Determination of Cremophor EL in plasma after sample preparation with solid phase extraction and plasma protein precipitation.

The non-ionic emulsifier Cremophor EL can be quantified using a special potentiometric titration technique with barium chloride activation and precipitation with sodium tetraphenylborate. The end point of the titration is indicated by an ionsensitive coated wire electrode which responds to an excess of tetraphenylborate ions. Sample preparation is necessary to quantify the excipient in plasma of patients receiving ciclosporin formulations with Cremophor EL (Sandimmun), since plasma proteins cause disturbances of the titration. Solid phase extraction was tested with various sorbent materials. Although some of the sorbents yielded good extraction rates of Cremophor EL from aqueous solutions, the extraction rates from plasma were significantly lower. Therefore, plasma protein precipitation with acetonitrile has been examined as an alternative to SPE and has been proved the superior method. Using the precipitation technique, a recovery rate of above 90% was achieved. Furthermore, the limit of detection from plasma was found to be 30 microg, in analogy to the determination from aqueous solutions. The combination of the plasma protein precipitation with the potentiometric titration allows quantitation and thus pharmakokinetic investigations of Cremophor EL in patients treated with Sandimmun after kidney-transplantation.

Ultrafiltration profiling and measurement of relative blood volume as strategies to reduce hemodialysis-related side effects.

Hemodialysis (HD) side effects, such as hypotension and muscle cramps, may be related to excessive ultrafiltration (UF) in relation to refilling of fluids from the extravascular space, resulting in hemoconcentration and reduction of relative blood volume (RBV). This study examines the suitability of RBV measurements and UF modeling to reduce the incidence of dialysis side effects. We followed up 188 dialysis sessions in 53 patients. RBV and incidence of side effects were evaluated. Six treatment regimens were examined: UF profile 0, with a constant UF rate; UF profile 1, with a linear decreasing UF rate; UF profile 2, with a stepwise decreasing UF rate; and UF profiles 3 through 5, with intermittent high UF rates interrupted by UF pauses. During dialyses with a constant UF rate (UF profile 0), 10.6% of the treatments were associated with symptomatic hypotension. UF profiles 2 through 5, intermittently using high UF rates, caused a marked increase in hypotensive episodes (18.4%). In contrast, UF profile 1, providing a continuously decreasing UF rate, showed a reduced incidence of hypotension at only 5.7%. Symptomatic hypotension occurred in 13 of 53 patients during one or more dialysis sessions. With the help of RBV measurements, a subgroup of 8 patients with hypovolemia-induced hypotension could be identified. In these patients, an individual threshold of RBV could be defined, below which 92.3% of all hypotensive episodes occurred. In the remaining 5 hypotension-prone patients, there was no correlation between the occurrence of symptomatic hypotension and low RBV during HD treatments. In conclusion, UF profiles intermittently using high UF pulses cannot be recommended. RBV measurements help define a subgroup of patients at risk for hypovolemia-induced hypotension. Only these patients may benefit from blood volume-controlled UF. The incidence of symptomatic hypotension can likely be reduced if an individual threshold of RBV is avoided during HD treatments, eg, using lower UF rates in these patients.

Pharmacokinetic principles during continuous renal replacement therapy: drugs and dosage.

Some drugs are removed significantly by continuous renal replacement therapies (CRRTs), and a substitutional dose is required to prevent underdosing of the substance. This review outlines the basic pharmacokinetic principles that determine whether a dose adjustment is required. Only the free non-protein-bound fraction of a drug can pass through the dialyzer membrane. In postdilution hemofiltration the drug clearance equals the ultrafiltration rate, while in predilution hemofiltration, the dilution of the blood prior to filtration needs to be considered when calculating clearance. In continuous hemodialysis, drugs are eliminated by diffusion. Drugs with a higher molecular weight will diffuse more slowly and show a lower clearance than smaller drugs. The clinical relevance of a given drug clearance caused by CRRT will mainly depend on the competing drug clearance by other elimination pathways. Even a high clearance for a drug may be irrelevant for overall drug removal if nonrenal clearance pathways provide a much higher clearance rate. The ideal drug to be removed by CRRT that requires a dose adjustment has: a low protein binding, a low volume of distribution, and a low nonrenal clearance. Examples include aminoglycosides, vancomycin, fosfomycin, and flucytosine. Even if there are no studies available on the pharmacokinetics of a particular drug during CRRT, knowledge of the basic concepts of drug elimination by continuous hemodialysis allows a prediction of whether or not a dose adjustment will be required during CRRT.

