Appropriate antibiotic dosage levels in the treatment of severe sepsis and septic shock

Analysis of Vancomycin Dosage and Plasma Levels in Critically Ill Adult Patients Requiring Extracorporeal Membrane Oxygenation (ECMO)

Introduction: Critically ill patients undergoing extracorporeal membrane oxygenation (ECMO) exhibit unique pharmacokinetics. This study aimed to assess the achievement of vancomycin therapeutic targets in these patients. Methods: This retrospective cohort study included patients on ECMO treated with vancomycin between January 2010 and December 2018. Ninety patients were analyzed based on ECMO connection modality, baseline creatinine levels, estimated glomerular filtration rate (eGFR), renal replacement therapy (RRT) requirements, and vancomycin loading dose administration. Results: Twenty-three percent of the patients achieved the therapeutic range defined by baseline levels. No significant differences in meeting the therapeutic goal were found in multivariate analysis considering ECMO cannulation modality, initial creatinine level, initial eGFR, RRT requirement, or loading dose use. All trough levels between 15 and 20 mcg/mL achieved an estimated area under the curve/minimum inhibitory concentration (AUC/MIC) between 400 and 600, almost all trough levels over 10 mcg/mL predicted an AUC/MIC >400. Discussion: Achieving therapeutic plasma levels in these patients remains challenging, potentially due to factors such as individual pharmacokinetics and pathophysiology. A trough plasma level between 12 and 20 estimated the therapeutic AUC/MIC for all models, proposing a possible lower target, maintaining exposure, and potentially avoiding adverse effects. Despite being one of the largest cohorts of vancomycin use in ECMO patients studied, its retrospective nature and single-center focus limits its broad applicability.

Pharmacokinetic of Cefiderocol in Critically Ill Patients Receiving Renal Replacement Therapy: A Case Series

Background: Cefiderocol is a novel parenteral siderophore cephalosporin, demonstrating enhanced activity against multidrug-resistant (MDR) Gram-negative bacteria and difficult-to-treat Acinetobacter baumannii (DTR-AB). Plasma-free trough concentration (fCtrough) over the minimum inhibitory concentration (MIC) was reported as the best pharmacokinetic parameter to describe the microbiological efficacy of cefiderocol. Materials and methods: We retrospectively described the pharmacokinetic and pharmacodynamic profile of three critically ill patients admitted to the intensive care unit, receiving cefiderocol under compassionate use to treat severe DTR-AB infections while undergoing continuous venovenous haemofiltration. Cefiderocol was administrated at a dosage of 2 g every 8 h infused over 3 h. Therapeutic drug monitoring (TDM) was assessed at the steady state. Cthrough was evaluated by assuming a plasma protein binding of 58.0%. The fCmin/MIC was calculated assuming a cefiderocol MIC equal to the PK-PD breakpoint of susceptibility ≤ 2. The association between the PK/PD parameters and microbiological outcome was assessed. Results: fCtrough/MIC were >12 in 2 patients and 2.9 in the 1 who rapidly recovered from renal failure. Microbiological cure occurred in 3/3 of patients. None of the 3 patients died within 30 days. Conclusions: A cefiderocol dosage of 2 g q8 h in critically ill patients with AKI undergoing CVVH may bring about a very high plasma concentration, corresponding to essentially 100% free time over the MIC for DTR-AB.

Ceftazidime dosing in obese patients: is it time for more?

INTRODUCTION

Ceftazidime is used for the treatment of many bacterial infections, including severe P. aeruginosa infections. Like other beta-lactams, inter-individual variability in ceftazidime pharmacokinetics has been described. Due to its related pathophysiological modifications, obesity might influence ceftazidime pharmacokinetics.

AREAS COVERED

The objective of this review is to assess the current state of knowledge about the impact of obesity on ceftazidime treatment. A literature search was conducted on PubMed-MEDLINE (2016-2021) to retrieve pharmacokinetic studies published in English, matching the terms 'ceftazidime' AND 'pharmacokinetics.'

EXPERT OPINION

The impact of obesity on pharmacokinetics is generally poorly known, mainly because obese patients are often excluded from clinical studies. However, the published literature clearly shows that obese patients have significantly lower ceftazidime concentrations. This could be explained by increased volume of distribution and clearance. This low exposure represents a major factor of therapeutic failure, potentially fatal for critically ill patients. While further studies would be useful to better assess the magnitude and understanding of this variability, the use of higher doses of ceftazidime is needed in obese patients. Moreover, therapeutic drug monitoring for dose adaptation is of major interest for these patients, as the efficacy of ceftazidime seems to be directly related to its plasma concentration.

