Antibiotic Dosing in Critically Ill Adult Patients Receiving Continuous Renal Replacement Therapy

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.

Pharmacokinetic profile of acyclovir in a child receiving continuous kidney replacement therapy for acute liver failure

BACKGROUND

Continuous venovenous hemodiafiltration (CVVHDF) is one of the treatments of critically ill children presenting severe acute liver failure. This affliction might be induced by HSV infection requiring a treatment by acyclovir. Continuous kidney replacement therapy (CKRT) can alter its pharmacokinetics, according to its physicochemical properties and CVVHDF settings.

CASE-DIAGNOSIS/TREATMENT

The patient was a 21-month-old female presenting liver failure with hyperammonemia treated by acyclovir with presumed HSV infection. CKRT was initiated on day 1 with substantial replacement and dialysate flow rates (respectively 75 and 220 mL/kg/h). Acyclovir was intravenously administered every 8 h with a 1-h infusion of 500 mg/m2. Plasma and effluent concentrations were measured by liquid chromatography-tandem mass spectrometry assay to estimate the area under a curve (AUC) and CKRT clearance by 2 methods (one based on pre- and post-filter concentrations and the other one on dialysate flow rates). Clearance was estimated between 19.2 and 26.3 mL/min with the first method and between 27.6 and 44.3 mL/min with the second one. Concentrations were highly above the therapeutic index (peak concentration was measured at 28 mg/L), but AUC was appropriate.

CONCLUSIONS

This case describes acyclovir pharmacokinetics during CKRT in a pediatric patient treated by acyclovir. The patient was treated with adapted exposure with the usual dosing, but lower dosing should be investigated with complementary studies.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02539407.

The Diagnosis and Management of Herpes Simplex Pneumonia in the Critical Care Setting: A Comprehensive Review

Herpes simplex virus (HSV) belongs to the Herpesviridae family and is divided into two subtypes: HSV-1 and HSV-2. It is known that herpesviruses lie dormant in neural ganglion cells and are reactivated during times of stress, trauma, fever, and immunosuppression. While HSV primarily causes mucosal infections such as cold sores or upper respiratory tract manifestations, it can also lead to serious, life-threatening infections, particularly in immunocompromised patients. Although HSV is occasionally detected in airway samples from critically ill patients, true HSV pneumonia is rare. HSV pneumonia is thought to result from the aspiration of salivary secretions that can travel from the pharynx and tracheobronchial areas to the lungs. It can be difficult to diagnose, and the presence of HSV in respiratory specimens does not necessarily indicate true infection. Treatment with antiviral drugs such as acyclovir should be considered based on the clinical presentation, corroborative findings, and the presence of cytopathological changes in the bronchoalveolar specimen. The prognosis of HSV pneumonia is generally poor and early detection is critical for better outcomes. This review discusses the risk factors, clinical presentation, diagnosis, treatment, and prognosis of HSV pneumonia and emphasizes the importance of distinguishing between true infection and carrier status.

Physiologically-based pharmacokinetic modeling for single and multiple dosing regimens of ceftriaxone in healthy and chronic kidney disease populations: a tool for model-informed precision dosing

Introduction: Ceftriaxone is one of commonly prescribed beta-lactam antibiotics with several label and off-label clinical indications. A high fraction of administered dose of ceftriaxone is excreted renally in an unchanged form, and it may accumulate significantly in patients with impaired renal functions, which may lead to toxicity. Methods: In this study, we employed a physiologically-based pharmacokinetic (PBPK) modeling, as a tool for precision dosing, to predict the biological exposure of ceftriaxone in a virtually-constructed healthy and chronic kidney disease patient populations, with subsequent dosing optimizations. We started developing the model by integrating the physicochemical properties of the drug with biological system information in a PBPK software platform. A PBPK model in an adult healthy population was developed and evaluated visually and numerically with respect to experimental pharmacokinetic data. The model performance was evaluated based on the fold error criteria of the predicted and reported values for different pharmacokinetic parameters. Then, the model was applied to predict drug exposure in CKD patient populations with various degrees of severity. Results: The developed PBPK model was able to precisely describe the pharmacokinetic behavior of ceftriaxone in adult healthy population and in mild, moderate, and severe CKD patient populations. Decreasing the dose by approximately 25% in mild and 50% in moderate to severe renal disease provided a comparable exposure to the healthy population. Based on the simulation of multiple dosing regimens in severe CKD population, it has been found that accumulation of 2 g every 24 h is lower than the accumulation of 1 g every 12 h dosing regimen. Discussion: In this study, the observed concentration time profiles and pharmacokinetic parameters for ceftriaxone were successfully reproduced by the developed PBPK model and it has been shown that PBPK modeling can be used as a tool for precision dosing to suggest treatment regimens in population with renal impairment.

Determination of vancomycin exposure target and individualized dosing recommendations for critically ill patients undergoing continuous renal replacement therapy

STUDY OBJECTIVE

Few studies have been conducted to quantify the exposure target of vancomycin in intensive care unit (ICU) patients undergoing continuous renal replacement therapy (CRRT) and provide optimized dosage regimens. We aimed to determine vancomycin exposure target and dosing recommendations using data from an open database in critically ill patients undergoing CRRT.

DESIGN

A retrospective observational cohort study.

DATA SOURCE

A large public database.

PATIENTS

The adult patients who received intravenous vancomycin and CRRT treatment in the database between 2017 and 2019 were reviewed to determine eligibility. A total of 180 patients with 1186 observations were included in the population pharmacokinetic (PPK) model development. The clinical efficacy of vancomycin was analyzed in 159 eligible patients.

METHODS

A PPK model was developed to estimate individual pharmacokinetic (PK) parameters. The area under the concentration-time curve (AUC) was estimated by a Bayesian approach based on individual vancomycin concentrations. Multivariate logistic regression analyses were performed to identify the factors of clinical outcomes. Threshold of vancomycin exposure in predicting efficacy was identified via receiver operating characteristic (ROC) curve. Dosing recommendations were designed using Monte Carlo Simulations (MCS) based on the optimized exposure target.

MEASUREMENTS AND MAIN RESULTS

On covariate analysis, CRRT intensity significantly affected vancomycin PK. The AUC above 427 mg*h/L was the only significant predictor of clinical efficacy (adjusted odds ratio (aOR): 1.008, 95% confidence interval (CI): 1.004-1.011, p = 0.000). MCS indicated that vancomycin dosage regimens of 5 mg/kg q12h or 7.5 mg/kg q12h were recommended for patients with CRRT intensities of 20-25 mL/kg/h or 25.1-45 mL/kg/h, respectively.

CONCLUSIONS

An AUC threshold of 427 mg*h/L (assuming the minimal inhibitory concentration (MIC) = 1 mg/L) was a recommended efficacy exposure target of vancomycin for critically ill patients undergoing CRRT. Vancomycin 5-7.5 mg/kg q12h is recommended as the initial dosage regimens for ICU patients undergoing CRRT.

"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.

Vancomycin therapeutic drug monitoring in patients on continuous renal replacement therapy: a retrospective study

Objectives

This study aimed to investigate vancomycin therapeutic drug monitoring (TDM) in patients on continuous renal replacement therapy (CRRT) and explore the risk factors for exceeding the target concentration.

