Pharmacokinetics and total elimination of meropenem and vancomycin in intensive care unit patients undergoing extended daily dialysis*

Removal of common antimicrobial agents by sustained low-efficiency dialysis

Adequate dosing of antimicrobials is paramount for treating infections in critically ill patients undergoing kidney replacement therapy; however, little is known about antimicrobial removal by sustained low-efficiency dialysis (SLED). The objective was to quantify the removal of cefepime, daptomycin, meropenem, piperacillin-tazobactam, and vancomycin in patients undergoing SLED. Adult patients ≥18 years with acute kidney injury (AKI) or end-stage kidney disease receiving one of the select antimicrobials and requiring SLED were included. Blood and dialysate flow rates were maintained at 250 and 100 mL/min, respectively. Simultaneous arterial and venous blood samples for the analysis of antibiotic concentrations were collected hourly for 8 hours during SLED (on-SLED). Arterial samples were collected every 2 hours for up to 6 hours while not receiving SLED (off-SLED) for the calculation of SLED clearance, half-life (t1/2) on-SLED and off-SLED, and the fraction of removal by SLED (fD). Twenty-one patients completed the study: 52% male, mean age (±SD) 53 ± 13 years, and mean weight of 98 ± 30 kg. Eighty-six percent had AKI, and 4 patients were receiving cefepime, 3 daptomycin, 10 meropenem, 6 piperacillin-tazobactam, and 13 vancomycin. The average SLED time was 7.3 ± 1.1 hours, and the mean ultrafiltration rate was 95 ± 52 mL/hour (range 10-211). The t1/2 on-SLED was substantially lower than the off-SLED t1/2 for all antimicrobials, and the SLED fD varied between 44% and 77%. An 8-hour SLED session led to significant elimination of most antimicrobials evaluated. If SLED is performed, modification of the dosing regimen is warranted to avoid subtherapeutic concentrations.

Antimicrobial pharmacokinetics and dosing in critically ill adults receiving prolonged intermittent renal replacement therapy: A systematic review

Prolonged intermittent renal replacement therapy (PIRRT) is gaining popularity as a renal replacement modality in intensive care units, but there is a relative lack of guidance regarding antimicrobial clearance and dosing when compared with other modalities. The objectives of this systematic review were to: (1) identify and describe the pharmacokinetics (PK) of relevant antimicrobials used in critically ill adults receiving PIRRT, (2) evaluate the quality of evidence supporting these data, and (3) propose dosing recommendations based on the synthesis of these data. A search strategy for multiple databases was designed and executed to identify relevant published evidence describing the PK of antimicrobials used in critically ill adults receiving PIRRT. Quality assessment, evaluation of reporting, and relevant data extraction were conducted in duplicate. Synthesis of PK/pharmacodynamic (PD) outcomes, dosing recommendations from study authors, and physicochemical properties of included antibiotics were assessed by investigators in addition to the quality of evidence to develop dosing recommendations. Thirty-nine studies enrolling 452 patients met criteria for inclusion and provided PK and/or PD data for 20 antimicrobials in critically ill adults receiving PIRRT. Nineteen studies describe both PK and PD outcomes. Vancomycin (12 studies, 171 patients), meropenem (7 studies, 84 patients), and piperacillin/tazobactam (5 studies, 56 patients) were the most frequent antimicrobials encountered. The quality of evidence was deemed strong for 7/20 antimicrobials, and strong dosing recommendations were determined for 9/20 antimicrobials. This systematic review updates and addresses issues of quality in previous systematic reviews on this topic. Despite an overall low quality of evidence, strong recommendations were able to be made for almost half of the identified antimicrobials. Knowledge gaps persist for many antimicrobials, and higher quality studies (i.e., population PK studies with assessment of PD target attainment) are needed to address these gaps.

Pharmacokinetics in Critically Ill Children with Acute Kidney Injury

Acute kidney injury (AKI) is a commonly encountered comorbidity in critically ill children. The coexistence of AKI disturbs drug pharmacokinetics and pharmacodynamics, leading to clinically significant consequences. This can complicate an already critical clinical scenario by causing potential underdosing or overdosing giving way to possible therapeutic failures and adverse reactions. Current available studies offer little guidance to help maneuver such complex dosing regimens and decision-making in pediatric patients as most of them are done on heterogeneous groups of adult populations. Though there are some studies on drug dosing during continuous renal replacement therapy (CRRT), their utility is in question because of the recent advances in CRRT technology. Our review aims to discuss the principles of pharmacokinetics pertinent for honing the existing practices of drug dosing in critically ill children with AKI, and the various complexities and intricate challenges involved. This in turn will provide a framework to help enable caretakers to tailor dosing regimens in complex clinical setups with further ease and precision.

Pharmacological profile and potential drug interactions in ovarian cancer hospitalized patients

The aim of this study was to identify the main therapeutic classes prescribed to ovarian cancer patients and the potential drug interactions (PDI) during hospitalization. This descriptive retrospective work was carried out in a referral gynecological cancer hospital from the Brazilian public health system. The first 24 h inpatients’ prescriptions were evaluated to obtain the pharmacological profile data. Clinical and epidemiological characteristics were collected through the analysis of electronic medical records. A total of 236 patients were included in the study, of which 154 (65.25%) had PDI, with a mean of 1.43 ± 1.76 interactions per patient. The main therapeutic classes prescribed were analgesics and antiemetics (35%), compatible with the oncologic supportive care. All PDI identified (n = 331) were categorized by severity, using the Micromedex database, resulting in: 1.51% contraindicated, 67.67% major, 24.77% moderate, and 6.04% minor. The more prevalent PDI were ondansetron/tramadol (22.05%) and metoclopramide/tramadol (7.25%), both major. An association between PDI and polypharmacy was observed, which did not occur between age or length of stay. Ongoing prescription review by the pharmaceutical team is necessary to identify, monitor, and manage PDI-related adverse events and carry out required interventions with patients, physicians, and nurses. Taken together the data showed that even in a specialized hospital, the complexity of the pharmacotherapy can cause harm to the ovarian cancer patient. The clinical pharmacist acting in a multidisciplinary team is important for improving patient safety in oncology services.