Dose Tailoring of Vancomycin Through Population Pharmacokinetic Modeling Among Surgical Patients in Pakistan

Background: Vancomycin is a narrow therapeutic agent, and it is necessary to optimize the dose to achieve safe therapeutic outcomes. The purpose of this study was to identify the significant covariates for vancomycin clearance and to optimize the dose among surgical patients in Pakistan. Methods: Plasma concentration data of 176 samples collected from 58 surgical patients treated with vancomycin were used in this study. A population pharmacokinetic model was developed on NONMEM^® using plasma concentration-time data. The effect of all available covariates was evaluated on the pharmacokinetic parameters of vancomycin by stepwise covariate modeling. The final model was evaluated using bootstrap, goodness-of-fit plots, and visual predictive checks. Results: The pharmacokinetics of vancomycin followed a one-compartment model with first-order elimination. The vancomycin clearance (CL) and volume of distribution (Vd) were 2.45 L/h and 22.6 l, respectively. Vancomycin CL was influenced by creatinine clearance (CRCL) and body weight of the patients; however, no covariate was significant for its effect on the volume of distribution. Dose tailoring was performed by simulating dosage regimens at a steady state based on the CRCL of the patients. The tailored doses were 400, 600, 800, and 1,000 mg for patients with a CRCL of 20, 60, 100, and 140 ml/min, respectively. Conclusion: Vancomycin CL is influenced by CRCL and body weight of the patient. This model can be helpful for the dose tailoring of vancomycin based on renal status in Pakistani patients.

NONMEM population pharmacokinetics and Monte Carlo dosing simulations of imipenem in critically ill patients with life-threatening severe infections during support with or without extracorporeal membrane oxygenation in an intensive care unit

STUDY OBJECTIVES

The objectives of this study were (i) to determine the population pharmacokinetic (PK) of imipenem in critically ill patients with life-threatening severe infections, (ii) to investigate the impact of extracorporeal membrane oxygenation (ECMO) on the population PK of imipenem during support with ECMO compared to those without ECMO support, and (iii) to assess the probability of target attainment (PTA) for finding the optimal dosage regimens of imipenem in critically ill patients with life-threatening severe infections.

DESIGN

Open-label, PK study.

SETTING

Academic tertiary care medical center.

PATIENTS

Fifty critically ill patients with or without ECMO by pooling data from previously published studiesand unpublished data from 14 patients.

INTERVENTION AND MEASUREMENTS

The population PK of imipenem was determined using NONMEM and a Monte Carlo simulation was performed to determine the PTAs of achieving 40% and 75% exposure times during which the plasma drug concentrations remained above the MIC.

MAIN RESULTS

The values of volume of distribution and total clearance were 30.5 L and 13.3 L/h, respectively. The ECMO circuit did not show a significant influence on the PK parameters of imipenem. For pathogens with a MIC of 4 mg/L, the PTA target of 75% fT>MIC in patients with normal renal function was achieved when the imipenem was administered by a 4-h infusion of 1 g q6h.

CONCLUSION

The ECMO circuit had little effect on enhancing the PK changes of imipenem that had already occurred in these patients. A high dosage of imipenem may be required for achieving the PK/pharmacodynamic targets against less susceptible pathogens, however, the dosage regimens in patients with renal impairment may not need to be as high as those required in patients with normal renal function. ClinicalTrials.gov: NCT03858387.

Pharmacokinetics and Monte Carlo Dosing Simulations of Imipenem in Critically Ill Patients with Life-Threatening Severe Infections During Support with Extracorporeal Membrane Oxygenation

Background

Extracorporeal membrane oxygenation (ECMO), a cardiopulmonary bypass device, has been found to increase the profound pathophysiological changes associated with life-threatening severe infections in patients with multiple comorbidities, which results in alterations of pharmacokinetic patterns for antibiotics.

Objectives

The aims of this study were (1) to determine the pharmacokinetics of imipenem and (2) to assess the probability of target attainment (PTA) for imipenem in critically ill patients with life-threatening severe infections during support with ECMO.

