Influence of renal function on trough serum concentrations of piperacillin in intensive care unit patients

Beta-Lactam Antibiotic Concentrations and the Acquisition of Multi-Drug Resistant Bacteria in Critically Ill Patients

Antimicrobial resistance (AMR) is a worldwide healthcare emergency. Whether insufficient beta-lactam antibiotic concentrations can be associated with AMR emergence remains controversial. This is a retrospective single-center cohort study including patients admitted to the intensive care unit of a tertiary university hospital from 2009 to 2014, who required a broad-spectrum beta-lactam antibiotic and had at least one therapeutic drug monitoring (TDM). Patients were categorized as having inadequate drug levels if the trough concentration (Cmin) fell below the clinical breakpoint for Pseudomonas aeruginosa. AMR was defined according to breakpoints recommended by the European Committee on Antimicrobial Susceptibility Testing (EUCAST) using the disk diffusion method. A total of 444 patients (male sex, n = 313, 71%; female sex, n = 131, 29%; mean age 58 ± 15 years) were enrolled in the study. Patients received piperacillin/tazobactam (n = 168), ceftazidime/cefepime (n = 58) or meropenem (n = 218); among them, 65 (15%) had insufficient drug levels. Nine of these 65 (13.8%) patients with insufficient antibiotic levels acquired at least one pathogen with AMR within 15 days of TDM, when compared to 84/379 (22%) in the other group (OR 0.56 [95%CI 0.27-1.19]; p = 0.13). In a multivariable competing-risk analysis including male gender, APACHE score on admission, previous colonization by other MDR bacteria, urinary catheter, central venous catheter, mechanical ventilation, previous hospitalization and previous surgery, insufficient antibiotic levels were not associated with AMR acquisition (sHR 0.84 [95% CI 0.42-1.68]). Similar results were found when a higher threshold was used to define insufficient drug levels (Cmin < 4 times the clinical breakpoint). In conclusion, insufficient beta-lactam levels were not independently associated with AMR acquisition. Future prospective studies are needed to evaluate better the relationship between low drug levels and antibiotic resistance acquisition.

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.

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.

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.

The estimation of glomerular filtration in acute and critical illness: Challenges and opportunities

Recent events have made it apparent that the creatinine based estimating equations for glomerular filtration have their flaws. Some flaws have been known for some time; others have prompted radical modification of the equations themselves. These issues persist in part owing to the behaviour of the creatinine molecule itself, particularly in acute and critical illness. There are significant implications for patient treatment decisions, including drug and fluid therapies and choice of imaging modality (contrast vs. non-contrast CT scan for example). An alternative biomarker, Cystatin C, has been used with some success both alone and in combination with creatinine to help improve the accuracy of particular estimating equations. Problems remain in certain circumstances and costs may limit the more widespread use of the alternative assay. This review will explore both the historical and more recent evidence for glomerular filtration estimation, including options to directly measure glomerular filtration (rather than estimate), perhaps the holy grail for both Biochemistry and Nephrology.

LC-MS/MS-Based Serum Metabolomics and Transcriptome Analyses for the Mechanism of Augmented Renal Clearance

Augmented Renal Clearance (ARC) refers to the increased renal clearance of circulating solute in critically ill patients. In this study, the analytical research method of transcriptomics combined with metabolomics was used to study the pathogenesis of ARC at the transcriptional and metabolic levels. In transcriptomics, 534 samples from 5 datasets in the Gene Expression Omnibus database were analyzed and 834 differential genes associated with ARC were obtained. In metabolomics, we used Ultra-Performance Liquid Chromatography-Quadrupole Time-of-Flight Mass Spectrometry to determine the non-targeted metabolites of 102 samples after matching propensity scores, and obtained 45 differential metabolites associated with ARC. The results of the combined analysis showed that purine metabolism, arginine biosynthesis, and arachidonic acid metabolism were changed in patients with ARC. We speculate that the occurrence of ARC may be related to the alteration of renal blood perfusion by LTB4R, ARG1, ALOX5, arginine and prostaglandins E2 through inflammatory response, as well as the effects of CA4, PFKFB2, PFKFB3, PRKACB, NMDAR, glutamate and cAMP on renal capillary wall permeability.

Continuous Infusion of Piperacillin/Tazobactam and Meropenem in ICU Patients Without Renal Dysfunction: Are Patients at Risk of Underexposure?

BACKGROUND AND OBJECTIVES

Morbidity and mortality from serious infections are common in intensive care units (ICUs). The appropriateness of the antibiotic treatment is essential to combat sepsis. We aimed to evaluate pharmacokinetic/pharmacodynamic target attainment of meropenem and piperacillin/tazobactam administered at standard total daily dose as continuous infusion in critically ill patients without renal dysfunction and to identify risk factors of non-pharmacokinetic/pharmacodynamic target attainment.

RESULTS

We included 118 patients (149 concentrations), 47% had microorganism isolation. Minimum inhibitory concentration (MIC) [median (interquartile range, IQR) values in isolated pathogens were: meropenem: 0.05 (0.02-0.12) mg/l; piperacillin: 3 (1-4) mg/l]. Pharmacokinetic/pharmacodynamic target attainments (100%fC_ss≥1xMIC, 100%fC_ss≥4xMIC and 100%fC_{ss ≥ 8xMIC}, respectively) were: 100%, 96.15%, 96.15% (meropenem) and 95.56%, 91.11%, 62.22% (piperacillin) for actual MIC; 98.11%, 71.70%, 47.17% (meropenem, MIC 2 mg/l), 95.83%, 44.79%, 6.25% (piperacillin, MIC 8 mg/l), 83.33%, 6.25%, 1.04% (piperacillin, MIC 16 mg/l) for EUCAST breakpoint of Enterobacteriaceae spp. and Pseudomonas spp. Multivariable linear analysis identified creatinine clearance (CrCL) as a predictive factor of free antibiotic concentrations (fC_ss) of both therapies (meropenem [β = - 0.01 (95% CI - 0.02 to - 0.0; p = 0.043)] and piperacillin [β = - 0.01 (95% CI - 0.02 to 0.01, p < 0.001)]). Neurocritical status was associated with lower piperacillin fC_ss [β = - 0.36 (95% CI - 0.61 to - 0.11; p = 0.005)].

