Pharmacokinetics and drug dosing adjustments during continuous venovenous hemofiltration or hemodiafiltration in critically ill patients

Impact of the first 24 h of continuous kidney replacement therapy on hemodynamics, ventilation, and analgo-sedation in critically ill children

BACKGROUND

In a group of children admitted to the paediatric intensive care unit (PICU) receiving continuous kidney replacement therapy (CKRT), we aim to evaluate the data about their hemodynamic, ventilation and analgo-sedation profile in the first 24 h of treatment and possible associations with mortality.

METHODS

Retrospective cohort study of children admitted to the PICU of the University Hospital of Padova undergoing CKRT between January 2011 and March 2021. Data was collected at baseline (T0), after 1 h (T1) and 24 h (T24) of CKRT treatment. The differences in outcome measures were compared between these time points, and between survivors and non-survivors.

RESULTS

Sixty-nine patients received CKRT, of whom 38 (55%) died during the PICU stay. Overall, the vasoactive inotropic score and the adrenaline dose increased at T1 compared to T0 (p = 0.012 and p = 0.022, respectively). Compared to T0, at T24 patients showed an improvement in the following ventilatory parameters: Oxygenation Index (p = 0.005), Oxygenation Saturation Index (p = 0.013) PaO2/FiO2 ratio (p = 0.005), SpO2/FiO2 ratio (p = 0.002) and Mean Airway Pressure (p = 0.016). These improvements remained significant in survivors (p = 0.01, p = 0.027, p = 0.01 and p = 0.015, respectively) but not in non-survivors. No changes in analgo-sedative drugs have been described.

CONCLUSIONS

CKRT showed a significant impact on hemodynamics and ventilation in the first 24 h of treatment. We observed a significant rise in the inotropic/vasoactive support required after 1 h of treatment in the overall population, and an improvement in the ventilation parameters at 24 h only in survivors.

Antimicrobial dosing recommendations during continuous renal replacement therapy: different databases, different doses

Meticulous antimicrobial management is essential among critically ill patients with acute kidney injury, particularly if renal replacement therapy is needed. Many factors affect drug removal in patients undergoing continuous renal replacement therapy CRRT. In this study, we aimed to compare current databases that are frequently used to adjust CRRT dosages of antimicrobial drugs with the gold standard. The dosage recommendations from various databases for antimicrobial drugs eliminated by CRRT were investigated. The book 'Renal Pharmacotherapy: Dosage Adjustment of Medications Eliminated by the Kidneys' was chosen as the gold standard. There were variations in the databases. Micromedex, UpToDate, and Sanford had similar rates to the gold standard of 45%, 35%, and 30%, respectively. The Micromedex database shows the most similar results to the gold standard source. In addition, a consensus was reached as a result of the expert panel meetings established to discuss the different antimicrobial dose recommendations of the databases.

Personalized antiseizure medication therapy in critically ill adult patients

Precision medicine has the potential to have a significant impact on both drug development and patient care. It is crucial to not only provide prompt effective antiseizure treatment for critically ill patients after seizures start but also have a proactive mindset and concentrate on epileptogenesis and the underlying cause of the seizures or seizure disorders. Critical illness presents different treatment issues compared with the ambulatory population, which makes it challenging to choose the best antiseizure medications and to administer them at the right time and at the right dose. Since there is a paucity of information available on antiseizure medication dosing in critically ill patients, therapeutic drug monitoring is a useful tool for defining each patient's personal therapeutic range and assisting clinicians in decision-making. Use of pharmacogenomic information relating to pharmacokinetics, hepatic metabolism, and seizure etiology may improve safety and efficacy by individualizing therapy. Studies evaluating the clinical implementation of pharmacogenomic information at the point-of-care and identification of biomarkers are also needed. These studies may make it possible to avoid adverse drug reactions, maximize drug efficacy, reduce drug-drug interactions, and optimize medications for each individual patient. This review will discuss the available literature and provide future insights on precision medicine use with antiseizure therapy in critically ill adult patients.

"CATCH" Study: Correct Antibiotic Therapy in Continuous Hemofiltration in the Critically Ill in Continuous Renal Replacement Therapy: A Prospective Observational Study

The proper posology of antibiotics in the critically ill in CRRT is difficult to assess. We therefore performed a prospective observational cohort study to make clear hints in this topic. Our results reveal a high Sieving Coefficient for all antibiotics, equal to or higher than those described in previous papers. CVVH clearance in relation to total body clearance was significant, (i.e., >than 25% for all classes). A strong correlation between the antibiotic concentrations obtained in plasma and ultrafiltrate was found both at the peak and in the valley, with the determination of two equations that allow a new method for calculating the amount of antibiotic lost in CVVH both for trough levels and peak. Based on the results of our study and considering the limitations we believe that we can extrapolate the following final considerations: (1) it is likely to carry out a loading dose for the main antibiotics (2) subsequent administrations must take into account the daily loss identified by the linear regression equation. This angular coefficient gives the idea that the average daily loss of given antibiotic is about 25%; this implies that on the basis of the linear regression equation that correlates ultrafiltered/plasma antibiotic concentration, the dosage should be increased by 25% every day, while still ensuring a daily plasma TDM of the drug.

Antibiotic Therapy in the Critically Ill with Acute Renal Failure and Renal Replacement Therapy: A Narrative Review

The outcome for critically ill patients is burdened by a double mortality rate and a longer hospital stay in the case of sepsis or septic shock. The adequate use of antibiotics may impact on the outcome since they may affect the pharmacokinetics (Pk) and pharmacodynamics (Pd) of antibiotics in such patients. Acute renal failure (ARF) occurs in about 50% of septic patients, and the consequent need for continuous renal replacement therapy (CRRT) makes the renal elimination rate of most antibiotics highly variable. Antibiotics doses should be reduced in patients experiencing ARF, in accordance with the glomerular filtration rate (GFR), whereas posology should be increased in the case of CRRT. Since different settings of CRRT may be used, identifying a standard dosage of antibiotics is very difficult, because there is a risk of both oversimplification and failing the therapeutic efficacy. Indeed, it has been seen that, in over 25% of cases, the antibiotic therapy does not reach the necessary concentration target mainly due to lack of the proper minimal inhibitory concentration (MIC) achievement. The aim of this narrative review is to clarify whether shared algorithms exist, allowing them to inform the daily practice in the proper antibiotics posology for critically ill patients undergoing CRRT.

Pharmacokinetics of Commonly Used Medications in Children Receiving Continuous Renal Replacement Therapy: A Systematic Review of Current Literature

BACKGROUND AND OBJECTIVE

The use of continuous renal replacement therapy (CRRT) for renal support has increased substantially in critically ill children compared with intermittent modalities owing to its preferential effects on hemodynamic stability. With the expanding role of CRRT, the quantification of extracorporeal clearance and the effect on primary pharmacokinetic parameters is of the utmost importance. Within this review, we aimed to summarize the current state of the literature and compare published pharmacokinetic analyses of commonly used medications in children receiving CRRT to those who are not.

METHODS

A systematic search of the literature within electronic databases PubMed, EMBASE, Cochrane Library, and Web of Science was conducted. Published studies that were included contained relevant information on the use of commonly administered medications to children, from neonates to adolescents, receiving CRRT. Pharmacokinetic parameters that were analyzed included volume of distribution, total clearance, extracorporeal clearance, area under the curve, and elimination half-life. Information regarding CRRT circuit, flow rates, and membrane components was analyzed to investigate differences in pharmacokinetics between each modality.