Methods

The pharmacokinetic studies were carried out following administration of 0.5 g of imipenem every 6 h on the 4th dose of drug administration in 10 patients and a Monte Carlo simulation was performed to determine the PTA of achieving 40% exposure time during which the plasma drug concentrations remained above minimum inhibitory concentration (T > _MIC) and 80% T > _MIC.

Results

The median values of volume of distribution and total clearance (CL) of imipenem in these patients were 13.98 L and 9.78 L/h, respectively. A high PTA (≥ 90%) for a target of 80% with a MIC of 4 μg/mL in patients with CL_CR 60–120 mL/min and flow rate of ECMO circuit 3–5.5 L/min was observed when imipenem was administered by a 4-h infusion of 1 g every 6 h.

Conclusions

A high dosage regimen such as 1 g every 6 h of imipenem may be required to achieve pharmacodynamic targets against less susceptible pathogens in this patient population.

ClinicalTrial.gov Identifier

NCT03776305, date of registration: 11 December 2018.

Electronic supplementary material

The online version of this article (10.1007/s13318-020-00643-3) contains supplementary material, which is available to authorized users.

Ultrasound-mediated therapies for the treatment of biofilms in chronic wounds: a review of present knowledge

Bacterial biofilms are an ever-growing concern for public health, featuring both inherited genetic resistance and a conferred innate tolerance to traditional antibiotic therapies. Consequently, there is a growing interest in novel methods of drug delivery, in order to increase the efficacy of antimicrobial agents. One such method is the use of acoustically activated microbubbles, which undergo volumetric oscillations and collapse upon exposure to an ultrasound field. This facilitates physical perturbation of the biofilm and provides the means to control drug delivery both temporally and spatially. In line with current literature in this area, this review offers a rounded argument for why ultrasound-responsive agents could be an integral part of advancing wound care. To achieve this, we will outline the development and clinical significance of biofilms in the context of chronic infections. We will then discuss current practices used in combating biofilms in chronic wounds and then critically evaluate the use of acoustically activated gas microbubbles as an emerging treatment modality. Moreover, we will introduce the novel concept of microbubbles carrying biologically active gases that may facilitate biofilm dispersal.

Acute-on-chronic liver failure alters meropenem pharmacokinetics in critically ill patients with continuous hemodialysis: an observational study

BACKGROUND

Infection and sepsis are a main cause of acute-on-chronic liver failure (ACLF). Adequate dosing of antimicrobial therapy is of central importance to improve outcome. Liver failure may alter antibiotic drug concentrations via changes of drug distribution and elimination. We studied the pharmacokinetics of meropenem in critically ill patients with ACLF during continuous veno-venous hemodialysis (CVVHD) and compared it to critically ill patients without concomitant liver failure (NLF).

METHODS

In this prospective cohort study, patients received meropenem 1 g tid short-term infusion (SI). Meropenem serum samples were analyzed by high-performance liquid chromatography. A population pharmacokinetic analysis was performed followed by Monte Carlo simulations of (A) meropenem 1 g tid SI, (B) 2 g loading plus 1 g prolonged infusion tid (C) 2 g tid SI, and (D) 2 g loading and continuous infusion of 3 g/day on days 1 and 7. Probability of target attainment (PTA) was assessed for 4× the epidemiological cut-off values for Enterobacterales (4 × 0.25 mg/L) and Pseudomonas spp. (4 × 2 mg/L).

RESULTS

Nineteen patients were included in this study. Of these, 8 patients suffered from ACLF. A two-compartment model with linear clearance from the central compartment described meropenem pharmacokinetics. The peripheral volume of distribution (V₂) was significantly higher in ACLF compared to NLF (38.6L versus 19.7L, p = .05). PTA for Enterobacterales was achieved in 100% for all dosing regimens. PTA for Pseudomonas spp. in ACLF on day 1/7 was: A: 18%/80%, B: 94%/88%, C: 85%/98% D: 100%/100% and NLF: A: 48%/65%, B: 91%/83%, C: 91%/93%, D: 100%/100%.

CONCLUSION

ALCF patients receiving CVVHD had a higher V₂ and may require a higher loading dose of meropenem. For Pseudomonas, high doses or continuous infusion are required to reach PTA in ACLF patients.

