Pharmacokinetic issues for antibiotics in the critically ill patient

A systematic review of the pharmacokinetics and pharmacodynamics of novel beta-lactams and beta-lactam with beta-lactamase inhibitor combinations for the treatment of pneumonia caused by carbapenem-resistant Gram-negative bacteria

BACKGROUND

Novel beta-lactams show activity against many multidrug-resistant Gram-negative bacteria that cause severe lung infections. Understanding pharmacokinetic/pharmacodynamic characteristics of these agents may help optimise outcomes in the treatment of pneumonia.

OBJECTIVES

To describe and appraise studies that report pulmonary pharmacokinetic and pharmacodynamic data of cefiderocol, ceftazidime/avibactam, ceftolozane/tazobactam, imipenem/cilastatin/relebactam and meropenem/vaborbactam.

METHODS

MEDLINE (PubMed), Embase, Web of Science and Scopus libraries were used for the literature search. Pulmonary population pharmacokinetic and pharmacokinetic/ pharmacodynamic studies on adult patients receiving cefiderocol, ceftazidime/avibactam, ceftolozane/tazobactam, imipenem/cilastatin/relebactam, and meropenem/vaborbactam published in peer-reviewed journals were included. Two independent authors screened, reviewed, and extracted data from included articles. A reporting guideline for clinical pharmacokinetic studies (ClinPK statement) was used for bias assessment. Relevant outcomes were included, such as population pharmacokinetic parameters and probability of target attainment of dosing regimens.

RESULTS

Twenty-four articles were included. There was heterogeneity in study methods and reporting of results, with diversity across studies in adhering to the ClinPK statement checklist. Ceftolozane/tazobactam was the most studied agent. Only two studies collected epithelial lining fluid samples from patients with pneumonia. All the other phase I studies enrolled healthy subjects. Significant population heterogeneity was evident among available population pharmacokinetic models. Probabilities of target attainment rates above 90% using current licensed dosing regiments were reported in most studies.

CONCLUSIONS

Although lung pharmacokinetics was rarely described, this review observed high target attainment using plasma pharmacokinetic data for all novel beta-lactams. Future studies should describe lung pharmacokinetics in patient populations at risk of carbapenem-resistant pathogen infections.

COVID-19 Drug Treatments Are Prone to Sequestration in Extracorporeal Membrane Oxygenation Circuits: An Ex Vivo Extracorporeal Membrane Oxygenation Study

Drug treatments for coronavirus disease 2019 (COVID-19) dramatically improve patient outcomes, and although extracorporeal membrane oxygenation (ECMO) has significant use in these patients, it is unknown whether ECMO affects drug dosing. We used an ex vivo adult ECMO model to measure ECMO circuit effects on concentrations of specific COVID-19 drug treatments. Three identical ECMO circuits used in adult patients were set up. Circuits were primed with fresh human blood (temperature and pH maintained within normal limits). Three polystyrene jars with 75 ml fresh human blood were used as controls. Remdesivir, GS-441524, nafamostat, and tocilizumab were injected in the circuit and control jars at therapeutic concentrations. Samples were taken from circuit and control jars at predefined time points over 6 h and drug concentrations were measured using validated assays. Relative to baseline, mean (± standard deviation [SD]) study drug recoveries in both controls and circuits at 6 h were significantly lower for remdesivir (32.2% [±2.7] and 12.4% [±2.1], p < 0.001), nafamostat (21.4% [±5.0] and 0.0% [±0.0], p = 0.018). Reduced concentrations of COVID-19 drug treatments in ECMO circuits is a clinical concern. Remdesivir and nafamostat may need dose adjustments. Clinical pharmacokinetic studies are suggested to guide optimized COVID-19 drug treatment dosing during ECMO.

Clinical guidance for unfractionated heparin dosing and monitoring in critically ill patients

INTRODUCTION

Unfractionated heparin is a widely used anticoagulant in critically ill patients. It has a well-established safety profile and remains an attractive option for clinicians due to its short half-life and reversibility. Heparin has a unique pharmacokinetic profile, which contributes to significant inter-patient and intra-patient variability in effect. The variability in anticoagulant effect combined with heparin's short half-life mean close monitoring is required for clinical efficacy and preventing adverse effects. To optimize heparin use in critically ill patients, effective monitoring assays and dose adjustment strategies are needed.

AREAS COVERED

This paper explores the use of heparin as an anticoagulant and optimal approaches to monitoring in critically ill patients.

EXPERT OPINION

Conventional monitoring assays for heparin dosing have significant limitations. Emerging data appear to favor using anti-Xa assay monitoring for heparin anticoagulation, which many centers have successfully adopted as the standard. The anti-Xa assay appears have important benefits relative to the aPTT for heparin monitoring in critically ill patients, and should be considered for broader use.

A pharmacokinetic framework describing antibiotic adsorption to cardiopulmonary bypass devices

Cardiopulmonary bypass (CPB) can alter pharmacokinetic (PK) parameters and the drug may adsorb to the CPB device, altering exposure. Cefazolin is a beta-lactam antibiotic used for antimicrobial prophylaxis during cardiac surgery supported by CPB. Adsorption of cefazolin could result in therapeutic failure. An ex vivo study was undertaken using CPB devices primed and then dosed with cefazolin and samples were obtained over 1 hour of recirculation. Twelve experimental runs were conducted using different CPB device sizes (neonate, infant, child, and adult), device coatings (Xcoating™, Rheoparin®, PH.I.S.I.O), and priming solutions. The time course of saturable binding, using Bmax (binding capacity), Kd (dissociation constant), and T2off (half-time of dissociation), described cefazolin adsorption. Bmax estimates for the device sizes were neonate 40.0 mg (95% CI 24.3, 67.4), infant 48.6 mg (95% CI 5.97, 80.2), child 77.8 mg (95% CI 54.9, 103), and adult 196 mg (95% CI 191, 199). The Xcoating™ Kd estimate was 139 mg/L (95% CI 27.0, 283) and the T2off estimate was 98.4 min (95% CI 66.8, 129). The Rheoparin® and PH.I.S.I.O coatings had similar binding parameters with Kd and T2off estimates of 0.169 mg/L (95% CI 0.01, 1.99) and 4.94 min (95% CI 0.17, 59.4). The Bmax was small (< 10%) relative to a typical total patient dose during cardiac surgery supported by CPB. A dose adjustment for cefazolin based solely on drug adsorption is not required. This framework could be extended to other PK studies involving CPB.

Antibiotic-Drug Interactions in the Intensive Care Unit: A Literature Review

Interactions between drugs are a common problem in Intensive Care Unit patients, as they mainly have a critical condition that often demands the administration of multiple drugs simultaneously. Antibiotics are among the most frequently used medications, as infectious diseases are often observed in ICU patients. In this review, the most important antibiotic-drug interactions, based on the pharmacokinetic and pharmacodynamic mechanisms, were gathered together and described. In particular, some of the most important interactions with main groups of antibacterial drugs were observed in patients simultaneously prescribed oral anticoagulants, NSAIDs, loop diuretics, and valproic acid. As a result, the activity of drugs can be increased or decreased, as dosage modification might be necessary. It should be noted that these crucial interactions can help predict and avoid negative consequences, leading to better patient recovery. Moreover, since there are other factors, such as fluid therapy or albumins, which may also modify the effectiveness of antibacterial therapy, it is important for anaesthesiologists to be aware of them.

Pharmacovigilance Strategies to Address Resistance to Antibiotics and Inappropriate Use-A Narrative Review

The spread of antimicrobial resistance (AMR) is a global challenge. Close and continuous surveillance for quick detection of AMR can be difficult, especially in remote places. This narrative review focuses on the contributions of pharmacovigilance (PV) as an auxiliary tool for identifying and monitoring the ineffectiveness, resistance, and inappropriate use of antibiotics (ABs). The terms "drug ineffective", "therapeutic failure", "drug resistance", "pathogen resistance", and "multidrug resistance" were found in PV databases and dictionaries, denoting ineffectiveness. These terms cover a range of problems that should be better investigated because they are useful in warning about possible causes of AMR. "Medication errors", especially those related to dose and indication, and "Off-label use" are highlighted in the literature, suggesting inappropriate use of ABs. Hence, the included studies show that the terms of interest related to AMR and use are not only present but frequent in PV surveillance programs. This review illustrates the feasibility of using PV as a complementary tool for antimicrobial stewardship activities, especially in scenarios where other resources are scarce.

Can linezolid be validly measured in endotracheal aspiration in critically ill patients? A proof-of-concept trial

BACKGROUND

Therapeutic drug monitoring (TDM) of anti-infectives such as linezolid is routinely performed in blood of intensive care unit (ICU) patients to optimize target attainment. However, the concentration at the site of infection is considered more important for a successful therapy. Until now, bronchoalveolar lavage (BAL) is the gold standard to measure intrapulmonary concentrations of anti-infective agents. However, it is an invasive method and unsuitable for regular TDM. The aim of this proof-of-concept study was to investigate whether it is possible to reliably determine the intrapulmonary concentration of linezolid from endotracheal aspiration (ENTA).

