Drug removal by continuous arteriovenous haemofiltration. A review of the evidence in poisoned patients

Antibiotics Removal by Continuous Venovenous Hemofiltration with a Novel Asymmetric Triacetate Membrane Hemofilter: An in vitro Study

INTRODUCTION

Continuous renal replacement therapies (CRRTs) are essential in the treatment of critically ill patients with acute kidney injury and are also discussed as a supporting sepsis therapy. CRRT can affect antibiotics plasma concentrations.

OBJECTIVE

The effect of continuous venovenous hemofiltration (CVVH) with an asymmetric triacetate (ATA) membrane hemofilter on concentrations of antibiotics with low (meropenem), medium (vancomycin), and high (daptomycin) protein binding (PB) was investigated.

METHODS

1 L human whole blood supplemented with antibiotics was recirculated and filtrated for 6 h in vitro. Clearances and sieving coefficients (SC) were determined from antibiotics concentrations measured at filter inlet, outlet, and filtrate side. Reservoir concentration data were fitted using a first-order kinetic model.

RESULTS

Meropenem and vancomycin concentrations decreased to 5-10% of the initial plasma level, while only 50% of daptomycin were removed. Clearances and SCs were (10.8 [10.8-17.4] mL/min, SC = 0.72 [0.72-1.16]) for meropenem, (13.4 [12.3-13.7] mL/min, 0.89 [0.82-0.92]) for vancomycin, and (2.1 [1.8-2.1] mL/min, 0.14 [0.12-0.14]) for daptomycin. Removal by adsorption was negligible.

CONCLUSIONS

The clearances and SCs presented are comparable with findings of other authors. Meropenem and vancomycin, which exhibit low and medium PB, respectively, were strongly removed, while considerably less daptomycin was removed because of its high PB. Our results suggest that in clinical use of the tested antibiotics during CRRT with the ATA hemofilter, the same factors have to be considered for determining the dosing strategy as with filters with other commonly applied membrane materials.

Once-daily 1 g ceftriaxone optimizes exposure in patients with septic shock and hypoalbuminemia receiving continuous veno-venous hemodiafiltration

PURPOSE

Ceftriaxone total and unbound pharmacokinetics (PK) can be altered in critically ill patients with septic shock and hypoalbuminemia receiving continuous veno-venous hemodiafiltration (CVVHDF). The objective of this study was to determine the dosing strategy of ceftriaxone that maximizes the probability of maintaining the concentration above the MIC of the susceptible bacteria (≤2 mg/L by the EUCAST) for a 100% of the dosing interval (100% ƒ_uT_>MIC).

METHODS

In a prospective PK study in the intensive care units of two tertiary Spanish hospitals, six timed blood samples were collected per patient; for each sample, ceftriaxone total and unbound concentrations were measured using a liquid chromatography coupled to tandem mass spectrometry method. Population PK analysis and Monte-Carlo simulations were performed using NONMEMv.7.3®.

RESULTS

We enrolled 8 critically ill patients that met the inclusion criteria (47 blood samples). Median age (range) was 70 years (47-85), weight 72.5 kg (40-95), albumin concentration 24.2 g/L (22-34), APACHE II score at admission 26 (17-36), and SOFA score on the day of study 12 (9-15). The unbound fraction (ƒ_u) of ceftriaxone was 44%, and total CL was 1.27 L/h, 25-30% higher than the CL reported in septic critically ill patients not receiving renal replacement therapies, and dependent on albumin concentration and weight. Despite this increment in ƒ_u and CL, Monte-Carlo simulations showed that a dose of 1 g once-daily ceftriaxone is sufficient to achieve a 100% ƒ_uT_>MIC for MICs ≤2 mg/L for any range of weight and albumin concentration.

CONCLUSION

Once-daily 1 g ceftriaxone provides optimal exposure in critically ill patients with septic shock and hypoalbuminemia receiving CVVHDF.

