Pharmacokinetic and pharmacodynamic parameters of antimicrobials: potential for providing dosing regimens that are less vulnerable to resistance

Dose Individualisation of Antimicrobials from a Pharmacometric Standpoint: The Current Landscape

Successful antimicrobial therapy depends on achieving optimal drug concentrations within individual patients. Inter-patient variability in pharmacokinetics (PK) and differences in pathogen susceptibility (reflected in the minimum inhibitory concentration, [MIC]) necessitate personalised approaches. Dose individualisation strategies aim to address this challenge, improving treatment outcomes and minimising the risk of toxicity and antimicrobial resistance. Therapeutic drug monitoring (TDM), with the application of population pharmacokinetic (popPK) models, enables model-informed precision dosing (MIPD). PopPK models mathematically describe drug behaviour across populations and can be combined with patient-specific TDM data to optimise dosing regimens. The integration of machine learning (ML) techniques promises to further enhance dose individualisation by identifying complex patterns within extensive datasets. Implementing these approaches involves challenges, including rigorous model selection and validation to ensure suitability for target populations. Understanding the relationship between drug exposure and clinical outcomes is crucial, as is striking a balance between model complexity and clinical usability. Additionally, regulatory compliance, outcome measurement, and practical considerations for software implementation will be addressed. Emerging technologies, such as real-time biosensors, hold the potential for revolutionising TDM by enabling continuous monitoring, immediate and frequent dose adjustments, and near patient testing. The ongoing integration of TDM, advanced modelling techniques, and ML within the evolving digital health care landscape offers a potential for enhancing antimicrobial therapy. Careful attention to model development, validation, and ethical considerations of the applied techniques is paramount for successfully optimising antimicrobial treatment for the individual patient.

Survey of the Knowledge, Attitudes and Practice towards Antibiotic Use among Prospective Antibiotic Prescribers in Serbia

The complex issue of antibacterial resistance (ABR) requires actions taken with the One Health approach, involving both human and veterinarian medicine. It can spread from animals to humans through the food chain or through direct contact. Health profession students, as the future antibiotic providers, can greatly impact antibiotic-related issues in the future. The study was conducted to evaluate knowledge, attitudes and practice of future antibiotic prescribers in relation to judicious use of antibiotics. This cross-sectional, questionnaire-based study was performed on 400 students of health professions who were allowed to prescribe antibiotics of the University of Novi Sad, Serbia. Students of medicine and students of dentistry showed a significantly higher knowledge score compared to students of veterinary medicine (p = 0.001). Multivariate regression identified predictors of adequate antibiotic knowledge: being a female student (B = 0.571; p = 0.020), higher grade average (B = 1.204; p = 0.001), students of medicine (B = 0.802; p = 0.006) and dentistry (B = 0.769; p = 0.026), and students who used a complete package of antibiotics during the last infection (B = 0.974; p = 0.001) or for the period recommended by the doctor (B = 1.964; p = 0.001). Out of the total sample, self-medication was reported among 42.8% of students. The identified predictors of self-medication were: more frequent (B = 0.587; p = 0.001) and irregular (B = 0.719; p = 0.007) antibiotic use, taking antibiotics until symptoms disappeared (B = 2.142; p = 0.001) or until the bottle was finished (B = 1.010; p = 0.001) during the last infection. It seems prudent to reevaluate the educational curricula regarding antibiotic use and ABR of prospective prescribers in Serbia.

Some Suggestions from PK/PD Principles to Contain Resistance in the Clinical Setting-Focus on ICU Patients and Gram-Negative Strains

The containment of the phenomenon of resistance towards antimicrobials is a priority, especially in preserving molecules acting against Gram-negative pathogens, which represent the isolates more frequently found in the fragile population of patients admitted to Intensive Care Units. Antimicrobial therapy aims to prevent resistance through several actions, which are collectively known as "antimicrobial stewardship", to be taken together, including the application of pharmacokinetic/pharmacodynamic (PK/PD) principles. PK/PD application has been shown to prevent the emergence of resistance in numerous experimental studies, although a straight translation to the clinical setting is not possible. Individualized antibiotic dosing and duration should be pursued in all patients, and even more especially when treating intensive care unit (ICU) septic patients in whom optimal exposure is both difficult to achieve and necessary. In this review, we report on the available data that support the application of PK/PD parameters to contain the development of resistance and we give some practical suggestions that can help to translate the benefit of PK/PD application to the bedside.