Pharmacokinetics of Imipenem in Critically Ill Patients with Life-threatening Severe Infections During Support with Extracorporeal Membrane Oxygenation

BACKGROUND

Extracorporeal membrane oxygenation (ECMO) has become increasingly used for lifesaving respiratory and/or cardiac failure support in critically ill patients, including those with life-threatening severe infections. This cardiopulmonary bypass device has been shown to enhance the profound pathophysiological changes in this patient population, resulting in an alteration of the pharmacokinetics of antimicrobial agents.

OBJECTIVE

The aim of this study was to determine the effect of ECMO on the pharmacokinetics of imipenem in critically ill patients supported by this cardiopulmonary bypass device.

METHODS

The study was conducted in critically ill patients with respiratory and/or cardiac failure and severe infections who were supported by ECMO. All patients received a 1-h infusion of 0.5 g of imipenem every 6 h and imipenem pharmacokinetics studies were carried out on the fourth dose of drug administration.

RESULTS

Ten patients were enrolled in this study. The pharmacokinetics parameters of imipenem were found to be highly variable. The volume of distribution, total clearance, elimination half-life and the area under the concentration-time curve between 0 and 6 h were 33.38 ± 13.89 L, 9.99 ± 10.47 L/h, 12.01 ± 29.63 h and 88.93 ± 54.07 mg∙h/L, respectively.

CONCLUSIONS

Pathophysiological changes in critically ill patients with severe infections during support with ECMO had a greater impact on altered pharmacokinetic patterns of imipenem than those that occur in critically ill patients without ECMO support. Therefore, the largest licensed dose, 1 g every 6 h, of imipenem, may be required to maintain adequate drug concentrations to achieve the pharmacokinetic/pharmacodynamic targets for effective antimicrobial therapy in this patient population.

A non-linear mixed effect model for innate immune response: In vivo kinetics of endotoxin and its induction of the cytokines tumor necrosis factor alpha and interleukin-6

Endotoxin, a component of the outer membrane of Gram-negative bacteria, has been extensively studied as a stimulator of the innate immune response. However, the temporal aspects and exposure-response relationship of endotoxin and resulting cytokine induction and tolerance development is less well defined. The aim of this work was to establish an in silico model that simultaneously captures and connects the in vivo time-courses of endotoxin, tumor necrosis factor alpha (TNF-α), interleukin-6 (IL-6), and associated tolerance development. Data from six studies of porcine endotoxemia in anesthetized piglets (n = 116) were combined and used in the analysis, with purified endotoxin (Escherichia coli O111:B4) being infused intravenously for 1–30 h in rates of 0.063–16.0 μg/kg/h across studies. All data were modelled simultaneously by means of importance sampling in the non-linear mixed effects modelling software NONMEM. The infused endotoxin followed one-compartment disposition and non-linear elimination, and stimulated the production of TNF-α to describe the rapid increase in plasma concentration. Tolerance development, observed as declining TNF-α concentration with continued infusion of endotoxin, was also driven by endotoxin as a concentration-dependent increase in the potency parameter related to TNF-α production (EC₅₀). Production of IL-6 was stimulated by both endotoxin and TNF-α, and four consecutive transit compartments described delayed increase in plasma IL-6. A model which simultaneously account for the time-courses of endotoxin and two immune response markers, the cytokines TNF-α and IL-6, as well as the development of endotoxin tolerance, was successfully established. This model-based approach is unique in its description of the time-courses and their interrelation and may be applied within research on immune response to bacterial endotoxin, or in pre-clinical pharmaceutical research when dealing with study design or translational aspects.

Fiber-Enhanced Raman Sensing of Cefuroxime in Human Urine

Fiber-enhanced Raman spectroscopy was developed for the chemically selective and sensitive quantification of the important antibiotic cefuroxime in human urine. A novel optical sensor fiber was drawn and precisely prepared. In this fiber structure, light is strongly confined in the selectively filled liquid core, and the Raman scattered signal is collected with unprecedented efficiency over an extended interaction length. The filling, emptying, and robustness are highly improved due to the large core size (>30 μm). Broadband step-index guidance allows the free choice of the most suitable excitation wavelength in complex body fluids. The limit of detection of cefuroxime in human urine was improved by 2 orders of magnitude (to μM level). The quantification of cefuroxime was achieved in urine after oral administration. This method has great potential for the point-of-care monitoring of antibiotics concentrations and is an important step forward to enable clinicians to rapidly adjust doses.

The Lysis of Pathogenic Escherichia coli by Bacteriophages Releases Less Endotoxin Than by β-Lactams

BACKGROUND.