RESULTS

Forty-five studies met the final inclusion criteria within this systematic review, totaling 833 pediatric patients, with 586 receiving CRRT. Antimicrobials were the most common pharmacological class represented within the literature, representing 81% (35/43) of studies analyzed. Children receiving CRRT largely had similar volume of distribution and total clearance to critically ill children not receiving CRRT, suggesting reno-protective dose adjustments may lead to subtherapeutic dosing regimens in these patients. Overall, there was a tendency for hydrophilic agents, with a low protein binding to undergo elevated total clearance in these children. However, results should be interpreted with caution because of the large variability amongst patient populations and heterogeneity with CRRT modalities, flow rates, and use of extracorporeal membrane oxygenation within studies. This review was able to identify that variation in solute removal, or CRRT modalities, properties (i.e., flow rates), and membrane composition, may have differing effects on the pharmacokinetics of commonly administered medications.

CONCLUSIONS

The current state of the literature regarding medications administered to children receiving CRRT largely focuses on antimicrobials. Significant gaps remain with other commonly used medications such as sedatives and analgesics. Overall reporting of patient clinical characteristics, CRRT settings, and circuit composition was poor, with only 10% of articles including all relevant information to assess the impact of CRRT on total clearance. Changes in pharmacokinetics because of CRRT often required higher than labeled doses, suggesting renally adjusted or reno-protective doses may lead to subtherapeutic dosing regimens. A thorough understanding of the interplay between patient, drug, and CRRT-circuit factors are required to ensure adequate delivery of dosing regimens to this vulnerable population.

Fomepizole dosing during continuous renal replacement therapy - an observational study

BACKGROUND

Fomepizole is the preferred antidote for treatment of methanol and ethylene glycol poisoning, acting by inhibiting the formation of the toxic metabolites. Although very effective, the price is high and the availability is limited. Its availability is further challenged in situations with mass poisonings. Therefore, a 50% reduced maintenance dose for fomepizole during continuous renal replacement therapy (CRRT) was suggested in 2016, based on pharmacokinetic data only. Our aim was to study whether this new dosing for fomepizole during CRRT gave plasma concentrations above the required 10 µmol/L. Secondly, we wanted to study the elimination kinetics of fomepizole during CRRT, which has never been studied before.

METHODS

Prospective observational study of adult patients treated with fomepizole and CRRT. We collected samples from arterial line (pre-filter) = plasma concentration, post-filter and dialysate for fomepizole measurements. Fomepizole was measured using high-pressure liquid chromatography with a reverse phase column.

RESULTS

Ten patients were included in the study. Seven were treated with continuous veno-venous hemodialysis (CVVHD) and three with continuous veno-venous hemodiafiltration (CVVHDF). Ninety-eight percent of the plasma samples were above the minimum plasma concentration of 10 µmol/L. Fomepizole was removed during CRRT with a median saturation/sieving coefficient of 0.85 and dialysis clearance of 28 mL/min.

CONCLUSION

Fomepizole was eliminated during CCRT. The new dosing recommendations for fomepizole and CRRT appeared safe, by maintaining the plasma concentration above the minimum value of 10 µmol/L. Based on these data, the fomepizole maintenance dose during CRRT could be reduced to half as compared to intermittent hemodialysis.

Population Pharmacokinetics of Vancomycin Under Continuous Renal Replacement Therapy Using a Polymethylmethacrylate Hemofilter

BACKGROUND

Although continuous hemodiafiltration (CHDF) is often performed in critically ill patients during sepsis treatment, the pharmacokinetics of vancomycin (VCM) during CHDF with a polymethylmethacrylate hemofilter (PMMA-CHDF) have not been revealed. In this study, the authors aimed to describe the population pharmacokinetics of VCM in critically ill patients undergoing PMMA-CHDF and clarify its hemofilter clearance (CLhemofilter).

METHODS

This single-center, retrospective study enrolled patients who underwent intravenous VCM therapy during PMMA-CHDF at the intensive care unit of Chiba University Hospital between 2008 and 2016. A population analysis was performed, and CLhemofilter was assessed.

RESULTS

Twenty-five patients were enrolled. Median body weight (BW) and Sequential Organ Failure Assessment (SOFA) score were 63 kg and 15, respectively. Mean conditions for CHDF were 107.5 ± 18.3 mL/min for blood flow rate and 26.3 ± 6.3 mL/kg/h for effluent flow rate. The mean parameter estimates were distribution volume of the central compartment (V1), 59.1 L; clearance of the central compartment (CL1), 1.35 L/h; distribution volume of the peripheral compartment (V2), 56.1 L; and clearance of the peripheral compartment (CL2), 3.65 L/h. BW and SOFA score were significantly associated with V1 (P < 0.05) and CL1 (P < 0.05), respectively, and were thus selected as covariates in the final model. The estimated dosage of VCM to achieve a target area under the concentration-time curve/minimum inhibitory concentration ≥400 was 27.1 mg/kg for loading and 9.7 mg/kg every 24 hours for maintenance; these dosages were affected by BW and SOFA score. Mean CLhemofilter obtained from 8 patients was 1.35 L/h, which was similar to CL1.

CONCLUSIONS

The authors clarified the pharmacokinetics and CLhemofilter of VCM in PMMA-CHDF patients. The PK of VCM in patients undergoing CHDF appeared to vary not only with the CHDF setting and BW but also with SOFA score.

Pharmacokinetics/Pharmacodynamics of Antiviral Agents Used to Treat SARS-CoV-2 and Their Potential Interaction with Drugs and Other Supportive Measures: A Comprehensive Review by the PK/PD of Anti-Infectives Study Group of the European Society of Antimicrobial Agents

There is an urgent need to identify optimal antiviral therapies for COVID-19 caused by SARS-CoV-2. We have conducted a rapid and comprehensive review of relevant pharmacological evidence, focusing on (1) the pharmacokinetics (PK) of potential antiviral therapies; (2) coronavirus-specific pharmacodynamics (PD); (3) PK and PD interactions between proposed combination therapies; (4) pharmacology of major supportive therapies; and (5) anticipated drug-drug interactions (DDIs). We found promising in vitro evidence for remdesivir, (hydroxy)chloroquine and favipiravir against SARS-CoV-2; potential clinical benefit in SARS-CoV-2 with remdesivir, the combination of lopinavir/ritonavir (LPV/r) plus ribavirin; and strong evidence for LPV/r plus ribavirin against Middle East Respiratory Syndrome (MERS) for post-exposure prophylaxis in healthcare workers. Despite these emerging data, robust controlled clinical trials assessing patient-centred outcomes remain imperative and clinical data have already reduced expectations with regard to some drugs. Any therapy should be used with caution in the light of potential drug interactions and the uncertainty of optimal doses for treating mild versus serious infections.

A Robust Statistical Approach to Analyse Population Pharmacokinetic Data in Critically Ill Patients Receiving Renal Replacement Therapy

BACKGROUND AND AIM

Current approaches to antibiotic dose determination in critically ill patients requiring renal replacement therapy are primarily based on the assessment of highly heterogeneous data from small number of patients. The standard modelling approaches limit the scope of constructing robust confidence boundaries of the distribution of pharmacokinetics (PK) parameters, especially when the evaluation of possible association of demographic and clinical factors at different levels of the distribution of drug clearance is of interest. Commonly used compartmental models generally construct the inferences through a linear or non-linear mean regression, which is inadequate when the distribution is skewed, multi-modal or effected by atypical observation. In this study, we discuss the statistical challenges in robust estimation of the confidence boundaries of the PK parameters in the presence of highly heterogenous patient characteristics.

METHODS

A novel stepwise approach to evaluate the confidence boundaries of PK parameters is proposed by combining PK modelling with mixed-effects quantile regression (MEQR) methods.

RESULTS

This method allows the assessment demographic and clinical factors' effects at any arbitrary quantiles of the outcome of interest, without restricting assumptions on the distributions. The MEQR approach allows us to investigate if the levels of association of the covariates are different at low, medium or high concentration.

