 0.0001), with mean difference of 3.1 mEq/l (95% limits of agreement, -3.4, 9.5 mEq/l). For 83 patients (27.6%), differences in AG values were as high as 5 mEq/l or more, and for 46% of patients whose AG value was outside the reference range with one technology, a value within normal limits was recorded with the other.     

Studies on Circulatory Stability During Bicarbonate Hemodialysis with Constant Dialysate Sodium Versus Acetate Hemodialysis with Sequential Dialysate Sodium

Eight stable patients on maintenance hemodialysis were studied while undergoing (a) acetate hemodialysis with a sequential dialysate sodium concentration from 147 to 137 mEq/L (SNa-HDA) and (b) bicarbonate hemodialysis with a constant dialysate sodium concentration of 140 mEq/L (HDB). Circulatory behavior was observed during both of these methods, and both were found to allow a high volume removal. However, as a consequence of the high sodium load during SNa-HDA, volume was shifted from the extra- to the intravascular space. This stabilizing effect on the circulation disappeared with the sequential decrease of dialysate sodium concentration (despite a constant plasma sodium concentration (despite a constant plasma sodium concentration of approximately 140 mEq/L), which was concomitant with a significant decline of the mean arterial blood pressure and an inadequate compensation of the metabolic acidosis. In contrast, a better circulatory response to comparable volume removal was found during HDB, expressed by a stable mean arterial blood pressure in the presence of well-balanced arterial acid-base values.     

Dialysis-induced change in erythrocyte volume: effect on change in blood volume calculated from packed cell volume

Blood volume (BV) change during hemodialysis is often monitored by packed cell volume (PCV). This assumes erythrocyte volume is constant. We tested this by dialyzing 5 patients for 2 hours against high (154 mmol/l), normal (140 mmol/l) and low (126 mmol/l) dialysate sodium concentrations. Erythrocyte water content, calculated from measured blood and plasma water contents, decreased with high and increased with low dialysate sodium concentrations. Erythrocyte volume, calculated from mean corpuscular hemoglobin concentration (MCHC) decreased 3.8% with high concentration dialysate and increased 2.5% when dialysate concentration was low. These changes correlated significantly (r = 0.80, p less than 0.01) with alterations in plasma sodium. Mean corpuscular volume (MCV), measured with a Coulter-S Plus Counter did not alter because of a methodological artefact. BV change can be calculated from PCV when plasma concentrations of osmotically active substances are changed only if allowance is made for altered erythrocyte volume.     

Sympathetic activity response to changes in the intake of sodium in chronic renal failure

Sympathetic response to differences in sodium intake in patients with chronic renal failure was investigated. All patients were on haemodialysis, first for 3 weeks with conventional dialysate containing 148 mEq/l of sodium, then for another 3 weeks with the conventional dialysate containing 131 mEq/l of sodium. Increase in noradrenaline (NA), adrenaline (A), dopamine (DA) concentrations and dopamine-beta-hydroxylase (DBH) activity were found during the high-sodium haemodialysis. However, DBH activity in patients was significantly lower than in healthy individuals. A significant correlation was found between the level of plasma NA and systolic blood pressure. The present results suggest that a higher intake of sodium causes dysfunction of the sympathetic system. Supported by the Polish Academy of Sciences.     

Bicarbonate hemodialysis: influence on plasma refilling and hemodynamic stability