The Japanese Clinical Practice Guidelines for Management of Sepsis and Septic Shock 2020 (J-SSCG 2020)

The Japanese Clinical Practice Guidelines for Management of Sepsis and Septic Shock 2020 (J-SSCG 2020), a Japanese-specific set of clinical practice guidelines for sepsis and septic shock created as revised from J-SSCG 2016 jointly by the Japanese Society of Intensive Care Medicine and the Japanese Association for Acute Medicine, was first released in September 2020 and published in February 2021. An English-language version of these guidelines was created based on the contents of the original Japanese-language version. The purpose of this guideline is to assist medical staff in making appropriate decisions to improve the prognosis of patients undergoing treatment for sepsis and septic shock. We aimed to provide high-quality guidelines that are easy to use and understand for specialists, general clinicians, and multidisciplinary medical professionals. J-SSCG 2016 took up new subjects that were not present in SSCG 2016 (e.g., ICU-acquired weakness [ICU-AW], post-intensive care syndrome [PICS], and body temperature management). The J-SSCG 2020 covered a total of 22 areas with four additional new areas (patient- and family-centered care, sepsis treatment system, neuro-intensive treatment, and stress ulcers). A total of 118 important clinical issues (clinical questions, CQs) were extracted regardless of the presence or absence of evidence. These CQs also include those that have been given particular focus within Japan. This is a large-scale guideline covering multiple fields; thus, in addition to the 25 committee members, we had the participation and support of a total of 226 members who are professionals (physicians, nurses, physiotherapists, clinical engineers, and pharmacists) and medical workers with a history of sepsis or critical illness. The GRADE method was adopted for making recommendations, and the modified Delphi method was used to determine recommendations by voting from all committee members.As a result, 79 GRADE-based recommendations, 5 Good Practice Statements (GPS), 18 expert consensuses, 27 answers to background questions (BQs), and summaries of definitions and diagnosis of sepsis were created as responses to 118 CQs. We also incorporated visual information for each CQ according to the time course of treatment, and we will also distribute this as an app. The J-SSCG 2020 is expected to be widely used as a useful bedside guideline in the field of sepsis treatment both in Japan and overseas involving multiple disciplines.

Vancomycin Population Pharmacokinetics in Critically Ill Adults During Sustained Low-Efficiency Dialysis

BACKGROUND

Sustained low-efficiency dialysis (SLED) is a hybrid form of dialysis that is increasingly used in critically ill patients with kidney injury and hemodynamic instability. Antimicrobial dosing for patients receiving SLED is informed by pharmacokinetic studies that describe the drug clearance. Studies available to assist in the dosing of vancomycin in the context of SLED are lacking.

OBJECTIVE

The objective of this prospective observational study was to describe the population pharmacokinetics of vancomycin in critically ill patients receiving SLED, and use simulation studies to propose dosing strategies.

METHODS

Serial serum samples were obtained from 31 critically ill patients prescribed vancomycin while receiving SLED. Vancomycin concentrations were quantified in plasma using a validated liquid chromatography mass spectrometry/mass spectrometry method. A population pharmacokinetic model was developed, and Monte Carlo simulation was used to determine the probability of target attainment at different doses.

RESULTS

From a total of 335 serum samples from 31 patients receiving 52 sessions of SLED therapy, a two-compartment linear model with zero-order input was developed. The mean (standard deviation) clearance of vancomycin on and off SLED was 5.97 (4.04) and 2.40 (1.46) L/h, respectively. Using pharmacodynamic targets for efficacy (area under the concentration-time curve from time zero to 24 h [AUC₂₄]/minimum inhibitory concentration [MIC] ≥ 400) and safety (AUC₂₄ ≥ 700), a loading dose of 2400 mg followed by daily doses of 1600 mg is recommended. Subsequent dosing should be informed by therapeutic drug monitoring of vancomycin levels.

CONCLUSIONS

In critically ill patients receiving SLED, vancomycin clearance is highly variable with a narrow therapeutic window. Empiric dosing is proposed but subsequent dosing should be guided by drug levels.

Meropenem Stability in Human Plasma at -20 °C: Detailed Assessment of Degradation

There are concerns about the stability of meropenem in plasma samples, even when frozen at −20 °C. Previous smaller studies suggested significant degradation of meropenem at −20 °C after 3–20 days. However, in several recent clinical studies, meropenem plasma samples were still stored at −20 °C, or the storage temperature and/or time were not mentioned in the paper. The aim of this study was to describe and model meropenem degradation in human plasma at −20 °C over 1 year. Stability of meropenem in human plasma at −20 °C was investigated at seven concentrations (0.44, 4.38, 17.5, 35.1, 52.6, 70.1, and 87.6 mg/L) representative for the range of relevant concentrations encountered in clinical practice. For each concentration, samples were stored for 0, 7, 14, 21, 28, 42, 56, 70, 84, 112, 140, 168, 196, 224, 252, 280, 308, 336, and 364 days at −20 °C before being transferred to −80 °C until analysis. Degradation was modeled using polynomial regression analysis and artificial neural network (ANN). Meropenem showed significant degradation over time in human plasma when stored at −20 °C. Degradation was present over the whole concentration range and increased with higher concentrations until a concentration of 35.1 mg/L. Both models showed accurate prediction of meropenem degradation. In conclusion, this study provides detailed insights into the concentration-dependent degradation of meropenem in human plasma stored at −20 °C over 1 year. Meropenem in human plasma is shown to be stable at least up to approximately 80 days when stored at −20 °C. The polynomial model allows calculating original meropenem concentrations in samples stored for a known period of time at −20 °C.

The Japanese Clinical Practice Guidelines for Management of Sepsis and Septic Shock 2020 (J-SSCG 2020)

The Japanese Clinical Practice Guidelines for Management of Sepsis and Septic Shock 2020 (J-SSCG 2020), a Japanese-specific set of clinical practice guidelines for sepsis and septic shock created as revised from J-SSCG 2016 jointly by the Japanese Society of Intensive Care Medicine and the Japanese Association for Acute Medicine, was first released in September 2020 and published in February 2021. An English-language version of these guidelines was created based on the contents of the original Japanese-language version. The purpose of this guideline is to assist medical staff in making appropriate decisions to improve the prognosis of patients undergoing treatment for sepsis and septic shock. We aimed to provide high-quality guidelines that are easy to use and understand for specialists, general clinicians, and multidisciplinary medical professionals. J-SSCG 2016 took up new subjects that were not present in SSCG 2016 (e.g., ICU-acquired weakness [ICU-AW], post-intensive care syndrome [PICS], and body temperature management). The J-SSCG 2020 covered a total of 22 areas with four additional new areas (patient- and family-centered care, sepsis treatment system, neuro-intensive treatment, and stress ulcers). A total of 118 important clinical issues (clinical questions, CQs) were extracted regardless of the presence or absence of evidence. These CQs also include those that have been given particular focus within Japan. This is a large-scale guideline covering multiple fields; thus, in addition to the 25 committee members, we had the participation and support of a total of 226 members who are professionals (physicians, nurses, physiotherapists, clinical engineers, and pharmacists) and medical workers with a history of sepsis or critical illness. The GRADE method was adopted for making recommendations, and the modified Delphi method was used to determine recommendations by voting from all committee members. As a result, 79 GRADE-based recommendations, 5 Good Practice Statements (GPS), 18 expert consensuses, 27 answers to background questions (BQs), and summaries of definitions and diagnosis of sepsis were created as responses to 118 CQs. We also incorporated visual information for each CQ according to the time course of treatment, and we will also distribute this as an app. The J-SSCG 2020 is expected to be widely used as a useful bedside guideline in the field of sepsis treatment both in Japan and overseas involving multiple disciplines.

Pharmacokinetics of Vancomycin in Critically Ill Patients Undergoing Sustained Low-Efficiency Dialysis

INTRODUCTION

Vancomycin pharmacokinetic data in critically ill patients receiving sustained low-efficiency dialysis (SLED) is limited. Published data using vancomycin with intermittent hemodialysis and continuous renal replacement therapy may not be applicable to hybrid dialysis modalities such as SLED. Current drug references lack recommendations for vancomycin dosing in patients receiving SLED.

OBJECTIVE

The objective of this study was to determine vancomycin pharmacokinetics during SLED.