Individualized drug dosage in patients treated with continuous hemofiltration.

BACKGROUND: Subtherapeutic drug dosing may be even more dangerous than overdosage, especially for intensive care patients requiring hemofiltration. PROPOSAL: According to Dettli's fundamental equation, body clearance of any drug (Cl) is a linear function of creatinine clearance (Cl = Cl anur + a x C(Cr)), with [a = (Cl norm - Cl anur)/C(Cr), norm]. We propose to individualize drug dosage during high-flux hemofiltration by basing it on Dettli's equation and on total C(Cr) (C(Cr) tot = C(Cr) ren + C(Cr) filt). Using this approach, drug clearance will eventually be overestimated for drugs with substantial tubular secretion and for high-efficiency hemofiltration (C(Cr) tot > 30 ml/min). CONCLUSION: In patients undergoing hemofiltration, the total C(Cr) approach might be a practical alternative to standardized dosing schemes for deriving an individualized dosage from published pharmacokinetic data and functions.

Recombinant hirudin (lepirudin) as anticoagulant in intensive care patients treated with continuous hemodialysis.

BACKGROUND: Recombinant hirudin (lepirudin) is a potent direct thrombin inhibitor, which has been approved for the treatment of heparin-induced thrombocytopenia type II (HIT). Because the drug is mainly eliminated by the kidneys, a single loading dose of hirudin may induce therapeutic anticoagulation for up to one week in patients with renal insufficiency. Thus, the use of hirudin in critically ill patients with renal failure could markedly increase their bleeding risk. In this study, hirudin was used in critically ill patients with suspected HIT while on continuous venovenous hemodialysis (CVVHD). METHODS: Hirudin anticoagulation was performed in seven critically ill patients with suspected HIT. Four patients were initially anuric. Three patients had residual renal function. In all 64 CVVHD treatments (mean duration 12 hr), a polysulfone high-flux hemodialyzer (0.75 m2) with a dialysate flow rate of 1.5 liter/hr and an ultrafiltration rate of up to 200 ml/hr was used. Hirudin was given either as continuous intravenous infusion or as repetitive intravenous boli. Monitoring of anticoagulation was performed by measurements of the systemic activated partial thromboplastin time (aPTT). RESULTS: Hirudin dosage had to be individualized according to the risk of bleeding or clotting. During CVVHD, a continuous intravenous infusion (0.006 to 0.025 mg/kg body wt/hr, N = 2) or repetitive intravenous boli (0.007 to 0.04 mg/kg, N = 5) were given. Two patients required blood transfusions prior to and during hirudin treatment. In five patients without a high bleeding risk, the hirudin dose was adjusted to achieve the target aPTT (1.5 to 2.0 x baseline) in order to prevent thrombotic complications or frequent clotting in the extracorporal circuit. Hirudin dose requirements depended on residual renal function and extracorporal clearance. CONCLUSIONS: We conclude from these first clinical data that anticoagulation with hirudin in critically ill patients on continuous hemodialysis can be performed without excessive bleeding risk by combining close clinical and laboratory monitoring. The hirudin dose has to be reduced because of renal failure, and may require adjustment for residual or recovering renal function and extracorporal elimination.

Titrimetric determination of Cremophor EL in aqueous solutions and biofluids: part 2: ruggedness of the method with respect to biofluids.

