Dogma disputed: postdialysis increase of aminotransferase values cannot be attributed to an inhibitor removal by hemodialysis.

The objective of this study was to assess changes of aspartate aminotransferase (AST [serum glutamic oxalacetic transaminase]) and alanine aminotransferase (ALT [serum glutamic pyruvic transaminase]) values after a hemodialysis (HD) session. Aspartate aminotransferase and ALT serum values were measured before and after a 4 h HD session in 37 stable patients (group A), before and after a 3.5 h isovolemic HD (IVHD, with a zero ultrafiltration rate) session in eight patients (group B), as well as before and after a session of "isolated ultrafiltration" (IUF) in eight more patients (group C). In group A, mean predialysis AST and ALT serum values that were 16.4 ± 4.3 and 16.0 ± 5.5 IU/L, increased to 20.1 ± 5.4 and 17.7 ± 6.2 IU/L, respectively (p < 0.0001, comparing pre- to postdialysis values, for both). When the postdialysis values were corrected for hemoconcentration induced by ultrafiltration, no differences were found in ALT values. However, postdialysis-corrected AST values (mean 17.7 ± 4.4 IU/l) remained higher compared with predialysis values (p < 0.001). The AST/ALT ratio was 1.13 ± 0.4 for predialysis values and 1.26 ± 0.5 for postdialysis values (p < 0.0001). Predialysis mean serum AST and ALT values did not show any difference after the 3.5 h IVHD sessions (group B), but increased significantly (p < 0.02) after the removal of 1.7 ± 0.2 L of fluid by IUF (group C). In chronic HD patients, postdialysis serum AST and ALT values increased significantly compared with predialysis values. This increment is mainly due to hemoconcentration induced by ultrafiltration and cannot be attributed to the removal of an aminotransferase inhibitor by HD.

Subtherapeutic serum vancomycin concentrations during on-line hemodiafiltration.

The aim of the study is to study vancomycin serum concentration changes during on-line hemodiafiltration (OL-HDF) and determine whether administration of vancomycin during the last hour of OL-HDF provides therapeutic serum concentrations. Vancomycin was administered intravenously at a dose of 15 mg/kg to 17 chronic hemodialysis patients who were enrolled into two study groups (A and B). In group A patients (n = 11), vancomycin was administered immediately postdialysis. Forty-three hours later, a 4-hour OL-HDF session was performed. Blood samples (S) for vancomycin measurement were drawn before, during, and after the session. In group B patients (n = 6), vancomycin was administered during the last hour of a 4-hour OL-HDF session on Monday. Vancomycin serum concentrations were measured postdialysis, as well as before and after the next two dialysis sessions of the week. In group A patients, mean vancomycin concentrations were reduced by 50% (S(pre): 10.2 ± 1.4 µg/ml, S(post): 5.0 ± 0.9 µg/ml). Vancomycin dialysance was 74.6 ± 29.3 ml/min, while the volume of distribution was 0.42 L/kg. In group B patients, mean vancomycin concentrations before the beginning of Wednesday and Friday dialysis sessions were 3.1 ± 0.7 and 1.4 ± 0.4 µg/ml, respectively. Postdialysis administration of vancomycin followed by OL-HDF resulted in a 50% reduction of vancomycin serum concentrations. Administration during the last treatment hour of OL-HDF results in subtherapeutic vancomycin serum concentrations over the course of the subsequent inter- and intradialytic intervals.

The anticoagulant activity of enoxaparin sodium during on-line hemodiafiltration and conventional hemodialysis.