Aminoglycosides in critically ill patients: which dosing regimens for which pathogens?

Modifications of antibiotic pharmacokinetic parameters have been reported in critically ill patients, resulting in a risk of treatment failure. We aimed to determine optimised amikacin (AMK), gentamicin (GEN) and tobramycin (TOB) intravenous dosing regimens in this patient population. Patients admitted to the medical ICU and treated with AMK, GEN or TOB were included. Analyses were performed using a parametric population approach. Monte Carlo simulations were performed and the probability of target attainment (PTA) was calculated using C_max/MIC ≥ 8 and trough concentrations as targets. A total of 117 critically ill hospitalised patients were studied. Median values (interindividual variability, ɷ²) of clearance were 3.51 (0.539), 3.53 (0.297), 2.70 (0.339) and 5.07 (0.339) L/h for AMK, GEN, TOB, and TOB in cystic fibrosis (CF), respectively. Median values (ɷ²) of central volume of distribution were 30.2 (0.215), 20.0 (0.109) and 25.6 (0.177) L for AMK, GEN and TOB, respectively. Simulations showed that doses should be adjusted to actual body weight and creatinine clearance (CLCR) for AMK and GEN, and according to CLCR and presence of CF for TOB. In conclusion, our recommendations for treating Pseudomonas aeruginosa infections in this population include using initial doses of 35 mg/kg for AMK or 10 mg/kg for TOB (CF and non-CF patients). GEN demonstrated the best rates of target attainment against Staphylococcus aureus infections with a dose of 5 mg/kg. As high aminoglycoside doses are required in this population, efficacy and safety targets are conflicting and therapeutic drug monitoring remains an important tool to manage this issue.

Meropenem/vaborbactam: a next generation β-lactam β-lactamase inhibitor combination

INTRODUCTION

infections due to carbapenem-resistant Enterobacterales (CRE) constitute a worldwide threat and are associated with significant mortality, especially in fragile patients, and costs. Meropenem-vaborbactam (M/V) is a combination of a group 2 carbapenem with a novel cyclic boronic acid-based β-lactamase inhibitor which has shown good efficacy against KPC carbapenemase-producing Klebsiella pneumoniae, which are amongst the most prevalent types of CRE.

AREAS COVERED

This article reviews the microbiological and pharmacological profile and current clinical experience and safety of M/V in the treatment of infections caused by CRE.

EXPERT OPINION

M/V is a promising drug for the treatment of infections due to KPC-producing CRE (KPC-CRE). It exhibited an almost complete coverage of KPC-CRE isolates from large surveillance studies and a low propensity for resistance selection, retaining activity also against strains producing KPC mutants resistant to ceftazidime-avibactam. Both meropenem and vaborbactam have a favorable pharmacokinetic profile, with similar kinetic properties, a good intrapulmonary penetration, and are efficiently cleared during continuous venovenous hemofiltration (CVVH). According to available data, M/V monotherapy is associated with higher clinical cure rates and lower rates of adverse events, especially in terms of nephrotoxicity, if compared to 'older' combination therapies.

Caspofungin PK in critically ill patients after the first and fourth doses: suggestions for therapeutic drug monitoring?

We describe caspofungin pharmacokinetics (PK) after the first and fourth doses in 20 critically ill septic patients. Monte Carlo simulation was used to analyze the probability of target attainment (PTA) (AUC/MIC > 865) for Candida spp. Caspofungin concentrations were analyzed by HPLC in plasma and urine. A great variability in PK parameters was observed after both doses. Patients were divided in two groups according to their AUC values (AUC ≤ 75 mg h/L cut-off). In the low-AUC group Cmax, Cmin and AUC were lower, while Vd and Cl were higher than in the high-AUC group (p < 0.05, both at day 1 and 4). The mean 24-h urinary recovery of the drug was 8 ± 6.3% (day1) and 9.8 ± 6.3 (day4). Monte Carlo simulation analysis (0.03-1 mg/L MIC-range) showed that PTA was guaranteed only for MICs ≤ 0.03 mg/L in the low-AUC group, and for MICs ≤ 0.06 mg/L in the high-AUC group. No group had a PTA ≥ 90% for 0.125 mg/L MIC (the epidemiological cut-off). Mortality was higher in low-AUC group (p < 0.01). In our 'real-world' population, no clinical data can predict which patient will have lower, suboptimal caspofungin exposure, therefore we suggest TDM to optimize caspofungin therapy and reduce the risk of selecting resistances (CEAVC, 32366/2015; OSS.15.114, NCT03798600).