METHODS

A total of 20 patients who were critically ill with oliguric or anuric renal failure who received vancomycin and SLED were included in the study. Surrounding one SLED session, serum vancomycin blood samples were drawn before the initiation of SLED, at the termination of SLED, and 4 hours after completion of SLED treatment. Following this, patients received vancomycin, dosed to target a goal peak of 20-30 mcg/ml. A vancomycin peak level was drawn 1 hour after the end of the infusion. SLED treatment duration was at least 7 hours. Continuous data are reported as median (interquartile range) and categorical data as percentage.

RESULTS

The vancomycin elimination rate and half-life were 0.051 hours (0.042-0.074 hours) and 13.6 hours (9.4-16.6 hours), respectively. SLED reduced vancomycin serum concentrations by 35.4% (31.5-43.8%), and vancomycin rebound was 9.8% (2.5-13.7%). The vancomycin dose administered post-SLED was 1000 mg (875-1125 mg). For 18 patients, the patient-specific volume of distribution was 0.88 L/kg (0.67-1.1 L/kg), vancomycin clearance was 3.5 L/hr (2.2-5.2 L/hr), and the area under the concentration-time curve during the study time period was 280.8 mg·hr/L (254.7-297.3 mg·hr/L).

CONCLUSION

Vancomycin is significantly removed during SLED with little rebound in serum concentrations 4 hours after completion of SLED. Based on study findings, patients who are critically ill require additional vancomycin dosing after each SLED session to maintain therapeutic post-SLED vancomycin concentrations. Therapeutic drug monitoring of vancomycin is recommended during SLED.

Vancomycin for Dialytic Therapy in Critically Ill Patients: Analysis of Its Reduction and the Factors Associated with Subtherapeutic Concentrations

This study aimed to evaluate the reduction in vancomycin through intermittent haemodialysis (IHD) and prolonged haemodialysis (PHD) in acute kidney injury (AKI) patients with sepsis and to identify the variables associated with subtherapeutic concentrations. A prospective study was performed in patients admitted at an intensive care unit (ICU) of a Brazilian hospital. Blood samples were collected at the start of dialytic therapy, after 2 and 4 h of treatment and at the end of therapy to determine the serum concentration of vancomycin and thus perform pharmacokinetic evaluation and PK/PD modelling. Twenty-seven patients treated with IHD, 17 treated with PHD for 6 h and 11 treated with PHD for 10 h were included. The reduction in serum concentrations of vancomycin after 2 h of therapy was 26.65 ± 12.64% and at the end of dialysis was 45.78 ± 12.79%, higher in the 10-h PHD group, 57.70% (40, 48–64, 30%) (p = 0.037). The ratio of the area under the curve to minimal inhibitory concentration (AUC/MIC) at 24 h in the PHD group was significantly smaller than at 10 h (p = 0.047). In the logistic regression, PHD was a risk factor for an AUC/MIC ratio less than 400 (OR = 11.59, p = 0.033), while a higher serum concentration of vancomycin at T0 was a protective factor (OR = 0.791, p = 0.009). In conclusion, subtherapeutic concentrations of vancomycin in acute kidney injury (AKI) patients in dialysis were elevated and may be related to a higher risk of bacterial resistance and mortality, besides pointing out the necessity of additional doses of vancomycin during dialytic therapy, mainly in PHD.

Pharmacokinetics and dosing of vancomycin in patients undergoing sustained low efficiency daily diafiltration (SLEDD-f): A prospective study

BACKGROUND/PURPOSE

The pharmacokinetics of vancomycin in patients who undergo sustained low efficiency daily diafiltration (SLEDD-f) is not clear. This study aimed to determine the appropriate vancomycin dosage regimen for patients receiving SLEDD-f.

METHODS

This prospectively observational study enrolled critically ill patients older than 18 years old that used SLEDD-f as renal replacement therapy and received vancomycin treatment. An 8-h SLEDD-f was performed with FX-60 (high-flux helixone membrane, 1.4 m²). Serial blood samples were collected before, during, and after SLEDD-f to analyse vancomycin serum concentrations. Effluent fluid samples (a mixture of dialysate and ultrafiltrate) were also collected to determine the amount of vancomycin removal.

RESULTS

Seventeen patients were enrolled, and 10 completed the study. The amount of vancomycin removal was 447.4 ± 88.8 mg (about 78.4 ± 18.4% of the dose administered before SLEDD-f). The vancomycin concentration was reduced by 57.5 ± 14.9% during SLEDD-f, and this reduction was followed by a rebound with duration of one to three hours. The elimination half-life of vancomycin decreased from 64.1 ± 35.7 h before SLEDD-f to 7.0 ± 3.0 h during SLEDD-f.

CONCLUSION

Significant amount of vancomycin removed during SLEDD-f. Despite the existence of post-dialysis rebound, a sufficient supplemental dose is necessary to maintain therapeutic range.

Effective treatment of vancomycin nephrotoxicity with continuous venous-venous haemodiafiltration (CVVHDF) in a paediatric patient

WHAT IS KNOWN AND OBJECTIVE

Vancomycin removal by dialysis uses methods that differ in type of dialysis membrane, dialysis fluxes and duration, ultrafiltration rate and Kt/V_urea (K = dialyser urea clearance, t = time on dialysis and V = total body water) in case of nephrotoxicity. We applied continuous venous-venous haemodiafiltration (CVVHDF) to treat a paediatric case of vancomycin nephrotoxicity caused by high serum trough concentrations.

CASE SUMMARY

We report the case of a 4-year and 7-month-old boy with serum trough concentration of vancomycin of 86.0 mg/L after a 2-day treatment with vancomycin. His serum creatinine increased from 13.3 μmol/L at baseline to 227.0 μmol/L. We discontinued vancomycin and performed a 22-hours CVVHDF with high-flux membrane. Vancomycin decreased by 69.4% (82.1-25.1 mg/L), and renal function improved.

WHAT IS NEW AND CONCLUSION

Therapeutic drug monitoring and laboratory indicator measurements should be performed early during vancomycin treatment in paediatric patients with nephrotoxicity risk factors. Vancomycin removal by CVVHDF can be effective in paediatric acute kidney injury (AKI) associated with vancomycin-associated nephrotoxicity (VAN).

A Pharmacokinetic Study Comparing the Clearance of Vancomycin during Haemodialysis Using Medium Cut-Off Membrane (Theranova) and High-Flux Membranes (Revaclear)

Medium cut-off membrane (MCO) dialysers have been shown to remove a range of middle molecules, which are associated with adverse outcomes in haemodialysis (HD) patients, more effectively than high-flux HD. Vancomycin is widely used in HD patients for treating a variety of infections. To avoid subtherapeutic trough concentrations, it is important to understand vancomycin clearance in patients undergoing HD with the MCO membrane. This open label single centre, cross-over clinical study compared the vancomycin pharmacokinetics in chronic HD patients using MCO membrane (Theranova) and high-flux membrane (Revaclear). Five patients established on chronic HD who were due to receive vancomycin were enrolled. The study used alternating Theranova and Revaclear dialysis membranes over six consecutive sessions. Vancomycin was administered over the last one to two hours of each HD session. The maintenance dose was adjusted based on pre-HD serum concentrations. Over the 210 study samples, vancomycin clearance was higher with MCO-HD compared to high-flux HD but not statistically significant. Median percentage of vancomycin removal at 120 min by MCO membrane was 39% (20.6-51.5%) compared with 34.1% (21.3-48.4%) with high-flux HD. MCO-HD removes a slightly higher percentage of vancomycin at 120 min into dialysis compared to high-flux membrane dialysis in HD patients with infections. Application of vancomycin during the last one to two hours of each dialysis is required to maintain therapeutic concentrations to minimise loss through the dialyser and maintain therapeutic levels.