The present study compares the effect of sodium bicarbonate (LoNaHCO3, Na = 134, HCO3 = 33 mEq/l) and sodium acetate (LoNaAc, Na = 134, acetate 33 mEq/1)dialysate on the extravascular fluid mobilization (VFM) and hemodynamic changes in 6 patients during 3 h of hemodialysis with equivalent fluid ultrafiltration of about 600 ml/h. The cumulative decrease in plasma volume after 1, 2 and 3 h of dialysis was significantly less during LoNaHCO3 dialysis than during LoNaAc dialysis, with plasma volume almost completely refilled by VFM during the first 2 h of LoNaHCO3 dialysis. High sodium acetate dialysate (HiNaAc, Na = 144, acetate = 33 mEq/1) with equivalent fluid ultrafiltration also resulted in less net decrease in plasma volume and greater VFM than LoNaAc, although the temporal pattern of refilling was somewhat different from that during LoNaHCO3: rapid and complete refilling during the early portion of LoNaHCO3, slower and more progressive refilling during HiNaAc, with similar cumulative refilling for LoNaHCO3 and HiNaAc by 3 h. Mean arterial pressure (MAP) tended to decrease during LoNaAc dialysis, whereas MAP remained stable during LoNaHCO3 and increased slightly during HiNaAc. This study, therefore, suggests that improved hemodynamic stability utilizing bicarbonate dialysate may be due, in part, to greater plasma refilling and better preservation of plasma volume.     

Potassium supplementation via the dialysate in continuous ambulatory peritoneal dialysis

A small percentage of patients treated with continuous ambulatory peritoneal dialysis (CAPD) may become hypokalemic. Since both the intravenous and oral routes for potassium repletion have disadvantages, we studied the feasibility, effectiveness, and safety of acute potassium loading via the dialysate in patients on CAPD. Five patients were studied during an exchange containing 20 mEq/L of potassium. This was well tolerated and led to a gradual increase in the plasma potassium concentration (.44 +/- .11 mEq/L) as about three-fourths of the intraperitoneal load was absorbed, most of it by two hours. The greatest increase in the plasma potassium concentration was .63 mEq/L. A separate patient developed intense abdominal pain during an exchange containing 40 mEq/L of potassium. We conclude that the dialysate is a safe and effective route for acute potassium repletion during CAPD when the dialysate potassium concentration does not exceed 20 mEq/L.     

Inappropriate vasopressin secretion (SIADH) in burned patients

To determine if concentration of plasma arginine vasopressin (AVP) is inappropriate for the plasma Na+ concentration in hyponatremic burned patients, we obtained 32 plasma samples from 20 patients with total burn size (TBS) 15 to 80% of body surface on or after postburn day (PBD) 4 in the morning following all-night recumbency. In the 25 samples (17 patients) with hyponatremia, AVP was elevated, 1.6 to 14.3 (normal less than 0.5) pg/ml. Most patients with normal serum Na+ had normal AVP values. Out of the total, nine patients (12 samples) without renal failure or sepsis, selected also for hyponatremia and urinary Na+ greater than or equal to 20 mEq/L, were considered separately. BUN of 11.7 +/- 1.8 mg/dl and plasma glucose of 130 +/- 5.6 mg/dl, Na+ of 130 +/- 1.1 mEq/L, calculated osmolality of 272 +/- 1.6 mosm/kg, and cortisol of 20.4 +/- 1.6 micrograms/dl were associated with a 24-hour fluid intake of 4.3 +/- 0.26 L and urinary output of 2.7 +/- 0.33 L, Na+ of 80 +/- 14 mEq/L, and osmolality of 520 +/- 73 mosm/kg (mean +/- SE). In all of the plasma samples, AVP was markedly elevated (6.9 +/- 1.1 pg/ml). In another study, four hyponatremic burned patients were given a standard water load. Excretion of the water was delayed, and further dilution of the initially hypotonic plasma resulted in a fall of urinary osmolality and plasma AVP. Cutaneous thermal injury can cause resetting of the mechanism linking plasma tonicity and AVP secretion resulting in dilutional hyponatremia. This syndrome occurs in the absence of gross physiologic perturbations such as volume depletion or adrenal insufficiency.     