Resistenze antibiotiche e nuove molecole: qual è lo scenario attuale?

Antibiotic resistance and new drugs in urologic setting: what we need to know? Urinary tract infections (UTIs) are among the most frequent infectious diseases, and represent an important public health problem with a substantial economic burden. In recent years the chemoresistance of the main uropathogens has significantly increased worldwide. Extended spectrum beta-lactamase (ESBL) production and multi-drug resistant (MDR) clones of Escherichia coli and Klebsiella pneumoniae are limiting available treatment options. Carbapenems and aminoglycosides are still effective in complicated UTI. New beta-lactam combinations such as ceftolozane-tazobactam and ceftazidime-avibactam may be highly useful in treating severe infections while contributing to the carbapenem sparing strategy. For uncomplicated UTI, within older antibiotics, fosfomycin trometamol may be considered a first-choice drug since it is still retaining a good activity against MDR uropathogens. On the other hand, there are extensive data showing that the administration of antimicrobials according to pharmacokinetic/pharmacodynamic (PK/PD) parameters improves the possibility of a positive clinical outcome, particularly in severely ill patients. Evidence is growing that when PK/PD parameters are used to target not only clinical cure. This article discusses the PK/PD characteristics of antimicrobial agents for the treatment of UTIs, and the pharmacological and therapeutic strategies for limiting or preventing bacterial resistance.

The GISA call to action for the appropriate use of antimicrobials and the control of antimicrobial resistance in Italy

The spread of antibiotic resistance is one of the leading public health problems in Italy. A European Centre for Disease Prevention and Control country visit recently confirmed the major challenges and made important suggestions. In response, the Ministry of Health published the National Plan for Antimicrobial Resistance Containment, and a group of experts belonging to the Italian Group of Antimicrobial Stewardship (GISA) convened to develop a summary of practical recommendations. The GISA document is intended for use by practising physicians; it aims to increase the rational use of antimicrobials in the treatment of infections, and to change the culture of infection control of antibiotic-resistant bacteria, through the translation of theoretical knowledge into priority actions. This document has been endorsed by several national scientific societies, and reflects the particular challenges that are faced in Italy. Nevertheless, it is considered that the general principles and approaches discussed are relevant, particularly to other developed economies.

Pharmacokinetic/pharmacodynamic parameters for treatment optimization of infection due to antibiotic resistant bacteria: a summary for practical purposes in children and adults

In the last years, there has been a tremendous increase in the incidence of bacterial infections due to resistant strains, especially multi-drug resistant Gram-negative bacilli. In Europe, a north to south and a west to east gradient was noticed, with more than one third of the K. pneumonia isolates being resistant to carbapenems in few countries. New antibiotics are lacking and, as a consequence, pharmacokinetic/pharmacodynamic parameters, normalized to pathogen minimal inhibitory concentration, are used with increased frequency to treat infections due to difficult-to-treat pathogens. These parameters are available at least for the adult population, but sparse in many different publications. This review wants to provide a comprehensive and 'easy to read' text for everyday practice, briefly summarizing the presently available knowledge on pharmacokinetic/pharmacodynamic parameters (normalized for minimal inhibitory concentration values) of different class drugs, that can be applied for an effective antibacterial treatment infections due to antibiotic-resistant pathogens.