A titration method for Cremophor EL, as a multicomponent mixture commonly used as non-ionic emulgent for manufacturing certain parenteralia, was developed for quantitative routine analysis in biofluids. A coated wire electrode is used as the end-point indicator in potentiometric titrations of Cremophor EL with sodium tetraphenylborate. The method tolerates a broad pH range, addition of alkanols and components of drug formulations and is sufficiently rugged. Reliable results are obtained at 20 degrees C. Disturbing ions from biofluid matrices can be masked or complexed by addition of formaldehyde, ethylenediaminetetraacetic acid and sodium fluoride. Sodium hydroxide is used for the required adjustment of the samples to pH 10. Cremophor EL spiked urine samples can be determined directly, whereas the true value of the emulgent content in the case of Cremophor EL spiked plasma samples is achieved by means of a conventional method.

Efficiency of haemoperfusion materials at removing the fungal toxin orellanine from human plasma.

Orellanine is the main toxin of various Cortinarius mushrooms and responsible for their nephrotoxicity. The present study was undertaken to estimate the value of haemoperfusion in Cortinarius intoxications. The efficiency of the haemoperfusion materials activated charcoal (DHP-1) and Amberlite XAD 4 resin at removing orellanine from plasma was tested in an in vitro model. Quantification of the toxin in plasma samples was carried out following a previously reported fluorodensitometric TLC method. Orellanine is sufficiently bound to both haemoperfusion materials. However, the rate of orellanine adsorption was four times higher on activated charcoal (DHP-1) compared to Amberlite XAD 4 resin.

Evaluation and optimisation of separation buffers for the determination of corticosteroids with micellar electrokinetic capillary chromatography (MECC).

Separation buffers for the determination of the corticosteroids cortisone, hydrocortisone, prednisone and prednisolone with micellar electrokinetic chromatography were developed with respect to separation efficacy and the migration times, depending on the type and the concentration of the organic modifier acetonitrile as well as on the addition of gamma-cyclodextrin. The buffer containing 50 mM SDS and 16% (v/v) acetonitrile enables the rapid profiling of prednisolone together with cortisone and prednisone. Addition of gamma-cyclodextrin alters the elution sequence, but does not further enhance resolution of the corticosteroids. Baseline separation at long migration times for cortisone, hydrocortisone, prednisone and prednisolone is achieved with a buffer containing 50 mM each of SDS, dehydrocholic acid sodium salt and glycodeoxycholic acid sodium salt.

Improved cytosolic free calcium mobilization and superoxide production in bicarbonate-based peritoneal dialysis solution.

BACKGROUND: Intraperitoneal phagocytes play an important role in local host defence to prevent CAPD peritonitis. The intracellular calcium [Ca2+]i is thought to be involved in the regulation of various cell functions. This study therefore investigates the effect of lactate-based dialysis solution (LBDS) and bicarbonate-based dialysis solution (BBDS) on cytosolic free calcium mobilization and superoxide production (SP) as important steps in signal transduction and bacterial killing. METHODS: We studied changes in [Ca2+]i and SP following stimulation with N-formyl-methionyl-leucyl-phenylalanine (fMLP) in polymorphonuclear neutrophils (PMNs) incubated in either LBDS-pH 5.2, LBDS adjusted to pH 7.4, 1:10 diluted spent and fresh LBDS or BBDS-pH 7.4 with different glucose concentrations, comparing the data with cells treated with Hanks buffer (HBSS) pH 7.4 as control. To elucidate the effect of glucose and lactate PMNs were additionally incubated in HBSS-pH 7.4, containing glucose (HBSS-Glu-pH 7.4) or lactate (HBSS-Lact-pH 7.4) in the same concentrations as contained in CAPD solutions and tested as above. PMNs were isolated from healthy blood donors and incubated with dialysis solution 10 min prior to stimulation with fMLP. RESULTS: [Ca2+]i mobilization and SP were completely inhibited in PMNs incubated in LBDS pH 5.2. pH adjustment of LBDS to 7.4 and 1:10 dilution of spent and fresh LBDS corrected some of the suppression of the calcium influx and superoxide production. BBDS pH 7.4, however, preserved physiological cell function significantly better at low (1.5 and 2.3%) glucose concentrations. CONCLUSION: In comparison to conventional lactate-based dialysis solution, pH adjusted and 1:10 diluted LBDS, bicarbonate-based dialysis solution is more biocompatible since it preserves significantly better neutrophil cell functions.