CONCLUSIONS

This methodological assessment is deemed as a background initial approach to support the development of a class of statistical algorithm in constructing robust confidence intervals of PK parameters which can be used for developing an optimised antibiotic dosing guideline for critically ill patients requiring renal replacement therapy.

Pharmacokinetics and Pharmacodynamics of Anti-infective Agents during Continuous Veno-venous Hemofiltration in Critically Ill Patients: Lessons Learned from an Ancillary Study of the IVOIRE Trial

Background

Hemofiltration rate, changes in blood and ultrafiltration flow, and discrepancies between the prescribed and administered doses strongly influence pharmacokinetics (PK) and pharmacodynamics (PD) of antimicrobial agents during continuous veno-venous hemofiltration (CVVH) in critically ill patients.

Methods

Ancillary data were from the prospective multicenter IVOIRE (hIgh VOlume in Intensive caRE) study. High volume (HV, 70 mL/kg/h) was at random compared with standard volume (SV, 35 mL/kg/h) CVVH in septic shock patients with acute kidney injury (AKI). PK/PD parameters for all antimicrobial agents used in each patient were studied during five days.

Results

Antimicrobial treatment met efficacy targets for both percentage of time above the minimal inhibitory concentration and inhibitory quotient. A significant correlation was observed between the ultrafiltration flow and total systemic clearance (Spearman test: P < 0.005) and between CVVH clearance and drug elimination half-life (Spearman test: P < 0.005). All agents were easily filtered. Mean sieving coefficient ranged from 38.7% to 96.7%. Mean elimination half-life of all agents was significantly shorter during HV-CVVH (from 1.29 to 28.54 h) than during SV-CVVH (from 1.51 to 33.85 h) (P < 0.05).

Conclusions

This study confirms that CVVH influences the PK/PD behavior of most antimicrobial agents. Antimicrobial elimination was directly correlated with convection rate. Current antimicrobial dose recommendations will expose patients to underdosing and increase the risk for treatment failure and development of resistance. Dose recommendations are proposed for some major antibiotic and antifungal treatments in patients receiving at least 25 mL/kg/h CVVH.

Pharmacokinetics of favipiravir during continuous venovenous haemofiltration in a critically ill patient with influenza

Favipiravir is a novel antiviral drug approved for influenza treatment in Japan. Little is known about favipiravir pharmacokinetics in critically ill patients. Here, we report a patient with influenza treated with favipiravir and undergoing continuous venovenous haemofiltration (CVVH) on the Intensive Care Unit of a tertiary hospital in the Netherlands. Pharmacokinetic analyses showed increased clearance and decreased plasma levels compared to healthy volunteers. CVVH has no clinically relevant contribution to total clearance. Despite susceptibility to favipiravir, the influenza virus was not cleared. A multi-disciplinary approach is needed to ensure optimal favipiravir treatment in critically ill patients.

Basic Principles of Antibiotics Dosing in Patients with Sepsis and Acute Kidney Damage Treated with Continuous Venovenous Hemodiafiltration

Sepsis is the leading cause of acute kidney damage in patients in intensive care units. Pathophysiological mechanisms of the development of acute kidney damage in patients with sepsis may be hemodynamic and non-hemodynamic. Patients with severe sepsis, septic shock and acute kidney damage are treated with continuous venovenous hemodiafiltration. Sepsis, acute kidney damage, and continuous venovenous hemodiafiltration have a significant effect on the pharmacokinetics and pharmacodynamics of antibiotics. The impact dose of antibiotics is increased due to the increased volume of distribution (increased administration of crystalloids, hypoalbuminemia, increased capillary permeability syndrome toproteins). The dose of antibiotic maintenance depends on renal, non-renal and extracorporeal clearance. In the early stage of sepsis, there is an increased renal clearance of antibiotics, caused by glomerular hyperfiltration, while in the late stage of sepsis, as the consequence of the development of acute renal damage, renal clearance of antibiotics is reduced. The extracorporeal clearance of antibiotics depends on the hydrosolubility and pharmacokinetic characteristics of the antibiotic, but also on the type of continuous dialysis modality, dialysis dose, membrane type, blood flow rate, dialysis flow rate, net filtration rate, and effluent flow rate. Early detection of sepsis and acute kidney damage, early target therapy, early administration of antibiotics at an appropriate dose, and early extracorporeal therapy for kidney replacement and removal of the inflammatory mediators can improve the outcome of patients with sepsis in intensive care units.

A Guide to Understanding Antimicrobial Drug Dosing in Critically Ill Patients on Renal Replacement Therapy

A careful management of antimicrobials is essential in the critically ill with acute kidney injury, especially if renal replacement therapy is required. Acute kidney injury may lead per se to clinically significant modifications of drugs' pharmacokinetic parameters, and the need for renal replacement therapy represents a further variable that should be considered to avoid inappropriate antimicrobial therapy. The most important pharmacokinetic parameters, useful to determine the significance of extracorporeal removal of a given drug, are molecular weight, protein binding, and distribution volume. In many cases, the extracorporeal removal of antimicrobials can be relevant, with a consistent risk of underdosing-related treatment failure and/or potential onset of bacterial resistance. It should also be taken into account that renal replacement therapies are often not standardized in critically ill patients, and their impact on plasma drug concentrations may substantially vary in relation to membrane characteristics, treatment modality, and delivered dialysis dose. Thus, in this clinical scenario, the knowledge of the pharmacokinetic and pharmacodynamic properties of different antimicrobial classes is crucial to tailor maintenance dose and/or time interval according to clinical needs. Finally, especially for antimicrobials known for a tight therapeutic range, therapeutic drug monitoring is strongly suggested to guide dosing adjustment in complex clinical settings, such as septic patients with acute kidney injury undergoing renal replacement therapy.

Pharmacokinetics-pharmacodynamics issues relevant for the clinical use of beta-lactam antibiotics in critically ill patients

Antimicrobials are among the most important and commonly prescribed drugs in the management of critically ill patients and beta-lactams are the most common antibiotic class used. Critically ill patient's pathophysiological factors lead to altered pharmacokinetics and pharmacodynamics of beta-lactams.A comprehensive bibliographic search in PubMed database of all English language articles published from January 2000 to December 2017 was performed, allowing the selection of articles addressing the pharmacokinetics or pharmacodynamics of beta-lactam antibiotics in critically ill patients.In critically ill patients, several factors may increase volume of distribution and enhance renal clearance, inducing high intra- and inter-patient variability in beta-lactam concentration and promoting the risk of antibiotic underdosing. The duration of infusion of beta-lactams has been shown to influence the fT > minimal inhibitory concentration and an improved beta-lactam pharmacodynamics profile may be obtained by longer exposure with more frequent dosing, extended infusions, or continuous infusions.The use of extracorporeal support techniques in the critically ill may further contribute to this problem and we recommend not reducing standard antibiotic dosage since no drug accumulation was found in the available literature and to maintain continuous or prolonged infusion, especially for the treatment of infections caused by multidrug-resistant bacteria.Prediction of outcome based on concentrations in plasma results in overestimation of antimicrobial activity at the site of infection, namely in cerebrospinal fluid and the lung. Therefore, although no studies have assessed clinical outcome, we recommend using higher than standard dosing, preferably with continuous or prolonged infusions, especially when treating less susceptible bacterial strains at these sites, as the pharmacodynamics profile may improve with no apparent increase in toxicity.A therapeutic drug monitoring-guided approach could be particularly useful in critically ill patients in whom achieving target concentrations is more difficult, such as obese patients, immunocompromised patients, those infected by highly resistant bacterial strains, patients with augmented renal clearance, and those undergoing extracorporeal support techniques.