Diagnosis and management of skin and soft-tissue infections (SSTI). A literature review and consensus statement: an update

Skin and soft-tissue infections (SSTIs) are among the most common bacterial infections, posing considerable diagnostic and therapeutic challenges. Fourteen members of the Italian Society of Infectious Diseases, after a careful review of the most recent literature using Medline database and their own clinical experience, updated a previous paper published in 2011 by preparing a draught manuscript of the statements. The manuscript was successively reviewed by all members and ultimately re-formulated the present manuscript during a full day consensus meeting. The microbiological and clinical aspects together with diagnostic features were considered for necrotizing and not necrotizing SSTIs in the light of the most recent guidelines and evidences published in the last five years. The antimicrobial therapy was considered as well - both empirical and targeted to methicillin-resistant Staphylococcus aureus and/or other pathogens, also taking into account the epidemiological and bacterial resistance data and the availability of new antibacterial agents.

Pharmacokinetics of meropenem after intravenous, intramuscular and subcutaneous administration to cats

OBJECTIVES

The aim of the study was to describe the pharmacokinetics and predicted efficacy of meropenem after intravenous (IV), intramuscular (IM) and subcutaneous (SC) administration to cats at a single dose of 10 mg/kg.

METHODS

Five adult healthy cats were used. Blood samples were withdrawn at predetermined times over a 12 h period. Meropenem concentrations were determined by microbiological assay. Pharmacokinetic analyses were performed with computer software. Initial estimates were determined using the residual method and refitted by non-linear regression. The time that plasma concentrations were greater than the minimum inhibitory concentration (T >MIC) was estimated by applying bibliographic MIC values and meropenem MIC breakpoint.

RESULTS

Maximum plasma concentrations of meropenem were 101.02 µg/ml (Cp(0), IV), 27.21 µg/ml (Cmax, IM) and 15.57 µg/ml (Cmax, SC). Bioavailability was 99.69% (IM) and 96.52 % (SC). Elimination half-lives for the IV, IM and SC administration were 1.35, 2.10 and 2.26 h, respectively.

CONCLUSIONS AND RELEVANCE

Meropenem, when administered to cats at a dose of 10 mg/kg q12h,, is effective against bacteria with MIC values of 6 μg/ml, 7 μg/ml and 10 μg/ml for IV, IM and SC administration, respectively. However, clinical trials are necessary to confirm clinical efficacy of the proposed dosage regimen.

Quantification of piperacillin, tazobactam, meropenem, ceftazidime, and linezolid in human plasma by liquid chromatography/tandem mass spectrometry

Therapeutic drug monitoring is a cornerstone of antibacterial therapy, especially in an era of increasing antibacterial resistance in individualizing antimicrobial therapy. Liquid chromatography/tandem mass spectrometry (LC-MS/MS) assay was used for the simultaneous measurement of piperacillin, tazobactam, meropenem, ceftazidime, and linezolid in 50 μl plasma samples over a wide range. The overall turnaround time for the assay was 20 minutes. Intra-assay precision and accuracy for quality control samples ranged within 1·8-8·5 and 91·4-106·7%, respectively. Inter-assay precision and accuracy ranged within 1·3-14·4 and 95·8-104·6%, respectively. The lower limit of quantification was below 1·5 μg/ml for all the five antibiotics. No ion suppression due to matrix effects was found. A simple and rapid LC-MS/MS method which provides high specificity, precision and accuracy for the simultaneous quantification of piperacillin, tazobactam, meropenem, ceftazidime, and linezolid in human plasma has been developed and validated. The present method is suitable for therapeutic drug monitoring in paediatrics.

Phage therapy: eco-physiological pharmacology

Bacterial virus use as antibacterial agents, in the guise of what is commonly known as phage therapy, is an inherently physiological, ecological, and also pharmacological process. Physiologically we can consider metabolic properties of phage infections of bacteria and variation in those properties as a function of preexisting bacterial states. In addition, there are patient responses to pathogenesis, patient responses to phage infections of pathogens, and also patient responses to phage virions alone. Ecologically, we can consider phage propagation, densities, distribution (within bodies), impact on body-associated microbiota (as ecological communities), and modification of the functioning of body "ecosystems" more generally. These ecological and physiological components in many ways represent different perspectives on otherwise equivalent phenomena. Comparable to drugs, one also can view phages during phage therapy in pharmacological terms. The relatively unique status of phages within the context of phage therapy as essentially replicating antimicrobials can therefore result in a confluence of perspectives, many of which can be useful towards gaining a better mechanistic appreciation of phage therapy, as I consider here. Pharmacology more generally may be viewed as a discipline that lies at an interface between organism-associated phenomena, as considered by physiology, and environmental interactions as considered by ecology.