Methods

This retrospective study enrolled patients aged ≥18 years who were admitted to the intensive care unit and treated with ≥3 intravenous vancomycin doses during CRRT, and who underwent vancomycin TDM. Demographic and other information were collected. Multivariate logistic regression was used assess the risk factors for exceeding the target concentration.

Results

Sixty-nine patients were included, and 40.6% patients underwent TDM. Additionally, 14.5% of patients reached the optimal concentration, and 87.5% of patients who exceeded the target received a daily dose adjustment. The cumulative dose of vancomycin and serum albumin were risk factors for exceeding the target concentration in patients on CRRT.

Conclusions

Patients on CRRT did not meet the optimal vancomycin management; <50% of the patients routinely received vancomycin TDM, and <15% achieved the optimal concentration. Fewer patients in the subtherapeutic group received a daily dose adjustment than those who exceeded the target concentration. Cumulative vancomycin and serum albumin doses before TDM were the risk factors for exceeding the target concentration in CRRT patients.

Clinical Pharmacokinetics and Pharmacodynamics of Cefepime

Cefepime is a broad-spectrum fourth-generation cephalosporin with activity against Gram-positive and Gram-negative pathogens. It is generally administered as an infusion over 30-60 min or as a prolonged infusion with infusion times from 3 h to continuous administration. Cefepime is widely distributed in biological fluids and tissues with an average volume of distribution of ~ 0.2 L/kg in healthy adults with normal renal function. Protein binding is relatively low (20%), and elimination is mainly renal. About 85% of the dose is excreted unchanged in the urine, with an elimination half-life of 2-2.3 h. The pharmacokinetics of cefepime is altered under certain pathophysiological conditions, resulting in high inter-individual variability in cefepime volume of distribution and clearance, which poses challenges for population dosing approaches. Consequently, therapeutic drug monitoring of cefepime may be beneficial in certain patients including those who are critically ill, have life-threatening infections, or are infected with more resistant pathogens. Cefepime is generally safe and efficacious, with a goal exposure target of 70% time of the free drug concentration over the minimum inhibitory concentration for clinical efficacy. In recent years, reports of neurotoxicity have increased, specifically in patients with impaired renal function. This review summarizes the pharmacokinetics, pharmacodynamics, and toxicodynamics of cefepime contemporarily in the setting of increasing cefepime exposures. We explore the potential benefits of extended or continuous infusions and therapeutic drug monitoring in special populations.

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.

Optimizing Antimicrobial Dosing for Critically Ill Patients with MRSA Infections: A New Paradigm for Improving Efficacy during Continuous Renal Replacement Therapy

The dosage regimen of vancomycin, teicoplanin and daptomycin remains controversial for critically ill patients undergoing continuous renal replacement therapy (CRRT). Monte Carlo simulation was applied to identify the optimal regimens of antimicrobial agents in patients with methicillin-resistant Staphylococcus aureus (MRSA) infections based on the mechanisms of different CRRT modalities on drug clearance. The optimal vancomycin dosage for patients received a CRRT doses ≤ 30 mL/kg/h was 20 mg/kg loading dose followed by 500 mg every 8 h, while 1 g every 12 h was appropriate when 35 mL/kg/h was prescribed. The optimal teicoplanin dosage under a CRRT dose ≤ 25 mL/kg/h was four loading doses of 10 mg/kg every 12 h followed by 10 mg/kg every 48 h, 8 mg/kg every 24 h and 6 mg/kg every 24 h for continuous veno-venous hemofiltration, continuous veno-venous hemodialysis and continuous veno-venous hemodiafiltration, respectively. When the CRRT dose increased to 30–35 mL/kg/h, the teicoplanin dosage should be increased by 30%. The recommended regimen for daptomycin was 6–8 mg/kg every 24 h under a CRRT dose ≤ 25 mL/kg/h, while 8–10 mg/kg every 24 h was optimal under 30–35 mg/kg/h. The CRRT dose has an impact on probability of target attainment and CRRT modality only influences teicoplanin.

Determinants of Vancomycin Trough Concentration in Patients Receiving Continuous Veno-Venous Hemodialysis

BACKGROUND

Vancomycin pharmacokinetics are altered in the critically ill and are further distorted by renal replacement therapy. Limited literature is available evaluating vancomycin dosing in continuous veno-venous hemodialysis (CVVHD).

OBJECTIVE

The goal of this analysis was to identify factors that affect vancomycin trough concentration in patients on CVVHD and to determine an appropriate dosing strategy.

METHODS

This was a single-center, retrospective cohort study of adult inpatients admitted to the Cleveland Clinic from May 2016-December 2017. Patients in the intensive care unit who received ≥ 2 doses of vancomycin during CVVHD were included. Patients with interruptions of CVVHD inappropriately timed troughs, a change in dialysate rate, and those who received different vancomycin dosages were excluded. Multivariable linear regression including age, sex, weight, Sequential Organ Failure Assessment score, albumin, 24-hour urine output (UOP), dialysate rate, filter type, and vancomycin dose was run to determine predictors of vancomycin concentration.

RESULTS

A total of 160 patients were included. The median vancomycin dose was 12.6 mg/kg with a trough of 24.6 mcg/mL. Weight, 24-hour UOP, vancomycin dose (mg/kg), and dialysate rate (mL/kg/h) were all determined to be independent predictors of vancomycin trough level. Patients who received <10 mg/kg doses of vancomycin (N=18) achieved a median trough of 21.5 mcg/mL, with 83% being therapuetic. In patients who received >10 mg/kg (N=142), the median trough was 25.5 mcg/mL, with 47% being therapeutic.

CONCLUSION AND RELEVANCE

Vancomycin dose, dialysate rate, UOP, and weight are independently associated with vancomycin trough concentration. In CVVHD patients, vancomycin dosed at 10 mg/kg every 24 hours may be an appropriate recommendation.

Pharmacokinetic/Pharmacodynamic Optimization of Hospital-Acquired and Ventilator-Associated Pneumonia: Challenges and Strategies

Hospital-acquired pneumonia (HAP) and ventilator-associated pneumonia (VAP) are correlated with high mortality rates worldwide. Thus, the administration of antibiotic therapy with appropriate dosing regimen is critical. An efficient antibiotic is needed to maintain an adequate concentration at the infection site, for a sufficient period of time, to achieve the best therapeutic outcome. It can, however, be challenging for antibiotics to penetrate the pulmonary system due to the complexity of its structure. Crossing the blood alveolar barrier is a difficult process determined by multiple factors that are either drug related or infection related. Thus, the understanding of pharmacokinetics/pharmacodynamics (PK/PD) of antibiotics identifies the optimum dosing regimens to achieve drug penetration into the epithelial lining fluid at adequate therapeutic concentrations. Critically ill patients in the ICU can express augmented renal clearance (ARC), characterized by enhanced renal function, or may have renal dysfunction necessitating supportive care such as continuous renal replacement therapy (CRRT). Both ARC and CRRT can alter drug elimination, thus affecting drug concentrations. PK of critically ill patients is less clear due to the multiple variabilities associated with their condition. Therefore, conventional dosing regimens often lead to therapeutic failure. Another major hurdle faced in optimizing treatment for HAP/VAP is the reduction of the in vitro potency. Therapeutic drug monitoring (TDM), if available, may allow health care providers to personalize treatment to maximize efficacy of the drug exposures while minimizing toxicity. TDM can be of significant importance in populations whom PK are less defined and for resistant infections to achieve the best therapeutic outcome.