METHODS

Intubated ICU patients receiving 600 mg intravenous linezolid twice daily were examined in steady state. First, preliminary experiments were performed in six patients to investigate which patients are suitable for linezolid measurement in ENTA. In a second step, trough and peak linezolid concentrations of plasma and ENTA were determined in nine suitable patients.

RESULTS

Linezolid can validly be detected in ENTA with viscous texture and > 0.5 mL volume. The mean (SD) linezolid trough concentration was 2.02 (1.27) mg/L in plasma and 1.60 (1.36) mg/L in ENTA, resulting in a median lung penetration rate of 104%. The mean (SD) peak concentration in plasma and ENTA was 10.77 (5.93) and 4.74 (2.66) mg/L.

CONCLUSIONS

Linezolid can validly be determined in ENTA with an adequate texture and volume. The penetration rate is comparable to already published BAL concentrations. This method might offer a simple and non-invasive method for TDM at the site of infection "lung". Due to promising results of the feasibility study, comparison of ENTA and BAL in the same patient should be investigated in a further trial.

Comparison of pharmacokinetics software for therapeutic drug monitoring of piperacillin in patients with severe infections

OBJECTIVE

To evaluate the predictive performance of population pharmacokinetic models for piperacillin (PIP) available in the software MwPharm, TDMx and ID-ODs for initial dosing selection and therapeutic drug monitoring (TDM) purposes.

METHODS

This is a prospective observational study in adult patients with severe infections receiving PIP treatment. Plasma concentrations were quantified by ultra-high performance liquid chromatography coupled to tandem mass spectrometry. The differences between predicted and observed PIP concentrations were evaluated with Bland-Altman plots; additionally, the relative and absolute bias and precision of the models were determined.

RESULTS

A total of 145 PIP plasma concentrations from 42 patients were analysed. For population prediction, MwPharm showed the best predictive performance with a mean relative difference of 34.68% (95% CI -197% to 266%) and a root mean square error (RMSE) of 60.42 µg/mL; meanwhile TDMx and ID-ODs under-predicted PIP concentrations. For individual prediction, the TDMx model was found to be the most precise with a mean relative difference of 7.61% (95% CI -57.63 to 72.86%), and RMSE of 17.86 µg/mL.

CONCLUSION

Current software for TDM is a valuable tool, but it may also include different population pharmacokinetic models in patients with severe infections, and should be evaluated before performing a model-based TDM in clinical practice. Considering the heterogeneous characteristics of patients with severe infections, this study demonstrates the need for therapy personalisation for PIP to improve pharmacokinetic/pharmacodynamic target attainment.

No Sequestration of Commonly Used Anti-Infectives in the Extracorporeal Membrane Oxygenation (ECMO) Circuit-An Ex Vivo Study

Patients undergoing extracorporeal membrane oxygenation (ECMO) often require therapy with anti-infective drugs. The pharmacokinetics of these drugs may be altered during ECMO treatment due to pathophysiological changes in the drug metabolism of the critically ill and/or the ECMO therapy itself. This study investigates the latter aspect for commonly used anti-infective drugs in an ex vivo setting. A fully functional ECMO device circulated an albumin-electrolyte solution through the ECMO tubes and oxygenator. The antibiotic agents cefazolin, cefuroxim, cefepime, cefiderocol, linezolid and daptomycin and the antifungal agent anidulafungin were added. Blood samples were taken over a period of four hours and drug concentrations were measured via high-pressure liquid chromatography (HPLC) with UV detection. Subsequently, the study analyzed the time course of anti-infective concentrations. The results showed no significant changes in the concentration of any tested anti-infectives throughout the study period. This ex vivo study demonstrates that the ECMO device itself has no impact on the concentration of commonly used anti-infectives. These findings suggest that ECMO therapy does not contribute to alterations in the concentrations of anti-infective medications in severely ill patients.

Exposure levels and target attainment of piperacillin/tazobactam in adult patients admitted to the intensive care unit: a prospective observational study

PURPOSE

The objective of this study was to evaluate the exposure and the pharmacodynamic target attainment of piperacillin/tazobactam (PTZ) in adult critically ill patients.

METHODS

We conducted a prospective observational study in the intensive care unit (ICU) of the Hôpital du Sacré-Cœur de Montréal (a Level I trauma centre in Montreal, QC, Canada) between January 2021 and June 2022. We included patients aged 18 yr or older admitted to the ICU who received PTZ by intravenous administration. Demographic and clinical characteristics were collected, and clinical scores were calculated. On study day 1 of antimicrobial therapy, three blood samples were collected at the following timepoints: one hour after PTZ dose administration and at the middle and at the end of the dosing interval. The sampling schedule was repeated on days 4 and 7 of therapy if possible. Samples were analyzed by ultra-high performance liquid chromatography with diode array detector to determine the total piperacillin concentration. Middle- and end-of-interval concentrations were used for target attainment analyses, and were defined as a concentration above the minimal inhibitory concentration of 16 mg·L-1, corresponding to the breakpoint of Enterobacteriaceae and Pseudomonas aeruginosa.

RESULTS

Forty-three patients were recruited and 202 blood samples were analyzed. The most prevalent dose was 3/0.375 g every six hours (n = 50/73 doses administered, 68%) with a 30-min infusion. We observed marked variability over the three sampling timepoints, and the median [interquartile range] piperacillin concentrations at peak, middle of interval, and end of interval were 109.4 [74.0-152.3], 59.3 [21.1-74.4], and 25.3 [6.8-44.6] mg·L-1, respectively. When assessing target attainment, 37% of patients did not reach the efficacy target of a trough concentration of 16 mg·L-1. The majority of patients who were underexposed were patients with normal to augmented renal clearance.

CONCLUSION

In this prospective observational study of adult ICU patients receiving intravenous PTZ, a large proportion had subtherapeutic concentrations of piperacillin. This was most notable in patients with normal to augmented renal clearance. More aggressive dosage regimens may be required for this subpopulation to ensure attainment of efficacy targets.

Piperacillin pharmacokinetics and pharmacodynamics in paediatric patients who received high frequency intra-operative piperacillin/tazobactam dosing

Piperacillin/tazobactam (PTZ) is a broad-spectrum antibiotic, typically dosed every six hours (q6h). Guidelines recommend dosing PTZ every 2 hours (q2h) intra-operatively for complex abdominal surgery, including liver transplant. The data supporting the guidelines for intra-operative dosing are sparse and the pharmacokinetics/pharmacodynamics (PK/PD) of q2h dosing has not been studied by simulation or in humans. In this study, PK/PD parameters of high-frequency intra-operative dosing and q6h post-operative dosing were compared in critically ill children. Paediatric patients who received PTZ during complex abdominal surgery or transplant and who had intra-operative and post-operative opportunistic samples were included. Using a published PK model and observed concentrations, individual piperacillin PK/PD parameters were estimated using Bayesian estimation. Alternative post-operative dosing strategies were simulated using the patients with the highest and lowest estimated piperacillin clearance. Thirteen patients were included (median age: 3.1 years, 85% liver transplant recipients). PK parameters in the intra-operative and post-operative phases were not significantly different (clearance: 15.8 ± 7.2 vs. 12.6 ± 6.3 L/h/70 kg, P=0.070; central volume: 13.4 [13.1, 13.8] vs. 15.2 [12.2, 16.0] L/70 kg, P=0.22). At an individual level, intra-operative clearance values were -35% to 139% of the post-operative values, whereas central volume intra-operative values were -40% to 77% of the post-operative values. Intra-operative piperacillin exposure was higher during high-frequency dosing compared with the post-operative period (AUC/h: 109 [93.4, 127] vs. 62.8 [41.6, 78.3] mg/L, P=0.002). Simulations showed great variation in optimal dosing strategies that would minimise toxicity and maximise efficacy, indicating a role for individualised dosing in paediatric surgical populations.

External Validation of Obese/Critically Ill Vancomycin Population Pharmacokinetic Models in Critically Ill Patients Who Are Obese

Obesity combined with critical illness might increase the risk of acquiring infections and hence mortality. In this patient population the pharmacokinetics of antimicrobials vary significantly, making antimicrobial dosing challenging. The objective of this study was to assess the predictive performance of published population pharmacokinetic models of vancomycin in patients who are critically ill or obese for a cohort of critically ill patients who are obese. This was a multi-center retrospective study conducted at 2 hospitals. Adult patients with a body mass index of ≥30 kg/m2 were included. PubMed was searched for published population pharmacokinetic studies in patients who were critically ill or obese. External validation was performed using Monolix software. A total of 4 models were identified in patients who were obese and 5 models were identified in patients who were critically ill. In total, 138 patients who were critically ill and obese were included, and the most accurate models for these patients were the Goti and Roberts models. In our analysis, models in patients who were critically ill outperformed models in patients who were obese. When looking at the most accurate models, both the Goti and the Roberts models had patient characteristics similar to ours in terms of age and creatinine clearance. This indicates that when selecting the proper model to apply in practice, it is important to account for all relevant variables, besides obesity.