Antimicrobial treatment of febrile neutropenia: pharmacokinetic-pharmacodynamic considerations

Patients with cancer or hematologic diseases are particularly at risk of infection leading to high morbidity, mortality and costs. Extensive data show that optimization of the administration of antimicrobials according to their pharmacokinetic and pharmacodynamic parameters improves clinical outcome. Evidence is growing that when pharmacokinetic and pharmacodynamic parameters are used to target not only clinical cure but also eradication, the selection resistance is also contained. This is of particular importance in patients with neutropenia in whom increasing rates of drug-resistant Gram-negative bacteria have been reported, particularly Pseudomonas aeruginosa. Based on experimental and clinical studies, pharmacokinetic and pharmacodynamic parameters are discussed in this review for each antibiotic used in febrile neutropenia in order to help physicians improve dosing and optimization of antimicrobial agents.

Developments in the pharmacokinetic/pharmacodynamic index of linezolid: a step toward dose optimization using Monte Carlo simulation in critically ill patients

OBJECTIVES

This study evaluated the efficacy of the pharmacokinetic/pharmacodynamic (PK/PD) index for increasing the success rate of linezolid treatment based on Monte Carlo simulation, and compared differences between the calculated PK/PD breakpoints and those defined by committee for critically ill patients with linezolid treatment.

METHODS

A Monte Carlo simulation involving 10000 subjects was used to analyze the pharmacokinetic parameters and microbiological data of linezolid for an effectiveness evaluation at the corresponding AUC24/MIC values (area under the serum concentration-time curve over 24h/minimum inhibitory concentration).

RESULTS

As the PK/PD index of linezolid increased from 80 to 120, the corresponding probability of target attainment (PTA) decreased from 99.91% to 18.97%, with a MIC of 2mg/l. Furthermore, the cumulative fraction of response (CFR) reached <90% for several pathogens at an AUC24/MIC of 100-120, revealing a relatively lower efficacy with recommended linezolid dosing.

CONCLUSIONS

These findings reveal that the target AUC24/MIC value of 80-120 requires further classification for more accurate assessment of the linezolid dose regimen. At a MIC of ≥2mg/l, the clinical outcome varies greatly for different AUC24/MIC values when applying the same dose of linezolid. In such cases, we suggest optimized adjustment of the linezolid dosage regimen.

Risk factors for colonization with ampicillin and high-level aminoglycoside-resistant enterococci during hospitalization in the ICU and the impact of prior antimicrobial exposure definition: a prospective cohort study

The aim of our prospective cohort study was to determine the incidence, genetic relatedness and risk factors for colonization with ampicillin and high-level aminoglycoside-resistant enterococci (ARHLARE) among patients hospitalized in the intensive care unit. During 15-month period, we included 105 patients. The only independent risk factor for ARHLARE colonization was days of cefotaxime/ceftriaxone therapy [odds ratio (OR): 1.13; 95% confidence interval (CI) 1.10-1.27; P  =  0.045]. Patients with higher total use of antibiotics, patients on prolonged mechanical ventilation, and patients with urinary tract infection (UTI), were also found to be at increased risk to become colonized with ARHLARE. Pulsed-field gel electrophoresis suggested multifocal origin of the majority of the colonizing strains. Our results show that an increase in total antibiotic consumption for 10 defined daily doses (DDD)/patient increased the odds of colonization with ARHLARE for 36%. Further efforts to optimize antimicrobial use in high risk patients are proposed.