Factors affecting serum concentration of vancomycin in critically ill oliguric pediatric patients receiving continuous venovenous hemodiafiltration

Vancomycin is known to be unintentionally eliminated by continuous renal replacement therapy, and the protein bound fraction of vancomycin is also known to be different in adults and children. However, there are only a few studies investigating the relationship between the dose of continuous venovenous hemodiafiltration (CVVHDF) parameters and serum concentration of vancomycin in pediatric patients. The aim of this study was to determine clinical and demographic parameters that significantly affect serum vancomycin concentrations. This retrospective cohort study was conducted at a pediatric intensive care unit in a tertiary university children’s hospital. Data from oliguric patients who underwent CVVHDF and vancomycin therapeutic drug monitoring were collected. The correlation between factors affecting serum concentration of vancomycin was analyzed using mixed effect model. A total of 177 serum samples undergoing vancomycin therapeutic drug monitoring were analyzed. The median age of study participants was 2.23 (interquartile range, 0.3–11.84) years, and 126 (71.19%) were male patients. Serum concentration of vancomycin decreased significantly as the effluent flow rate (EFR; P < 0.001), dialysate flow rate (DFR; P = 0.009), replacement fluid flow rate (RFFR; P = 0.008), the proportion of RFFR in the sum of DFR and RFFR (P = 0.025), and residual urine output increased. The adjusted R² of the multivariate regression model was 0.874 (P < 0.001) and the equation was as follows: Vancomycin trough level (mg/L) = (0.283 × daily dose of vancomycin [mg/kg/d]) + (365.139 / EFR [mL/h/kg])–(15.842 × residual urine output [mL/h/kg]). This study demonstrated that the serum concentration of vancomycin was associated with EFR, DFR, RFFR, the proportion of RFFR, and residual urine output in oliguric pediatric patients receiving CVVHDF.

Pharmacokinetics and Pharmacodynamics of Antimicrobials in Critically Ill Patients

Critically ill patients with severe infections often have altered pharmacokinetic and pharmacodynamic variables that lead to challenging treatment decisions. These altered variables can often lead to inadequate dosing and poor treatment outcomes. The pharmacokinetic parameters include absorption, distribution, metabolism, and excretion. Pharmacodynamics is the relationship between drug serum concentrations and pharmacologic and toxicologic properties of the medication. In addition to these altered parameters, these critically ill patients frequently are receiving organ support in the forms of continuous renal replacement therapy or extra-corporeal membrane oxygenation. Altered pharmacodynamics can lead to decreased end-organ perfusion, which can ultimately lead to treatment failure or exposure-related toxicity. The most common antimicrobials utilized in the intensive care unit are classified by the pharmacodynamic principles of time-dependent, concentration-dependent, and concentration dependent with time-dependence. Thus, the aim of this review is to outline pharmacokinetic and pharmacodynamic changes of critically ill patients with severe infections and provide strategies for optimal antibiotic agent dosing in these patients.

Pentobarbital Removal During Continuous Venovenous Hemofiltration: Case Report and Review of the Literature

BACKGROUND:

Renal replacement therapy may enhance the elimination of barbiturates. Pentobarbital clearance during continuous venovenous hemofiltration (CVVH) has not been described previously. We report a patient case involving the measurement of serial pentobarbital levels during CVVH and review relevant literature characterizing extracorporeal pentobarbital elimination.

METHODS:

The following is a retrospective report of a previously healthy 26-year-old woman who sustained a severe traumatic brain injury (TBI) and required administration of pentobarbital on hospital day 0 for intracranial pressure (ICP) control. Given concern for interference with the patient's ongoing neurologic assessments, pentobarbital was discontinued on hospital day 4. The patient's hospital course was complicated by acute kidney injury (AKI), requiring initiation of CVVH on hospital day 5. Daily serum pentobarbital levels were obtained during CVVH.

RESULTS:

While on CVVH, the patient's estimated pentobarbital clearance ranged from 6 to 44 mL/min and the elimination half-life ranged from 17.7 to 65.9 hours. Based on reductions in pentobarbital clearance during CVVH interruption, the elimination of drug was dependent upon extracorporeal removal in this patient. CVVH facilitated pentobarbital elimination in a manner approaching endogenous clearance in healthy individuals.

CONCLUSION:

We report clinically significant pentobarbital removal by CVVH in a patient with severe TBI. Application of CVVH may expedite reliable neurologic assessments and facilitate the application of clinical brain death examination following pentobarbital exposure.

Antiepileptic Drug Removal by Continuous Renal Replacement Therapy: A Review of the Literature

Continuous renal replacement therapy (CRRT) is used for managing acute kidney injury in critically ill patients. Removal of antiepileptic drugs (AEDs) by CRRT could be significant and may complicate patients' intensive care unit stay. The objective of the current review was to summarize the available evidence for AED removal by CRRT. An electronic literature search of PubMed (1946 to May 2016), Medline (1946 to May 2016), and Embase (1974 to May 2016) databases for studies discussing AED removal by CRRT was conducted. A total of 31 case reports discussing 32 patients were found. AEDs reported were levetiracetam (n = 3), valproic acid (n = 9), carbamazepine (n = 10), phenytoin (n = 3), phenobarbital (n = 4), lacosamide (n = 1), gabapentin (n = 1), and topiramate (n = 1). Two-thirds of the reports were about using CRRT in drug overdose and one-third was about AED removal by CRRT during therapy. Based on the current limited evidence and pharmacokinetic characteristics of AEDs, renally eliminated AEDs and/or AEDs with limited protein binding such as levetiracetam are more likely to be removed by CRRT than AEDs that are mainly metabolized and extensively protein bound such as carbamazepine. In conclusion, there is not enough evidence to provide robust dosing recommendations for AEDs in patients undergoing CRRT. Further studies are needed.

Individualised antimicrobial dosing in critically ill patients undergoing continuous renal replacement therapy: focus on total drug clearance

Background

Continuous renal replacement therapy (CRRT) is common practice in critical care patients with acute renal failure.

Objectives

To evaluate the adequacy of antimicrobial doses calculated based on the total drug clearance and dose recommended by different guides in critically ill patients undergoing CRRT.

Methods

Retrospective observational study. Patients admitted to a critical care unit during May 2014 to May 2016 and subjected to CRRT were included. The recommended dose was established as the product of the usual dose of the drug by total drug clearance.

Results

177 antimicrobial agents, used in 64 patients were analysed; 45 (25.4%) antimicrobials were given in an insufficient dose (<20%) according to the theoretical calculation. Following the recommendations in the revised guidelines, between 10% and 20% of antimicrobials were given in insufficient doses. A higher success rate of treatment in those patients not receiving a low drug dosage was seen (35.2% vs 24.0%).

Conclusions

There is a great disparity between the antimicrobial dose prescribed, recommended and calculated based on drug clearance in critically ill patients undergoing CRRT.

Milrinone Dosing Issues in Critically Ill Children With Kidney Injury: A Review

Milrinone is an inotropic drug used in a variety of clinical settings in adults and children. The efficacy of milrinone in pediatric low-cardiac output syndrome after cardiac surgery is reported. Its primary route of removal from the body is through the kidney as unchanged drug in the urine. Milrinone is not known to be efficiently removed by extracorporeal dialytic therapies and thus has the potential to cause serious adverse effects and potentially worsens renal function in patients experiencing acute kidney injury (AKI). AKI is an important public health issue that is associated with increased morbidity, mortality, and cost. It is a known risk factor for the development of chronic kidney disease. There are no specific therapies to mitigate AKI once it has developed, and interventions are focused on supportive care and dose adjustment of medications. Estimating glomerular filtration rate based on height and serum creatinine is the most commonly used clinical method for assessing kidney function and modification of medication doses. The purpose of this review is to discuss our current understanding of milrinone pharmacokinetics and pharmacodynamics in children with AKI and to describe the potential use of urinary biomarkers to guide therapeutic decision making for milrinone dosing.