Lipopolysaccharide binding protein: a marker for intraperitoneal bacterial infection in patients with CAPD peritonitis.

During systemic infection, the serum lipopolysaccharide binding protein (LBP) binds to the lipid A component of bacterial endotoxins and facilitates its delivery to the CD 14 receptor on the cell surface of macrophages, where proinflammatory cytokines are released. There is no knowledge to date whether LBP is also present in the effluent of patients with continuous ambulatory peritoneal dialysis (CAPD)-associated peritonitis. We investigated the dialysis effluent of 37 patients with CAPD peritonitis for immunoreactive LBP, tumor necrosis factor (TNF)-alpha, and interleukin (IL)-1 beta and compared the findings with the cytokine levels in 20 noninfected CAPD patients. The mean +/- SEM concentrations of LBP, TNF-alpha, and IL-1 beta were significantly higher in the effluent of patients with peritonitis than in noninfected CAPD effluent. In comparison to controls (0.23 +/- 0.05 microgram/mL), LBP was 0.68 +/- 0.13 microgram/mL in the effluent of patients with CAPD-associated infectious peritonitis. For TNF-alpha, levels were 0.50 +/- 0.25 pg/mL in the control effluent versus 124.7 +/- 46.6 pg/mL in the effluent of peritonitis patients. For IL-1 beta the levels were 0.24 +/- 0.14 pg/mL in the control effluent and 71.23 +/- 17.53 pg/mL in the peritonitis patients. Our findings demonstrate that LBP is significantly elevated in the effluent of CAPD patients during an episode of CAPD-associated peritonitis and might be used as a marker of intraperitoneal bacterial infection.

Pharmacokinetics and bactericidal activity of a single daily dose of netilmicin in the treatment of CAPD-associated peritonitis.

Single daily dosage of netilmicin is generally accepted in systemic infections, due to biphasic bactericidal activity and prolonged postantibiotic effect of aminoglycosides. Since little is known about the efficacy of single daily intraperitoneal application of netilmicin in the treatment of CAPD-associated peritonitis, we conducted this prospective study. Seven patients with CAPD-associated peritonitis were treated with a single daily dose of netilmicin (loading dose 1.5 mg/kg, followed by 40 mg/21 bag/day). Serum and intraperitoneal levels as well as bactericidal activity of netilmicin against Acinetobacter baumanii, E. coli and Pseudomonas aeruginosa were measured for 48 hours. Serum and peritoneal levels widely varied among the patients due to different interindividual plasma clearance of netilmicin. The intraperitoneal antibacterial action of netilmicin was decreased, more over, substantial differences in the bactericidal activity were found among the patients. However, with high initial netilmicin levels sufficient bactericidal activity was found for Acinetobacter and E. coli, but not for Pseudomonas aeruginosa. Hence, a single daily dosage of netilmicin can be a suitable treatment of CAPD-associated peritonitis, only if the dose is adapted according to the first serum and peritoneal levels. In infections with Pseudomonas aeruginosa higher peritoneal levels of netilmicin and the combination with other antibiotics will be needed for a sufficient peritoneal bactericidal activity.

Reduction of granulocyte activation during hemodialysis with regional citrate anticoagulation: dissociation of complement activation and neutropenia from neutrophil degranulation.