Evaluating amikacin dosage regimens in intensive care unit patients: a pharmacokinetic/pharmacodynamic analysis using Monte Carlo simulation

The objectives of this study were to conduct a comparative pharmacokinetic/pharmacodynamic (PK/PD) evaluation using Monte Carlo simulation of conventional versus high-dose extended-interval dosage (HDED) regimens of amikacin (AMK) in intensive care unit (ICU) patients for an Acinetobacter baumannii infection model. The simulation was performed in five populations (a control population and four subpopulations of ICU patients). Using a specific AMK PK/PD model and Monte Carlo simulation, the following were generated: simulated AMK steady-state plasma level curves; PK/PD efficacy indexes [time during which the serum drug concentration remains above the minimum inhibitory concentration (MIC) for a dosing period (%T>MIC) and ratio of peak serum concentration to MIC (Cmax/MIC)]; evolution of bacterial growth curves; and adaptive resistance to treatment. A higher probability of bacterial resistance was observed with the HDED regimen compared with the conventional dosage regimen. A statistically significant increase in Cmax/MIC and a statistically significant reduction in %T>MIC with the HDED regimen were obtained. A multiple linear relationship between CFU values at 24h with Cmax/MIC and %T>MIC was obtained. In conclusion, with the infection model tested, the likelihood of resistance to treatment may be higher against pathogens with a high MIC with the HDED regimen, considering that in many ICU patients the %T>MIC may be limited. If a sufficient value of %T>MIC (≥60%) is not reached, even though the Cmax/MIC is high, the therapeutic efficacy of the treatment may not be guaranteed. This study indicates that different AMK dosing strategies could directly influence the efficacy results in ICU patients.

Pharmacokinetics of imipenem after intravenous, intramuscular and subcutaneous administration to cats

The study describes the pharmacokinetics and predicted efficacy of imipenem after intravenous (IV), intramuscular (IM) and subcutaneous (SC) administration to five adult cats at a dose of 5 mg/kg. Susceptibility to imipenem [minimum inhibitory concentration (MIC)] was determined for antimicrobial resistant Escherichia coli (n = 13) and staphylococci (n = 3) isolated from domestic cat infections (urinary system, skin and conjunctiva). Maximum plasma concentrations of imipenem were 13.45 µg/ml (IV), 6.47 µg/ml (IM) and 3.83 µg/ml (SC). Bioavailability was 93.18% (IM) and 107.90% (SC). Elimination half-lives for IV, IM and SC administration were 1.17, 1.44 and 1.55 h, respectively. All tested bacteria were susceptible to imipenem; MIC values were 0.03 µg/ml for Staphylococcus species and <0.25-0.5 µg/ml for E coli. Mean imipenem concentrations remained above a MIC of 0.5 µg/ml for approximately 4 h (IV and IM) and 9 h (SC). Imipenem would be predicted to be effective for the treatment of antimicrobial resistant bacterial infections in cats at a dosage of 5 mg/kg every 6-8 h (IV, IM), or longer for the SC route. However, clinical trials are mandatory to establish its efficacy and proper dosing.

A survey on infection management practices in Italian ICUs

Introduction

An online survey was conducted to characterize current infection management practices in Italian intensive care units (ICUs), including the antibacterial and antifungal drug regimens prescribed for various types of infections.

Methods

During February and March 2011, all 450 ICUs in public hospitals in Italy were invited to take part in an online survey. The questionnaire focused on ICU characteristics, methods used to prevent, diagnose, and treat infections, and antimicrobials prescribing policies. The frequency of each reported practice was calculated as a percentage of the total number of units answering the question. The overall response rate to the questionnaire was 38.8% (175 of the 450 ICUs contacted) with homogeneous distribution across the country and in terms of unit type.

Results

Eighty-eight percent of the responding facilities performed periodical surveillance cultures on all patients. In 71% of patients, cultures were also collected on admission. Endotracheal/bronchial aspirates were the most frequently cultured specimens at both time points. Two-thirds of the responding units had never performed screening cultures for methicillin-resistant Staphylococcus aureus. Around 67% of the ICUs reported the use of antimicrobial de-escalation strategies during the treatment phase. In general, the use of empirical antimicrobial drug regimens was appropriate. Although the rationale for the choice was not always clearly documented, the use of a combination therapy was preferred over antibiotic monotherapy. The preferred first-line agents for invasive candidiasis were fluconazole and an echinocandin (64% and 25%, respectively). Two-thirds of the ICUs monitored vancomycin serum levels and administered it by continuous infusion in 86% of cases. For certain antibiotics, reported doses were too low to ensure effective treatment of severe infections in critically ill patients; conversely, inappropriately high doses were administered for certain antifungal drugs.