The Effects of Continuous Renal Replacement on Anti-infective Therapy in the Critically Ill

Acute renal failure represents a frequent, severe complication in critically ill patients leading to a direct increase in mortality and resource utilization. Today, continuous renal replacement therapy (CRRT) has replaced traditional hemodialysis, providing more precise fluid and metabolic control and decreased hemodynamic instability. There are a limited number of studies conducted for the ideal dosing of individual anti-infective agents for patients receiving CRRT. However, knowledge of the basic principles of CRRT, in conjunction with pharmacokinetics and pharmacodynamics of anti-infectives, allows sound dosing recommendations to be formulated to ensure maximal killing effects with minimal risk of toxicity in patients receiving CRRT.

Antimicrobial Doses in Continuous Renal Replacement Therapy: A Comparison of Dosing Strategies

Purpose. Drug dose recommendations are not well defined in patients undergoing continuous renal replacement therapy (CRRT) due to limited published data. Several guidelines and pharmacokinetic equations have been proposed as tools for CRRT drug dosing. Dose recommendations derived from these methods have yet to be compared or prospectively evaluated. Methods. A literature search of PubMed, Micromedex, and Embase was conducted for 40 drugs commonly used in the ICU to gather pharmacokinetic data acquired from patients with acute and chronic kidney disease as well as healthy volunteers. These data and that obtained from drug package inserts were gathered for use in three published CRRT drug dosing equations. Doses calculated for a model patient using each method were compared to doses suggested in a commonly used dosing text. Results. Full pharmacokinetic data was available for 18, 31, and 40 agents using acute kidney injury, end stage renal disease, and normal patient data, respectively. On average, calculated doses differed by 30% or more from the doses recommended by the renal dosing text for >50% of the medications. Conclusion. Wide variability in dose recommendations for patients undergoing CRRT exists when these equations are used. Alternate, validated dosing methods need to be developed for this at-risk patient population.

Improving antimicrobial dosing in critically ill patients receiving continuous venovenous hemofiltration and the effect of pharmacist dosing adjustment

BACKGROUND

Appropriate antimicrobial dosing for patients receiving continuous venovenous hemofiltration (CVVH) is complex. Pharmacist participation in antimicrobial dosing adjustment for patients receiving CVVH may be advantageous.

METHODS

A comparative study was performed in a China hospital intensive care unit (ICU).Patients receiving CVVH in the intervention group received antimicrobial dosing adjustment service by pharmacists from January 2012 to June 2012, whereas patients in the control group received routine medical care between July 2012 and December 2012. The primary outcomes including patients' length of ICU stay, mortality in ICU, ICU hospitalization costs, and the occurrence of adverse drug events (ADEs) were then compared.

RESULTS

87 and 93 patients were included in the control and intervention groups. During the intervention period, pharmacists made 256 antimicrobial dosing adjustment recommendations for 93 enrolled patients receiving CVVH, of which 224 (87.5%) recommendations were accepted by physicians. Changing in CVVH-related variables (175, 68.4%) were the most common risk factors for dosing errors, whereas β-lactams (131, 51.2%) were the most frequency of antimicrobials associated with dosing errors. Compared with the control group, pharmacist dosing adjustment resulted in £1637.7 cost savings per patient, and 2.36 times reduction of antimicrobial-related adverse drug events (ADEs) (11 vs 26, P=0.002), while length of ICU stay and mortality in ICU showed no significant difference (P>0.05).

CONCLUSIONS

The involvement of pharmacist to participate in the ICU team rounds for patients receiving CVVH is associated with cost savings and reduction of ADEs. Hospital may consider employing ICU pharmacists.

The challenges of multiple organ dysfunction syndrome and extra-corporeal circuits for drug delivery in critically ill patients

The multiple organ dysfunction syndrome (MODS) is characterized by more than one organ system failing, especially during critical illness. MODS is the leading cause of morbidity and mortality in current ICU practice; moreover, multiple organ dysfunction, especially liver and kidneys, may significantly affect the pharmacokinetics (PKs) of different drugs that are currently administered in critically ill patients. These PK alterations may either result in insufficient drug concentrations to achieve the desired effects or in blood and tissue accumulation, with the development of serious adverse events. The use of extra-corporeal circuits, such as extracorporeal membrane oxygenation (ECMO) and continuous renal replacement therapy (CRRT), may further contribute to PKs changes in this patients' population. In this review, we have described the main PK changes occurring in all these conditions and how drug concentrations may potentially be affected. The lack of prospective studies on large cohorts of patients makes impossible any specific recommendation on drug regimen adjustment in ICU patients. Nevertheless, the clinicians should be aware of these abnormalities in order to better understand some unexpected therapeutic issues occurring in such patients.

Effectiveness of pharmacist dosing adjustment for critically ill patients receiving continuous renal replacement therapy: a comparative study

Background

The impact of continuous renal replacement therapy (CRRT) on drug removal is complicated; pharmacist dosing adjustment for these patients may be advantageous. This study aims to describe the development and implementation of pharmacist dosing adjustment for critically ill patients receiving CRRT and to examine the effectiveness of pharmacist interventions.

Methods

A comparative study was conducted in an intensive care unit (ICU) of a university-affiliated hospital. Patients receiving CRRT in the intervention group received specialized pharmacy dosing service from pharmacists, whereas patients in the no-intervention group received routine medical care without pharmacist involvement. The two phases were compared to evaluate the outcome of pharmacist dosing adjustment.

Results

The pharmacist carried out 233 dosing adjustment recommendations for patients receiving CRRT, and 212 (90.98%) of the recommendations were well accepted by the physicians. Changes in CRRT-related variables (n=144, 61.81%) were the most common risk factors for dosing errors, whereas antibiotics (n=168, 72.10%) were the medications most commonly associated with dosing errors. Pharmacist dosing adjustment resulted in a US$2,345.98 ICU cost savings per critically ill patient receiving CRRT. Suspected adverse drug events in the intervention group were significantly lower than those in the preintervention group (35 in 27 patients versus [vs] 18 in eleven patients, P<0.001). However, there was no significant difference between length of ICU stay and mortality after pharmacist dosing adjustment, which was 8.93 days vs 7.68 days (P=0.26) and 30.10% vs 27.36% (P=0.39), respectively.

Conclusion

Pharmacist dosing adjustment for patients receiving CRRT was well accepted by physicians, and was related with lower adverse drug event rates and ICU cost savings. These results may support the development of strategies to include a pharmacist in the multidisciplinary ICU team.

A stepwise approach for the management of poisoning with extracorporeal treatments

The use of an extracorporeal treatment (ECTR) in a poisoned patient may be life-saving in a limited number of scenarios. The decision-processes surrounding the use of ECTR in poisoning is complex: most nephrologists are not trained to assess a poisoned patient while clinical toxicologists rarely prescribe ECTRs. Deciding on which ECTR is most appropriate for a poison requires a good understanding of the poison's physicochemical and pharmacokinetic properties. Further, a detailed understanding of the capabilities and limitations of the different ECTRs can be useful to select the most appropriate ECTR for a given clinical situation. This manuscript provides a stepwise approach to assess the usefulness of ECTRs in poisoning.

Treatment with echinocandins during continuous renal replacement therapy

Echinocandins are indicated as first-line treatment for invasive candidiasis in moderate to severe illness. As sepsis is the main cause of acute kidney injury, the combination of echinocandin treatment and continuous renal replacement therapy (CRRT) is common. Optimizing antibiotic dosage in critically ill patients receiving CRRT is challenging. The pharmacokinetics of echinocandins have been studied under various clinical conditions; however, data for CRRT patients are scarce. Classically, drugs like echinocandins with high protein binding and predominantly non-renal elimination are not removed by CRRT, indicating that no dosage adjustment is required. However, recent studies report different proportions of echinocandins lost by filter adsorption. Nevertheless, the clinical significance of these findings remains unclear.