Neutropenia and degranulation of neutrophils during hemodialysis with cellulosic membranes have been linked to complement activation, whereas in the synthetic polymethyl methacrylate (PMMA) membrane, degranulation occurs without notable complement activation. The mechanisms of neutrophil degranulation under these conditions have not yet been elucidated. Ionized calcium is an important prerequisite of granulocyte activation during in vitro blood contact with both types of artificial surfaces. This study compared the effect of normal ionized calcium during heparin anticoagulation with the effect of extracorporeal calcium depletion during regional citrate anticoagulation on activation of blood components. Because ionized calcium is reduced only in the extra-corporeal circuit, citrate anticoagulation in addition helps to differentiate between extracorporeal and systemic activation phenomena. Twelve chronic hemodialysis patients were dialyzed with polymethyl methacrylate (PMMA, 16 treatments) or cuprophane (CUP, 16 treatments) membranes either during regional citrate anticoagulation or while anticoagulated with heparin. During hemodialysis with CUP, anticoagulation with citrate significantly reduced neutropenia, C3a levels, and lactoferrin release. Elastase concentrations, however, were not reduced by citrate, probably because elastase release occurred not locally in the cuprophane dialyzer, but mostly in the systemic circulation of the patient. PMMA did not elevate C3a levels, and neutropenia was only mild. Both parameters were not influenced by citrate anti-coagulation. However, PMMA profoundly induced elastase and lactoferrin release during heparin anti-coagulation. Depletion of ionized calcium markedly reduced PMMA-mediated neutrophil degranulation in the extracorporeal circuit. The results indicate that ionized calcium is a requirement for neutrophil degranulation during hemodialysis. In PMMA membranes, neutrophil degranulation occurs independent of high complement levels, occurs at least partially inside the dialyzer, and requires the presence of ionized calcium in the extracorporeal circuit. In cuprophane membranes, degranulation was uncoupled from neutropenia and did not correlate with the degree of complement activation. Even in cuprophane dialysis, degranulation of secondary granules was markedly dependent on ionized calcium levels in the extracorporeal circuit.

Single dose kinetics of piperacillin during continuous arteriovenous hemodialysis in intensive care patients.

Piperacillin (Pi) kinetics in patients with acute renal failure treated by continuous arteriovenous hemodialysis (CAVHD) are not known. Therefore, dosing regimens have been based on kinetic data derived from patients with chronic renal failure and principal pharmacokinetic considerations [Reetze-Bonorden et al. 1993]. From these estimations it has been predicted that approximately 30% of the dose of Pi is removed by CAVHD (dialysate/ultrafiltrate (D/UF) flow rate 1.5 liter/hour). To confirm this estimate single dose (4g i.v.) Pi kinetics were studied in 12 intensive care patients with anuric acute renal failure due to septicemia treated by CAVHD. Pi plasma and D/UF levels were measured by HPLC. Sieving/Saturation of Pi in the D/UF was 0.71 +/- 0.21 (+/- SD). With a mean D/UF flow rate of 20.4 +/- 1.5 ml/min, the mean extracorporal clearance (Clextra) was 12.2 +/- 1.0 ml/min and accounted for 29% (range 14-48%) of total body clearance (ClB = 47.1 +/- 22.3 ml/min). In 7 out of 12 patients the fraction of the dose eliminated by CAVHD reached a significant value above 25%. The mean volume of distribution (Vd) and elimination half life (t1/2) were 25.8 +/- 3.8 liter and 7.4 +/- 2.9 hours, respectively. In conclusion the extent of extracorporal elimination of Pi by CAVHD was well in agreement with the estimation previously published. In intensive care patients with acute renal failure on continuous hemodialysis Pi dosing should take into account the possibly significant elimination of Pi. The usual dose for anuric patients may be increased by 50% to avoid underdosing in these critically ill patients.

Persistent inhibition of neutrophil function by glucose based dialysis solutions.

Local defense mechanisms play an important role in prevention of peritonitis, a major complication of continuous ambulatory peritoneal dialysis (CAPD) therapy. The authors have shown that hypertonic, lactate containing glucose based dialysis solutions (GBDS) used in CAPD lead to an immediate and complete pH-dependent inhibition of actin polymerization and phagocytosis in polymorphonuclear neutrophils (PMN) in vitro. Earlier studies have shown that the pH of the fluid equilibrates from 5.2 to approximately 6.4 during the first 30 min of intraperitoneal dwell time. Thus, the authors designed the current study to determine whether the inhibition of cytoskeletal function and intracellular acidosis induced by acidic solutions are reversed by this pH adjustment. To this end, actin polymerization, phagocytosis, and intracellular pH were studied in PMN isolated from healthy human donors during a 10 min incubation in commercially available GBDS at pH 5.2 and again after pH adjustment to 6.4. Actin polymerization was assessed by measuring F-actin content using NBD phallacidin staining and fluorescence activated cell scanner analysis. Phagocytosis was assessed using zymosan particles, and intracellular pH was monitored by spectrofluorometry. The impairment of cytoskeletal alterations in cells exposed to GBDS at pH 5.2 was persistent and not fully reversed by adjusting the pH. Likewise, phagocytosis remained markedly inhibited and intracellular pH did not rise after adjustment of pH. Thus, the results demonstrate a persistent cytotoxic effect of CAPD solutions on human phagocytes. The authors think that CAPD solutions must be modified to provide a more physiologic pH environment for proper phagocyte function.