Other than numerous experimental data assessing phage therapy efficacy, questions regarding safety of this approach are not sufficiently addressed. In particular, as phages can kill bacterial cells within <10 minutes, the associated endotoxin release (ER) in severe infections caused by gram-negative bacteria could be a matter of concern.

METHODS.

Two therapeutic virulent phages and 4 reference antibiotics were studied in vitro for their ability to kill 2 pathogenic strains of Escherichia coli and generate an ER. The early interaction (first 3 hours) between these actors was assessed over time by studying the instantaneous cell viability, the colony-forming unit count, the concentration of free endotoxin released, and the cell morphology under light microscope.

RESULTS.

While β-lactams have a relatively slow effect, both tested phages, as well as amikacin, were able to rapidly abolish the bacterial growth. Even when considering the fastest phage (cell lysis in 9 minutes), the concentrations of phage-induced ER never reached the highest values, which were recorded with antibiotic treatments. Cumulative concentrations of endotoxin over time in phage-treated conditions were lower than those observed with β-lactams and close to those observed with amikacin. Whereas β-lactams were responsible for strong cell morphology changes (spheroplast with imipenem, filamentous cells with cefoxitin and ceftriaxone), amikacin and phages did not modify cell shape but produced intracellular inclusion bodies.

CONCLUSIONS.

This work provides important and comforting data regarding the safety of phage therapy. Therapeutically relevant phages, with their low endotoxin release profile and fast bactericidal effect, are not inferior to β-lactams.

Population pharmacokinetics of meropenem in elderly patients: dosing simulations based on renal function

OBJECTIVES

The aim of this study was to evaluate different dosage regimens of meropenem in elderly patients in relation with renal function using a population pharmacokinetic (popPK) model.

METHODS

The data of 178 elderly patients treated with meropenem was collected from different sources. A popPK model was developed by using NONMEM® and the influence of different covariates on meropenem CL and V₁ was observed. Monte Carlo dosing simulations were performed at steady state to observe the % T > MIC for targets of 40, 60 and 80% of dosage intervals at different levels of creatinine clearance (CL_CR).

RESULTS

The data was described by a two-compartment model and the values of parameter estimates for CL, V₁, Q and V₂ were 5.27 L/h, 17.2 L, 9.92 L/h and 10.6 L, respectively. The CL_CR, body weight and centre had a significant influence on meropenem CL while no direct influence of age was observed. Extended infusions had pharmacokinetic and pharmacodynamic (PK/PD) breakpoint one dilution greater than corresponding short infusion regimens for each target of % T > MIC.

CONCLUSION

Meropenem CL was significantly lower in the elderly compared to CL reported in younger patients due to the reduced renal function. An extended infusion of 1000 mg q8h can be considered for empirical treatment of infections in elderly patients when CL_CR is ≤ 50 mL/min. A continuous infusion of 3000 mg daily dose is preferred if CL_CR > 50 mL/min. However, a higher daily dose of meropenem would be required for resistant strains (MIC >8 mg/L) of bacteria if CL_CR is >100 mL/min.

Population Pharmacokinetics and Pharmacodynamics Modeling To Optimize Dosage Regimens of Sulbactam in Critically Ill Patients with Severe Sepsis Caused by Acinetobacter baumannii

Sulbactam is being considered as an alternative concomitant medication with other effective antibiotics for the treatment of multidrug-resistant (MDR) Acinetobacter baumannii infections. Pathophysiological changes in critically ill patients with severe sepsis, resulting in altered pharmacokinetic (PK) patterns for antibiotics, are important factors in determining therapeutic success. The aims of this study were (i) to examine the population PK parameters and (ii) to assess the probability of target attainment (PTA) for sulbactam in patients with severe sepsis caused by A. baumannii PK studies were carried out following administration of 2 g of sulbactam every 12 h on the 4th day of drug administration in 27 patients, and a Monte Carlo simulation was performed to determine the PTA of achieving 40% exposure time during which the plasma drug concentration remained above the MIC (T_>MIC) and 60% T_>MIC The central and peripheral volumes of distribution were 14.56 and 9.55 liters, respectively, and total clearances of sulbactam were 2.26 liters/h and 7.64 liters/h in patients aged >65 years and ≤65 years, respectively. The high PTAs (≥90%) for targets of 40% T_>MIC and 60% T_>MIC with a MIC of 4 μg/ml were observed when sulbactam was administered by a 4-h infusion of 1 g every 12 h and 1 g every 8 h, respectively. Sulbactam would be an alternative antibiotic option to coadminister with colistin for the treatment of infections caused by MDR A. baumannii However, for pathogens with MICs of >4 μg/ml, higher dosage regimens of sulbactam are required.