Effect of Kidney Function on Drug Kinetics and Dosing in Neonates, Infants, and Children

Neonates, infants, and children differ from adults in many aspects, not just in age, weight, and body composition. Growth, maturation and environmental factors affect drug kinetics, response and dosing in pediatric patients. Almost 80% of drugs have not been studied in children, and dosing of these drugs is derived from adult doses by adjusting for body weight/size. As developmental and maturational changes are complex processes, such simplified methods may result in subtherapeutic effects or adverse events. Kidney function is impaired during the first 2 years of life as a result of normal growth and development. Reduced kidney function during childhood has an impact not only on renal clearance but also on absorption, distribution, metabolism and nonrenal clearance of drugs. 'Omics'-based technologies, such as proteomics and metabolomics, can be leveraged to uncover novel markers for kidney function during normal development, acute kidney injury, and chronic diseases. Pharmacometric modeling and simulation can be applied to simplify the design of pediatric investigations, characterize the effects of kidney function on drug exposure and response, and fine-tune dosing in pediatric patients, especially in those with impaired kidney function. One case study of amikacin dosing in neonates with reduced kidney function is presented. Collaborative efforts between clinicians and scientists in academia, industry, and regulatory agencies are required to evaluate new renal biomarkers, collect and share prospective pharmacokinetic, genetic and clinical data, build integrated pharmacometric models for key drugs, optimize and standardize dosing strategies, develop bedside decision tools, and enhance labels of drugs utilized in neonates, infants, and children.

Antimicrobial dosing in critically ill patients with sepsis-induced acute kidney injury

Severe sepsis often leads to multiple organ dysfunction syndromes (MODS) with acute kidney injury (AKI). AKI affects approximately, 35% of Intensive Care Unit patients, and most of these are due to sepsis. Mortality rate of sepsis-induced AKI is high. Inappropriate use of antimicrobials may be responsible for higher therapeutic failure, mortality rates, costs and toxicity as well as the emergence of resistance. Antimicrobial treatment is particularly difficult due to altered pharmacokinetic profile, dynamic changes in patient's clinical status and, in many cases, need for renal replacement therapy. This article aims to describe the appropriate antimicrobial dosing and reviews the factors contributing to the difficulties in establishing precise guidelines for antimicrobial dosing in sepsis-induced AKI patients.

SEARCH STRATEGY

Text material was collected by systematic search in PubMed, Google (1978-2013) for original articles.

Understanding renal replacement therapy and dosing of drugs in pediatric patients with kidney disease

Multifaceted factors need to be considered when prescribing renal replacement therapy (RRT) and dosing of drugs in pediatric patients with kidney disease. RRTs in pediatrics such as intermittent hemodialysis, continuous venovenous hemofiltration, continuous venovenous hemodialysis, and continuous venovenous hemodiafiltration affect solute and drug clearance. Drug properties such as molecular weight, molecular charge, volume of distribution, and protein binding affect drug clearance. RRT prescription parameters such as blood flow rate, ultrafiltration rate, membrane size, and pore size can also influence drug clearance. Furthermore, the pediatric patient presents additional concerns because of developmental factors in children that affect both pharmacokinetics of drugs.

FHD: an index to evaluate drug elimination by hemodialysis

BACKGROUND

In hemodialyzed patients, physicians have to (1) adjust drug dosage for a creatinine clearance lower than 10-15 ml/min and (2) know whether or not the drug will be removed by the dialysis session to decide whether it may be administered before or after the session on dialysis days. However, of several indices being used to evaluate drug removal by dialysis none is appropriate and we suggest a novel index named F(HD), which reflects the role of hemodialysis clearance of a drug in its overall clearance during the session.

METHODS

Pharmacokinetic simulations were performed to test the influence of dialysis on the pharmacokinetics of some drugs, whether F(HD) was considered or not, to determine when to administer the drug. F(HD) was then calculated for several drugs and its value compared with other indices. Five hemodialysis patients from our department for whom the time of drug administration was determined according to F(HD) were included in a small study and their drugs' trough concentrations were monitored.

RESULTS

F(HD) emphasized that considering hemodialysis clearance alone may lead to false interpretations of the potential dialyzability of some drugs. In our patients, who received their treatment according to the 'F(HD) rule', monitoring of trough levels gave satisfactory results.

CONCLUSION

The use of the 'F(HD) rule' should be tested on a long-term administration basis to confirm our conclusion. F(HD )could be the index of choice to determine when to administer a drug, before or after the session, in hemodialysis patients.