Population Pharmacokinetic Model of Linezolid and Probability of Target Attainment in Patients with COVID-19-Associated Acute Respiratory Distress Syndrome on Veno-Venous Extracorporeal Membrane Oxygenation-A Step toward Correct Dosing

During veno-venous extracorporeal membrane oxygenation (vv ECMO) therapy, antimicrobial drugs are frequently used, and appropriate dosing is challenging due to there being limited data to support the dosage. Linezolid is effective against multidrug-resistant Gram-positive pathogens frequently isolated in ECMO patients. In total, 53 steady-state linezolid levels were obtained following 600 mg intravenous (IV) injections every 8 h, and these were used to develop a population pharmacokinetic (PopPK) model in patients with COVID-19-associated acute respiratory distress syndrome (CARDS) on vv ECMO. The data were analyzed using a nonlinear mixed-effects modelling approach. Monte Carlo simulation generated 5000 patients' individual PK parameters and corresponding concentration-time profiles using the PopPK model, following the administration of 600 mg/8 h (a higher-than-standard dosing) and 600 mg/12 h (standard). The probabilities of pharmacokinetic/pharmacodynamic (PK/PD) target attainment (PTA) and the cumulative fraction of responses (CFR) for three pathogens were calculated and compared between the two dosing scenarios. Linezolid 600 mg/8 h was predicted to achieve greater than or equal to 85%Tf>MIC in at least 90% of the patients with CARDS on vv ECMO compared to only approximately two thirds of the patients after dosing every 12 h at a minimal inhibitory concentration (MIC) of 2 mg/L. In addition, for the same MIC, fAUC24/MIC ≥ 80 was achieved in almost three times the number of patients following an 8-h versus a 12-h interval. PopPK simulation predicted that a significantly higher proportion of the patients with CARDS on vv ECMO would achieve the PK/PD targets following the 8-h dosing interval compared to standard linezolid dosing. Nevertheless, the safety concern, in particular, for thrombocytopenia, with higher-than-standard linezolid dosage is reasonable, and consequently, monitoring is essential.

Impact of augmented renal clearance on anticoagulant therapy in critically ill patients with coronavirus disease 2019: A retrospective cohort study

INTRODUCTION

This study aimed to determine the impact of augmented renal clearance (ARC) on anticoagulation therapy in critically ill patients with coronavirus disease 2019 (COVID-19).

METHODS

This retrospective cohort study included adult patients with severe COVID-19 with ARC who had been treated at our hospital between 2020 and 2021. We measured the estimated glomerular filtration rate calculated by the Chronic Kidney Disease Epidemiology Collaboration formula (eGFRCKD-EPI) every morning, and ARC condition was defined as eGFRCKD-EPI ≥ 130 mL/min/1.73 m2. Multivariate regression analysis with Huber-White sandwich estimator was performed to examine the association of unfractionated heparin (UH) dosage between blood test timings with activated partial thromboplastin time (APTT) compared with and without ARC.

RESULTS

We identified 38 enrolled patients: seven and 31 in the ARC and non-ARC groups, respectively. In the ARC coexisting condition, a higher dose of UH, which corresponded to the total dose in 24 h from the previous day, was required to achieve the same APTT prolongation, with a significant difference (p < 0.001).

CONCLUSIONS

Our study suggests that careful monitoring and consideration of higher UH doses in critically ill patients with COVID-19 is necessary because anticoagulation failure can occur during ARC.

Effect of albumin substitution on pharmacokinetics of piperacillin/tazobactam in patients with severe burn injury admitted to the ICU

BACKGROUND

Pathophysiological changes in severely burned patients alter the pharmacokinetics (PK) of anti-infective agents, potentially leading to subtherapeutic concentrations at the target site. Albumin supplementation, to support fluid resuscitation, may affect pharmacokinetic properties by binding drugs. This study aimed to investigate the PK of piperacillin/tazobactam in burn patients admitted to the ICU before and after albumin substitution as total and unbound concentrations in plasma.

PATIENTS AND METHODS

Patients admitted to the ICU and scheduled for 4.5 g piperacillin/tazobactam administration and 200 mL of 20% albumin substitution as part of clinical routine were included. Patients underwent IV microdialysis, and simultaneous arterial plasma sampling, at baseline and multiple timepoints after drug administration. PK analysis of total and unbound drug concentrations under steady-state conditions was performed before and after albumin supplementation.

RESULTS

A total of seven patients with second- to third-degree burns involving 20%-60% of the total body surface were enrolled. Mean (SD) AUC0-8 (h·mg/L) of total piperacillin/tazobactam before and after albumin substitution were 402.1 (242)/53.2 (27) and 521.8 (363)/59.7 (32), respectively. Unbound mean AUC0-8 before and after albumin supplementation were 398.9 (204)/54.5 (25) and 456.4 (439)/64.5 (82), respectively.

CONCLUSIONS

Albumin supplementation had little impact on the PK of piperacillin/tazobactam. After albumin supplementation, there was a numerical increase in mean AUC0-8 of total and unbound piperacillin/tazobactam, whereas similar Cmax values were observed. Future studies may investigate the effect of albumin supplementation on drugs with a higher plasma protein binding.

Potential benefits of therapeutic drug monitoring for beta-lactam antibiotics in augmented renal clearance patients: a case report

Augmented renal clearance (ARC) is commonly described in critically ill patients, making drug pharmacokinetics even harder to predict in this population. This case report displays the value of therapeutic drug monitoring (TDM) of piperacillin/tazobactam (PTZ) in this population. We identified two patients with ARC and intermittent administration of PTZ who took part in a prospective, descriptive study conducted at Hôpital du Sacré-Cœur de Montréal. Both had plasma samples drawn at peak, middle, and end of their dosing intervals of PTZ. Minimal inhibitory concentrations (MICs) of 4 and 8 mg/L were chosen to evaluate therapeutic target attainment at middle and end of dosing interval. The first patient was a 52-year-old male with a renal clearance rate estimated at 147 mL/min who received 3.375 g PTZ every 6 h. The second patient, a 49-year-old male, had an estimated renal clearance rate of 163 mL/min and received the same regimen. Both patients had piperacillin concentrations above the target MICs at middle of the dosing interval, but they failed to reach a trough concentration above 8 mg/L. The present case report showcases two patients with subtherapeutic PTZ concentrations despite strict following of local administration protocols. This suboptimal administration could not only lead to treatment failure, but also to the selection and growth of resistant pathogens. Implementing TDM would offer the possibility to adjust drug regimens in real-time and prevent situations like these from occurring.

Serum concentration of continuously administered vancomycin influences efficacy and safety in critically ill adults: a systematic review

OBJECTIVES

Vancomycin is used to treat Gram-positive infections in critically ill adults. For vancomycin administered by continuous infusion (CI), various target ranges have been used, ranging from 15-20 mg/L to 30-40 mg/L. This systematic literature review was conducted to investigate the impact of steady-state serum concentration (Css) of CI on safety and efficacy of therapy in critically ill adults.

METHODS

Relevant literature was identified by searching two electronic databases (PubMed, Cochrane Library) and Google Scholar from inception until July 2023, focusing on studies reporting measured Css and treatment outcomes (e.g. mortality, nephrotoxicity) with CI. Due to study heterogeneity, a narrative synthesis of the evidence was performed.

RESULTS

Twenty-one publications were included with a total of 2949 patients. Mortality was higher (two studies, n = 388 patients) and clinical cure was lower (one study, n = 40 patients) with Css < 15 mg/L measured 24 h after initiation of CI (C24). An adequate loading dose appeared most important for maintaining higher C24. Generally, higher Css was associated with higher rates of acute kidney injury (AKI) (15 studies, n = 2331 patients). It was calculated that Css < 25 mg/L (versus ≥25 mg/L) was preferable for reducing nephrotoxicity (three studies, n = 515 patients).

CONCLUSIONS

Despite sparse data availability, the target range of 15-25 mg/L in CI may increase clinical cure and reduce mortality and AKI. In future research, vancomycin Css cohorts should be formed to allow evaluation of the impact of Css of CI on treatment outcomes.

Efficiency of dosing software using Bayesian forecasting in achieving target antibiotic exposures in critically ill patients, a prospective cohort study

INTRODUCTION

Broad-spectrum antibiotics such as beta-lactams and vancomycin are frequently used to treat critically ill patients, however, a significant number do not achieve target exposures. Therapeutic drug monitoring (TDM) combined with Bayesian forecasting dosing software may improve target attainment in these patients. This study aims to describe the efficiency of dosing software for achieving target exposures of selected beta-lactam antibiotics and vancomycin in critically ill patients.

METHODS

A prospective cohort study was undertaken in an adult intensive care unit (ICU). Patients prescribed vancomycin, piperacillin-tazobactam and meropenem were included if they exhibited a subtherapeutic or supratherapeutic exposure informed by TDM. The dosing software, ID-ODS™, was used to generate dosing recommendations which could be either accepted or rejected by the treating team. Repeat antibiotic TDM were requested to determine if target exposures were achieved.