To study and compare the anticoagulant activity of enoxaparin sodium during on-line hemodiafiltration (OL-HDF) and conventional hemodialysis (C-HD). Enoxaparin was administered as an anticoagulant to 21 hemodialysis patients at the beginning of a single 4-hour OL-HDF session as an intravenous bolus dose of 80 IU/kg [DOSAGE ERROR CORRECTED] On-line hemodiafiltration was performed using a high-flux polyester polymer alloy dialyzer and a total of 18 L replacement fluid (session A). One week later, the study was repeated in the same patients during a single 4-hour session of C-HD using a low-flux polysulfone dialyzer (session B). Blood samples for the measurement of Hb, blood urea and nitrogen (BUN), activated partial thromboplastin time (APTT), and anti-Xa levels were taken before each study session and 5-minute postdialysis. In 13 more patients, the same study was performed during OL-HDF using a high-flux polysulfone dialyzer (session C). No differences were found between sessions A, B, and C when predialysis values for Hb, BUN, APTT, and anti-Xa were compared. The mean postdialysis APTT and anti-Xa values were 32.5+/-3.8 seconds and 0.19+/-0.11 IU/mL, respectively, in session A, 39.0+/-5.0 seconds and 0.71+/-0.17 IU/mL in session B, and 33.8+/-3.1 seconds and 0.35+/-17 IU/mL in session C (A vs. B, P<0.0001, for both parameters, A vs. C, P<0.003 for anti-XA, and B vs. C, P<0.005, for both parameters). The anticoagulant activity of enoxaparin sodium is decreased significantly during a 4-hour OL-HDF session compared with to a similar session of C-HD. The degree of the reduction seems to depend on the dialyzer's membrane.

HCO3 increment in arterial line can reveal significant vascular access recirculation in high-flux hemodialysis: a preliminary report.

We report a new and simple way that can reveal the presence of vascular access recirculation (VAR) in patients undergoing hemodialysis (HD). Acid-base and blood gas parameters (pH, pO(2), pCO(2), and HCO(3)) were measured in blood samples drawn from an arterial fistula needle before the initiation of HD and from arterial and venous lines simultaneously 5 min later, in 31 patients (group A). Vascular access recirculation was measured using the glucose infusion test (GIT) immediately after the withdrawal of the 5-min samples. The same study was repeated in 30 patients in whom HD lines were reversed (group B). A comparison with baseline (predialysis) values of an analysis of the arterial line in group A at 5 min revealed that pCO(2) increased by 1.14+/-2.5 mmHg and HCO(3) by 0.6+/-0.6 mM/L (p<0.02 and p<0.00001, respectively). The corresponding pO(2) and pH values did not show significant differences. Glucose infusion test at 5 min (GITa) was -0.058+/-0.03%. A comparison with baseline (predialysis) values of an analysis of the arterial line in group B at 5 min revealed that pCO(2) increased by 7.7+/-3.5 mmHg and HCO(3) by 2.9+/-1.0 mM/L (p<0.000001 in each case). The pH level was significantly lower in comparison with baseline values (p<0.00001), while pO(2) did not show a significant difference. Glucose infusion test at 5 min (GITb) was 12.0+/-6.1% (p<0.000001 in comparison with GITa values). Clinically significant VAR was defined as HCO(3) increment >1.8 mM/L, based on the receiver-operating characteristics curve, which showed a threshold value of HCO(3) increment >1.8 mmol/L as a predictor of GIT recirculation. Five minutes after the initiation of high-flux HD with a 0 ultrafiltration rate, there is a small increment in arterial HCO(3) values relative to predialysis values. Clinically significant VAR is present when this increment is higher than 1.8 mM/L.

pO2 and pCO2 increment in post-dialyzer blood: the role of dialysate.