Pharmacokinetic and Pharmacodynamic Characteristics of Vancomycin and Meropenem in Critically Ill Patients Receiving Sustained Low-efficiency Dialysis

PURPOSE

Antibiotic dosing is challenge in critically ill patients undergoing renal replacement therapy. Our aim was to evaluate the pharmacokinetic and pharmacodynamic (PK/PD) characteristics of meropenem and vancomycin in patients undergoing SLED.

METHODS

Consecutive ICU patients undergoing SLED and receiving meropenem and/or vancomycin were prospectively evaluated. Serial blood samples were collected before, during, and at the end of SLED sessions. Antimicrobial concentrations were determined using a validated HPLC method. Noncompartmental PK analysis was performed. AUC was determined for vancomycin. For meropenem, time above MIC was calculated.

FINDINGS

A total of 24 patients receiving vancomycin and 21 receiving meropenem were included; 170 plasma samples were obtained. Median serum vancomycin and meropenem concentrations before SLED were 24.5 and 28.0 μg/mL, respectively; after SLED, 14 and 6 μg/mL. Mean removal was 42% with vancomycin and 78% with meropenem. With vancomycin, 19 (83%), 16 (70%), and 15 (65%) patients would have achieved the target (AUC_0-24 >400) considering MICs of 1, 2, and 4 mg/L, respectively. With meropenem, 17 (85%), 14 (70%), and 10 (50%) patients would have achieved the target (100% of time above MIC) if infected with isolates with MICs of 1, 4, and 8 mg/L, respectively.

IMPLICATIONS

SLED clearances of meropenem and vancomycin were 3-fold higher than the clearance described by continuous methods. Despite this finding, overall high PK/PD target attainments were obtained, except for at higher MICs. We suggest a maintenance dose of 1 g TID or BID of meropenem. With vancomycin, a more individualized approach using therapeutic drug monitoring should be used, as commercial assays are available.

Principles of Drug Dosing in Sustained Low Efficiency Dialysis (SLED) and Review of Antimicrobial Dosing Literature

The use of sustained low-efficiency dialysis (SLED) as a renal replacement modality has increased in critically ill patients with both acute kidney injury (AKI) and hemodynamic instability. Unfortunately, there is a paucity of data regarding the appropriate dosing of medications for patients undergoing SLED. Dose adjustment in SLED often requires interpretation of pharmacodynamics and pharmacokinetic factors and extrapolation based on dosing recommendations from other modes of renal replacement therapy (RRT). This review summarizes published trials of antimicrobial dose adjustment in SLED and discusses pharmacokinetic considerations specific to medication dosing in SLED. Preliminary recommendation is provided on selection of appropriate dosing for medications where published literature is unavailable.

Pediatric Continuous Renal Replacement Therapy (PCRRT) expert committee recommendation on prescribing prolonged intermittent renal replacement therapy (PIRRT) in critically ill children

INTRODUCTION

Recently, prolonged intermittent renal replacement therapies (PIRRT) have emerged as cost-effective alternatives to conventional CRRT and their use in the pediatric population has started to become more prominent. However, there is a lack of consensus guidelines on the use of PIRRT in pediatric patients in an intensive care setting.

METHODS

A literature search was performed on PubMed/Medline, Embase, and Google Scholar in conjunction with medical librarians from both India and the Cleveland Clinic hospital system to find relevant articles. The Pediatric Continuous Renal Replacement Therapy workgroup analyzed all articles for relevancy, proposed recommendations, and graded each recommendation for their strength of evidence.

RESULTS

Of the 60 studies eligible for review, the workgroup considered data from 37 studies to formulate guidelines for the use of PIRRT in children. The guidelines focused on the definition, indications, machines, and prescription of PIRRT.

CONCLUSION

Although the literature on the use of PIRRT in children is limited, the current studies give credence to their benefits and these expert recommendations are a valuable first step in the continued study of PIRRT in the pediatric population.

Antibiotic Dosing for Critically Ill Adult Patients Receiving Intermittent Hemodialysis, Prolonged Intermittent Renal Replacement Therapy, and Continuous Renal Replacement Therapy: An Update

Objective: To summarize current antibiotic dosing recommendations in critically ill patients receiving intermittent hemodialysis (IHD), prolonged intermittent renal replacement therapy (PIRRT), and continuous renal replacement therapy (CRRT), including considerations for individualizing therapy. Data Sources: A literature search of PubMed from January 2008 to May 2019 was performed to identify English-language literature in which dosing recommendations were proposed for antibiotics commonly used in critically ill patients receiving IHD, PIRRT, or CRRT. Study Selection and Data Extraction: All pertinent reviews, selected studies, and references were evaluated to ensure appropriateness for inclusion. Data Synthesis: Updated empirical dosing considerations are proposed for antibiotics in critically ill patients receiving IHD, PIRRT, and CRRT with recommendations for individualizing therapy. Relevance to Patient Care and Clinical Practice: This review defines principles for assessing renal function, identifies RRT system properties affecting drug clearance and drug properties affecting clearance during RRT, outlines pharmacokinetic and pharmacodynamic dosing considerations, reviews pertinent updates in the literature, develops updated empirical dosing recommendations, and highlights important factors for individualizing therapy in critically ill patients. Conclusions: Appropriate antimicrobial selection and dosing are vital to improve clinical outcomes. Dosing recommendations should be applied cautiously with efforts to consider local epidemiology and resistance patterns, antibiotic dosing and infusion strategies, renal replacement modalities, patient-specific considerations, severity of illness, residual renal function, comorbidities, and patient response to therapy. Recommendations provided herein are intended to serve as a guide in developing and revising therapy plans individualized to meet a patient's needs.

Optimal vancomycin dosing regimens for critically ill patients with acute kidney injury during continuous renal replacement therapy: A Monte Carlo simulation study

PURPOSE

This study aims to determine the optimal vancomycin dosing in critically ill patients with acute kidney injury receiving continuous renal replacement therapy (CRRT) using Monte Carlo simulation.

METHODS

A one compartment pharmacokinetic model was conducted to define vancomycin deposition for the initial 48hours of therapy. Pharmacokinetic parameters were gathered from previously published studies. The AUC₂₄/MIC ratio of at least 400 and an average of AUC_0-24 at > 700mgh/L were utilized to evaluate efficacy and nephrotoxicity, respectively. The doses achieved at least 90% of the probability of target attainment (PTA) with the lowest risk of nephrotoxicity defined as the optimal dose.