Therapeutic drug monitoring of meropenem and piperacillin-tazobactam in the Singapore critically ill population - A prospective, multi-center, observational study (BLAST 1)

PURPOSE

To determine percentage of patients with sub-therapeutic beta-lactam exposure in our intensive care units (ICU) and to correlate target attainment with clinical outcomes.

MATERIALS AND METHODS

Multi-centre, prospective, observational study was conducted in ICUs from three hospitals in Singapore from July 2016 to May 2018. Adult patients (≥21 years) receiving meropenem or piperacillin-tazobactam were included. Four blood samples were obtained during a dosing interval to measure and determine attainment of therapeutic targets: unbound beta-lactam concentration above (i) minimum inhibitory concentration (MIC) at 40% (meropenem) or 50% (piperacillin) of dosing interval (40-50%fT > MIC) and (ii) 5 × MIC at 100% of dosing interval (100%fT > 5 × MIC). Correlation to clinical outcomes was evaluated using Cox regression.

RESULTS

Beta-lactam levels were highly variable among 61 patients, with trough meropenem and piperacillin levels at 21.5 ± 16.8 mg/L and 101.6 ± 81.1 mg/L respectively. Among 85 sets of blood samples, current dosing practices were able to achieve 94% success for 40-50%fT > MIC and 44% for 100%fT > 5 × MIC. Failure to achieve 40-50%fT > MIC within 48 h was significantly associated with all-cause mortality (HR: 9.0, 95% CI: 1.8-45.0), after adjustment for APACHE II score. Achievement of 100%fT > 5 × MIC within 48 h was significantly associated with shorter length of hospital stay.

CONCLUSION

Current dosing practices may be suboptimal for ICU patients. Beta-lactam TDM may be useful.

Dose Optimization of Vancomycin for Critically Ill Patients Undergoing CVVH: A Prospective Population PK/PD Analysis

The optimal dose of vancomycin in critically ill patients receiving continuous venovenous hemofiltration (CVVH) remains unclear. The objective of this study was to identify factors that significantly affect pharmacokinetic profiles and to further investigate the optimal dosage regimens for critically ill patients undergoing CVVH based on population pharmacokinetics and pharmacodynamic analysis. A prospective population pharmacokinetic analysis was performed at the surgical intensive care unit in a level A tertiary hospital. We included 11 critically ill patients undergoing CVVH and receiving intravenous vancomycin. Serial blood samples were collected from each patient, with a total of 131 vancomycin concentrations analyzed. Nonlinear mixed effects models were developed using NONMEM software. Monte Carlo Simulation was used to optimize vancomycin dosage regimens. A two-compartment model with first-order elimination was sufficient to characterize vancomycin pharmacokinetics for CVVH patients. The population typical vancomycin clearance (CL) was 1.15 L/h and the central volume of distribution was 16.9 L. CL was significantly correlated with ultrafiltration rate (UFR) and albumin level. For patients with normal albumin and UFR between 20 and 35 mL/kg/h, the recommended dosage regimen was 10 mg/kg qd. When UFR was between 35 and 40 mL/kg/h, the recommended dosage regimen was 5 mg/kg q8h. For patients with hypoalbuminemia and UFR between 20 and 25 mL/kg/h, the recommended dosage regimen was 5 mg/kg q8h. When UFR was between 25 and 40 mL/kg/h, the recommended dosage regimen was 10 mg/kg q12h. We recommend clinicians choosing the optimal initial vancomycin dosage regimens for critically ill patients undergoing CVVH based on these two covariates.

The landscape of renal replacement therapy in Veterans Affairs Medical Center intensive care units

Background

Outpatient dialysis is standardized with several evidence-based measures of adequacy and quality that providers aim to meet while providing treatment. By contrast, in the intensive care unit (ICU) there are different types of prolonged and continuous renal replacement therapies (PIRRT and CRRT, respectively) with varied strategies for addressing patient care and a dearth of nationally accepted quality parameters. To eventually describe appropriate quality measures for ICU-related renal replacement therapy (RRT), we first aimed to capture the variety and prevalence of basic strategies and equipment utilized in the ICUs of Veteran Affairs (VA) medical facilities with inpatient hemodialysis capabilities.

Methods

Via email to the dialysis directors of all VA facilities that provided inpatient hemodialysis during 2018, we requested survey participation regarding aspects of RRT in VA ICUs. Questions centered around the mode of therapy, equipment, solutions, prescription authority, nursing, anticoagulation, antimicrobial dosing, and access.

Results

Seventy-six centers completed the questionnaire, achieving a response rate of 87.4%. Fifty-five centers reported using PIRRT or CRRT in addition to intermittent hemodialysis. Of these centers, 42 reported being specifically CRRT-capable. Over half of respondents had the capabilities to perform PIRRT. Twelve centers (21.8%) were equipped to use slow low efficient dialysis (SLED) alone. Therapy was largely prescribed by nephrologists (94.4% of centers).

Conclusions

Within the VA system, ICU-related RRT practice is quite varied. Variation in processes of care, prescription authority, nursing care coordination, medication management, and safety practices present opportunities for developing cross-cutting measures of quality of intensive care RRT that are agnostic of modality choice.

Evaluation of dosing strategies and trough concentrations of vancomycin in patients undergoing continuous venovenous hemofiltration

STUDY OBJECTIVE

Recommendations regarding vancomycin dosing in critically ill patients on continuous venovenous hemofiltration (CVVH) are limited. The purpose of this study was to evaluate current dosing practices of pharmacists for patients treated with CVVH, develop guidelines for optimal dosing and monitoring of vancomycin to improve target trough attainment, and reduce pharmacist workload.

DESIGN

A retrospective cohort study. was performed of critically ill adult patients from January 2015 to December 2018. Patients were included if they received vancomycin during CVVH for at least 48 h. Patients with significant residual kidney function, defined as daily urine output >400 ml or significant fluctuations (≥1000 ml/h in a 24-h period) in their hemofiltration rates, were excluded. Interruptions in CVVH up to 6 h/day were permitted. Dosing strategies with two dosing categories were defined: (1) dosing based on random serum levels (dosing by level, DBL) or (2) scheduled vancomycin dosing (SD).

SETTING

Academic medical center in Detroit, Michigan.

PATIENTS

Critically ill adult patients.

MEASUREMENTS AND MAIN RESULTS

During the study period, 942 patients were evaluated and 200 met inclusion criteria, for a total of 586 serum vancomycin levels. There were 141 patients with 443 random vancomycin serum levels in the DBL group and 59 patients with143 vancomycin trough levels in the SD group. Mean vancomycin trough levels were similar between groups (17.1 ± 6 vs. 16.5 ± 4 mcg/ml) for the DBL and SD groups, respectively. For the primary end point of overall target trough achievement of 15-20 mcg/ml, significantly more trough levels in the SD group were in the 15-20 mcg/ml range compared with the DBL group, 50% vs. 38%; p < 0.001, respectively. When target trough range was extended to 10-20 mcg/ml, success rates were similar between groups (74% DBL vs. 82% SD, p = 0.021). The number of interventions required by the pharmacist, including notes per day and orders per day, were reduced by approximately 50% when the SD strategy was utilized. Scheduled vancomycin dosing regimens of 15-22 mg/kg every 12-24 h were required to yield trough levels in the 15-20 mcg/ml range.