Pharmacokinetics of ganciclovir during continuous venovenous hemodiafiltration in critically ill patients

Ganciclovir is an antiviral agent that is frequently used in critically ill patients with cytomegalovirus (CMV) infections. Continuous venovenous hemodiafiltration (CVVHDF) is a common extracorporeal renal replacement therapy in intensive care unit patients. The aim of this study was to investigate the pharmacokinetics of ganciclovir in anuric patients undergoing CVVHDF. Population pharmacokinetic analysis was performed for nine critically ill patients with proven or suspected CMV infection who were undergoing CVVHDF. All patients received a single dose of ganciclovir at 5 mg/kg of body weight intravenously. Serum and ultradiafiltrate concentrations were assessed by high-performance liquid chromatography, and these data were used for pharmacokinetic analysis. Mean peak and trough prefilter ganciclovir concentrations were 11.8 ± 3.5 mg/liter and 2.4 ± 0.7 mg/liter, respectively. The pharmacokinetic parameters elimination half-life (24.2 ± 7.6 h), volume of distribution (81.2 ± 38.3 liters), sieving coefficient (0.76 ± 0.1), total clearance (2.7 ± 1.2 liters/h), and clearance of CVVHDF (1.5 ± 0.2 liters/h) were determined. Based on population pharmacokinetic simulations with respect to a target area under the curve (AUC) of 50 mg · h/liter and a trough level of 2 mg/liter, a ganciclovir dose of 2.5 mg/kg once daily seems to be adequate for anuric critically ill patients during CVVHDF.

Impact of pharmacist antimicrobial dosing adjustments in septic patients on continuous renal replacement therapy in an intensive care unit

BACKGROUND

Correct dosing of antimicrobial drugs in septic patients receiving continuous renal replacement therapy (CRRT) is complex. This study aimed to evaluate the effects of dosing adjustments performed by pharmacists on the length of intensive care unit (ICU) stay, ICU cost, and antimicrobial adverse drug events (ADEs).

METHODS

A single-center, 2-phase (pre-/post-intervention) study was performed in an ICU of a university-affiliated hospital. Septic patients receiving CRRT in the post-intervention phase received a specialized antimicrobial dosing service from critical care pharmacists, whereas patients in the pre-intervention phase received routine medical care without involving pharmacists. The 2 phases were compared to evaluate the outcomes of pharmacist interventions.

RESULTS

Pharmacists made 183 antimicrobial dosing adjustment recommendations for septic patients receiving CRRT. Changes in CRRT-related variables (116, 63.4%) were the most common risk factors for dosing errors, and β-lactams (101, 55.2%) were the antimicrobials most commonly associated with dosing errors. Dosing adjustments were related to a reduced length of ICU stay from 10.7 ± 11.1 days to 7.7 ± 8.3 days (p = 0.037) in the intervention group, and to cost savings of $3525 (13,463 ± 12,045 vs. 9938 ± 8811, p = 0.038) per septic patient receiving CRRT in the ICU. Suspected antimicrobial adverse drug events in the intervention group were significantly fewer than in the pre-intervention group (19 events vs. 8 events, p = 0.048).

CONCLUSIONS

The involvement of pharmacists in antimicrobial dosing adjustments in septic patients receiving CRRT is associated with a reduced length of ICU stay, lower ICU costs, and fewer ADEs. Hospitals may consider employing clinical pharmacists in ICUs.

Variability of antibiotic concentrations in critically ill patients receiving continuous renal replacement therapy: a multicentre pharmacokinetic study

OBJECTIVES

In critically ill patients receiving continuous renal replacement therapy, we aimed to assess the variability of antibiotic trough concentrations, the influence of effluent flow rates on such concentrations, and the incidence of suboptimal antibiotic dosage.

DESIGN

Prospective, observational, multicenter, pharmacokinetic study.

SETTING

Four tertiary intensive care units within the multicenter RENAL randomized controlled trial of continuous renal replacement therapy intensity.

PATIENTS

Twenty-four critically ill adult patients with acute kidney injury receiving ciprofloxacin, meropenem, piperacillin/tazobactam, or vancomycin during continuous renal replacement therapy.

INTERVENTIONS

We obtained trough blood samples and measured antibiotic concentrations.

MEASUREMENTS AND MAIN RESULTS

We obtained data from 40 dosing intervals and observed wide variability in trough concentrations (6.7-fold for meropenem, 3.8-fold for piperacillin, 10.5-fold for tazobactam, 1.9-fold for vancomycin, and 3.9-fold for ciprofloxacin). The median (interquartile range) trough concentrations (mg/L) for meropenem was 12.1 (7.8-18.4), 105.0 (74.4-204.0)/3.8 (3.4-21.8) for piperacillin/tazobactam, 12.0 (9.8-16.0) for vancomycin, and 3.7 (3.0-5.6) for ciprofloxacin. Overall, 15% of dosing intervals did not meet predetermined minimum therapeutic target concentrations, 40% did not achieve the higher target concentration, and, during 10% of dosing intervals, antibiotic concentrations were excessive. No difference, however, was found between patients on the basis of the intensity of continuous renal replacement therapy; this effect may have been obscured by differences in dosing regimens, time off the filter, or altered pharmacokinetics.

CONCLUSIONS

There is significant variability in antibiotic trough concentrations in critically ill patients receiving continuous renal replacement therapy, which did not only appear to be influenced by effluent flow rate. Here, empirical dosing of antibiotics failed to achieve the target trough antibiotic concentration during 25% of the dosing intervals.

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.

Pharmacokinetic evaluation of voriconazole treatment in critically ill patients undergoing continuous venovenous hemofiltration

INTRODUCTION

Voriconazole represents an essential part of antimicrobial therapy in critically ill patients. The aim of this study was to exclude a significant alteration in voriconazole pharmacokinetics in critically ill patients undergoing continuous venovenous hemofiltration (CVVH).

METHODS

Six patients dependent on CVVH with evidence of an invasive mycotic infection treated with intravenous voriconazole at the standard dosing regimen were investigated. The total serum concentration of voriconazole in arterial blood and the concentration in ultrafiltrate were measured by reverse-phase high-performance liquid chromatography with ultraviolet detection. The authors profiled a 5-point pharmacokinetic concentration-time curve during the 12-hour standard maintenance dosing interval and derived the basic pharmacokinetic parameters.

RESULTS

The serum voriconazole concentration did not decrease <1.0 mg/L at any time point, and the mean was 4.3 ± 2.6 mg/L and the median (range) 3.6 (9.0) mg/L. The sieving coefficient of the drug did not exceed 0.30 in any patient (0.22 ± 0.08). The mean serum AUC0-12, the mean total clearance, and the mean clearance via CVVH were 53.52 ± 29.97 mg·h/L [the median (range) of 57.74 (62.34) mg·h/L], 0.11 ± 0.07 L·h-1·kg-1, and 0.007 ± 0.003 L·h-1·kg-1, respectively. The clearance by the CVVH method ranged from 4% to 20% of the total drug clearance. The disposition of voriconazole was not compromised. The mean elimination half-life was 27.58 ± 35.82 hours [the median of 13.10 (92.21) hours], and the mean distribution volume value was 3.28 ± 3.10 L/kg [the median of 2.01 (8.10) L/kg]. Marked variability in serum concentrations, elimination half-life, distribution volume, and total clearance was seen. Half of the patients showed some drug accumulation.

CONCLUSIONS

The clearance of voriconazole by CVVH is not clinically significant. In view of this finding, voriconazole dose adjustment in patients undergoing the standard method of CVVH is not required. However, the observed potential for an unpredictable voriconazole accumulation suggests the usefulness for monitoring its levels in critically ill patients.