RESULTS

Between March 2020 and December 2021, 70 were included in the analysis. Software recommendations were accepted for 56 patients (80%) with 50 having repeated antibiotic measurements. Forty-three of the 50 patients (86%) achieved target exposures after one software recommendation, with 3 of the remaining 7 patients achieving target exposures after 2. Forty-seven patients out of the 50 patients (94%) achieved the secondary outcome of clinical cure. There were no antibiotic exposure-related adverse events reported.

CONCLUSION

The use of TDM combined with Bayesian forecasting dosing software increases the efficiency for achieving target antibiotic exposures in the ICU. Clinical trials comparing this approach with other dosing strategies are required to further validate these findings.

Ceftriaxone Pharmacokinetics and Pharmacodynamics in 2 Pediatric Patients on Extracorporeal Membrane Oxygenation Therapy

BACKGROUND

Critically ill patients with cardiac or respiratory failure may require extracorporeal membrane oxygenation (ECMO). Antibiotics are frequently administered when the suspected cause of organ failure is an infection. Ceftriaxone, a β-lactam antibiotic, is commonly used in patients who are critically ill. Although studies in adults on ECMO have suggested minimal impact on ceftriaxone pharmacokinetics, limited research exists on ceftriaxone pharmacokinetics/pharmacodynamics (PK/PD) in pediatric ECMO patients. We report the PK profiles and target attainment of 2 pediatric patients on ECMO who received ceftriaxone.

METHODS

Ceftriaxone concentrations were measured in 2 pediatric patients on ECMO using scavenged opportunistic sampling. PK profiles were generated and individual PK parameters were estimated using measured free ceftriaxone concentrations and a published population PK model in children who are critically ill, using Bayesian estimation.

RESULTS

Patient 1, an 11-year-old boy on venovenous ECMO for respiratory failure received 2 doses of 52 mg/kg ceftriaxone 12 hours apart while on ECMO and additional doses every 12 hours off ECMO. On ECMO, ceftriaxone clearance was 13.0 L/h/70 kg compared with 7.6 L/h/70 kg off ECMO, whereas the model-predicted mean clearance in children who are critically ill without ECMO support was 6.54 L/h/70 kg. Patient 2, a 2-year-old boy on venoarterial ECMO due to cardiac arrest received 50 mg/kg ceftriaxone every 12 hours while on ECMO for >7 days. Only clearance while on ECMO could be estimated (9.1 L/h/70 kg). Trough concentrations in both patients were >1 mg/L (the breakpoint for Streptococcus pneumoniae ) while on ECMO.

CONCLUSIONS

ECMO increased ceftriaxone clearance above the model-predicted clearances in the 2 pediatric patients studied. Twelve-hour dosing allowed concentrations to remain above the breakpoint for commonly targeted bacteria but not 4 times the breakpoint in one patient, suggesting that precision dosing may be beneficial to ensure target attainment in children on ECMO.

Real-world experience of therapeutic drug monitoring and PK/PD achievement of ceftaroline administered by different infusion regimens in patients with confirmed infections caused by Gram-positive bacteria

BACKGROUND

Ceftaroline is a novel cephalosporin active against MDR Gram-positive (GP) bacteria. For β-lactam antibiotics, such as ceftaroline, prolonged infusions and therapeutic drug monitoring (TDM) are used for dosage optimization based on their pharmacokinetics/pharmacodynamics (PK/PD).

OBJECTIVES

To describe our experience with TDM and PK/PD target attainment of ceftaroline administered by intermittent and prolonged infusion in a cohort of patients with MDR-GP bacterial infections.

METHODS

Patients treated with ceftaroline administered by continuous (24 h), extended (3 h/6 h) and intermittent infusion (1 h) and undergoing TDM of plasma concentrations were included. A 100%fT>4×MIC was the pre-specified PK/PD target and 100%fT>10×MIC was considered overexposure. Dose recommendations were made based on TDM results and each patient's clinical condition.

RESULTS

Twelve patients [83.3% male, median age of 73 (38-83) years] were included. Nine patients (75%) achieved 100%fT>4×MIC, all under prolonged infusions. In one patient, the 100%fT was >10×MIC but no toxicity was observed. Based on TDM results, initial doses were recommended to be maintained in eight patients, decreased in three and increased in one.

CONCLUSIONS

The administration of ceftaroline by prolonged infusion together with TDM may be a useful strategy for achieving the desired PK/PD target in these patients. However, more studies evaluating the relationship between PK/PD attainment and clinical outcomes are needed.

Anakinra Removal by Continuous Renal Replacement Therapy: An Ex Vivo Analysis

OBJECTIVES

Patients with sepsis are at significant risk for multiple organ dysfunction, including the lungs and kidneys. To manage the morbidity associated with kidney impairment, continuous renal replacement therapy (CRRT) may be required. The extent of anakinra pharmacokinetics in CRRT remains unknown. The objectives of this study were to investigate the anakinra-circuit interaction and quantify the rate of removal from plasma.

DESIGN

The anakinra-circuit interaction was evaluated using a closed-loop ex vivo CRRT circuit. CRRT was performed in three phases based on the method of solute removal: 1) hemofiltration, 2) hemodialysis, and 3) hemodiafiltration. Standard control samples of anakinra were included to assess drug degradation.

SETTING

University research laboratory.

PATIENTS

None.

INTERVENTIONS

Anakinra was administered to the CRRT circuit and serial prefilter blood samples were collected along with time-matched control and hemofiltrate samples. Each circuit was run in triplicate to assess inter-run variability. Concentrations of anakinra in each reference fluid were measured by enzyme-linked immunosorbent assay. Transmembrane filter clearance was estimated by the product of the sieving coefficient/dialysate saturation constant and circuit flow rates.

MEASUREMENTS AND MAIN RESULTS

Removal of anakinra from plasma occurred within minutes for each CRRT modality. Average drug remaining (%) in plasma following anakinra administration was lowest with hemodiafiltration (34.9%). The average sieving coefficient was 0.34, 0.37, and 0.41 for hemodiafiltration, hemofiltration, and hemodialysis, respectively. Transmembrane clearance was fairly consistent across each modality with the highest during hemodialysis (5.53 mL/min), followed by hemodiafiltration (4.99 mL/min), and hemofiltration (3.94 mL/min). Percent drug remaining within the control samples (93.1%) remained consistent across each experiment, indicating negligible degradation within the blood.

CONCLUSIONS

The results of this analysis are the first to demonstrate that large molecule therapeutic proteins such as anakinra, are removed from plasma with modern CRRT technology. Current dosing recommendations for patients with severe renal impairment may result in subtherapeutic anakinra concentrations in those receiving CRRT.

Predicting Beta-Lactam Target Non-Attainment in ICU Patients at Treatment Initiation: Development and External Validation of Three Novel (Machine Learning) Models

In the intensive care unit (ICU), infection-related mortality is high. Although adequate antibiotic treatment is essential in infections, beta-lactam target non-attainment occurs in up to 45% of ICU patients, which is associated with a lower likelihood of clinical success. To optimize antibiotic treatment, we aimed to develop beta-lactam target non-attainment prediction models in ICU patients. Patients from two multicenter studies were included, with intravenous intermittent beta-lactam antibiotics administered and blood samples drawn within 12-36 h after antibiotic initiation. Beta-lactam target non-attainment models were developed and validated using random forest (RF), logistic regression (LR), and naïve Bayes (NB) models from 376 patients. External validation was performed on 150 ICU patients. We assessed performance by measuring discrimination, calibration, and net benefit at the default threshold probability of 0.20. Age, sex, serum creatinine, and type of beta-lactam antibiotic were found to be predictive of beta-lactam target non-attainment. In the external validation, the RF, LR, and NB models confirmed good discrimination with an area under the curve of 0.79 [95% CI 0.72-0.86], 0.80 [95% CI 0.73-0.87], and 0.75 [95% CI 0.67-0.82], respectively, and net benefit in the RF and LR models. We developed prediction models for beta-lactam target non-attainment within 12-36 h after antibiotic initiation in ICU patients. These online-accessible models use readily available patient variables and help optimize antibiotic treatment. The RF and LR models showed the best performance among the three models tested.

Pharmacokinetic and pharmacodynamic considerations for antifungal therapy optimisation in the treatment of intra-abdominal candidiasis

Intra-abdominal candidiasis (IAC) is one of the most common of invasive candidiasis observed in critically ill patients. It is associated with high mortality, with up to 50% of deaths attributable to delays in source control and/or the introduction of antifungal therapy. Currently, there is no comprehensive guidance on optimising antifungal dosing in the treatment of IAC among the critically ill. However, this form of abdominal sepsis presents specific pharmacokinetic (PK) alterations and pharmacodynamic (PD) challenges that risk suboptimal antifungal exposure at the site of infection in critically ill patients. This review aims to describe the peculiarities of IAC from both PK and PD perspectives, advocating an individualized approach to antifungal dosing. Additionally, all current PK/PD studies relating to IAC are reviewed in terms of strength and limitations, so that core elements for the basis of future research can be provided.