Blood returning from a dialyzer during hemodialysis has a higher pO2 and pCO2 content than blood entering the dialyzer, and this has been attributed to the dialysate. The present study investigates this phenomenon. Acid-base and blood-gas parameters (pH, pO2, pCO2 and HCO3) were measured in three groups of stable chronic hemodialysis patients (A, B, and C) undergoing high-flux hemodialysis. In group A (n = 15), "arterial" (a) and "venous" (v) samples were withdrawn simultaneously before dialysis (samples A0), 5 min after circulation of the blood with the dialysate in the by-pass mode (samples A5), and 5 min after high-flux hemodialysis at a zero ultrafiltration rate (samples A10). In group B (n = 11) (a) and (v) samples were withdrawn simultaneously before dialysis (samples B0), 5 min after isolated-ultrafiltration with closed dialysate ports ("isolated-closed" ultrafiltration) (samples B5), and 5 min after high-flux hemodialysis at a zero ultrafiltration rate (samples B10). In group C (n = 14), after an initial arterial blood sample withdrawal before hemodialysis (sample C0), high-flux hemodialysis at a zero ultrafiltration rate was initiated. Five minutes later, blood and dialysate samples were withdrawn simultaneously from the hemodialysis lines (samples C5). In all cases blood and dialysate (bicarbonate) flow rates were set at 0.300 and 0.700 L/min, respectively. FLX-18 hemodialyzers (membrane PEPA 1.8 m2) were used in this study. Analysis of variance revealed significant changes only in venous samples. A comparison of arterial and venous samples revealed no differences between groups A and B before the initiation of dialysis (A0a vs. A0v and B0a vs. B0v, P = NS). The pO2 content was higher in A5v samples than in A5a samples (83.5 +/- 11.2 vs. 88.8 +/- 14.0 mm Hg, P < 0.02), while the level of HCO(3) was higher in A5a samples than in A5v samples (20.8 +/- 2.0 vs. 20.4 +/- 1.8 mEq/L, P < 0.05). A10a samples possessed a higher pH and lower levels of pO2, pCO2, and HCO3 in comparison to A10v samples (P < 0.001 for all). Mean pO2 and pCO2 values in A5v and A10v samples increased by 6.3% and 12.1% and by 1.29% and 52% in comparison to corresponding values of A5a and A10a samples, respectively. The pO2 level was the only parameter that differed significantly between B5a and B5v samples (B5a = 84.6 +/- 10.1 vs. B5v = 98.0 +/- 12.6 mm Hg, P < 0.005). B10a samples possessed a higher pH and lower levels of pCO2, pO2, and HCO3 in comparison to B10v samples (P < 0.0005 for all comparisons). Mean pO2 and pCO2 values in B5v and B10v samples increased by 16.2% and 16.3% and by -0.29% and 64.8% in comparison to corresponding values of B5a and B10a samples, respectively. C5a samples possessed a higher pH and lower levels of pCO2, pO2, and HCO3 in comparison to C5v samples (P < 0.001 for all). Mean pO2 and pCO2 values in C5v samples were, respectively, 16.0% and 65.0% higher than corresponding values of C5a samples. These results indicate that blood returning from the dialyzer after 5 min of high-flux hemodialysis has a higher pO2 and pCO2 than blood entering the dialyzer, and that this difference is due to O2 and CO2 transfer from the dialysate space into the blood.

Heparin solution locked in acute hemodialysis catheters: impact on activated partial thromboplastin time.

Fifteen patients on hemodialysis, wearing acute dual lumen hemodialysis catheters (DLHCs) locked with a 4 ml heparin solution (HS) containing 7,500 IU of conventional heparin (3,750 IU/lumen), were studied. After the preexisting HS was aspirated and discarded, 10 ml of blood was withdrawn from each lumen in a syringe. Then, two 3 ml blood samples (A and B) were withdrawn in a row from the venous lumen; a third blood sample (C) was withdrawn from a peripheral vein, and the 20 ml of blood in the syringe was returned to the patient. Patient to control ratios of activated partial thromboplastin time (aPTT) in samples A, B, and C were 2.87 +/- 1.04, 2.02 +/- 0.85, and 1.06 +/- 0.14, respectively (p < 0.002 comparing A to B and B to C). In these patients, we also studied the effect of the same HS on the aPTT, 10 minutes after the filling of the DLHCs postdialysis. A blood sample (H1) was withdrawn at the end of the session; 10 minutes after injecting each lumen of the DLHC with a 2 ml HS containing 3,750 IU of heparin, a second blood sample (H2) was drawn from a peripheral vein. The aPTT ratios in samples H1 and H2 were 1.15 +/- 0.13 and 3.58 +/- 0.61 respectively (p < 0.0001). We concluded that even after the aspiration of 15 ml from the venous lumen of a DLHC filled with a 2 ml HS containing 3,750 IU of heparin, the next blood sample remains contaminated by heparin. Filling each lumen of a DLHC with the same HS results in a significant increment of the aPTT 10 minutes later.