RESULTS

The regimens of 1.75grams every 24hours and 1.5grams loading followed by 500mg every 8hours were recommended for empirical therapy of an MRSA infection with expected MIC ≤1mg/L, and definite therapy with actual MIC of 1mg/L. The probabilities of nephrotoxic results from these regimens were 35%.

CONCLUSIONS

A higher dose of vancomycin than the current literature-based recommendation was needed in CRRT patients.

Vancomycin Removal During High-Volume Peritoneal Dialysis in Acute Kidney Injury Patients

Studies on vancomycin pharmacokinetics in acute kidney injury (AKI) patients on high-volume peritoneal dialysis (HVPD) are lacking. We studied the pharmacokinetics of intravenous (IV) vancomycin in AKI patients treated by HVPD who received a prescribed single IV dose of vancomycin (15 - 20 mg/kg total body weight) to determine the extent of vancomycin removal and to establish vancomycin dosing guidelines for the empirical treatment of AKI patients receiving HVPD. The application of 18 mg/kg vancomycin every 48 - 72 hours in AKI patients undergoing HVPD was required to maintain therapeutic concentrations.

In vitro removal of anti-infective agents by a novel cytokine adsorbent system

Objectives:

The aim of this study is to describe the in vitro adsorption of anti-infective drugs onto an extracorporeal cytokine adsorber.

Methods:

Various anti-infective drugs (β-lactams, quinolones, aminoglycosides, glycopeptides, azole antimycotics) were prepared in normal saline 0.9% and human albumin 5%, and pumped through a cytokine cartridge (CytoSorb®; CytoSorbents Corporation, Monmouth Junction, NJ, USA) at a flow rate of 1.2 L/h for 1.5 h. In addition, meropenem and ciprofloxacin were dissolved in reconstituted blood and run through a CytoSorb cartridge, which was integrated into a continuous renal replacement therapy circuit with a flow rate of 2 L/h for 18 h. Samples from the solution, pre- and post-filter, were quantified by high-performance liquid chromatography with ultraviolet detection and fluorescence polarisation immunoassay.

Results:

Observed mean clearance of the drugs in normal saline was 1.22 ± 0.07 L/h. In human albumin, clearance was 1.29 ± 0.08 L/h. In reconstituted blood, clearance of meropenem decreased from 5.4 to 1.4 L/h and for ciprofloxacin from 6.3 to 4.3 L/h within the first 1.5 h because of early drug adsorption. Continuous renal replacement therapy clearance measured without CytoSorb was stable at 2 and 1.7 L/h, respectively. Approximately 400 mg of meropenem and 300 mg of ciprofloxacin had been adsorbed by CytoSorb, suggesting that these amounts are the maximum adsorptive capacity for these drugs.

Conclusion:

In these settings, all tested drugs were adsorbed by the cartridge in relevant amounts. The identified maximum adsorptive capacity and the rapid decline in concentration during the first 1.5 h of CytoSorb use suggest that the administration of an additional dose within the first hours of CytoSorb treatment may be reasonable. In addition, early therapeutic drug monitoring should be considered.

Scaling beta-lactam antimicrobial pharmacokinetics from early life to old age

AIMS

Beta-lactam dose optimization in critical care is a current priority. We aimed to review the pharmacokinetics (PK) of three commonly used beta-lactams (amoxicillin ± clavulanate, piperacillin-tazobactam and meropenem) to compare PK parameters reported in critically and noncritically ill neonates, children and adults, and to investigate whether allometric and maturation scaling principles could be applied to describe changes in PK parameters through life.

METHODS

A systematic review of PK studies of the three drugs was undertaken using MEDLINE and EMBASE. PK parameters and summary statistics were extracted and scaled using allometric principles to 70 kg individual for comparison. Pooled data were used to model clearance maturation and decline using a sigmoidal (Hill) function.

RESULTS

A total of 130 papers were identified. Age ranged from 29 weeks to 82 years and weight from 0.9-200 kg. PK parameters from critically ill populations were reported with wider confidence intervals than those in healthy volunteers, indicating greater PK variability in critical illness. The standard allometric size and sigmoidal maturation model adequately described increasing clearance in neonates, and a sigmoidal model was also used to describe decline in older age. Adult weight-adjusted clearance was achieved at approximately 2 years postmenstrual age. Changes in volume of distribution were well described by the standard allometric model, although amoxicillin data suggested a relatively higher volume of distribution in neonates.

CONCLUSIONS

Critical illness is associated with greater PK variability than in healthy volunteers. The maturation models presented will be useful for optimizing beta-lactam dosing, although a prospective, age-inclusive study is warranted for external validation.

Vancomycin Removal During High-Volume Peritoneal Dialysis in Acute Kidney Injury Patients: A Prospective Cohort Clinical Study

Introduction

Vancomycin pharmacokinetic data in patients with acute kidney injury (AKI) on high-volume peritoneal dialysis (HVPD) are lacking. The aims were to study the pharmacokinetics of i.v. vancomycin in patients with AKI treated by HVPD who received an i.v. dose of vancomycin (15–20 mg/kg), to determine the vancomycin removal, and to establish vancomycin dosing and evaluation pharmacokinetics target attainment achievement for the empirical treatment of patients with AKI treated by HVPD.

Methods

Vancomycin was administered 1 hour before dialysis start. Samples of all dialysate were collected for a 24-hour period. Blood samples were collected after 1, 2, 4, and 24 hours of therapy. Vancomycin concentrations were determined using a liquid chromatographic (high-performance liquid chromatography)–fluorescence method. Pharmacokinetic calculations were completed assuming a 1-compartment model.

Results

Ten patients completed the study. The mean vancomycin dose administered was 18.0 ± 2.95 mg/kg (14.7–21.8 mg/kg) on the day of study (first day) and the mean percentage of vancomycin removal by HVPD was 21.7% ± 2.2% (16%–29%). Peritoneal clearance was 8.1 ± 2.2 ml/min (5.3–12 ml/min). The serum vancomycin half-life was 71.2 ± 24.7 hours (42–110 hours) during HVPD session, the maximum serum concentration was 26.2 ± 3.5 mg/l, which occurred 1 hour after vancomycin administration and HVPD start. Area under the curve (AUC)0–24/minimum inhibitory concentration (MIC) ratio ≥400 was achieved in all patients when MIC = 1 mg/l was considered.

Conclusion

HVPD removes considerable amounts of vancomycin in septic patients with AKI. Administration of 18 mg/kg vancomycin each 48 to 72 hours in patients with AKI undergoing HVPD was required to reach and maintain therapeutic concentrations.

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.

Antibiotic Dosing in Sustained Low-Efficiency Dialysis in Critically Ill Patients

Purpose of review

Sustained low-efficiency dialysis (SLED) is increasingly used as a renal replacement modality in critically ill patients with acute kidney injury (AKI) and hemodynamic instability. There is, therefore, a greater need for the understanding of the antibiotic dosage and pharmacokinetics in these patients, to provide them with optimal therapy.

Sources of information

PubMed/Medline, Embase, and Google Scholar.

Methods

PubMed/Medline, Embase, and Google Scholar databases were searched using a combination of key words: dialysis, end stage renal disease, renal failure, sustained low efficiency dialysis, extended daily dialysis, prolonged intermittent renal replacement therapy (PIRRT), and antibiotic dosing. Studies that investigated antibiotic dosing and pharmacokinetics during SLED/extended daily dialysis/PIRRT were selected for this review.