Effects of simvastatin on lipoprotein (a) and lipoprotein composition in patients with nephrotic syndrome.

The influence of simvastatin, a competitive inhibitor of 3-hydroxy-3-methyl glutaryl coenzyme A reductase, on quantitative and qualitative changes in lipoprotein metabolism was investigated in 18 patients (group I, 10 with primary kidney disease and group II, 8 with diabetic nephropathy) with nephrotic syndrome. Nephrotic patients exhibited severe hyperlipidemia (serum cholesterol 390 +/- 17 mg/dl and triglyceride 335 +/- 42 mg/dl; mean +/- SEM) and had significantly higher lipoprotein (a) [Lp(a)] levels (54 +/- 12 mg/dl; median 31 mg/dl, p < 0.01) compared with 20 healthy subjects (mean 12 +/- 1.8 mg/dl; median 7 mg/dl). Fifty-six percent of the patients and 15% of the controls had values greater than 30 mg/dl. Treatment with simvastatin in increasing doses over a period of three months (13 patients received 40 mg/day and 5 patients 20 mg/day at the end of the third month) reduced LDL-cholesterol in both groups of patients (35% and 54%) as well as apolipoprotein B (apoB) (31% and 46%) significantly, but Lp(a) levels were not influenced (57 +/- 21 vs 59 +/- 20 and 50 +/- 14 vs 53 +/- 16 mg/dl, respectively). On the other hand a complex change in lipoprotein composition occurred. The ratio of LDL apoB/LDL cholesterol-ester increased significantly (0.75 +/- 0.03 to 0.84 +/- 0.03 and 0.80 +/- 0.03 to 1.02 +/- 0.1, respectively) and cholesterol concentration in VLDL (64 +/- 16 to 39 +/- 7 and 74 +/- 18 to 55 +/- 74 mg/dl, respectively) was reduced.(ABSTRACT TRUNCATED AT 250 WORDS)

Bicarbonate-based dialysis solution preserves granulocyte functions.

OBJECTIVE: Intraperitoneal phagocytes play an important role in local defense in preventing continuous ambulatory peritoneal dialysis (CAPD) peritonitis. This study therefore investigates the effect of the conventional lactate-based dialysis solution-pH 5.2 (LBDS-pH 5.2) and a bicarbonate-based dialysis solution (BBDS) on various cell functions. DESIGN: We studied C5a-induced actin polymerization (AP) as a measure of the cytoskeletal alteration, phagocytosis of zymosan particles, and chemotaxis in neutrophils incubated in either LBDS-pH 5.2, LBDS-pH 7.4, or BBDS-pH 7.4, comparing the data with cells treated with phosphate-buffered saline-pH 7.4 (PBS-pH 7.4) as a control. SUBJECTS: Polymorphonuclear neutrophils (PMNs) were isolated from the blood of healthy donors and incubated with dialysis solution prior to the experiment. RESULTS: C5a-induced AP was dramatically inhibited in PMNs incubated in LBDS-pH 5.2, paralleled by a complete inhibition of phagocytosis and C5a-induced chemotaxis. In comparison, BBDS improved AP to values above the control and also nearly normalized phagocytosis. Chemotaxis markedly improved in cells treated with the low glucose-containing BBDS (Bic 20), containing high glucose concentrations (Bic 30). CONCLUSION: In comparison with conventional lactate-based dialysis solution-pH 5.2, bicarbonate-based dialysis solution at low osmolality better preserves neutrophil functions that involve the cytoskeleton.