Hydrostatic Ultrafiltration During Hemodialysis Using Decreasing Sodium Dialysate

Twelve patients underwent hemodialysis using dialysate containing 130 mEq/L sodium, and, on a separate occasion, dialysis using a dialysate of constantly decreasing sodium concentration (from 150 to 133 mEq/L). Hydrostatic ultra-filtration during dialysis was performed at a constant rate (900 ml/hr) during both treatments, and was continued until a substantial drop in mean arterial pressure (-15%) or symptoms were observed. A double-blind comparison of the two treatment modalities was thus achieved.
At the end of ultrafiltration, significantly more fluid had been removed using decreasing sodium dialysate (2.9 ± 0.3 kg) than when using the low-sodium dialysate (1.9 ± 0.2 kg, P<0.001). Plasma sodium concentration at the end of ultra filtration using decreasing sodium dialysate was not significantly different from the predialysis level.
Hydrostatic ultrafiltration using a dialysate of decreasing sodium level may prove to be a useful means of removing excess fluid asymptomatically from dialysis patients.     

Circulating sodium in acute meningitis

BACKGROUND: In acute meningitis hyponatremia is common and traditionally attributed exclusively to inappropriate water retention. However, the exact mechanisms underlying hyponatremia are unknown. METHODS: The files of 300 pediatric patients with acute bacterial (n = 190) or aseptic (n = 110) meningitides were retrospectively analyzed. RESULTS: The plasma sodium level ranged from 122 to 148 mmol/l and was low (<133 mmol/l) in 97 patients. Fluid volume contraction was significantly more pronounced in hyponatremia (median 6.0. 10(-2)) than in normonatremia (median 2.0. 10(-2)). The fractional sodium excretion was less than 1.00. 10(-2) in the 26 hyponatremic children with this measurement. CONCLUSION: In acute meningitis hyponatremia is not exclusively brought about by inappropriate water retention.     

Clinical effects of long-term use of neutralized dialysate for continuous ambulatory peritoneal dialysis.

The long-term effects of neutralized dialysate used in continuous ambulatory peritoneal dialysis (CAPD) were evaluated in 8 well-controlled patients. Twelve milliliters of 8.4% sodium bicarbonate was added to Dianeal PD-1 immediately before every administration. The final pH was 6.8 and the concentration of sodium bicarbonate was 6 mmol/l. The final sodium level was 138 mEq/l. This dialysate was used for 5 months. For 2 months before and 3 months after this period, Dianeal PD-2 was used as the dialysate for comparison. Blood bicarbonate levels significantly improved during the use of the neutralized dialysate. Blood sodium, chloride and magnesium levels and the effluent volume significantly increased. Sodium balance improved during the period when neutralized dialysate was used. Total leukocyte counts in the effluent decreased, and leukocyte viability increased. Abdominal distention, abdominal pain during instillation, nausea and headache improved. No side effects, including peritonitis, occurred during the trial of neutralized dialysate. The results suggest that this dialysate was less irritating to the peritoneal membrane than the control dialysate and that the therapeutic effects were satisfactory.     

Sodium modeling in hemodiafiltration.

A computer model was developed to simulate sodium and water kinetics during hemodiafiltration (HDF), acetate-free biofiltration (AFB) and hemodialysis (HD). Multiple regression analysis of the results of 3,240 simulated applications of the model (1,620 HDF, 1,080 AFB, 540 HD) showed that, during HDF and AFB, there is a close correlation (R2 = 0.92 and 0.91) between plasma water sodium concentration [( Na+P]) and a set of three variables: 1) the sodium gradient between plasma water and dialysate, 2) the sodium concentration of the substitution fluid and 3) ultrafiltration (UF) rate. With HD, a close correlation (R2 = 0.94) was found between changes in [Na+P] and combined changes in sodium gradient and the UF rate. On this basis, a regression equation was formulated for each procedure which allowed a reliable prediction of final [Na+P] to be made on the basis of knowledge of the imposed Na gradient, the programmed infusion (during HDF and AFB), and the UF rate. Clinical validation of the model was obtained in 12 patients: predicted final [Na+P] agreed well with the values measured by means of direct potentiometry (141.9 vs. 142.1 mEq/liter; P = NS), with a mean difference (-0.16 mEq/liter) and limits of agreement (+0.8 to -1.03 mEq/liter) fully acceptable for clinical purposes.(ABSTRACT TRUNCATED AT 250 WORDS)