Glomerular hyperfiltration in patients with severe trauma

BACKGROUND AND OBJECTIVE

Augmented renal clearance or glomerular hyperfiltration (GHF) can significantly affect the clinical outcomes of renally eliminated drugs by promoting subtherapeutic drug exposure. The aggression suffered in patients who suffer severe trauma is a predisposition to manifest GHF and the identification of these patients remains a clinical challenge. The main objective of this study was to describe the prevalence of GHF in a cohort of critically ill trauma patients.

MATERIALS AND METHODS

Prospective observational study of a cohort of adult patients admitted after suffering severe trauma or polytrauma in the Anesthesiology ICU of the University Hospital of Albacete (Spain). Creatinine clearance (ClCr) was calculated in a 4-h urine collection sample at 24, 72 and 168 h after admission applying the formula; CrCl: [Diuresis in ml (urine/4 h) × Creatinine in urine (mg/dl)] ÷ [240 (minutes) × Creatinine in plasma (mg/dl)]. A CrCl above 130 mL/min was considered GHF. The analyses were performed with the statistical software R version 4.0.4.

RESULTS

85 patients were included. The median age of the patients was 51 years (IQR 26), 78.82% male. 68 patients were male (78.82%). 75.29% of the patients were polytraumatized. 61 patients (71.76%) presented GHF at some point in the CrCl determination. At 24 h of admission, 56.34% of the patients presented GHF with a mean CrCl of 195.8 ml/min, 61.11% of the patients presented it at 72 h with a mean CrCl of /min and 56.52% presented GHF at 168 h of admission with a mean CrCl of 207 ml/min. A significant positive relationship (p = 0.07) was found between GHF manifested at 72 h and at 168 h. We observed a statistically significant relationship between this phenomenon with younger ages, lower ISS scores and lower plasma creatinines.

CONCLUSIONS

GHF are a common condition in critically ill patients admitted for severe trauma. We recommend the use of CrCl to assess renal function and make dosage adjustments. Studies are required to understand the clinical impact of these phenomena on drug elimination and to be able to establish the ideal dosage in those cases.

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.

The clinical application of beta-lactam antibiotic therapeutic drug monitoring in the critical care setting

Critically ill patients have increased variability in beta-lactam antibiotic (beta-lactam) exposure due to alterations in their volume of distribution and elimination. Therapeutic drug monitoring (TDM) of beta-lactams, as a dose optimization and individualization tool, has been recommended to overcome this variability in exposure. Despite its potential benefit, only a few centres worldwide perform beta-lactam TDM. An important reason for the low uptake is that the evidence for clinical benefits of beta-lactam TDM is not well established. TDM also requires the availability of specific infrastructure, knowledge and expertise. Observational studies and systematic reviews have demonstrated that TDM leads to an improvement in achieving target concentrations, a reduction in potentially toxic concentrations and improvement of clinical and microbiological outcomes. However, a small number of randomized controlled trials have not shown a mortality benefit. Opportunities for improved study design are apparent, as existing studies are limited by their inclusion of heterogeneous patient populations, including patients that may not even have infection, small sample size, variability in the types of beta-lactams included, infections caused by highly susceptible bacteria, and varied sampling, analytical and dosing algorithm methods. Here we review the fundamentals of beta-lactam TDM in critically ill patients, the existing clinical evidence and the practical aspects involved in beta-lactam TDM implementation.

Linezolid dosing in critically ill patients undergoing various modalities of renal replacement therapy: a pooled population pharmacokinetic analysis

The altered pharmacokinetics (PK) of linezolid are pronounced in critically ill patients undergoing different modalities of renal replacement therapy (RRT). This study aimed to provide a pooled population PK analysis of linezolid in patients undergoing RRT, and to evaluate the pharmacodynamic target attainment of linezolid standard dosing (600 mg q12h). In total, 414 pooled linezolid concentration observations from 69 patients undergoing intermittent haemodialysis (IHD), sustained low-efficiency dialysis (SLED) or continuous RRT were used to develop the population PK model. The probability of target attainment (PTA) for the efficacy markers of 85% T>minimum inhibitory concentration (MIC) and area under the concentration-time curve (AUC)/MIC >100 was evaluated, and the risk of toxicity was estimated based on Cmin ≥10 mg/L. Linezolid concentration data were described adequately by a two-compartment model. Renal function and body weight were identified as significant modifiers for endogenous clearance of linezolid. Simulations demonstrated that the PTA of 85% T>MIC and AUC/MIC>100 was unacceptably low (0-58.6%, MIC ≥1 mg/L) in RRT patients with preserved renal function, while desirable 85% T>MIC attainment (≥ 90%, MIC ≤2 mg/L) was achieved in anuric RRT patients. The predicted risk of toxicity was negligible (<1.0%) in patients with preserved renal function (regardless of RRT modality), while the probability of reaching Cmin ≥10 mg/L was high (17.9-20.9%) for the anuric patient population undergoing IHD or SLED. In conclusion, standard linezolid dosing is adequate for anuric RRT patients with MIC ≤2 mg/L.

Pharmacokinetic relevance of glomerular hyperfiltration for drug dosing

In chronic kidney disease (CKD) patients, hypofiltration may lead to the accumulation of drugs that are cleared mainly by the kidney and, vice versa, hyperfiltration may cause augmented renal excretion of the same drugs. In this review we mainly focus on the issue of whether hyperfiltration significantly impacts the renal clearance of drugs and whether the same alteration may demand an up-titration of the doses applied in clinical practice. About half of severely ill, septic patients and patients with burns show glomerular hyperfiltration and this may lead to enhanced removal of drugs such as hydrophilic antibiotics and a higher risk of antibiotic treatment failure. In general, hyperfiltering obese individuals show higher absolute drug clearances than non-obese control subjects, but this depends on the body size descriptor adopted to adjust for fat excess. Several mechanisms influence pharmacokinetics in type 2 diabetes, including renal hyperfiltration, reduced tubular reabsorption and augmented tubular excretion. However, no consistent pharmacokinetic alteration has been identified in hyperfiltering obese subjects and type 2 diabetics. Non-vitamin K antagonist oral anticoagulants (NOACs) have exhibited lower plasma concentrations in hyperfiltering patients in some studies in patients with atrial fibrillation, but a recent systematic review failed to document any excess risk for stroke and systemic embolism in these patients. Hyperfiltration is common among severely ill patients in intensive care units and drug levels should be measured whenever possible in these high-risk patients to prevent underdosing and treatment failure. Hyperfiltration is also common in patients with obesity or type 2 diabetes, but no consistent pharmacokinetic alteration has been described in these patients. No NOAC dose adjustment is indicated in patients with atrial fibrillation being treated with these drugs.

The Significance of Bayesian Pharmacokinetics in Dosing for Critically Ill Patients: A Primer for Clinicians Using Vancomycin as an Example

Antibiotic use is becoming increasingly challenging with the emergence of multidrug-resistant organisms. Pharmacokinetic (PK) alterations result from complex pathophysiologic changes in some patient populations, particularly those with critical illness. Therefore, antibiotic dose individualization in such populations is warranted. Recently, there have been advances in dose optimization strategies to improve the utilization of existing antibiotics. Bayesian-based dosing is one of the novel approaches that could help clinicians achieve target concentrations in a greater percentage of their patients earlier during therapy. This review summarizes the advantages and disadvantages of current approaches to antibiotic dosing, with a focus on critically ill patients, and discusses the use of Bayesian methods to optimize vancomycin dosing. The Bayesian method of antibiotic dosing was developed to provide more precise predictions of drug concentrations and target achievement early in therapy. It has benefits such as the incorporation of personalized PK/PD parameters, improved predictive abilities, and improved patient outcomes. Recent vancomycin dosing guidelines emphasize the importance of using the Bayesian method. The Bayesian method is able to achieve appropriate antibiotic dosing prior to the patient reaching the steady state, allowing the patient to receive the right drug at the right dose earlier in therapy.

Influence of arterial blood gases on the renal arterial resistive index in intensive care unit

BACKGROUND

Renal artery Doppler sonography with resistive index (RI) determination is a noninvasive, fast, and reliable diagnostic tool increasingly used in the intensive care unit (ICU) to predict and assess the reversibility of acute kidney injury (AKI). However, interpreting the RI can be challenging due to numerous influencing factors. While some studies have explored various confounding factors, arterial blood gases have received limited attention. Therefore, our study aims to evaluate the impact of arterial blood gases on the RI in the ICU setting.

METHODS

This prospective observational study enrolled ICU patients who required blood gas analysis and had not experienced significant hemodynamic changes recently. The RI was measured using standardized Doppler ultrasound within an hour of the arterial blood gases sampling and analysis.