CONCLUSIONS

Target vancomycin trough achievement of 15-20 mcg/ml occurred more frequently when vancomycin was scheduled at a dose of 15-22 mg/kg every 12-24 h based on ultrafiltration rate and may alleviate the time and cost associated with frequent vancomycin serum monitoring.

Aminoglycosides in Critically Ill Septic Patients With Acute Kidney Injury Receiving Continuous Renal Replacement Therapy: A Multicenter, Observational Study

PURPOSE

Data on aminoglycoside stewardship in critically ill septic patients with acute kidney injury (AKI) needing continuous renal replacement therapy (CRRT) are scarce. The objectives of the study were to determine, during CRRT, the time window with low likelihood for safe reinjection and the proportion of inappropriate reinjection.

METHODS

A post hoc observational analysis of a multicenter randomized trial comparing the risk of hemodialysis catheter infection with ethanol lock vs placebo in critically ill patients with AKI was conducted. Eligible patients were adults in intensive care units from 6 French hospitals. Any patient with AKI needing CRRT and receiving an antimicrobial therapy for a septic episode occurring before (≤24 hours) or during CRRT was included. The aminoglycoside orders were left to the physicians' discretion, but high dose once daily was the schedule of aminoglycoside administration.

FINDINGS

A total of 145 septic episodes treated by aminoglycosides were analyzed in patients receiving CRRT. A mean (SD) of 1.6 (0.8) amikacin and 1.8 (1.2) gentamicin administrations per patient were observed. During CRRT, C_max was 17.3 mg/L (interquartile range, 13.2-22.5 mg/L) for gentamicin and 50 mg/L (interquartile range, 43.7-76.6 mg/L) for amikacin. The plasma drug concentration at 24 hours (C_H24) was 2.3 mg/L (interquartile range, 1.6-3.2 mg/L) for gentamicin and 9.3 (interquartile range, 6.6-12.0 mg/L) for amikacin. Sixty-five C_min dosages remained above the reinjection threshold. Inappropriate reinjection was observed in 11 of 65 episodes (17%). Inappropriate reinjection (defined by, at the reinjection time, C_min dosages above the threshold; ie, C_min >2 mg/L for gentamicin and >5 mg/L for amikacin) was observed in 17% of analyzed episodes. Most patients did not need reinjection until approximately ≥30 hours after their initial administration.

IMPLICATIONS

During CRRT, as indicated by the C_H24 value, which was higher than the recommended threshold, the interval to obtain a C_min low enough to allow for redosing aminoglycosides is significantly longer than 24 hours. This interval is not always respected and leads to an of inappropriate reinjection rate of 17%. ClinicalTrials.gov identifier: ISRCTNCT00875069. (Clin Ther. 2021;XX:XXX-XXX) © 2021 Elsevier HS Journals, Inc.

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.

Therapeutic Drug Monitoring Can Improve Linezolid Dosing Regimens in Current Clinical Practice: A Review of Linezolid Pharmacokinetics and Pharmacodynamics

Linezolid is an antibiotic used to treat infections caused by drug-resistant gram-positive organisms, including vancomycin-resistant Enterococcus faecium, multi-drug resistant Streptococcus pneumoniae, and methicillin-resistant Staphylococcus aureus. The adverse effects of linezolid can include thrombocytopenia and neuropathy, which are more prevalent with higher exposures and longer treatment durations. Although linezolid is traditionally administered at a standard 600 mg dose every 12 hours, the resulting exposure can vary greatly between patients and can lead to treatment failure or toxicity. The efficacy and toxicity of linezolid are determined by the exposure achieved in the patient; numerous clinical and population pharmacokinetics (popPK) studies have identified threshold measurements for both parameters. Several special populations with an increased need for linezolid dose adjustments have also been identified. Therapeutic Drug Monitoring (TDM) is a clinical strategy that assesses the response of an individual patient and helps adjust the dosing regimen to maximize efficacy while minimizing toxicity. Adaptive feedback control and model-informed precision dosing are additional strategies that use Bayesian algorithms and PK models to predict patient-specific drug exposure. TDM is a very useful tool for patient populations with sparse clinical data or known alterations in pharmacokinetics, including children, patients with renal insufficiency or those receiving renal replacement therapy, and patients taking co-medications known to interact with linezolid. As part of the clinical workflow, clinicians can use TDM with the thresholds summarized from the current literature to improve linezolid dosing for patients and maximize the probability of treatment success.

Optimizing Pharmacokinetics-Pharmacodynamics of Antimicrobial Management in Patients with Sepsis: A Review

Critically ill patients with sepsis or septic shock are at an increased risk of death. Early and aggressive interventions are essential for improving clinical outcomes. There are a number of therapeutic and practical challenges in the management of antimicrobials in patients with sepsis. These include the timely selection and administration of appropriate antimicrobials, significant physiological alterations that can influence antimicrobial pharmacokinetics, and significant interpatient variability of antimicrobial concentrations using standard dosing approaches. Understanding the impact of these factors on the probability of attaining pharmacokinetic-pharmacodynamic target goals is essential to guide optimal therapy. Using rapid diagnostic technology could facilitate timely selection of antimicrobials, and therapeutic drug monitoring would provide a more individualized dosing approach. Using an interdisciplinary sepsis team would also be beneficial in coordinating efforts to overcome the challenges encountered during this critical period to ensure optimal care.

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

INTRODUCTION

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Optimizing ceftaroline dosing in critically ill patients undergoing continuous renal replacement therapy

BACKGROUND AND OBJECTIVES

Currently, no dosing information exists for ceftaroline fosamil in patients undergoing continuous renal replacement therapy (CRRT). The objectives of this study are to characterize the pharmacokinetics of ceftaroline in critically ill patients undergoing CRRT modalities and to derive individualized dosing recommendations.

METHODS

This pharmacokinetic study aimed to enroll critically ill patients receiving ceftaroline fosamil and any CRRT modality from adult intensive care units. Selection of the specific CRRT modality and dosing regimen was based on clinical discretion. Pre-filter, post-filter, and ultrafiltrate samples were obtained before the administration of the fourth dose, after the completion of the infusion, and up to five additional time points post-infusion. Plasma concentrations were measured using a validated ultra-high performance liquid chromatography assay. Individual pharmacokinetic parameters were calculated using non-compartmental analysis.

RESULTS

Four patients were enrolled to investigate the need for dosing adjustments. The average sieving coefficient for ceftaroline was 0.81 ± 0.1, indicating high filter efficiency. The average volume of distribution was 41.8 L (0.48 L/kg) and is within the previously reported range in patients with normal renal function. Non-renal clearance accounted for more than 50% of the total clearance observed in patients. The observed pharmacokinetic profiles suggest that the pharmacodynamic target for 2-log10  CFU reduction from baseline (%fT >1 mg/L of 50%) was met for each patient. Due to the impact of CRRT and non-renal clearance, dosing recommendations were derived for different ranges of effluent flow rates and adjusted body weights. For a patient with an adjusted body weight of 70 kg and receiving CRRT at an effluent flow rate of 3 L/h, a ceftaroline fosamil dosing regimen of 400 mg every 12 h is proposed.