Key findings

Eleven studies met inclusion criteria and selected for data extraction. The data with regard to dialysis specifications, type of antibiotic including dosages, drug clearances, and dosage recommendations are summarized in Table 1. It is a challenge to find therapeutic doses for antibiotics during SLED therapy because, in general, only aminoglycosides and vancomycin can be assayed in clinical laboratories.

Limitations

Although current studies on antibiotic dosing in SLED are limited due to diverse and undersized patient populations, antibiotic dosage adjustments for patients receiving SLED discussed here will serve as a valuable guide. Future large-scale research should focus on establishing guidelines for antibiotic dosage in SLED.

Implications

Pharmacokinetic principles should be taken into consideration for the appropriate dosing of drugs during SLED, yet it is vital to monitor response to drug to make sure therapeutic goals are achieved. Antibiotic dosing and timing relative to the initiation of SLED may be important to maximize either the time above the minimum inhibitory concentration (MIC) (time-dependent) or the peak to MIC ratio (concentration-dependent), balancing efficacy and toxicity concerns. Critical care physicians should liaise with nephrologists to make decisions regarding appropriate antibiotic dosing in patients undergoing SLED.

Prolonged intermittent renal replacement therapy in children

Wide ranges of age and weight in pediatric patients makes renal replacement therapy (RRT) in acute kidney injury (AKI) challenging, particularly in the pediatric intensive care unit (PICU), wherein children are often hemodynamically unstable. Standard hemodialysis (HD) is difficult in this group of children and continuous veno-venous hemofiltration/dialysis (CVVH/D) has been the accepted modality in the developed world. Unfortunately, due to cost constraints, CVVH/D is often not available and peritoneal dialysis (PD) remains the common mode of RRT in resource-poor facilities. Acute PD has its drawbacks, and intermittent HD (IHD) done slowly over a prolonged period has been explored as an alternative. Various modes of slow sustained IHD have been described in the literature with the recently introduced term prolonged intermittent RRT (PIRRT) serving as an umbrella terminology for all of these modes. PIRRT has been widely accepted in adults with studies showing it to be as effective as CVVH/D but with an added advantage of being more cost-effective. Pediatric data, though scanty, has been promising. In this current review, we elaborate on the practical aspects of undertaking PIRRT in children as well as summarize its current status.

Development of a vancomycin dosing approach for critically ill patients receiving hybrid hemodialysis using Monte Carlo simulation

Objectives

Prolonged intermittent renal replacement therapy is an increasingly popular treatment for acute kidney injury in critically ill patients that runs at different flow rates and durations than conventional hemodialysis or continuous renal replacement therapies. Pharmacokinetic studies conducted in patients receiving prolonged intermittent renal replacement therapy are scarce; consequently, clinicians are challenged to dose antibiotics effectively. The purpose of this study was to develop vancomycin dosing recommendations for patients receiving prolonged intermittent renal replacement therapy.

Methods

Monte Carlo simulations were performed in thousands of virtual patients derived from previously published demographic, pharmacokinetic, and dialytic information derived from critically ill patients receiving vancomycin and other forms of renal replacement therapy. We conducted "in silico" vancomycin pharmacokinetic/pharmacodynamics analyses in these patients receiving prolonged intermittent renal replacement therapy to determine what vancomycin dose would achieve vancomycin 24-h area under the curve (AUC_24h) of 400-700 mg·h/L, a target associated with positive clinical outcomes. Nine different vancomycin dosing regimens were tested using four different, commonly used prolonged intermittent renal replacement therapy modalities. A dosing nomogram based on serum concentration data achieved after the third dose was developed to individualize vancomycin therapy.

Results

An initial vancomycin dose of 15 or 20 mg/kg immediately followed by 15 mg/kg after subsequent prolonged intermittent renal replacement therapy treatments achieved AUC_24h of ≥400 mg·h/L for ≥90% of patients regardless of prolonged intermittent renal replacement therapy duration, modality, or time of vancomycin dose relative to prolonged intermittent renal replacement therapy. Many patients experienced AUC_24h of ≥700 mg·h/L, but once the dosing nomogram was applied to serum concentrations obtained after the third vancomycin dose, 67%-88% of patients achieved AUC_24h of 400-700 mg·h/L.

Conclusion

An initial loading dose of 15-20 mg/kg followed by a maintenance regimen of 15 mg/kg after every prolonged intermittent renal replacement therapy session coupled with serum concentration monitoring should be used to individualize vancomycin dosing. These predictions need clinical verification.

Population pharmacokinetics of vancomycin in critically ill patients receiving prolonged intermittent renal replacement therapy

OBJECTIVES

The aim of this study was to describe the population pharmacokinetics of vancomycin during prolonged intermittent renal replacement therapy (PIRRT) in critically ill patients with acute kidney injury.

METHODS

Critically ill patients prescribed vancomycin across two sites had blood samples collected during one to three dosing intervals during which PIRRT was performed. Plasma samples were assayed with a validated immunoassay method. Population pharmacokinetic analysis and Monte Carlo simulations were performed using Pmetrics^®. The target vancomycin exposures were the area under the concentration-time curve within a 24-h period (AUC_0-24)/minimum inhibitory concentration (MIC) ratio of 400 for efficacy and AUC_0-24 700 for toxicity.

RESULTS

Eleven critically ill patients (seven male) were enrolled and contributed 192 plasma samples. The patient's mean ± standard deviation (SD) age, weight and body mass index (BMI) were 57 ± 13 years, 98 ± 43 kg and 31 ± 9 kg/m², respectively. A two-compartment linear model adequately described the data. The mean ± SD population pharmacokinetic parameter estimates were PIRRT clearance (CL) 3.47 ± 1.99 L/h, non-PIRRT CL 2.15 ± 2.07 L/h, volume of distribution of the central compartment (Vc) 41.85 ± 24.33 L, distribution rate constant from central to peripheral compartment 5.97 ± 7.93 per h and from peripheral to central compartment 5.29 ± 6.65 per h. Assuming a MIC of 1 mg/L, vancomycin doses of 25 mg/kg per day are suggested to be efficacious, whilst minimising toxic, exposures.

CONCLUSIONS

This is the first population pharmacokinetic study of vancomycin in patients receiving PIRRT and we observed large pharmacokinetic variability. Empirically, weight-based doses that are appropriate for the duration of PIRRT, should be selected and supplemented with therapeutic drug monitoring.

Pharmacokinetics of meropenem in septic patients on sustained low-efficiency dialysis: a population pharmacokinetic study

BACKGROUND

The aim of the study was to describe the population pharmacokinetics (PK) of meropenem in critically ill patients receiving sustained low-efficiency dialysis (SLED).

METHODS

Prospective population PK study on 19 septic patients treated with meropenem and receiving SLED for acute kidney injury. Serial blood samples for determination of meropenem concentrations were taken before, during and after SLED in up to three sessions per patient. Nonparametric population PK analysis with Monte Carlo simulations were used. Pharmacodynamic (PD) targets of 40% and 100% time above the minimal inhibitory concentration (f T _{> MIC}) were used for probability of target attainment (PTA) and fractional target attainment (FTA) against Pseudomonas aeruginosa.

