Continuous Hemofiltration

CWH, continuous venovenous hemofiltration CWHD, continuous venovenous hemodialysis CVVHDF, continuous venovenous hemodiafil-tration. 

Pond, S.M., S.C. Johnston, D.D. Schoof, E.C. Hampson, M. Bowles, D.M. Wright, and JJ. Petrie. 1987. Repeated hemoperfusion and continuous arteriovenous hemofiltration in a paraquat poisoned patient. Clin. Toxicol. 25 305-316. 

Metabolism/Excretion - In the first 24 hours, approximately 75% of a dose is excreted in urine by glomerular filtration. Elimination half-life is 4 to 6 hours in adults and 2 to 3 hours in children. About 60% of an intraperitoneal dose administered during peritoneal dialysis is absorbed systemically in 6 hours. Accumulation occurs in renal failure. Serum half-life in anephric patients is approximately 7.5 days. Vancomycin is not significantly removed by hemodialysis or continuous ambulatory peritoneal dialysis, although there have been reports of increased clearance with hemoperfusion and hemofiltration. 

Peritoneal dialysis Supplemental doses of valacyclovir should not be required following chronic ambulatory peritoneal dialysis (CARD) or continuous arteriovenous hemofiltration/hemodialysis (CAVHD). 

Peritoneal Dialyis There is no information specific to administration of VALTREX in patients receiving peritoneal dialysis. The effect of chronic ambulatory peritoneal dialysis (CARD) and continuous arteriovenous hemofiltration/dialysis (CAVHD) on acyclovir pharmacokinetics has been studied. The removal of acyclovir after CARD and CAVHD is less pronounced than with hemodialysis, and the pharmacokinetic parameters closely resemble those observed in patients with ESRD not receiving hemodialysis. Therefore, supplemental doses of VALTREX should not be required following CARD or CAVHD. 

The results of hemodialysis in biguanide-induced lactic acidosis are variable. Metformin and buformin are dialy-sable, but phenformin is poorly eliminated. Successful continuous venovenous hemofiltration has been reported (81). 

As mentioned already, the artificial kidney is a classic example of chemical engineering prowess. The proper design of such devices requires a description of both water and solute transport to and from blood, across membranes, and to and from an adjacent fluid known as the dialysate. Variations on this theme include hemodilution, hemoconcentration, and hemofiltration. Applications of these same principles have been used to examine continuous ambulatory peritoneal dialysis. Oxygenation of blood,... 

Hemodialysis (383,552,553), sometimes with additional continuous venovenous hemofiltration dialysis (554,555), continues to be described as a successful intervention for lithium poisoning. Peritoneal dialysis is a far less efficient way to clear lithium from the body. One patient treated in this way had permanent neurological abnormalities and another died a third toxic patient who also had diabetic ketoacidosis died after treatment with hydration and insulin (556). On the other hand, a 51-year-old woman who took 50 slow-release lithium carbonate tablets (450 mg) had a serum lithium concentration of 10.6 mmol/1 13 hours later, but no evidence of neurotoxicity or nephrotoxicity. She was treated conservatively with intravenous fluids and recovered fully (557). Acute lithium overdose is often better tolerated than chronic intoxication. 

Two teenagers with neurological toxicity (serum concentrations 5.4 mmol/1 and 4.81 mmol/1) were treated successfully with hemodialysis followed by continuous venovenous hemofiltration, which prevented a post-dialysis rebound in serum lithium concentrations (554). 

Meyer RJ, Flynn JT, Brophy PD, Smoyer WE, Kershaw DB, Custer JR, Bunchman TE. Hemodialysis followed by continuous hemofiltration for treatment of hthium intoxication in children. Am J Kidney Dis 2001 37(5) 1044-7. 

Continuous arteriovenous hemofiltration CAVH 0 -h -h -h-h Artery-vein Yes... 

Hemofiltration is a prominent feature of many continuous renal replacement therapies (Table 6.2). How-ever continuous hemodialysis can also be employed to accelerate solute removal (16). The contribution of both processes to extracorporeal drug clearance will be considered separately in the context of continuous renal replacement therapy. 

Some of the renal replacement therapies listed in Table 6.2 incorporate continuous hemodialysis or a combination of continuous hemofiltration and hemodialysis. Continuous hemodialysis differs importantly from conventional intermittent hemodialysis in that the flow rate of dialysate is much lower than is countercurrent blood flow through the dialyzer. As a result/ concentrations of many solutes in dialysate leaving the dialyzer (Cd) will have nearly equilibrated with their plasma concentrations in blood entering the dialyzer (Cp) (16/31). The extent to which this equilibration is complete is referred to as the dialysate saturation (Sd) and is calculated as the following ratio ... 

Golper TA. Continuous arteriovenous hemofiltration in acute renal failure. Am J Kidney Dis 1985 6 373-386. 

Golper TA, Wedel SK, Kaplan AA, Saad A-M, Donta ST, Paganini EP. Drug removal during continuous arteriovenous hemofiltration Theory and clinical observations. Int J Artif Organs 1985 8 307-12. 

Lau AH, Kronfol NO. Effect of continuous hemofiltration on phenytoin elimination. Ther Drug Monitor 1994 16 53-7. 

Kroh UF, Lennartz H, Edwards DJ, Stoeckel K. Pharmacokinetics of ceftriaxone in patients undergoing continuous veno-venous hemofiltration. J Clin Pharmacol 1996 36 1114-9. 

Lau AH, Pyle K, Kronfol NO, Libertin CR. Removal of cephalosporins by continuous arteriovenous ultrafiltration (CAVU) and hemofiltration (CAVH). Int J Artif Organs 1989 12 379-83. 

Domoto DT, Brown WW, Bruggensmith P. Removal of toxic levels of N-acetylprocainamide with continuous arteriovenous hemofiltration or continuous arteriovenous hemodiafiltration. Ann Intern Med 1987 106(4) 550-2. 

Continuous infusion of amphotericin has been assessed in an open study in six lung transplant recipients with invasive or semi-invasive bronchopulmonary azole-resistant candidal infections who were treated for 40 (17-73) days by 24-hour continuous infusions of amphotericin 1 mg/kg (113). They received at least 1000 ml/day of 0.9% saline intravenously. Apart from ciclosporin, five patients received aminoglycosides for at least 2 weeks, and four received ganciclovir. Calculated creatinine clearance fell from 57 (43-73) ml/minute to a nadir of 35 (28-39) and recovered to 52 (33-60) after the end of therapy. One patient needed temporary hemofiltration for 7 days. Besides three episodes of mild hypokalemia there were no adverse effects attributable to amphotericin. Asymptomatic colonization with Candida persisted for 10 months in one case, but the other five patients were cured. 

Successful continuous venovenous hemofiltration has been reported (58). 

The pharmacokinetics of intravenous ciprofloxacin have been studied in intensive care unit patients during continuous venovenous hemofiltration (n — 5) or hemo-diafiltration (n — 5) (67). Ciprofloxacin clearance was not altered. A dosage of 400 mg/day was sufficient to maintain effective drug plasma concentrations in patients undergoing continuous renal replacement therapy. 

Hansen E, Bucher M, Jakob W, Lemberger P, Kees F. Pharmacokinetics of levofloxacin during continuous veno-venous hemofiltration. Intensive Care Med 2001 27(2) 371-5. 

An agitated, confused, disoriented 52-year-old woman who took an overdose of lithium recovered fully after high-volume continuous venovenous hemofiltration (452). 

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