How to optimize drug delivery in renal replacement therapy

Drug dosing in the setting of acute kidney injury (AKI) is complicated by several factors such as pharmacokinetic changes in renal failure, inaccuracy of renal estimating equations in this setting, lack of therapeutic drug monitoring capability for most drugs, and use of extracorporeal renal replacement. Pharmacokinetic changes include decreases in protein binding and drug metabolism. Renal estimating equations most often overestimate renal clearance in AKI. Additionally, it is well recognized that some drugs are significantly cleared by extracorporeal therapy. Patients with AKI are therefore at risk for adverse outcomes of drug therapy. It has been reported that approximately half of patients with reduced renal clearance receive drug doses that are 2.5 times higher than the recommended maximum dose. To ensure efficacy and prevent toxicity, therapeutic drug monitoring is highly recommended. However, in the absence of drug monitoring, adequate concentrations can only be inferred from clinical response. A clinician must weigh the risks and benefits of possible over-dosing or under-dosing based on the therapeutic index of the drug and the clinical situation. This article will review the important factors to consider for drug dosing in patients with AKI receiving continuous renal replacement therapy and sustained low-efficiency dialysis.

Appropriate antibiotic dosing in severe sepsis and acute renal failure: factors to consider

Severe sepsis and septic shock cause considerable morbidity and mortality. Early appropriate empiric broad-spectrum antibiotics and advanced resuscitation therapy are the cornerstones of treatment for these conditions. In prescribing an antibiotic regimen in septic patients with acute renal failure treated with continuous renal replacement therapy, several factors should be considered: pharmacokinetics, weight, residual renal function, hepatic function, mode of renal replacement therapy (membrane and surface area, sieving coefficient, effluent and dialysate rate, and blood flow rate), severity of illness, microorganism, minimum inhibitory concentration, and others. Studies that determine the serum antibiotic concentrations are very useful in establishing the correct dosage in critical patients.

Peramivir pharmacokinetics in two critically ill adults with 2009 H1N1 influenza A concurrently receiving continuous renal replacement therapy

STUDY OBJECTIVE

To determine the pharmacokinetics of intravenous peramivir-an investigational neuraminidase inhibitor for the treatment of 2009 H1N1 infection or nonsubtypable influenza A thought to be the 2009 H1N1 virus-in patients concurrently receiving continuous renal replacement therapy (CRRT).

DESIGN

Pharmacokinetic analysis.

SETTING

Critical care unit at a university-affiliated hospital.

PATIENTS

Two critically ill women with 2009 H1N1 influenza A treated with compassionate-use intravenous peramivir administered as a daily infusion of 600 mg over 30 minutes while receiving continuous venovenous hemodiafiltration (CVVHDF), a form of CRRT.

MEASUREMENTS AND MAIN RESULTS

Plasma samples were collected from the two patients before and 30 minutes after the fourth (first patient) and ninth (second patient) peramivir infusion to estimate minimum (C(min)) and maximum (C(max)) plasma concentrations, respectively. Two additional postinfusion concentrations were measured from each patient to estimate noncompartmental pharmacokinetic parameters of peramivir while receiving CVVHDF. In the two patients, respectively, C(min) was 2170 and 251 ng/ml, C(max) was 18,400 and 20,300 ng/ml, area under the plasma concentration-time curve from 0-24 hours (AUC(0-24)) was 178,000 and 94,400 ng·hour/ml, drug clearance was 56 and 106 ml/minutes, and plasma half-life was 7.6 and 3.7 hours. The volume of distribution adjusted for ideal body weight at steady state was 0.51 and 0.54 L/kg, respectively.

CONCLUSION

The first patient had a slower peramivir plasma clearance compared with the second patient, but both patients had higher peramivir clearances as calculated from AUC(0-24) than those predicted by CRRT. Thus, the dosage of intravenous peramivir was appropriate in these patients. Additional pharmacokinetic data are needed to confirm these results and help guide dosing in patients receiving various forms of CRRT.

Influence of continuous venovenous hemofiltration and continuous venovenous hemodiafiltration on the disposition of doripenem

The pharmacokinetics, safety, and tolerability of a single 1-hour, 500-mg intravenous infusion of doripenem were assessed in dialysis-dependent subjects with stage 5 chronic kidney disease undergoing continuous renal replacement therapy (CRRT) via 12-hour continuous venovenous hemofiltration (CVVH) (n = 6) or continuous venovenous hemodiafiltration (CVVHDF) (n = 5). Healthy volunteers were also assessed (n = 12). Concentrations of doripenem and the primary metabolite doripenem-M-1 were measured in plasma and ultrafiltrate or ultrafiltrate/dialysate by a validated liquid chromatography-tandem mass spectrometry method. In dialysis-dependent subjects, levels of systemic exposure to doripenem and doripenem-M-1 were approximately 3- and 5-fold greater, respectively, than those in healthy subjects: for doripenem, 98 μg·h/ml for CVVH and 77 μg·h/ml for CVVHDF versus 32 μg·h/ml for healthy subjects, and for doripenem-M-1, 24 μg·h/ml for CVVH and 22 μg·h/ml for CVVHDF versus 4.7 μg·h/ml for healthy subjects. The mean sieving coefficients and saturation coefficients were >0.67 for both doripenem and doripenem-M-1. During CVVH and CVVHDF, respectively, the percentages of administered doripenem dose removed were 38% and 29%, and clearances of doripenem were 22 and 25 ml/min. Both CVVH and CVVHDF efficiently removed doripenem and doripenem-M-1. Despite significant removal of drug by CVVH and CVVHDF, a single 1-hour, 500-mg doripenem infusion produced significantly higher plasma concentrations of doripenem, higher systemic exposure (area under the plasma concentration-time curve from time zero to 12 h after the start of infusion [AUC(0-12)]), and longer half-life (t(1/2)) in subjects receiving CVVH or CVVHDF than in healthy volunteers. The recovery of drug in ultrafiltrate and ultrafiltrate/dialysate and the enhanced rate of reduction of plasma concentrations indicate that CVVH and CVVHDF significantly augmented residual total body clearance of doripenem in subjects receiving CRRT. Doripenem dosage regimens for patients receiving CRRT thus need to be adjusted.

Extracorporeal removal of drugs and toxins

Renal replacement therapies (RRT) are increasingly used for the treatment of acute and chronic kidney diseases as well as intoxications and accidental drug overdoses. These therapies offer a mechanism for the removal of toxic substances from the patient's blood and supplement the standard detoxification protocols. If instituted early, RRT can have a significant effect on the course of the toxicity; however, this process is not selective for the removal of only harmful products and can also result in the clearance of medications intended for therapeutic use.

Trimethoprim/Sulfamethoxazole pharmacokinetics in two patients undergoing continuous venovenous hemodiafiltration

OBJECTIVE

To determine the extent of elimination of trimethoprim (TMP) and sulfamethoxazole (SMX) via continuous venovenous hemodiafiltration (CVVHDF) in 2 critically ill patients with renal failure.

CASE SUMMARY

A 62-year-old woman with Pneumocystis jirovecii pneumonia (PCP) was admitted to our intensive care unit for severe acute respiratory distress syndrome. A 77-year-old man was admitted for aortic root replacement and developed septic shock and nosocomial pneumonia due to Stenotrophomonas maltophilia. Both patients developed acute renal failure, necessitating CVVHDF. They were treated with intravenous TMP/SMX adapted to renal function. The first patient received TMP 6.4 mg/kg/day and SMX 32 mg/kg/day, corresponding to 50% of the recommended high-dose TMP/SMX regimen in PCP patients. The second patient received TMP 1.7 mg/kg/day and SMX 8.6 mg/kg/day, corresponding to 50% of the usual dose in bacterial infections. We determined peak and trough serum TMP and SMX concentrations and the extent of TMP/SMX CVVHDF clearance at steady-state while the patients were still anuric and oliguric.