The Management of Tricyclic Antidepressant Poisoning

Although there have been descriptive, uncontrolled clinical reports of removal of tablet debris by gastric lavage, there have been no clinical studies that have demonstrated that this has any impact on outcome in patients with tricyclic antidepressant (TCA) poisoning. There is also the possibility that lavage may increase drug absorption by pushing tablets into the small intestine. Furthermore, gastric lavage in patients with TCA poisoning may induce hypoxia and a tachycardia potentially increasing the risk of severe complications such as arrhythmias and convulsions. In view of the paucity of evidence that gastric lavage removes a significant amount of drug and the risk of complications associated with the procedure, the routine use of gastric lavage in the management of patients with TCA poisoning is not appropriate. Volunteer studies have shown generally that activated charcoal is more likely to reduce drug absorption if it is administered within 1 hour of drug ingestion. In the one volunteer study that looked at later administration of activated charcoal, there was a 37% decrease in plasma concentration associated with administration of activated charcoal at 2 hours post-ingestion. There have been no clinical studies that enable an estimate of the effect of activated charcoal administration on outcome in the management of patients with TCA poisoning. Volunteer studies have shown that multiple-dose activated charcoal increases the elimination of therapeutic doses of amitriptyline and nortriptyline, but not of doxepin or imipramine; however, these studies cannot be directly extrapolated to the management of patients with TCA poisoning. There have been no well designed controlled studies that have assessed the impact of multiple-dose activated charcoal in the management of patients with TCA poisoning. Because of the large volume of distribution of TCAs, it would not be expected that their elimination would be significantly increased by multiple-dose activated charcoal.Haemoperfusion, haemodialysis and the combination of these procedures do not result in significant removal of TCAs and are not recommended in the management of patients with TCA poisoning.

Poisonings and overdoses in the intensive care unit: General and specific management issues

OBJECTIVE

To provide current information on general and specific interventions for overdoses likely to require intensive care.

DESIGN

Review of literature relevant to selected interventions for general management of overdoses and specific poisons.

RESULTS

The benefit of interventions to decrease absorption or enhance elimination of toxins is limited to a relatively small number of specific agents. Antidotes and certain interventions may be helpful in preventing or treating toxicity in specific poisonings when used appropriately. Intensive supportive care is also necessary to achieve good outcomes.

CONCLUSION

Knowledge of the indications and limitations of current interventions for poisonings and overdoses is important for care of the critically ill poisoned patient.

Efficacy of continuous venovenous hemodialysis in the treatment of severe lithium toxicity

The syndrome of lithium toxicity has been well described. Hemodialysis is the recommended treatment for severe toxicity. We report a case in which continuous venovenous hemodialysis was used in the treatment of lithium toxicity. The calculated average lithium clearance was 23 mL per minute, comparing favorably with that of normal renal clearance (20-30 mL/min) and of intermittent hemodialysis (50-100 mL/min). This report discusses the potential benefits of this therapy in a hemodynamically unstable patient who may not tolerate hemodialysis.

[Influence of arteriovenous hemofiltration on teicoplanin pharmacokinetics]

OBJECTIVE

To assess the pharmacokinetics of a single dose of teicoplanin in critically ill patients treated with continuous arteriovenous haemofiltration (CAVH).

STUDY DESIGN

Prospective open clinical study.

PATIENTS

Eleven patients with acute renal insufficiency and suspected of a Gram negative infection.

METHOD

After injection of teicoplanin, 6 mg.kg-1 over 30 minutes the plasma and haemofiltrate concentrations were measured over 24 hours with high power liquid chromatography (HPLC).

RESULTS

In plasma, the mean half-life of the first phase was 0.6 +/- 0.2 hour and terminal half-life was 16.4 +/- 5 8 hours, total clearance 30.4 +/- 7.1 mL.h-1.kg-1, volume of distribution was 0.7 +/- 0.3 L.kg-1 and the mean resident time 19.2 +/- 7.4 hours. In the haemofiltrate, the amount of teicoplanin eliminated after 24 hours was less than 1% in seven patients, between 1.8 and 3.7% in three and reached 7% in one patient.