CONCLUSION

Ceftaroline is cleared extensively in critically ill patients receiving CRRT and may impact pharmacodynamic target achievement. Dose adjustments should be based on the intensity of the CRRT regimen, patient weight, and the clinical status of the patient.

Pharmacokinetics and Pharmacodynamics of Linezolid in Patients With Sepsis Receiving Continuous Venovenous Hemofiltration and Extended Daily Hemofiltration

BACKGROUND

This prospective study compared pharmacokinetics (PK) and pharmacodynamics (PD) of linezolid in patients with sepsis receiving continuous venovenous hemofiltration (CVVH) with patients receiving extended daily hemofiltration (EDH).

METHODS

Patients with sepsis treated with linezolid and CVVH or EDH were included. Serial blood samples were collected and linezolid concentrations measured. PKs were analyzed using Pmetrics. Monte Carlo simulations were used to evaluate PD target achievement.

RESULTS

From 20 patients, 320 blood samples were collected for PK and PD analysis. PK profiles of linezolid were best described by a 2-compartment model. PK parameters were not significantly different between EDH and CVVH groups and were associated with body weight, renal replacement therapy (RRT) duration, and sequential organ failure assessment score. Monte Carlo simulations showed poor fractional target attainment for a minimum inhibitory concentration (MIC) of 2 mg/L with standard 600 mg intravenous administration every 12 hours.

CONCLUSIONS

Patients with sepsis receiving RRT exhibited variability in PK/PD parameters for linezolid. PK parameters were not significantly different between CVVH- and EDH-treated patients. Higher probability of target attainment would be achievable at a MIC of 2 mg/L in EDH patients. Higher linezolid doses should be considered for patients on RRT to achieve adequate blood levels.

Optimal levofloxacin dosing regimens in critically ill patients with acute kidney injury receiving continuous renal replacement therapy

PURPOSES

To determine appropriate dosing of levofloxacin in critically ill patients receiving continuous renal replacement therapy (CRRT).

METHODS

All necessary pharmacokinetic and pharmacodynamic parameters from critically ill patients were obtained to develop mathematical models with first order elimination. Levofloxacin concentration-time profiles were calculated to determine the efficacy based on the probability of target attainment (PTA) of AUC_24h/MIC ≥50 for Gram-positive and AUC_24h/MIC ≥125 for Gram-negative infections. A group of 5000 virtual patients was simulated and tested using Monte Carlo simulations for each dose in the models. The optimal dosing regimens were defined as the dose achieved target PTA at least 90% of the virtual patients.

RESULTS

No conventional, FDA approved regimens achieved at least 90% of PTA for Gram-negative infection with Pseudomonas aeruginosa at MIC of 2 mg/L. The successful dose (1750 mg on day 1, then 1500 mg q 24 h) was far exceeded the maximum FDA-approved doses. For Gram-positive infections, a levofloxacin 750 mg q 24 h was sufficient to attain PTA target of ~90% at the MIC of 2 mg/L for Streptococcus pneumoniae.

CONCLUSIONS

Levofloxacin cannot be recommended as an empiric monotherapy for serious Gram-negative infections in patients receiving CRRT due to suboptimal efficacy.

Meropenem dosing recommendations for critically ill patients receiving continuous renal replacement therapy

PURPOSES

To gather available meropenem pharmacokinetics and define drug dosing regimens for Asian critically ill patients receiving CRRT.

METHODS

All necessary pharmacokinetic and pharmacodynamic data from Asian population were gathered to develop mathematic models with first order elimination. Meropenem concentration-time profiles were calculated to evaluate efficacy based on the probability of target attainment (PTA) of 40%fT_>4MIC. A group of 5000 virtual patients was created and tested using Monte Carlo simulations for each dose in the models. The optimal dosing regimens were defined as the doses achieved at least 90% of the PTA.

RESULTS

The recommended meropenem dosing regimen for Asian critically ill patients receiving CRRT with standard (20-25 mL/kg/h) and high (35 mL/kg/h) effluent rates was 750 mg q 8 h to manage Gram negative infections with expected MIC < 2 mg/L in virtual Asian patients. Some meropenem dosages from available clinical resources could not achieve the aforementioned target. The volume of distribution, body weights and nonrenal clearance significantly contributed to drug dosing adaptation especially in the specific population.

CONCLUSIONS

A meropenem regimen of 750 mg q 8 h was recommended for Asian critically ill patients receiving 2 different CRRT modalities with standard and high effluent rates. Clinical validation of these results is needed.

Developing an isotope dilution UHPLC-MS/MS method to quantify linezolid in human plasma: application to therapeutic drug monitoring

Aim: To optimize clinical efficacy and reduce the drug-exposure-related toxicity of linezolid, whose concentrations show wide inter-variabilities, a simple and reliable quantitative assay for therapeutic drug monitoring is necessary. Results: A UHPLC-MS/MS assay has been established for determination of linezolid in human plasma and fully validated according to the US FDA guidelines. After a simple, isotope-dilluted precipitation with methanol, the analytes were separated by a straightforward isocratic mode and the MS/MS was conducted under the ESI⁺ mode fitted with SRM. The calibration curves proved acceptable linearity in the range of 0.1-30.0 µg/ml. Conclusion: The present assay is currently used in routine clinical practice, being applied to therapeutic drug monitoring and helps to optimize individual dosing regimens and manage adverse effects in ICU patients.

Uremic Toxins and Ciprofloxacin Affect Human Tenocytes In Vitro

Tendinopathy is a rare but serious complication of quinolone therapy. Risk factors associated with quinolone-induced tendon disorders include chronic kidney disease accompanied by the accumulation of uremic toxins. Hence, the present study explored the effects of the representative uremic toxins phenylacetic acid (PAA) and quinolinic acid (QA), both alone and in combination with ciprofloxacin (CPX), on human tenocytes in vitro. Tenocytes incubated with uremic toxins +/- CPX were investigated for metabolic activity, vitality, expression of the dominant extracellular tendon matrix (ECM) protein type I collagen, cell-matrix receptor β1-integrin, proinflammatory interleukin (IL)-1β, and the ECM-degrading enzyme matrix metalloproteinase (MMP)-1. CPX, when administered at high concentrations (100 mM), suppressed tenocyte metabolism after 8 h exposure and at therapeutic concentrations after 72 h exposure. PAA reduced tenocyte metabolism only after 72 h exposure to very high doses and when combined with CPX. QA, when administered alone, led to scarcely any cytotoxic effect. Combinations of CPX with PAA or QA did not cause greater cytotoxicity than incubation with CPX alone. Gene expression of the pro-inflammatory cytokine IL-1β was reduced by CPX but up-regulated by PAA and QA. Protein levels of type I collagen decreased in response to high CPX doses, whereas PAA and QA did not affect its synthesis significantly. MMP-1 mRNA levels were increased by CPX. This effect became more pronounced in the form of a synergism following exposure to a combination of CPX and PAA. CPX was more tenotoxic than the uremic toxins PAA and QA, which showed only distinct suppressive effects.