Pharmacist independent prescribing in critical care: results of a national questionnaire to establish the 2014 UK position

OBJECTIVES

Clinical pharmacist practice is well established in the safe and effective use of medicines in the critically ill patient. In the UK, independent pharmacist prescribers are generally recognised as a valuable and desirable resource. However, currently, there are only anecdotal reports of pharmacist-independent prescribing in critical care. The aim of this questionnaire was to determine the current and proposed future independent prescribing practice of UK clinical pharmacists working in adult critical care.

METHODS

The questionnaire was distributed electronically to UK Clinical Pharmacy Association members (closed August 2014).

KEY FINDINGS

There were 134 responses to the questionnaire (response rate at least 33%). Over a third of critical care pharmacists were practising independent prescribers in the specialty, and 70% intended to be prescribers within the next 3 years. Pharmacists with ≥5 years critical care experience (P < 0.001) or worked in a team (P = 0.005) were more likely to be practising independent prescribers. Pharmacists reported significant positives to the use of independent prescribing in critical care both in patient care and job satisfaction. Independently, prescribing was routine in: dose adjustment for multi-organ failure, change in route or formulation, correction prescribing errors, therapeutic drug monitoring and chronic medication. The majority of pharmacist prescribers reported they spent ≤5% of their clinical time prescribing and accounted for ≤5% of new prescriptions in critical care patients.

CONCLUSIONS

Most critical care pharmacists intend to be practising as independent prescribers within the next 3 years. The extent and scope of critical care pharmacist prescribing appear to be of relatively low volume and within niche prescribing areas.

Population pharmacokinetics and Monte Carlo dosing simulations of meropenem during the early phase of severe sepsis and septic shock in critically ill patients in intensive care units

Pathophysiological changes during the early phase of severe sepsis and septic shock in critically ill patients, resulting in altered pharmacokinetic (PK) patterns for antibiotics, are important factors influencing therapeutic success. The aims of this study were (i) to reveal the population PK parameters and (ii) to assess the probability of target attainment (PTA) for meropenem. The PK studies were carried out following administration of 1 g of meropenem every 8 h during the first 24 h of severe sepsis and septic shock in nine patients, and a Monte Carlo simulation was performed to determine the PTA of achieving 40% exposure time during which the free plasma drug concentration remains above the MIC (fT>MIC) and 80% fT>MIC. The volume of distribution (V) and total clearance (CL) of meropenem in these patients were 23.7 liters and 7.82 liters/h, respectively. For pathogens with MICs of 4 μg/ml, the PTAs of 40% fT>MIC following administration of meropenem as a 1-h infusion of 1 g every 8 h and a 4-h infusion of 0.5 g every 8 h were 92.52% and 90.29%, respectively. For pathogens with MICs of 2 μg/ml in immunocompromised hosts, the PTAs of 80% fT>MIC following administration of 1-h and 4-h infusions of 2 g of meropenem every 8 h were 84.32% and 94.72%, respectively. These findings indicated that the V of meropenem was greater and the CL of meropenem was lower than the values obtained in a previous study with healthy subjects. The maximum recommended dose, i.e., 2 g of meropenem every 8 h, may be required for treatment of life-threatening infections in this patient population.

β-Lactam pharmacokinetics during extracorporeal membrane oxygenation therapy: A case-control study