RESULTS

A two-compartment linear population PK model was most appropriate with residual diuresis supported as significant covariate affecting meropenem clearance. In patients without residual diuresis the PTA for both targets (40% and 100% f T _{> MIC}) and susceptible P. aeruginosa (MIC ≤ 2 mg/L) was > 95% for a dose of 0.5 g 8-hourly. In patients with a residual diuresis of 300 mL/d 1 g 12-hourly and 2 g 8-hourly would be required to achieve a PTA of > 95% and 93% for targets of 40% f T _{> MIC} and 100% f T _{> MIC}, respectively. A dose of 2 g 8-hourly would be able to achieve a FTA of 97% for 100% f T _{> MIC} in patients with residual diuresis.

CONCLUSIONS

We found a relevant PK variability for meropenem in patients on SLED, which was significantly influenced by the degree of residual diuresis. As a result dosing recommendations for meropenem in patients on SLED to achieve adequate PD targets greatly vary. Therapeutic drug monitoring may help to further optimise individual dosing.

TRIAL REGISTRATION

Clincialtrials.gov, NCT02287493 .

Population pharmacokinetics and dosing simulations of ceftazidime in critically ill patients receiving sustained low-efficiency dialysis

Objectives

To describe the population PKs of ceftazidime in critically ill patients receiving sustained low-efficiency dialysis (SLED).

Patients and methods

This study was performed in ICUs of a university hospital. We collected blood samples during three consecutive days of SLED sessions in patients receiving ceftazidime. Concentration versus time curves were analysed using a population PKs approach with Pmetrics ® . Monte Carlo simulation for the first 24 h including a 6 h SLED session was performed with the final model. The fractional target attainment against the MIC of Pseudomonas aeruginosa was executed using targets of 50 and 100% fT  >   MIC .

Results

In total, 211 blood samples of 16 critically ill patients under SLED were collected. SLED treatments were 299.3 (68.4) min in duration. A two-compartment linear population PK model was most appropriate. The mean (SD) CL of ceftazidime on SLED, and off SLED were 5.32 (3.2), 1.06 (1.0) L/h respectively. The PTA for 50% fT  >   MIC for a dose of 1 g intravenously every 8 h was 98%. Assuming a target of 100% fT  >   MIC a dose of 2 g every 12 h covers isolates with MIC ≤8 mg/L with a PTA of 96%.

Conclusion

In critically ill patients receiving SLED, ceftazidime 1 g every 8 h and ceftazidime 2 g every 12 h appear to be sufficient for achieving traditional (50% fT  >   MIC ) and aggressive PD targets (100% fT  >   MIC ) for susceptible isolates (MIC ≤8 mg/L), respectively.

Survey of pharmacists’ antibiotic dosing recommendations for sustained low-efficiency dialysis

BACKGROUND

The use of hybrid renal replacement therapies like sustained low efficiency dialysis (SLED) is increasing in ICUs worldwide. However, pharmacokinetic studies designed to inform therapeutic antibiotic dosing in critically ill patients receiving SLED are limited. SLED operational characteristics vary across institutions. Pharmacists in institutions that utilize SLED are challenged to recommend therapeutic doses for antibiotics.

OBJECTIVE

To characterize pharmacist-recommended antibiotic regimens for SLED.

METHODS

An electronic survey was sent to pharmacist members of the American College of Clinical Pharmacy in the Nephrology or Critical Care Practice and Research Network. Dosing recommendations for a hypothetical critically ill septic patient were collected for cefepime, ceftaroline, daptomycin, levofloxacin, meropenem, and piperacillin/tazobactam. Main outcome measure Antibiotic regimens for the six antibiotics, their frequency, pharmacist’s experience with renal replacement therapies (RRT), post-graduate training, years of clinical experience, number of staffed beds in their hospital, and RRT employed in their ICUs.

RESULTS

The survey was completed by 69 clinical pharmacists who had 8.5 ± 7.5 (mean ± SD) years of experience. All pharmacists had experience dosing medications for patients receiving RRT. The most frequently recommended regimen for each antibiotic was: cefepime 1000 mg every 24 h, ceftaroline 200 mg every 12 h, daptomycin 6 mg/kg every 24 h, levofloxacin 500 mg every 24 h, meropenem 1000 mg every 12 h, and piperacillin/tazobactam 2250 mg every 8 h. Up to nine distinct regimens were recommended for each antibiotic, and the total daily dose between these regimens ranged by as much as a 12-fold. Neither pharmacist’s experience with SLED, post-graduate training, nor years of clinical experience were significantly associated with particular dosing recommendations for the antibiotics.

CONCLUSION

Pharmacists working in institutions that utilize SLED make antibiotic dosing recommendations that vary 4–12-fold depending on the drug. Published research does not provide adequate guidance to optimally dose antibiotics in patients receiving SLED. More SLED pharmacokinetic trials, real-time serum concentration monitoring and advanced pharmacokinetic modeling techniques are necessary to ensure therapeutic dosing in patients receiving SLED.

Prolonged Intermittent Renal Replacement Therapy

Prolonged intermittent renal replacement therapy (PIRRT) is becoming an increasingly popular alternative to continuous renal replacement therapy in critically ill patients with acute kidney injury. There are significant practice variations in the provision of PIRRT across institutions, with respect to prescription, technology, and delivery of therapy. Clinical trials have generally demonstrated that PIRRT is non-inferior to continuous renal replacement therapy regarding patient outcomes. PIRRT offers cost-effective renal replacement therapy along with other advantages such as early patient mobilization and decreased nursing time. However, due to lack of standardization of the procedure, PIRRT still poses significant challenges, especially pertaining to appropriate drug dosing. Future guidelines and clinical trials should work toward developing consensus definitions for PIRRT and ensure optimal delivery of therapy.

Can we use an ex vivo continuous hemofiltration model to describe the adsorption and elimination of meropenem and piperacillin?

OBJECTIVES

To determine the adsorption and elimination characteristics of meropenem and piperacillin during simulated continuous renal replacement therapy (CRRT), and to compare the observed data from this ex vivo study with previous data from clinical studies.

METHOD

This was an experimental study utilizing a modified CRRT circuit and polysulfone membrane (1.2 m2), circulated with a blood-crystalloid mixture. Adsorption onto the CRRT circuit was tested over a 4-h period, and clearance was assessed separately using variable continuous hemofiltration settings.

RESULTS

A rapid 9% reduction in circulating meropenem and piperacillin concentrations was observed at approximately 0.5 and 1.0 h for each antibiotic, respectively. The post-dilution setting was associated with a significantly higher sieving coefficient (Sc) and filter clearance (CLfilter) (mean ± SD) (Sc 1.14 ± 0.10 versus 1.06 ± 0.04; CLfilter 19.05 ± 1.63 versus 17.59 ± 0.62 ml/min, P values < 0.05) for meropenem. No significant differences were observed for piperacillin pharmacokinetics. Clinically comparable Sc data were observed between data obtained from the ex vivo study and data from previous clinical studies, for both antibiotics.