RESULTS

A total of sixty-four patients were included in the analysis. Univariate analysis revealed a correlation between the RI and several variables, including PaCO2 (R = 0.270, p = 0.03), age (R = 0.574, p < 0.0001), diastolic arterial pressure (DAP) (R = - 0.368, p = 0.0028), and SaO2 (R = - 0.284, p = 0.0231). Multivariate analysis confirmed that age > 58 years and PaCO2 were significant factors influencing the RI, with respective odds ratios of 18.67 (p = 0.0003) and 1.132 (p = 0.0267).

CONCLUSION

The interpretation of renal arterial RI should take into account thresholds for PaCO2, age, and diastolic arterial pressure. Further studies are needed to develop a comprehensive scoring system that incorporates all these cofactors for a reliable analysis of RI levels. Trial registration This observational study, registered under number 70-0914, received approval from local Ethical Committee of Toulouse University Hospital.

β-Lactam Pharmacokinetic/Pharmacodynamic Target Attainment in Intensive Care Unit Patients: A Prospective, Observational, Cohort Study

BACKGROUND

The aims of this study were to describe pharmacokinetic/pharmacodynamic target attainment in intensive care unit (ICU) patients treated with continuously infused ß-lactam antibiotics, their associated covariates, and the impact of dosage adjustment.

METHODS

This prospective, observational, cohort study was performed in three ICUs. Four ß-lactams were continuously infused, and therapeutic drug monitoring (TDM) was performed at days 1, 4, and 7. The primary pharmacokinetic/pharmacodynamic target was an unbound ß-lactam plasma concentration four times above the bacteria's minimal inhibitory concentration during the whole dosing interval. The demographic and clinical covariates associated with target attainment were evaluated.

RESULTS

A total of 170 patients were included (426 blood samples). The percentages of empirical ß-lactam underdosing at D1 were 66% for cefepime, 43% for cefotaxime, 47% for ceftazidime, and 14% for meropenem. Indexed creatinine clearance was independently associated with treatment underdose if increased (adjusted odds ratio per unit, 1.01; 95% CI, 1.00 to 1.01; p = 0.014) or overdose if decreased (adjusted odds ratio per unit, 0.95; 95% CI, 0.94 to 0.97; p < 0.001). Pharmacokinetic/pharmacodynamic target attainment was significantly increased after ß-lactam dosage adjustment between day 1 and day 4 vs. no adjustment (53.1% vs. 26.2%; p = 0.018).

CONCLUSIONS

This study increases our knowledge on the optimization of ß-lactam therapy in ICU patients. A large inter- and intra-patient variability in plasmatic concentrations was observed, leading to inadequate exposure. A combined indexed creatinine clearance and TDM approach enables adequate dosing for better pharmacokinetic/pharmacodynamic target attainment.

Towards model-informed precision dosing of piperacillin: multicenter systematic external evaluation of pharmacokinetic models in critically ill adults with a focus on Bayesian forecasting

PURPOSE

Inadequate piperacillin (PIP) exposure in intensive care unit (ICU) patients threatens therapeutic success. Model-informed precision dosing (MIPD) might be promising to individualize dosing; however, the transferability of published models to external populations is uncertain. This study aimed to externally evaluate the available PIP population pharmacokinetic (PopPK) models.

METHODS

A multicenter dataset of 561 ICU patients (11 centers/3654 concentrations) was used for the evaluation of 24 identified models. Model performance was investigated for a priori (A) predictions, i.e., considering dosing records and patient characteristics only, and for Bayesian forecasting, i.e., additionally including the first (B1) or first and second (B2) therapeutic drug monitoring (TDM) samples per patient. Median relative prediction error (MPE) [%] and median absolute relative prediction error (MAPE) [%] were calculated to quantify accuracy and precision.

RESULTS

The evaluation revealed a large inter-model variability (A: MPE - 135.6-78.3% and MAPE 35.7-135.6%). Integration of TDM data improved all model predictions (B1/B2 relative improvement vs. A: |MPE|median_all_models 45.1/67.5%; MAPEmedian_all_models 29/39%). The model by Kim et al. was identified to be most appropriate for the total dataset (A/B1/B2: MPE - 9.8/- 5.9/- 0.9%; MAPE 37/27.3/23.7%), Udy et al. performed best in patients receiving intermittent infusion, and Klastrup et al. best predicted patients receiving continuous infusion. Additional evaluations stratified by sex and renal replacement therapy revealed further promising models.

CONCLUSION

The predictive performance of published PIP models in ICU patients varied considerably, highlighting the relevance of appropriate model selection for MIPD. Our differentiated external evaluation identified specific models suitable for clinical use, especially in combination with TDM.

Nanosilver: An Old Antibacterial Agent with Great Promise in the Fight against Antibiotic Resistance

Antibiotic resistance in bacteria is a major problem worldwide that costs 55 billion USD annually for extended hospitalization, resource utilization, and additional treatment expenditures in the United States. This review examines the roles and forms of silver (e.g., bulk Ag, silver salts (AgNO3), and colloidal Ag) from antiquity to the present, and its eventual incorporation as silver nanoparticles (AgNPs) in numerous antibacterial consumer products and biomedical applications. The AgNP fabrication methods, physicochemical properties, and antibacterial mechanisms in Gram-positive and Gram-negative bacterial models are covered. The emphasis is on the problematic ESKAPE pathogens and the antibiotic-resistant pathogens of the greatest human health concern according to the World Health Organization. This review delineates the differences between each bacterial model, the role of the physicochemical properties of AgNPs in the interaction with pathogens, and the subsequent damage of AgNPs and Ag+ released by AgNPs on structural cellular components. In closing, the processes of antibiotic resistance attainment and how novel AgNP-antibiotic conjugates may synergistically reduce the growth of antibiotic-resistant pathogens are presented in light of promising examples, where antibiotic efficacy alone is decreased.

Individualized antibiotic dosage regimens for patients with augmented renal clearance

Objectives: Augmented renal clearance (ARC) is a state of enhanced renal function commonly observed in 30%-65% of critically ill patients despite normal serum creatinine levels. Using unadjusted standard dosing regimens of renally eliminated drugs in ARC patients often leads to subtherapeutic concentrations, poor clinical outcomes, and the emergence of multidrug-resistant bacteria. We summarized pharmaceutical, pharmacokinetic, and pharmacodynamic research on the definition, underlying mechanisms, and risk factors of ARC to guide individualized dosing of antibiotics and various strategies for optimizing outcomes. Methods: We searched for articles between 2010 and 2022 in the MEDLINE database about ARC patients and antibiotics and further provided individualized antibiotic dosage regimens for patients with ARC. Results: 25 antibiotic dosage regimens for patients with ARC and various strategies for optimization of outcomes, such as extended infusion time, continuous infusion, increased dosage, and combination regimens, were summarized according to previous research. Conclusion: ARC patients, especially critically ill patients, need to make individualized adjustments to antibiotics, including dose, frequency, and method of administration. Further comprehensive research is required to determine ARC staging, expand the range of recommended antibiotics, and establish individualized dosing guidelines for ARC patients.

Optimizing the Use of Beta-Lactam Antibiotics in Clinical Practice: A Test of Time

Despite their limitations, the pharmacokinetics (PK) and pharmacodynamics (PD) indices form the basis for our current understanding regarding antibiotic development, selection, and dose optimization. Application of PK-PD in medicine has been associated with better clinical outcome, suppression of resistance, and optimization of antibiotic consumption. Beta-lactam antibiotics remain the cornerstone for empirical and directed therapy in many patients. The percentage of time of the dosing interval that the free (unbound) drug concentration remains above the minimal inhibitory concentration (MIC) (%fT > MIC) has been considered the PK-PD index that best predicts the relationship between antibiotic exposure and killing for the beta-lactam antibiotics. Time dependence of beta-lactam antibiotics has its origin in the acylation process of the serine active site of penicillin-binding proteins, which subsequently results in bacteriostatic and bactericidal effects during the dosing interval. To enhance the likelihood of target attainment, higher doses, and prolonged infusion strategies, with/or without loading doses, have been applied to compensate for subtherapeutic levels of antibiotics related to PK-PD changes, especially in the early phase of severe sepsis. To minimize resistance and maximize clinical outcome, empirical therapy with a meropenem loading dose followed by high-dose-prolonged infusion should be considered in patients with high inoculum infections presenting as severe (Gram negative) sepsis. Subsequent de-escalation and dosing of beta-lactam antibiotics should be considered as an individualized dynamic process that requires dose adjustments throughout the time course of the disease process mediated by clinical parameters that indirectly assess PK-PD alterations.

Therapeutic Drug Monitoring of Antimicrobials in Critically Ill Obese Patients

Obesity is a significant global public health concern that is associated with an elevated risk of comorbidities as well as severe postoperative and nosocomial infections. The treatment of infections in critically ill obese patients can be challenging because obesity affects the pharmacokinetics and pharmacodynamics of antibiotics, leading to an increased risk of antibiotic therapy failure and toxicity due to inappropriate dosages. Precision dosing of antibiotics using therapeutic drug monitoring may help to improve the management of this patient population. This narrative review outlines the pharmacokinetic and pharmacodynamic changes that result from obesity and provides a comprehensive critical review of the current available data on dosage adjustment of antibiotics in critically ill obese patients.