Recommendation of Antimicrobial Dosing Optimization During Continuous Renal Replacement Therapy

Continuous Renal Replacement Therapy (CRRT) is more and more widely used in patients for various indications recent years. It is still intricate for clinicians to decide a suitable empiric antimicrobial dosing for patients receiving CRRT. Inappropriate doses of antimicrobial agents may lead to treatment failure or drug resistance of pathogens. CRRT factors, patient individual conditions and drug pharmacokinetics/pharmacodynamics are the main elements effecting the antimicrobial dosing adjustment. With the development of CRRT techniques, some antimicrobial dosing recommendations in earlier studies were no longer appropriate for clinical use now. Here, we reviewed the literatures involving in new progresses of antimicrobial dosages, and complied the updated empirical dosing strategies based on CRRT modalities and effluent flow rates. The following antimicrobial agents were included for review: flucloxacillin, piperacillin/tazobactam, ceftriaxone, ceftazidime/avibactam, cefepime, ceftolozane/tazobactam, sulbactam, meropenem, imipenem, panipenem, biapenem, ertapenem, doripenem, amikacin, ciprofloxacin, levofloxacin, moxifloxacin, clindamycin, azithromycin, tigecycline, polymyxin B, colistin, vancomycin, teicoplanin, linezolid, daptomycin, sulfamethoxazole/trimethoprim, fluconazole, voriconazole, posaconzole, caspofungin, micafungin, amphotericin B, acyclovir, ganciclovir, oseltamivir, and peramivir.

Development of Vancomycin Dose Individualization Strategy by Bayesian Prediction in Patients Receiving Continuous Renal Replacement Therapy

PURPOSE

Vancomycin (VCM) concentration is often out of therapeutic range (10-20 μg/ml) in patients receiving continuous renal replacement therapy (CRRT). The purposes of this study were to develop a practical VCM population pharmacokinetic (PPK) model and to evaluate the potential of Bayesian prediction-based therapeutic drug monitoring (Bayes-TDM) in VCM dose individualization for patients receiving CRRT.

METHODS

We developed a VCM PPK model using 80 therapeutic concentrations in 17 patients receiving CRRT. Bayes-TDM with the VCM PPK model was evaluated in 23 patients after PPK modeling.

RESULTS

We identified the covariates reduced urine output (RUO, <0.5 ml/kg/h) and effluent flow rate of CRRT for the VCM PPK model. The mean VCM non CRRT clearance (CL_nonCRRT) was 2.12 l/h. RUO lowered CL_nonCRRT to 0.34 l/h. The volume of distribution was 91.3 l/70 kg. The target concentration attainment rate by Bayes-TDM was higher (87.0%) than that by the PPK modeling period (53.8%, P = 0.046). The variance of the second measured concentrations by the Bayes-TDM was lower (11.5, standard deviation: 3.4 μg/ml) than that by the PPK modeling period (50.5, standard deviation: 7.1 μg/ml, P = 0.003).

CONCLUSIONS

Bayes-TDM could be a useful tool for VCM dose individualization in patients receiving CRRT.

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.

In vitro Evaluation of Linezolid and Doripenem Clearance with Different Hemofilters

INTRODUCTION

Renal replacement therapy (RRT) is widely used in the treatment of septic acute kidney injury. However, little is known about how the adsorption properties of hemofilters used in RRT affect antibiotic concentration. Because a cytokine-adsorption membrane is frequently used in RRT, it is important to determine the antibiotic adsorption capacity of this membrane.

OBJECTIVE

The present study aimed to investigate the antibiotic adsorption capacity of different hemofilter membranes by in vitro experiments using 2 antibacterial agents (linezolid and doripenem).

METHODS

We performed experimental hemofiltration in vitro using polyacrylonitrile (AN69ST), polymethylmethacrylate (PMMA), and polysulfone (PS) hemofilters for 1,440 min. The test solution was a 1,000-mL substitution fluid containing 30 µg/mL linezolid and 120 µg/mL doripenem. We measured drug concentrations at the inlet, outlet, and filtrate ports of the hemofilters for 1,440 min and calculated the sieving coefficient (SC) and adsorption rate (Ra) of the drugs onto the hemofilters.

RESULTS

The amount of linezolid adsorbed onto AN69ST, PMMA, and PS membranes was decreased relative to that in the control group at 15 min (p < 0.05). However, no SC for linezolid was obtained thereafter. The Ra of linezolid onto AN69ST, PMMA, and PS membranes was higher than that in the control group (p < 0.05). In contrast, no significant differences were observed in the concentrations and Ra values of doripenem adsorbed onto AN69ST, PMMA, and PS membranes compared with those in the control group.

CONCLUSIONS

Doripenem was not adsorbed onto PMMA, PS, and AN69ST membranes. Linezolid was adsorbed onto PMMA, PS, and AN69ST membranes, but only temporarily, and this did not affect drug bioavailability.

Novel Population Pharmacokinetic Model for Linezolid in Critically Ill Patients and Evaluation of the Adequacy of the Current Dosing Recommendation

Antimicrobial treatment in critically ill patients remains challenging. The aim of this study was to develop a population pharmacokinetic model for linezolid in critically ill patients and to evaluate the adequacy of current dosing recommendation (600 mg/12 h). Forty inpatients were included, 23 of whom were subjected to continuous renal replacement therapies (CRRT). Blood and effluent samples were drawn after linezolid administration at defined time points, and linezolid levels were measured. A population pharmacokinetic model was developed, using NONMEM 7.3. The percentage of patients that achieved the pharmacokinetic/pharmacodynamic (PK/PD) targets was calculated (AUC₂₄/MIC > 80 and 100% T_>MIC). A two-compartment model best described the pharmacokinetics of linezolid. Elimination was conditioned by the creatinine clearance and by the extra-corporeal clearance if the patient was subjected to CRRT. For most patients, the standard dose of linezolid did not cover infections caused by pathogens with MIC ≥ 2 mg/L. Continuous infusion may be an alternative, especially when renal function is preserved.

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 and Pharmacodynamics of Extended-Infusion Cefepime in Critically Ill Patients Receiving Continuous Renal Replacement Therapy: A Prospective, Open-Label Study

STUDY OBJECTIVE

To evaluate extended-infusion (EI) cefepime pharmacokinetics (PK) and pharmacodynamic target attainment in critically ill patients receiving continuous venovenous hemofiltration (CVVH) or continuous venovenous hemodialysis (CVVHD).

DESIGN

Prospective, open-label, PK study.

SETTING

Intensive care units at a large, academic, tertiary-care medical center.

PATIENTS

Ten critically ill adults who were receiving cefepime 2 g intravenously every 8 hours as a 4-hour infusion while receiving CVVH (eight patients) or CVVHD (two patients).

INTERVENTION

Two sets of five serum cefepime concentrations were collected for each patient to assess pharmacokinetics before and during presumed steady state. Concurrent serum and CRRT effluent samples were collected at hours 1, 2, 3, 4, and 8 after the first cefepime dose and after either the fourth, fifth, or sixth (steady-state) cefepime doses.