CONCLUSIONS

Meropenem and piperacillin appear to be rapidly adsorbed into the CRRT circuit, and the delivery site of fluid replacement significantly influences meropenem pharmacokinetics. However, these findings are likely to be clinically insignificant and not affect dosing requirements. This ex vivo method could be a surrogate for future clinical pharmacokinetic studies of CRRT. Further research is required to explore the applicability of the ex vivo method to further characterize antibiotic pharmacokinetics during CRRT.

Impact of the introduction of real-time therapeutic drug monitoring on empirical doses of carbapenems in critically ill burn patients

PURPOSE

Adequate empirical antibiotic dose selection for critically ill burn patients is difficult due to extreme variability in drug pharmacokinetics. Therapeutic drug monitoring (TDM) may aid antibiotic prescription and implementation of initial empirical antimicrobial dosage recommendations. This study evaluated how gradual TDM introduction altered empirical dosages of meropenem and imipenem/cilastatin in our burn ICU.

METHODS

Imipenem/cilastatin and meropenem use and daily empirical dosage at a five-bed burn ICU were analyzed retrospectively. Data for all burn admissions between 2001 and 2011 were extracted from the hospital's computerized information system. For each patient receiving a carbapenem, episodes of infection were reviewed and scored according to predefined criteria. Carbapenem trough serum levels were characterized. Prior to May 2007, TDM was available only by special request. Real-time carbapenem TDM was introduced in June 2007; it was initially available weekly and has been available 4 days a week since 2010.

RESULTS

Of 365 patients, 229 (63%) received antibiotics (109 received carbapenems). Of 23 TDM determinations for imipenem/cilastatin, none exceeded the predefined upper limit and 11 (47.8%) were insufficient; the number of TDM requests was correlated with daily dose (r=0.7). Similar numbers of inappropriate meropenem trough levels (30.4%) were below and above the upper limit. Real-time TDM introduction increased the empirical dose of imipenem/cilastatin, but not meropenem.

CONCLUSIONS

Real-time carbapenem TDM availability significantly altered the empirical daily dosage of imipenem/cilastatin at our burn ICU. Further studies are needed to evaluate the individual impact of TDM-based antibiotic adjustment on infection outcomes in these patients.

How can we ensure effective antibiotic dosing in critically ill patients receiving different types of renal replacement therapy?

Determining appropriate antibiotic dosing for critically ill patients receiving renal replacement therapy (RRT) is complex. Worldwide unstandardized and heterogeneous prescribing of RRT as well as altered patient physiology and pathogen susceptibility all cause drug disposition to be much different to that seen in non-critically ill patients. Significant changes to pharmacokinetic parameters, including volume of distribution and clearance, could be expected, in particular, for antibiotics that are hydrophilic with low plasma protein binding and that are usually primarily eliminated by the renal system. Antibiotic clearance is likely to be significantly increased when higher RRT intensities are used. The combined effect of these factors that alter antibiotic disposition is that non-standard dosing strategies should be considered to achieve therapeutic exposure. In particular, an aggressive early approach to dosing should be considered and this may include administration of a 'loading dose', to rapidly achieve therapeutic concentrations and maximally reduce the inoculum of the pathogen. This approach is particularly important given the pharmacokinetic changes in the critically ill as well as the increased likelihood of less susceptible pathogens. Dose individualization that applies knowledge of the RRT and patient factors causing altered pharmacokinetics remains the key approach for ensuring effective antibiotic therapy for these patients. Where possible, therapeutic drug monitoring should also be used to ensure more accurate therapy. A lack of pharmacokinetic data for antibiotics during the prolonged intermittent RRT and intermittent hemodialysis currently limits evidence-based antibiotic dose recommendations for these patients.

Antibiotic Dosing in Patients With Acute Kidney Injury: "Enough But Not Too Much"

Increasing evidence suggests that antibiotic dosing in critically ill patients with acute kidney injury (AKI) often does not achieve pharmacodynamic goals, and the continued high mortality rate due to infectious causes appears to confirm these findings. Although there are compelling reasons why clinicians should use more aggressive antibiotic dosing, particularly in patients receiving aggressive renal replacement therapies, concerns for toxicity associated with higher doses are real. The presence of multisystem organ failure and polypharmacy predispose these patients to drug toxicity. This article examines the pharmacokinetic and pharmacodynamic consequences of critical illness, AKI, and renal replacement therapy and describes potential solutions to help clinicians give "enough but not too much" in these very complicated patients.

Dimethylarginines ADMA and SDMA: the real water-soluble small toxins?

Uremia occurs if the kidney loses the ability to eliminate toxic compounds at a sufficient rate into the urine. In 1970, N-N, N-G- and N-G,N׳-G-dimethyl-arginine (asymmetric dimethylarginine [ADMA] and symmetric dimethylarginine) were isolated from human urine. It was anticipated that both substances might be important in the pathophysiology and for the diagnosis of various pathologic states. It took 22 years, however, before this idea materialized when it was found that ADMA, which is increased in hemodialysis patients, inhibits the synthesis of the endothelial-derived relaxing factor, identified as nitric oxide. ADMA correlates with traditional and nontraditional cardiovascular risk factors and is a strong predictor of cardiovascular events and death in both patients with chronic kidney disease and in the general population. It also seems to mediate adverse cardiovascular effects of drugs such as proton pump inhibitors. To date, we have no specific pharmacologic therapy at hand to neutralize the deleterious effects of ADMA, curbing the enthusiasm for this marker and mediator of cardiovascular disease.

Vancomycin clearance in high-volume venovenous hemofiltration

OBJECTIVE

To report the pharmacokinetic and pharmacodynamic properties of vancomycin in 4 patients undergoing high-volume continuous venovenous hemofiltration (CVVH).

CASE SUMMARY

Data from 4 patients prescribed high-volume CVVH for acute renal failure treated with vancomycin were analyzed. Vancomycin plasma concentrations were measured 4 and 24 hours after the end of a 1-hour vancomycin infusion. The mean therapy fluid rate on initiation of vancomycin was 56.2 mL/kg/h (range 48.0-65.5). The mean loading dose of vancomycin was 18.3 mg/kg (range 14.7-19.7). Median vancomycin concentration 4 hours after the dose was 18.1 mg/L (range 13.1-30.0). At 24 hours after the dose, only 1 patient had a detectable vancomycin concentration (5.2 mg/L).

DISCUSSION

There was a large variability in the clearance of vancomycin in this patient population. Current strategies for dosing vancomycin may lead to subtherapeutic trough concentrations. Vancomycin dosing in this patient population should be based on a detailed assessment of the CVVH prescription, vancomycin concentrations, and clinical needs and response.

CONCLUSIONS

An initial vancomycin dose of 20-25 mg/kg with frequent monitoring and adjustment is recommended for patients receiving high-volume CVVH.

[Strategies to avoid antibiotic resistance]

Antibiotics are used very frequently in critically ill patients as a causal and often life-saving treatment; however, the high density of use of broad spectrum antibiotics contributes to a further deterioration in resistance trends, which makes a rational prescription behavior mandatory. This particularly includes measures which lead to the reduction of antibiotic use, i.e. rigorous indications, targeted de-escalation and limited duration. For optimal efficacy of a necessary treatment the integration of pharmacokinetic and pharmacodynamic principles can be helpful.