Change of dexmedetomidine and midazolam concentrations by simultaneous injection in an in vitro extracorporeal circuit

PURPOSE

Patient sedation and analgesia are vital for safety and comfort during extracorporeal membrane oxygenation (ECMO). However, adsorption by the circuit may alter drug pharmaco-kinetics and remains poorly characterized. This study is the first to examine the concentrations of DEX and MDZ in the presence of drug-drug interactions using an in vitro extracorporeal circuit system that incorporates a polymer-coated polyvinyl chloride tube, but not a membrane oxygenator.

METHODS AND RESULTS

Nine in vitro extracorporeal circuits were prepared using polymer-coated PVC tubing. Once the circuits were primed and running, either a single drug or two drugs were injected as boluses into the circuit with three circuits per drug. Drug samples were drawn following injection at 2, 5, 15, 30, 60, and 120 min and at 4, 12, and 24 h. They were then analyzed using high-performance liquid chromatography with mass spectrometry. When compared with an injection of DEX alone, the combination of DEX and MDZ is highly changed, with DEX and MDZ affecting the availability of free drugs in the circuit.

CONCLUSIONS

The change of DEX and MDZ concentrations was confirmed by a combination of both drugs as compared with either single-infusion DEX or MDZ in an in vitro extracorporeal circuit. Drug-drug interactions developed between DEX and MDZ through albumin in an extracorporeal circuit; as a result, the unbounded drugs might change in the circuit.

Optimizing Betalactam Clinical Response by Using a Continuous Infusion: A Comprehensive Review

INTRODUCTION

Antimicrobial resistance is a major healthcare issue responsible for a large number of deaths. Many reviews identified that PKPD data are in favor of the use of continuous infusion, and we wanted to review clinical data results in order to optimize our clinical practice.

METHODOLOGY

We reviewed Medline for existing literature comparing continuous or extended infusion to intermittent infusion of betalactams.

RESULTS

In clinical studies, continuous infusion is as good as intermittent infusion. In the subset group of critically ill patients or those with an infection due to an organism with high MIC, a continuous infusion was associated with better clinical response.

CONCLUSIONS

Clinical data appear to confirm those of PK/PD to use a continuous infusion in severely ill patients or those infected by an organism with an elevated MIC, as it is associated with higher survival rates. In other cases, it may allow for a decrease in antibiotic daily dosage, thereby contributing to a decrease in overall costs.

Is the Pharmacokinetics of First-Line Anti-TB Drugs a Cause of High Mortality Rates in TB Patients Admitted to the ICU? A Non-Compartmental Pharmacokinetic Analysis

BACKGROUND

Patients with tuberculosis (TB) may develop multi-organ failure and require admission to intensive care. In these cases, the mortality rates are as high as 78% and may be caused by suboptimal serum concentrations of first-line TB drugs. This study aims to compare the pharmacokinetics of oral rifampin, isoniazid, pyrazinamide and ethambutol patients in intensive care units (ICU) to outpatients and to evaluate drug serum concentrations as a potential cause of mortality.

METHODS

A prospective pharmacokinetic (PK) study was performed in Amazonas State, Brazil. The primary PK parameters of outpatients who achieved clinical and microbiological cure were used as a comparative target in a non-compartmental analysis.

RESULTS

Thirteen ICU and twenty outpatients were recruited. The clearance and volume of distribution were lower for rifampin, isoniazid, pyrazinamide and ethambutol. ICU thirty-day mortality was 77% versus a cure rate of 89% in outpatients.

CONCLUSIONS

ICU patients had a lower clearance and volume of distribution for rifampin, isoniazid, pyrazinamide and ethambutol compared to the outpatient group. These may reflect changes to organ function, impeded absorption and distribution to the site of infection in ICU patients and have the potential to impact clinical outcomes.

Outcomes of Intravenous Push versus Intermittent Infusion Administration of Cefepime in Critically Ill Patients

The equivalence of intravenous push (IVP) and piggyback (IVPB) administration has not been evaluated in the critically ill population for most medications, but it is especially relevant for antibiotics, such as cefepime, that exhibit time-dependent bactericidal activity. A single center, retrospective, observational pre/post-protocol change study included critically ill adults who received cefepime as empiric therapy between August 2015 and 2021. The primary outcome was treatment failure, which was defined as a composite of escalation of antibiotic regimen or all-cause mortality. Secondary outcomes included adverse drug events, days of cefepime therapy, total days of antibiotic therapy, and ICU and hospital length of stay. Outcomes were compared using Chi-squared, Mann Whitney U, and binary logistic regression as appropriate. A total of 285 patients were included: 87 IVPB and 198 IVP. Treatment failure occurred in 18% (n = 16) of the IVPB group and 27% (n = 54) of the IVP group (p = 0.109). There were no significant differences in secondary outcomes. Longer duration of antibiotics (odds ratio [OR] 1.057, 95% confidence interval [CI] 1.013-1.103), SOFA score (OR 1.269, 95% CI 1.154-1.397) and IVP administration of cefepime (OR 2.370, 95% CI 1.143-4.914) were independently associated with treatment failure. Critically ill patients who received IVP cefepime were more likely to experience treatment failure in an adjusted analysis. The current practice of IVP cefepime should be reevaluated, as it may not provide similar clinical outcomes in the critically ill population.

Adverse Drug Reactions Relevant to Drug Resistance and Ineffectiveness Associated with Meropenem, Linezolid, and Colistin: An Analysis Based on Spontaneous Reports from the European Pharmacovigilance Database

Antimicrobial resistance is considered one of the major threats to public health and is an important factor that influences the patient's outcome in the intensive care unit. Pharmacovigilance can help raise awareness of potential drug resistance (DR) or ineffectiveness (DI) through adverse drug reaction reports that are submitted to different spontaneous reporting systems. Based on spontaneous Individual Case Safety Reports from EudraVigilance, we conducted a descriptive analysis of adverse drug reactions associated with meropenem, colistin, and linezolid, with a focus on DR and DI. Of the total adverse drug reactions (ADRs) reported for each analyzed antibiotic by 31 December 2022, between 2.38-8.42% and 4.15-10.14% of the reports were related to DR and DI, respectively. A disproportionality analysis was conducted to evaluate the frequency of reporting adverse drug reactions relevant to the DR and DI of the analyzed antibiotics compared to other antimicrobials. Based on the analysis of the collected data, this study underlines the importance of post-marketing drug safety monitoring in raising a warning signal regarding antimicrobial resistance, thereby potentially contributing to the reduction in antibiotic treatment failure in an intensive care setting.

Aminoglycosides for the Treatment of Severe Infection Due to Resistant Gram-Negative Pathogens

Aminoglycosides are a family of rapidly bactericidal antibiotics that often remain active against resistant Gram-negative bacterial infections. Over the past decade, their use in critically ill patients has been refined; however, due to their renal and cochleovestibular toxicity, their indications in the treatment of sepsis and septic shock have been gradually reduced. This article reviews the spectrum of activity, mode of action, and methods for optimizing the efficacy of aminoglycosides. We discuss the current indications for aminoglycosides, with an emphasis on multidrug-resistant Gram-negative bacteria, such as extended-spectrum β-lactamase-producing Enterobacterales, carbapenemase-producing Enterobacterales, multidrug-resistant Pseudomonas aeruginosa, and carbapenem-resistant Acinetobacter baumannii. Additionally, we review the evidence for the use of nebulized aminoglycosides.

A Systematic Review on Antimicrobial Pharmacokinetic Differences between Asian and Non-Asian Adult Populations

While the relevance of inter-ethnic differences to the pharmacokinetic variabilities of antimicrobials has been reported in studies recruiting healthy subjects, differences in antimicrobial pharmacokinetics between Asian and non-Asian patients with severe pathologic conditions require further investigation. For the purpose of describing the potential differences in antimicrobial pharmacokinetics between Asian and non-Asian populations, a systematic review was performed using six journal databases and six theses/dissertation databases (PROSPERO record CRD42018090054). The pharmacokinetic data of healthy volunteers and non-critically ill and critically ill patients were reviewed. Thirty studies on meropenem, imipenem, doripenem, linezolid, and vancomycin were included in the final descriptive summaries. In studies recruiting hospitalised patients, inconsistent differences in the volume of distribution (V_d) and drug clearance (CL) of the studied antimicrobials between Asian and non-Asian patients were observed. Additionally, factors other than ethnicity, such as demographic (e.g., age) or clinical (e.g., sepsis) factors, were suggested to better characterise these pharmacokinetic differences. Inconsistent differences in pharmacokinetic parameters between Asian and non-Asian subjects/patients may suggest that ethnicity is not an important predictor to characterise interindividual pharmacokinetic differences between meropenem, imipenem, doripenem, linezolid, and vancomycin. Therefore, the dosing regimens of these antimicrobials should be adjusted according to patients' demographic or clinical characteristics that can better describe pharmacokinetic differences.