CONCLUSION

During CAVH, the elimination of a single dose of teicoplanin in the haemofiltrate is low.

The effects of haemofiltration on cefazolin levels during cardiopulmonary bypass

Ultrafiltration has been shown to affect cardiac drug concentrations during cardiopulmonary bypass (CPB), based on their respective pharmacological properties. In an attempt to understand the aetiology of sternal wound infections, a study was performed to eliminate the use of ultrafiltration as a possible cause. We compared cefazolin levels at three time intervals during the course of routine CPB with ultrafiltration to those levels in a control group in which ultrafiltration was not used. Our results indicate that there is little difference in the rate of decay of antibiotic levels with or without the use of a haemoconcentrator. This implies that ultrafiltration procedures do not put the patient at any increased risk for infection and that additional measures beyond that which we would normally use at our institution need not be taken.

Pharmacokinetics of ceftriaxone in patients undergoing continuous veno-venous hemofiltration

Continuous hemofiltration is used widely in the management of patients with acute renal failure, but administration guidelines for many drugs have yet to be established. In this study, the pharmacokinetics of ceftriaxone were compared in patients with normal renal function (n = 9), mild renal insufficiency (n = 5), and acute renal failure receiving continuous veno-venous hemofiltration (n = 6). Pharmacokinetic parameters were determined under steady state conditions. Patients with mild renal insufficiency had a significantly lower renal clearance and longer half-life of ceftriaxone; however, drug recovery in the ultrafiltrate with continuous veno-venous hemofiltration was similar to that in the urine of patients with normal renal function. Pharmacokinetic parameters for renal, nonrenal, and systemic clearance and for volume of distribution and half-life were also similar between patients receiving continuous veno-venous hemofiltration and those with normal renal function. The sieving coefficient (S) of ceftriaxone (0.69) significantly exceeded the expected free fraction in plasma, confirming previous reports that protein binding does not limit the sieving of this compound. The results suggest that a reduction in the usual daily dose of ceftriaxone is not required in patients with acute renal failure receiving continuous veno-venous hemofiltration.

Filtration of fentanyl is not the cause of the elevation of arterial blood pressure associated with post-bypass ultrafiltration in children

Modified ultrafiltration after cardiopulmonary bypass in children has been shown to be associated with an increase in arterial blood pressure. As part of a series of studies to investigate the possible causes of this blood pressure elevation, the hypothesis that if filtration was removing a significant amount of fentanyl, then the increase in blood pressure might be due to pain was proposed. Ten children, aged between 0.5 and 9.3 years (median 3.8 years), weighing 5.9 to 25.5 kg (median 15.7 kg), underwent corrective cardiac surgery (incorporating modified ultrafiltration). A standard anesthetic protocol was followed, with up to 78 micrograms/kg of fentanyl given prebypass for analgesia. After completion of cardiopulmonary bypass, modified ultrafiltration was commenced at 100 mL/min until a hematocrit of 35% was reached. Samples were taken of arterial blood (prefiltration, 3, 10, and 20 minutes postfiltration), the venous reservoir blood (prefiltration) and the filtrate (5 and 10 minutes into filtration). Hemodynamic data were recorded both prefiltration and postfiltration. The hemodynamic data showed the expected rise in both systemic arterial pressure and cardiac index after ultrafiltration. The plasma fentanyl concentrations did not significantly change after ultrafiltration: 1.59 to 12.39 ng/mL (median 6.27 ng/mL) prefiltration and 2.05 to 15.59 ng/mL (6.29 ng/mL) at 3 minutes, 2.22 to 12.64 ng/mL (6.87 ng/mL) at 10 minutes, and 1.83 to 11.52 ng/mL (5.85 ng/mL) at 20 minutes postfiltration.(ABSTRACT TRUNCATED AT 250 WORDS)