DISCUSSION

Data on TMP and SMX pharmacokinetics in CVVHDF are lacking and dosing recommendations are inconclusive. In both patients, CVVHDF clearance of TMP ranged from 21.5 to 28.9 mL/min, corresponding with normal renal clearance (20-80 mL/min). SMX clearance in CVVHDF showed high variability (18.7, 26.7, and 42.6 mL/min) and exceeded renal clearance values in normal renal function (1-5 mL/min). Accordingly, peak TMP serum concentrations were within the recommended range in the patient treated with a reduced TMP/SMX dose for PCP, whereas her SMX peak concentrations were only one third of recommended target concentrations.

CONCLUSIONS

Our data indicate that both TMP and SMX are removed by CVVHDF to a significant degree, and dose reduction of TMP/SMX in CVVHDF bears the risk of underdosing. Given variability in drug exposure in critically ill patients, therapeutic drug monitoring is advisable in anuric or oliguric patients undergoing continuous renal replacement therapy to ensure optimal TMP/SMX dosing.

Meropenem dosing in critically ill patients with sepsis receiving high-volume continuous venovenous hemofiltration

Use of high ultrafiltrate flow rates with continuous venovenous hemofiltration (CVVHF) in critically ill patients is an emerging setting, for which there are few data to guide drug dosing. The objectives of this study were, firstly, to investigate the pharmacokinetics of meropenem in critically ill patients with severe sepsis who are receiving high-volume CVVHF with high-volume exchanges (> or = 4 liters/h); secondly, to determine whether standard dosing regimens (1,000 mg intravenously [i.v.] every 8 h) are sufficient for treatment of less susceptible organisms such as Burkholderia pseudomallei (MIC, 4 mg/liter); and, finally, to compare the clearances observed in this study with data from previous studies using lower-volume exchanges (1 to 2 liters/h). We recruited 10 eligible patients and collected serial pre- and postfilter blood samples and ultrafiltrate and urine samples. A noncompartmental method was used to determine meropenem pharmacokinetics. The cohort had a median age of 56.6 years, a median weight of 70 kg, and a median APACHE II (acute physiology and chronic health evaluation) score of 25. The median (interquartile range) values for meropenem were as follows: terminal elimination half-life, 4.3 h (2.9 to 6.0); terminal volume of distribution, 0.2 liters/kg (0.2 to 0.3); trough concentration, 7.7 mg/liter (6.2 to 12.9); total clearance, 6.0 liters/h (5.2 to 6.2); hemofiltration clearance, 3.5 liters/h (3.4 to 3.9). In comparing the meropenem clearance here with those in previous studies, ultrafiltration flow rate was found to be the parameter that accounted for the differences in clearance of meropenem (R(2) = 0.89). In conclusion, high-volume CVVHF causes significant clearance of meropenem, necessitating steady-state doses of 1,000 mg every 8 h to maintain sufficient concentrations to treat less susceptible organisms such as B. pseudomallei.

[Acute renal failure in critically ill patients]

BACKGROUND

Acute renal failure is common in critically ill patients and is associated with a high mortality rate. This paper reviews current management of patients with acute renal failure admitted to an intensive care unit.

MATERIAL AND METHODS

Literature search in databases (Medline, Cochrane database of systematic reviews, UpToDate).

RESULTS

The prevalence of acute renal failure is 5-20 % in patients admitted to intensive care units; the associated hospital mortality is 30-60 %. The aetiology is usually multifactorial; inflammation (sepsis, surgery), hypovolaemia and drug toxicity commonly precipitate acute renal failure. There is no effective drug treatment, but early onset of renal replacement therapies with haemodialysis or haemofiltration is likely to prolong survival.

INTERPRETATION

Despite modern intensive care, mortality is high in acute renal failure and preventive measures should therefore be vigorously pursued. Haemodialysis and haemofiltration should be introduced early in acute renal failure, and should be available in all intensive care units.

Continuous-infusion beta-lactam antibiotics during continuous venovenous hemofiltration for the treatment of resistant gram-negative bacteria

OBJECTIVE

To describe the rationale, principles, and dosage calculations for continuous-infusion beta-lactam antibiotics to treat multidrug-resistant bacteria in patients undergoing continuous venovenous hemofiltration (CVVH).

DATA SOURCES

A MEDLINE search (1968-November 2008) of the English-language literature was performed using the terms continuous infusion and Pseudomonas or Acinetobacter; hemofiltration or CVVH or hemodiafiltration or CVVHDF or continuous renal replacement therapy or pharmacokinetics; and terms describing different beta-lactam antibiotics.

STUDY SELECTION AND DATA EXTRACTION

In vitro, in vivo, and human studies were evaluated that used continuous-infusion beta-lactam antibiotics to treat Pseudomonas aeruginosa and Acinetobacter baumannii infections. Studies were reviewed that described the pharmacokinetics of beta-lactam antibiotics during CVVH as well as other modalities of continuous renal replacement therapy.

DATA SYNTHESIS

Continuous infusion of beta-lactam antibiotics, maintaining drug concentrations 4-5 times higher than the minimum inhibitory concentration, is a promising approach for managing infections caused by P. aeruginosa and A. baumannii. Safe yet effective continuous infusion therapy is made difficult by the occurrence of acute renal failure and the need for renal replacement therapy. Case series and pharmacokinetic properties indicate that several beta-lactam antimicrobials that have been studied for continuous infusion, such as cefepime, ceftazidime, piperacillin, ticarcillin, clavulanic acid, and tazobactam, are significantly cleared by hemofiltration. Methodology and formulas are provided that allow practitioners to calculate dosage regimens and reach target drug concentrations for continuous beta-lactam antibiotic infusions during CVVH based on a literature review, pharmacokinetic principles, and our experience at the National Institutes of Health Clinical Center.

CONCLUSIONS

Continuous infusion of beta-lactam antibiotics may be a useful treatment strategy for multidrug-resistant gram-negative infections in the intensive care unit. Well-established pharmacokinetic and pharmacodynamic principles can be used to safely reach and maintain steady-state target concentrations of beta-lactam antibiotics in critical illness complicated by acute renal failure requiring CVVH.

Ertapenem clearance during modeled continuous renal replacement therapy

PURPOSE

To determine ertapenem transmembrane clearance (CLtm) during continuous renal replacement therapy (CRRT) using a validated in vitro model.

METHODS

Ertapenem clearance during continuous hemofiltration and hemodialysis was assessed with AN69 and polysulfone hemodiafilters at 4 dialysate (Qd) and ultrafiltration rates (Quf): 1, 2, 3, and 6 l/hour. Blood and dialysate samples were collected at each flow rate and assayed for urea (control solute) and ertapenem concentrations. The experiment was repeated 5 times for each hemodiafilter type. Ertapenem and urea sieving coefficient (SC) and saturation coefficient (SA) were assessed, and CLtm calculated.

RESULTS

In continuous hemofiltration mode, urea and ertapenem SC ranged from 1.00 to 1.19 at all Quf and did not differ between hemodiafilter types. Consequently, convective CLtm also did not differ between hemodiafilters. In continuous dialysis mode, urea Cltm did not differ between hemodiafilter types at any Qd. However, ertapenem SA and CLtm were significantly different between hemodiafilter types at Qd 6l/hour (p<0.001). As Qd increased, mean +/- SD AN69 SA declined significantly from 0.87 +/- 0.12 at Qd 1 l/hour to 0.45 +/- 0.02 at Qd 6 l/hour (p<0.001). Ertapenem SA did not differ at any Qd with the polysulfone hemodiafilter (range 0.71-0.80).

CONCLUSION

Ertapenem was cleared substantially in these in vitro CRRT models. However, our findings illustrate discordance between our observed SC and SA and the published unbound fraction of ertapenem. This finding has been reported with many other drugs, including carbapenem antibiotics. If in vivo studies corroborate our SA and SC findings, dosage adjustment for patients receiving CRRT will be required.