MEASUREMENTS AND MAIN RESULTS

Reversed-phase high-performance liquid chromatography was used to determine free cefepime concentrations. PK analyses included CRRT clearance, half-life, and sieving coefficient or saturation coefficient. Cefepime peak (4 hrs) concentrations, trough (8 hrs) concentrations (C_min ), and minimum inhibitory concentration breakpoint of 8 µg/ml for the pathogen (MIC₈ ) were used to evaluate attainment of pharmacodynamic targets: 100% of the dosing interval that free drug remains above MIC₈ (100% fT > MIC₈ ), 100% fT > 4 × MIC₈ (optimal), percentage of time fT > 4 × MIC₈ (%fT > 4 × MIC₈ ) at steady state, and ratio of C_min to MIC₈ (fC_min /MIC₈ ). Total CRRT effluent flow rate was a mean ± SD of 30.1 ± 5.4 ml/kg/hr, CRRT clearance was 39.6 ± 9.9 ml/min, and half-life was 5.3 ± 1.7 hours. Sieving coefficient or saturation coefficient were 0.83 ± 0.13 and 0.69 ± 0.22, respectively. First and steady-state dose C_min were 23.4 ± 10.1 µg/ml and 45.2 ± 14.6 µg/ml, respectively. All patients achieved 100% fT > MIC₈ on first and steady-state doses. First and steady-state dose 100% fT > 4 × MIC₈ were achieved in 22% (2/9 patients) and 87.5% (7/8 patients) of patients, respectively. The mean %fT > 4 × MIC₈ at steady state was 97.5%. The fC_min /MIC₈ was 2.92 ± 1.26 for the first dose and 5.65 ± 1.83 at steady state.

CONCLUSION

Extended-infusion cefepime dosing in critically ill patients receiving CRRT successfully attained 100% fT > MIC₈ in all patients and an appropriate fC_min /MIC₈ for both first and steady-state doses. All but one patient achieved 100% fT > 4 × MIC₈ at steady state. No significant differences were observed in PK properties between first and steady-state doses among or between patients. It may be reasonable to initiate an empiric or definitive regimen of EI cefepime in critically ill patients receiving concurrent CRRT who are at risk for resistant organisms. Further research is needed to identify the optimal dosing regimen of EI cefepime in this patient population.

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.

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.

Population pharmacokinetics of ticarcillin in critically ill patients receiving extended daily diafiltration

The aim of this study was to describe the population pharmacokinetics of ticarcillin during extended daily diafiltration (EDDf) in critically ill patients with acute kidney injury. Blood samples were collected from critically ill patients prescribed ticarcillin during one to two dosing intervals during which EDDf was performed. Plasma samples were measured using a validated ultra high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method. Concentration-time data were analysed using a population pharmacokinetics approach with Pmetrics®. A total of 53 blood samples were collected from six critically ill patients (three male). The mean ± standard deviation patient age, weight and body mass index (BMI) was 43 ± 22 years, 88 ± 14 kg and 31 ± 5 kg/m², respectively. A two-compartment linear model adequately described the data. Median population pharmacokinetic parameter estimates were as follows: clearance in the presence of EDDf (CL_EDDf), 6.41 L/h; clearance of EDDf (CL_non-EDDf), 4.97 L/h; volume of distribution of the central compartment (V_c), 56.46 L; intercompartmental clearance from the central to peripheral compartment (k_CP), 13.54 L/h; and intercompartmental clearance from the peripheral to central compartment (k_PC), 21.93 L/h. This is the first population pharmacokinetic model of ticarcillin in patients receiving EDDf. Large pharmacokinetic variability was found, supporting further investigation of the pharmacokinetics of less-studied β-lactam antibiotics in prolonged intermittent renal replacement therapy.

Population pharmacokinetic analysis of vancomycin in pediatric continuous renal replacement therapy

BACKGROUND AND OBJECTIVES

Dosing of vancomycin in pediatric patients undergoing continuous venous-venous hemodiafiltration (CVVHDF) is challenging. Characterization of vancomycin pharmacokinetics can assist with dosing and attainment of goal serum concentrations.

DESIGN, SETTING, PARTICIPANTS, AND MEASUREMENTS

Patients less than 19 years of age who received vancomycin and had post-dose vancomycin concentrations while undergoing CVVHDF were identified. Data collection included the following: patient demographics, vancomycin dosing and serum concentrations, CVVHDF variables, serum creatinine (SCR), blood urea nitrogen (BUN), albumin, hematocrit, and urine output. Fat-free mass was calculated. Data were summarized with descriptive statistical methods, and population pharmacokinetic analysis was performed with NONMEM 7.2 and PDx-Pop 5.2. Simulation was performed to identify dosing regimens with the highest percentage of goal serum concentration < 20 mg/L and AUC_0-24:MIC ≥ 400 attainment.

RESULTS

A total of 138 patients met study criteria (45.6% male, median age 4.9 years (IQR (1.0, 14.5))). Mean vancomycin dose was 14.3 ± 1.6 mg/kg/dose (19.5 ± 3.0 mg/kg/dose by FFM). Patients had a median of six (IQR 2, 12) vancomycin serum concentrations sampled 13.6 ± 8.4 h after the dose, and the mean vancomycin serum concentration was 11.3 ± 3.4 mg/L. Vancomycin pharmacokinetics were characterized by a two-compartment model with allometric scaling on fat-free mass and significant covariates of SCR, BUN, dialysate flow rate, and ultrafiltration rate on clearance. Simulation identified doses of 40-50 mg/kg/day that divided every 8-12 h had the highest percentage of patients with a serum concentration < 20 mg/L and an AUC_0-24:MIC ≥ 400.

CONCLUSIONS

Vancomycin pharmacokinetics are characterized by fat-free mass, serum creatinine, blood urea nitrogen, dialysate flow rate, and ultrafiltration rate in the pediatric CVVHDF population. Dosing of 40-50 mg/kg/day on fat-free mass divided every 8-12 h with frequent vancomycin serum sampling is recommended.

Clindamycin clearance during Cytosorb® hemoadsorption: A case report and pharmacokinetic study

Panton-Valentine leucocidin producing methicillin-resistant Staphylococcus aureus infections are rare but associated with very high mortality rates. We report the case of a 14-year-old patient with Panton-Valentine leucocidin producing methicillin-resistant Staphylococcus aureus infection and Influenza B pneumonia requiring veno-arterial extra-corporeal membrane oxygenator for refractory shock. In the absence of response to conventional therapy, we have inserted a Cytosorb® cartridge within the extra-corporeal membrane oxygenator circuit. A spectacular decrease in vasopressor requirements followed. Since clindamycin, a key component of Panton-Valentine leucocidin producing methicillin-resistant Staphylococcus aureus treatment, might be removed by Cytosorb® hemoadsorption, we have performed serial plasma concentrations measurements of the drug. Based on these measurements, we were able to develop a pharmacokinetic model incorporating variable plasma clearance. Patient's exposure was estimated before, during and after Cytosorb® hemoadsorption. According to this model, Cytosorb® hemoadsorption did not seem to result in significant clindamycin removal. Cytosorb® hemoadsorption during Panton-Valentine leucocidin producing methicillin-resistant Staphylococcus aureus infection appears safe and feasible and no adaptation of clindamycin dosage seems necessary.