Conclusions

Although infection control policies and management practices are generally appropriate in Italian ICUs, certain aspects, such as the extensive use of multidrug empirical regimens and the inappropriate antimicrobial dosing, deserve careful management and closer investigation.

Colorectal surgery surgical site infection reduction program: a national surgical quality improvement program--driven multidisciplinary single-institution experience

BACKGROUND

Surgical site infections (SSI) are a major cause of morbidity in surgical patients and they increase health care costs considerably. Colorectal surgery is consistently associated with high SSI rates. No single intervention has demonstrated efficacy in reducing colorectal SSIs. The American College of Surgeons National Surgical Quality Improvement Program (ACS NSQIP) is a nationally validated system that uses clinically abstracted data on surgical patients and their outcomes to assist participating institutions drive quality improvement.

STUDY DESIGN

A multidisciplinary team was assembled to develop a colorectal SSI-reduction bundle at an academic tertiary care medical center. The ACS NSQIP data were used to identify patterns of SSIs during a 2-year period. Multiple interventions across the entire surgical episode of care were developed and implemented in January 2011. Monthly ACS NSQIP data were used to track progress.

RESULTS

Our ACS NSQIP overall colorectal SSI rate for 2009 and 2010 was 9.8%. One year after implementation of the SSI reduction bundle, we demonstrated a significant decline (p < 0.05) in both overall and superficial SSIs, to 4.0% and 1.5%, respectively. Organ space infections declined to 2.6%, which was not a significant change (p = 0.10). During the entire analysis period (2009 to 2011), there was no change in our colorectal-specific Surgical Care Improvement Program performance.

CONCLUSIONS

Using our ACS NSQIP colorectal SSI outcomes, a multidisciplinary team designed a colorectal SSI reduction bundle that resulted in a substantial and sustained reduction in SSIs. Our study is not able to identify which specific elements contributed to the reduction.

Empiric antibiotic selection strategies for healthcare-associated pneumonia, intra-abdominal infections, and catheter-associated bacteremia

Initial selection and early deployment of appropriate/adequate empiric antimicrobial therapy is critical to minimize the significant morbidity and mortality associated with hospital- or healthcare-associated infections (HAIs). Initial empiric therapy that inadequately covers the pathogen(s) causing a serious HAI has been associated with increased mortality, longer hospital stay, and elevated healthcare costs. Moreover, subsequent modification of initial inadequate therapy, later in the disease process when culture results become available, may not remedy the impact of the initial choice. Because of this, it is important that initial empiric therapy covers the most likely pathogens associated with infection in a particular patient, even if this initial regimen turns out to be unnecessarily broad, based on subsequent culture results. The current paradigm for management of serious HAIs is to initiate empiric therapy with a broad-spectrum regimen covering likely pathogens, based on local surveillance and susceptibility data, and presence of risk factors for involvement of a resistant microorganism. Subsequent modification (de-escalation) of the initial regimen becomes possible later, when culture results are available and clinical status can be better assessed, 2 to 4 days after initiation of empiric therapy. When possible, de-escalation and other steps to modify antimicrobial exposure are important for minimizing risk of antimicrobial resistance development. This article examines the general process for selection of initial empiric antibiotic therapy for patients with HAIs, illustrated through 3 case studies dealing with healthcare-associated pneumonia, complicated intra-abdominal infection, and catheter-associated bacteremia, respectively.

Year in review 2010: Critical Care--Infection

Infections remain among the most important concerns in critically ill patients. Early and reliable diagnosis of infection still poses difficulties in this setting but also represents a crucial step toward appropriate antimicrobial therapy. Increasing antimicrobial resistance challenges established approaches to the optimal management of infections in the intensive care unit. Rapid infection diagnosis, antibiotic dosing and optimization through pharmacologic indices, progress in the implementation of effective antimicrobial stewardship and infection control programs, and management of fungal infections are some of the most relevant issues in this special patient population. During the last 18 months, Critical Care and other journals have provided a wide array of descriptive and interventional clinical studies and scientific reports helping clinical investigators and critical care physicians to improve diagnosis, management, and therapy of infections in critically ill patients.