Most adult patients receiving extracorporeal membrane oxygenation (ECMO) require antibiotic therapy, however the pharmacokinetics of β-lactams have not been well studied in these conditions. In this study, data from all patients receiving ECMO support and meropenem (MEM) or piperacillin/tazobactam (TZP) were reviewed. Drug concentrations were measured 2h after the start of a 30-min infusion and just before the subsequent dose. Therapeutic drug monitoring (TDM) results in ECMO patients were matched with those in non-ECMO patients for (i) drug regimen, (ii) renal function, (iii) total body weight, (iv) severity of organ dysfunction and (v) age. Drug concentrations were considered adequate if they remained 4-8× the clinical MIC breakpoint for Pseudomonas aeruginosa for 50% (TZP) or 40% (MEM) of the dosing interval. A total of 41 TDM results (27 MEM; 14 TZP) were obtained in 26 ECMO patients, with 41 matched controls. There were no significant differences in serum concentrations or pharmacokinetic parameters between ECMO and non-ECMO patients, including Vd [0.38 (0.27-0.68) vs. 0.46 (0.33-0.79)L/kg; P=0.37], half-life [2.6 (1.8-4.4) vs. 2.9 (1.7-3.7)h; P=0.96] and clearance [132 (66-200) vs. 141 (93-197)mL/min; P=0.52]. The proportion of insufficient (13/41 vs. 12/41), adequate (15/41 vs. 19/41) and excessive (13/41 vs. 10/41) drug concentrations was similar in ECMO and non-ECMO patients. Achievement of target concentrations of these β-lactams was poor in ECMO and non-ECMO patients. The influence of ECMO on MEM and TZP pharmacokinetics does not appear to be significant.

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

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

Emergency department antimicrobial considerations in severe sepsis

Severe sepsis and septic shock are common problems in the emergency department patient population and require expert clinical skill by members of the emergency department team to maximize optimal patient outcomes. Although various guidelines have been developed for the management of these patients, issues around antimicrobial-related considerations in critically ill patients require further evidence-based attention. In this review article, important factors related to patient illness, microorganism, timing of antimicrobial administration, and source control are discussed.

Rapid quantification of six β-lactams to optimize dosage regimens in severely septic patients

A fast analytical procedure was developed for the simultaneous quantification of cefepime (CEF), meropenem (MEM), ceftazidime (CZA), cefuroxime (CFX), aztreonam (AZT), and piperacillin (PIP) in serum of intensive care patients. The β-lactam pharmacokinetic parameters can be altered in severe sepsis due to changes in the distribution, the metabolism and the elimination process. Therapeutic drug monitoring (TDM) of β-lactams is therefore recommended in critically ill patients. The plasma samples were spiked with cefoperazone as internal standard and proteins were precipitated with methanol. The different β-lactams were separated with high performance liquid chromatography within 18 min, and quantified by UV spectrophotometry with a diode array detector. The method was validated by means of the accuracy profile approach based on β expectation tolerance intervals. The acceptance limits were settled at ± 30% according to the regulatory requirements. Assay validation demonstrated good performance for all β-lactams analyzed in terms of trueness, repeatability, linearity and intermediate precision over the range of 2-200 μg/mL. The simple extraction procedure provides respective absolute and relative recoveries ranging from 70% to 86% and from 66% to 89% for all the β-lactams analyzed. Few interferences were observed and the method was easily applicable to TDM in intensive care patients. The quantification of β-lactams should allow for antibiotic regimen adjustment in critically ill patients.

Management of antimicrobial use in the intensive care unit

Critically ill patients admitted to the intensive care unit (ICU) are frequently treated with antimicrobials. The appropriate and judicious use of antimicrobial treatment in the ICU setting is a constant clinical challenge for healthcare staff due to the appearance and spread of new multiresistant pathogens and the need to update knowledge of factors involved in the selection of multiresistance and in the patient's clinical response. In order to optimize the efficacy of empirical antibacterial treatments and to reduce the selection of multiresistant pathogens, different strategies have been advocated, including de-escalation therapy and pre-emptive therapy as well as measurement of pharmacokinetic and pharmacodynamic (pK/pD) parameters for proper dosing adjustment. Although the theoretical arguments of all these strategies are very attractive, evidence of their effectiveness is scarce. The identification of the concentration-dependent and time-dependent activity pattern of antimicrobials allow the classification of drugs into three groups, each group with its own pK/pD characteristics, which are the basis for the identification of new forms of administration of antimicrobials to optimize their efficacy (single dose, loading dose, continuous infusion) and to decrease toxicity. The appearance of new multiresistant pathogens, such as imipenem-resistant Pseudomonas aeruginosa and/or Acinetobacter baumannii, carbapenem-resistant Gram-negative bacteria harbouring carbapenemases, and vancomycin-resistant Enterococcus spp., has determined the use of new antibacterials, the reintroduction of other drugs that have been removed in the past due to toxicity or the use of combinations with in vitro synergy. Finally, pharmacoeconomic aspects should be considered for the choice of appropriate antimicrobials in the care of critically ill patients.