Continuous renal replacement therapy for critically ill patients: an update

Despite continuous progress in intensive care during the last decades, the outcome of critically ill patients in whom acute renal failure (ARF) develops is still poor. This outcome may be explained partially by the frequent occurrence of ARF as part of multiple organ systems failure (MOSF). In this complex and unstable patient population, the provision of adequate renal support with either intermittent hemodialysis or peritoneal dialysis may pose major problems. Continuous renal replacement therapy (CRRT) is now increasingly accepted as the preferred treatment modality in the management of ARF in these patients. The technique offers adequate control of biochemistry and fluid balance in hemodynamically unstable patients, thereby enabling aggressive nutritional and inotropic support without the risk of exacerbating azotemia or fluid overload. In addition, experimental and clinical data suggest that CRRT may have a beneficial influence on hemodynamics and gas exchange in patients with septic shock and (nonrenal) MOSF, independent of an impact on fluid balance. We review both technical and clinical aspects of various continuous therapies, including their impact on serum drug levels and nutrient balance. In addition, an attempt is made to clarify the possible beneficial role of CRRT in reducing patient morbidity and mortality in the ICU.

Resource package: haemofiltration

Use of haemofiltration is increasing in general intensive therapy units in the United Kingdom, yet few nursing staff working with this technology are trained in renal nursing. They thus need special support while caring for patients being treated with haemofiltration. This package offers a practical working knowledge-base for clinical use. Normal renal physiology is revised, the principles of haemofiltration are discussed, and some areas of concern are examined. Recommendations for practice are given where appropriate. Specific reference is made to the Hospal BSM 22 blood pump, and the Hemospal AN69s filter.

Comparison of imipenem pharmacokinetics in patients with acute or chronic renal failure treated with continuous hemofiltration

The total clearance of imipenem, a carbapenem antibiotic, is reduced from approximately 230 mL/min in patients with normal renal function to approximately 50 mL/min in patients with chronic renal failure. This decline in clearance results not only from the loss of renal clearance, but also from a reduction in the nonrenal clearance from 130 to 50 mL/min. Current dosing recommendations for the administration of imipenem to patients with acute or chronic renal failure are based on this reduced clearance rate. We investigated the pharmacokinetics of imipenem in critically ill patients with acute or chronic renal failure to determine whether published dosing guidelines were applicable to both patient populations. Imipenem pharmacokinetic parameters were determined in 10 anuric patients with renal failure managed by continuous venovenous hemofiltration (CVVH). Seven patients had acute renal failure, while the other three had preexisting chronic renal failure. Imipenem serum concentration data were incorporated into a first-order, single-compartment pharmacokinetic model. Determinations of the area under the serum concentration-time curve were made by the trapezoidal rule. Dosing regimens were calculated from clearance data to achieve a mid-dose imipenem serum concentration of 12 mg/L. The total clearance of imipenem in patients with acute renal failure (108.3 +/- 13.8 mL/min; mean +/- SD) was significantly greater than the total clearance measured in patients with chronic renal failure (64.4 +/- 10.5 mL/min; P < 0.02). This increased clearance resulted from a greater nonrenal clearance of the drug in patients with acute renal failure (95.0 +/- 13.8 v 51.1 +/- 10.5 mL/min; P < 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)

Continuous arteriovenous hemofiltration

CAVH is a bedside form of dialysis that is used in the treatment of fluid and electrolyte disorders seen in critically ill patients. The major advantages of the procedure include (1) gradual, continuous therapy, which is ideal in hemodynamically unstable patients; (2) control of fluid balance; and (3) ease of administration in the ICU. The major disadvantages of CAVH include (1) a requirement for arterial access, (2) the need for anticoagulation, (3) the risks of infection from long-term indwelling vascular lines, and (4) the potential for significant volume depletion. The effectiveness of CAVH may continue to improve owing to technical developments in filter composition and the application of clinical tactics such as suction-assisted filtration, predilution fluid replacement, or regional heparinization. The next step in bedside dialysis is represented by CAVHD, which offers all of the advantages of CAVH as well as improved urea clearance.

The assessment and treatment of theophylline poisoning

Theophylline poisoning long has been recognized as difficult to treat and still has an over-all mortality rate of about 10%. In recent years, the increasing use of sustained-release preparations has changed the pattern of toxicity. The management of theophylline toxicity is compounded by clinical differences between chronic (overmedication) intoxication and acute single ingestions of a large amount of the drug, inter- and intraindividual variability in theophylline metabolism and dose-dependent kinetics in poisoned patients. Management decisions should be based on both clinical assessment and laboratory information (particularly theophylline concentrations).