Use of pharmacodynamic principles to inform β-lactam dosing: "S" does not always mean success

Dose optimization is one of the key strategies for enhancing antimicrobial stewardship. There have been tremendous strides in our understanding of antibiotic exposure-response relationships over the past 25 years. For many antibiotics, the "pharmacodynamic" or the exposure variable associated with outcome has been identified. With advances in mathematical modeling, it is possible to apply our understanding of antimicrobial pharmacodynamics (PD) into clinical practice and design empirical regimens that have a high probability of achieving the PD target linked to effect. By optimizing antibiotic doses to achieve PD targets predictive of efficacy, clinicians can improve care and minimize drug toxicity. For β-lactams, the PD parameter most predictive of maximal bactericidal activity is the duration of time free drug concentrations remain above the minimum inhibitory concentration (MIC) during the dosing interval (fT > MIC). Unfortunately, the conventional intermittent β-lactam dosing schemes often used in practice have suboptimal PD profiles. Prolonging the infusion time of β-lactams is one method to maximize the probability of achieving concentrations in excess of the MIC for the majority of the dosing interval, especially against pathogens with elevated MIC values. Prolonged infusions of intravenous β-lactams are not only associated with improved probability of target attainment (PTA) profiles but offer possible cost savings and greater potential for reducing emergence of resistance relative to intermittent infusions.

Cefazolin bolus and continuous administration for elective cardiac surgery: improved pharmacokinetic and pharmacodynamic parameters

OBJECTIVE

Cefazolin (1-2 g bolus at induction possibly repeated after cardiopulmonary bypass) remains the standard for antibiotic prophylaxis in cardiac surgery. Data indicate, however, that it is underdosed with this dosing schedule. A prospective, randomized study comparing intermittent versus loading dose plus continuous infusion for the same total dose of cefazolin was performed to assess which modality is pharmacokinetically and pharmacodynamically advantageous.

METHODS

Patients received 2 g cefazolin as a starting dose and then were divided into an intermittent group (receiving another 1 g at 3, 9, and 15 hours after the first dose) and a continuous group (continuous infusion started after the first dose, providing 1 g every 6 hours for 18 hours). Cefazolin levels were measured in blood and atria.

RESULTS

Mean total and calculated free trough concentrations in blood varied greatly among patients in the intermittent group and were lower than those in the continuous group (P < .05 at 15, 18 and 24 hours). For 9 of 10 (90%) patients in the continuous infusion group, the targeted pharmacokinetic and pharmacodynamic goal (time above minimal inhibitory concentration >90%) was achieved, whereas the goal was met for only 3 of 10 (30%) in the intermittent group (P < .05). The mean atrial tissue concentration was also higher with continuous infusion (P < .05).

CONCLUSIONS

Administration of cefazolin as bolus plus continuous infusion has pharmacokinetic and pharmacodynamic advantages relative to intermittent administration. It provides more stable serum levels, lower interpatient variability, and higher myocardial tissue penetration.

Review on pharmacokinetics and pharmacodynamics and the aging kidney

In people who are aged >65 years, pharmacokinetics are influenced more by the loss of kidney function than by the aging process of any other organ. A GFR of 30 to 60 ml/min, suggestive of stage 3 kidney disease, is observed in 15 to 30% of elderly people. Drug dosing must be adjusted to both changing pharmacokinetics and pharmacodynamics; the pharmacodynamics might be influenced by the aging of other organs, too. Using our NEPharm database, we extracted abstracts with pharmacokinetic parameters since 1999 from a weekly PubMed search. The recorded data were analyzed and compared with published recommendations on drug dosage and use in the elderly. Purely age-related changes in pharmacokinetic parameters were recorded from publications on 127 drugs. The analysis of our NEPharm records revealed an average (mean +/- SD) age-related prolongation of half-life of 1.39-fold (corresponding to +39 +/- 61%). Contrasting to common opinion, mean changes in clearance (-1 +/- 54%) and volume of distribution (+24 +/- 56%) were even less. The modest changes in pharmacokinetics do not suggest general dosage modifications in the elderly for most drugs. Changes in pharmacodynamics justify the common medication rule in the elderly-"start low + go slow"-especially for drugs that act on the central nervous system; however, in the case of anti-infective and anticancer therapy, the rule should be "hit hard = start high + go fast" to produce the target effect also in the elderly.