Monitoring of tobramycin serum concentrations in selected critically ill patients receiving selective decontamination of the digestive tract: a retrospective evaluation

INTRODUCTION

Selective decontamination of the digestive tract (SDD) is a strategy in mechanically ventilated patients to reduce mortality. Treatment consists of enterally administered non-absorbable antibiotics, i.e., tobramycin. However, most intensive care unit (ICU) patients with SDD appear to have detectable tobramycin serum concentrations. The Rijnstate Hospital implemented a protocol for therapeutic drug monitoring (TDM) of tobramycin in patients at risk. The aim of this study was to evaluate the necessity of TDM in these patients and to optimize the current protocol.

METHODS

This retrospective observational study included ICU patients with SDD treatment for ≥ 7 days and renal failure. These patients were considered eligible for monitoring of tobramycin. Tobramycin serum concentrations, relevant laboratory parameters (i.e., renal function, lactate), and patient data were extracted from the National Intensive Care Evaluation database and the hospital electronic patient data system.

RESULTS

In 23 subjects, a total of 43 tobramycin serum concentrations was determined. The median tobramycin serum concentration was 0.33 (IQR 0.17-0.49) mg/L of which 12 (27.9%) samples had concentrations < 0.2 mg/L, 30 (69.8%) had concentrations 0.2-1.0 mg/L and 1 (2.3%) had a toxic concentration > 1.0 mg/L. In 3 (7.0%) cases, an intervention was conducted based on the tobramycin serum concentration.

CONCLUSION

The majority (83.7%) of samples had detectable tobramycin serum concentrations. Monitoring of tobramycin serum concentrations can be considered necessary in patients at risk. However, the current protocol should be optimized to intercept patients more precise.

Overview of antifungal dosing in invasive candidiasis

In the past, most antifungal therapy dosing recommendations for invasive candidiasis followed a 'one-size fits all' approach with recommendations for lowering maintenance dosages for some antifungals in the setting of renal or hepatic impairment. A growing body of pharmacokinetic/pharmacodynamic research, however now points to a widespread 'silent epidemic' of antifungal underdosing for invasive candidiasis, especially among critically ill patients or special populations who have altered volume of distribution, protein binding and drug clearance. In this review, we explore how current adult dosing recommendations for antifungal therapy in invasive candidiasis have evolved, and special populations where new approaches to dose optimization or therapeutic drug monitoring may be needed, especially in light of increasing antifungal resistance among Candida spp.

Effect of Extracorporeal Membrane Oxygenation on the New Vancomycin Dosing Regimen in Critically Ill Patients Receiving Continuous Venovenous Hemofiltration

BACKGROUND

The optimal dosing regimen of vancomycin for critically ill patients receiving continuous venovenous hemofiltration (CVVH) remains controversial, not to mention those with concurrent use of extracorporeal membrane oxygenation (ECMO). We aimed to determine if a new dosing regimen can achieve the target vancomycin trough concentration (Ctrough) of 10-20 mcg/mL in patients receiving CVVH with or without ECMO.

METHODS

We conducted a retrospective study by enrolling patients who received vancomycin while undergoing CVVH. The vancomycin dosing regimen was 15-20 mg/kg as the loading dose and 7.5 mg/kg every 12 hours as the maintenance doses. Serum concentration was determined after at least 4 doses of vancomycin were given.

RESULTS

A total of 38 patients were enrolled, of which 21 were also on ECMO. The ultrafiltration rate of CVVH was 30.6 ± 5.5 mL·kg·h with the Ctrough of 14.7 ± 3.5 mcg/mL. Ctrough was within the target range in 82% of patients. All CVVH-only patients achieved the target concentration, whereas only 76.2% of those with concurrent ECMO did (P = 0.031).

CONCLUSIONS

All patients receiving CVVH achieved the target Ctrough with this new dosing regimen, but those with concurrent ECMO did not. Ctrough must be more closely monitored in patients using ECMO simultaneously.

Use of Colistin in Critically Ill Patients

Due to lack of better therapeutic options, colistin use for extensively drug-resistant Gram-negative organisms was revived in the past two decades, including in patients in intensive-care units (ICU). There are multiple knowledge gaps pertaining to the clinical use and utility of colistin in critically-ill patients, but due to lack of options, it is used in these high risk patients. In this chapter, we critically review the various topics pertaining to colistin use in critically-ill patients, while highlighting the (lack of) controlled evidence supporting common current practices pertaining to colistin use by clinicians.

Clinical Pharmacokinetics, Pharmacodynamics and Toxicodynamics of Polymyxins: Implications for Therapeutic Use

The availability of sensitive, accurate and specific analytical methods for the measurement of polymyxins in biological fluids has enabled an understanding of the pharmacokinetics of these important antibiotics in healthy humans and patients. Colistin is administered as its inactive prodrug colistin methanesulfonate (CMS) and has especially complex pharmacokinetics. CMS undergoes conversion in vivo to the active entity colistin, but the rate of conversion varies from brand to brand and possibly from batch to batch. The extent of conversion is generally quite low and depends on the relative magnitudes of the conversion clearance and other clearance pathways for CMS of which renal excretion is a major component. Formed colistin in the systemic circulation undergoes very extensive tubular reabsorption; the same mechanism operates for polymyxin B which is administered in its active form. The extensive renal tubular reabsorption undoubtedly contributes to the propensity for the polymyxins to cause nephrotoxicity. While there are some aspects of pharmacokinetic behaviour that are similar between the two clinically used polymyxins, there are also substantial differences. In this chapter, the pharmacokinetics of colistin, administered as CMS, and polymyxin B are reviewed, and the therapeutic implications are discussed.

Invasive Candidiasis in the Elderly: Considerations for Drug Therapy

Candida infections in the elderly are an important and expanding clinical problem, with significantly higher mortality in this group than in younger patients. The increasing problem of invasive Candida infections may be related to higher prevalence of immunocompromised older people and the emergence of treatment resistance. Older people, especially the frail and critically ill, are at higher risk of medication-related harmful effects due to changes in pharmacokinetics and pharmacodynamics, which may be further complicated by organ dysfunction, diminished homeostatic control, co-morbidities and polypharmacy. Here, we review the available options for the treatment of Candida infections and provide insights into the challenges surrounding the optimal use of antifungal drugs in the elderly.

Metronidazole- and levofloxacin-induced psychotic disorders in chronic kidney patient

We present a case which reports the occurrence of psychotic disorders after metronidazole and levofloxacin therapy in a chronic kidney patient while being treated for enterocolitis and urinary infection. A 48-year-old female was admitted to a hospital for the placement of a peritoneal dialysis catheter due to indicated peritoneal dialysis. During admission, symptoms of enterocolitis and urinary infection had occurred, so metronidazole and levofloxacin were introduced into therapy, respectively. After 4 days of metronidazole and 3 days of levofloxacin therapy, the patient became confused, disoriented, with signs of delirium. Since the diagnosis of psychoorganic disorder was made, the therapy with lorazepam and haloperidol was initiated, while metronidazole and levofloxacin were discontinued. Complete recovery 4 days after discontinuation indicates that the patient has experienced antibiotics-induced neurotoxicity. This is the first report of expressed neurotoxicity after the combination of metronidazole and levofloxacin in chronic kidney patients.

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.