Clearance of Piperacillin-Tazobactam and Vancomycin During Continuous Renal Replacement With Regional Citrate Anticoagulation

BACKGROUND

The use of regional citrate anticoagulation during continuous venovenous hemodiafiltration (CVVHDF) has increased worldwide. However, data on its effect on the pharmacokinetics of antibiotics are limited. In this study, the authors aimed to measure the clearance of piperacillin-tazobactam and vancomycin in patients receiving CVVHDF with regional citrate anticoagulation.

METHODS

This study measured piperacillin-tazobactam and vancomycin concentrations in patients receiving CVVHDF with regional citrate anticoagulation. Dosing regimens were independently selected by intensivists. Arterial blood and effluent fluid samples were obtained over a single dosing interval and analyzed using ultra-high-performance liquid chromatography with tandem mass spectrometry.

RESULTS

Seventeen sampling intervals in 15 patients (9 receiving piperacillin-tazobactam only, 4 receiving vancomycin only, and 2 receiving both) were used. The median overall clearance for piperacillin was 35.2 mL/min [interquartile range (IQR): 32.2-38.6], 70 mL/min (IQR: 62.7-76.2) for tazobactam, and 29.5 mL/min (IQR: 26.2-32) for vancomycin.

CONCLUSIONS

This is the first study to quantify the pharmacokinetics of vancomycin and piperacillin-tazobactam in patients receiving CVVHDF with regional citrate anticoagulation. These results indicate high clearance and provide key information to guide optimal dosing.

The Current Status and Future Perspectives of Beta-Lactam Therapeutic Drug Monitoring in Critically Ill Patients

Beta-lactams (BL) are the first line agents for the antibiotic management of critically ill patients with sepsis or septic shock. BL are hydrophilic antibiotics particularly subject to unpredictable concentrations in the context of critical illness because of pharmacokinetic (PK) and pharmacodynamics (PD) alterations. Thus, during the last decade, the literature focusing on the interest of BL therapeutic drug monitoring (TDM) in the intensive care unit (ICU) setting has been exponential. Moreover, recent guidelines strongly encourage to optimize BL therapy using a PK/PD approach with TDM. Unfortunately, several barriers exist regarding TDM access and interpretation. Consequently, adherence to routine TDM in ICU remains quite low. Lastly, recent clinical studies failed to demonstrate any improvement in mortality with the use of TDM in ICU patients. This review will first aim at explaining the value and complexity of the TDM process when translating it to critically ill patient bedside management, interpretating the results of clinical studies and discussion of the points which need to be addressed before conducting further TDM studies on clinical outcomes. In a second time, this review will focus on the future aspects of TDM integrating toxicodynamics, model informed precision dosing (MIPD) and “at risk” ICU populations that deserve further investigations to demonstrate positive clinical outcomes.

Differential expression of outer membrane proteins and quinolone resistance determining region mutations can lead to ciprofloxacin resistance in Salmonella Typhi

Multi-drug resistance in Salmonella Typhi remains a public health concern globally. This study aimed to investigate the function of quinolone resistance determining region (QRDR) of gyrA and parC in ciprofloxacin (CIP) resistant isolates and examine the differential expression of outer membrane proteins (OMPs) on exposure to sub-lethal concentrations of CIP in S. Typhi. The CIP-resistant isolates were screened for mutations in the QRDR and analyzed for bacterial growth. Furthermore, major OMPs encoding genes such as ompF, lamB, yaeT, tolC, ompS1, and phoE were examined for differential expression under the sub-lethal concentrations of CIP by real-time PCR and SDS-PAGE. Notably, our study has shown a single-point mutation in gyrA at codon 83 (Ser83-tyrosine and Ser83-phenylalanine), also the rare amino acid substitution in parC gene at codon 80 (Glu80-glycine) in CIP-resistant isolates. Additionally, CIP-resistant isolates showed moderate growth compared to susceptible isolates. Although most of the OMP-encoding genes (tolC, ompS1, and phoE) showed some degree of upregulation, a significant level of upregulation (p < 0.05) was observed only for yaeT. However, ompF and lamB genes were down-regulated compared to CIP-susceptible isolates. Whereas OMPs profiling using SDS-PAGE did not show any changes in the banding pattern. These results provide valuable information on the QRDR mutation, and the difference in the growth, and expression of OMP-encoding genes in resistant and susceptible isolates of S. Typhi. This further provides insight into the involvement of QRDR mutation and OMPs associated with CIP resistance in S. Typhi.

Population Pharmacokinetic Study of Benzylpenicillin in Critically Unwell Adults

Pharmacokinetics are highly variable in critical illness, and suboptimal antibiotic exposure is associated with treatment failure. Benzylpenicillin is a commonly used beta-lactam antibiotic, and pharmacokinetic data of its use in critically ill adults are lacking. We performed a pharmacokinetic study of critically unwell patients receiving benzylpenicillin, using data from the ABDose study. Population pharmacokinetic modelling was undertaken using NONMEM version 7.5, and simulations using the final model were undertaken to optimize the pharmacokinetic profile. We included 77 samples from 12 participants. A two-compartment structural model provided the best fit, with allometric weight scaling for all parameters and a creatinine covariate effect on clearance. Simulations (n = 10,000) demonstrated that 25% of simulated patients receiving 2.4 g 4-hourly failed to achieve a conservative target of 50% of the dosing interval with free drug above the clinical breakpoint MIC (2 mg/L). Simulations demonstrated that target attainment was improved with continuous or extended dosing. To our knowledge, this study represents the first full population PK analysis of benzylpenicillin in critically ill adults.

Update on Therapeutic Drug Monitoring of Beta-Lactam Antibiotics in Critically Ill Patients—A Narrative Review

Beta-lactam antibiotics remain one of the most preferred groups of antibiotics in critical care due to their excellent safety profiles and their activity against a wide spectrum of pathogens. The cornerstone of appropriate therapy with beta-lactams is to achieve an adequate plasmatic concentration of a given antibiotic, which is derived primarily from the minimum inhibitory concentration (MIC) of the specific pathogen. In a critically ill patient, the plasmatic levels of drugs could be affected by many significant changes in the patient’s physiology, such as hypoalbuminemia, endothelial dysfunction with the leakage of intravascular fluid into interstitial space and acute kidney injury. Predicting antibiotic concentration from models based on non-critically ill populations may be misleading. Therapeutic drug monitoring (TDM) has been shown to be effective in achieving adequate concentrations of many drugs, including beta-lactam antibiotics. Reliable methods, such as high-performance liquid chromatography, provide the accurate testing of a wide range of beta-lactam antibiotics. Long turnaround times remain the main drawback limiting their widespread use, although progress has been made recently in the implementation of different novel methods of antibiotic testing. However, whether the TDM approach can effectively improve clinically relevant patient outcomes must be proved in future clinical trials.

The Influence of Extracorporeal Membrane Oxygenation on Antibiotic Pharmacokinetics

Extracorporeal membrane oxygenation (ECMO) is becoming increasingly utilized to support critically ill patients who experience life-threatening cardiac or pulmonary compromise. The provision of this intervention poses challenges related to its complications and the optimization of medication therapy. ECMO's mechanical circulatory support is facilitated via various devices and equipment that have been shown to sequester lipophilic- and protein-bound medications, including anti-infectives. Since infectious outcomes are dependent on achieving specific anti-infectives' pharmacodynamic targets, the understanding of these medications' pharmacokinetic parameters in the setting of ECMO is important to clinicians. This narrative, non-systematic review evaluated the findings of the most recent and robust pharmacokinetic analyses for commonly utilized anti-infectives in the setting of ECMO. The data from available literature indicates that anti-infective pharmacokinetic parameters are similar to those observed in other non-ECMO critically ill populations, but considerable variability in the findings was observed between patients, thus prompting further evaluation of therapeutic drug monitoring in this complex population.

Dispersive solid phase extraction of metronidazole and clarithromycin from human plasma using a β-cyclodextrin grafted polyethylene polymer composite

In this work, for the first time, a polymeric composite based on β-cyclodextrin grafted with polyethylene has been prepared through ball milling and used as an efficient sorbent for dispersive solid phase extraction of metronidazole and clarithromycin from plasma samples. The prepared sorbent was characterized using Fourier transform infrared spectrophotometry, X-ray diffraction, and scanning electron microscopy. In the extraction process, after precipitating the proteins, the sorbent was added into the sample solution, and the mixture was vortexed to facilitate and speed up the sorption of the analytes onto the sorbent surface. After centrifuging, the sorbent particles were contacted with methanol to elute the analytes under the vortexing process. After this step, an aliquot of the eluate was taken and injected into high-performance liquid chromatography-diode array detector for quantitative analysis. Under the optimum extraction conditions, the extraction recoveries for metronidazole and clarithromycin were 76 and 83%, respectively. The limits of detection were 2.6 and 2.2 ng/ml for metronidazole and clarithromycin, respectively. The repeatability of the offered approach, expressed as relative standard deviation, was equal to or less than 4.7%. Finally, the method was successfully applied to plasma samples of the patients treated with metronidazole and clarithromycin.