CONCLUSION

Standard total daily dose of meropenem allowed achieving pharmacokinetic/pharmacodynamic target attainments in ICU patients without renal dysfunction. Higher doses of piperacillin/tazobactam would be needed to cover microorganisms with MIC > 8 mg/l. CrCL was the most powerful factor predictive of fC_ss in both therapies.

A narrative review on antimicrobial therapy in septic shock: updates and controversies

PURPOSE OF REVIEW

Antibiotics are an essential treatment for septic shock. This review provides an overview of the key issues in antimicrobial therapy for septic shock. We include a summary of available evidence with an emphasis on data published in the last few years.

RECENT FINDINGS

We examine apparently contradictory data supporting the importance of minimizing time to antimicrobial therapy in sepsis, discuss approaches to choosing appropriate antibiotics, and review the importance and challenges presented by antimicrobial dosing. Lastly, we evaluate the evolving concepts of de-escalation, and optimization of the duration of antimicrobials.

SUMMARY

The topics discussed in this review provide background to key clinical decisions in antimicrobial therapy for septic shock: timing, antibiotic choice, dosage, de-escalation, and duration. Although acknowledging some controversy, antimicrobial therapy in septic shock should be delivered early, be of the adequate spectrum, appropriately and individually dosed, rationalized when possible, and of minimal effective duration.

Neurological and Psychiatric Adverse Effects of Antimicrobials

Antimicrobials are a widely used class of medications, but several of them are associated with neurological and psychiatric side effects. The exact incidence of neurotoxicity with anti-infectives is unknown, although it is estimated to be < 1%. Neurotoxicity occurs with all classes of antimicrobials, such as antibiotics, antimycobacterials, antivirals, antifungals and antiretrovirals, with side effects ranging from headaches, anxiety and depression to confusion, delirium, psychosis, mania and seizures, among others. It is important to consider these possible side effects to prevent misdiagnosis or delayed treatment as drug withdrawal can be associated with reversibility in most cases. This article highlights the different neurotoxic effects of a range of antimicrobials, discusses proposed mechanisms of onset and offers general management recommendations. The effects of antibiotics on the gut microbiome and how they may ultimately affect cognition is also briefly examined.

Risk Factors and Clinical Outcomes Associated With Augmented Renal Clearance in Trauma Patients

BACKGROUND

Augmented renal clearance (ARC; i.e., creatinine clearance [CL_Cr] ≥ 130 mL/min) has an incidence of 14%-80% in critically ill patients and has been associated with therapy failures for renally cleared drugs. However, the clinical implications of ARC are poorly defined. We hypothesize that modifiable risk factors that contribute to ARC can be identified in severely injured trauma patients and that these risk factors influence clinical outcome.

METHODS

In 207 trauma intensive care unit patients, 24-h CL_Cr was correlated with clinical estimates of glomerular filtration rate (by Cockroft-Gault, modification of diet in renal disease, or chronic kidney disease epidemiology), and clinical outcomes (infection, venous thromboembolism [VTE], length of stay, and mortality).

RESULTS

The population was 45 ± 20 y, 68% male, 77% blunt injury with injury severity score of 24 (17-30). Admission serum creatinine was 1.02 ± 0.35 mg/dL, CL_Cr was 154 ± 77 mL/min, VTE incidence was 15%, ARC incidence was 57%, and mortality was 11%. Clinical estimates of glomerular filtration rate by Cockroft-Gault, modification of diet in renal disease, chronic kidney disease epidemiology underestimated actual CL_Cr by 20%, 22%, or 15% (all P < 0.01). CL_Cr was higher in males and those who survived, and lower in those with hypertension, diabetes, positive cultures, receiving transfusions, or pressors (all P < 0.05). On multivariate analysis, male gender (odds ratio [OR] 2.9 [1.4-6.1]), age (OR 0.97 [0.95-0.99]), and packed red blood cells transfusion (OR 0.31 [0.15-0.66]) were the only independent predictors of ARC.

CONCLUSIONS

ARC occurs in more than half of all high-risk trauma intensive care unit patients and is underestimated by standard clinical equations. ARC was not associated with increased incidence of VTE or infection but rather is associated with younger healthier males and reduced mortality. ARC seems to be a beneficial compensatory response to trauma.

Augmented renal clearance: a common condition in critically ill children

BACKGROUND

Augmented renal clearance (ARC), an increase in kidney function with enhanced elimination of circulating solute, has been increasingly recognized in critically ill adults. In a pediatric intensive care setting, data are scarce. The primary objective of this study was to investigate the prevalence of ARC in critically ill children. Secondary objectives included a risk factor analysis for the development of ARC and a comparison of two methods for assessment of renal function.

METHODS

In 105 critically ill children between 1 month and 15 years of age, glomerular filtration rate (GFR) was measured by means of a daily 24-h creatinine clearance (24 h Cl_Cr) and compared to an estimated GFR using the revised Schwartz formula. Logistic regression analysis was used to identify risk factors for ARC.

RESULTS

Overall, 67% of patients expressed ARC and the proportion of ARC patients decreased during consecutive days. ARC patients had a median Cl_Cr of 142.2 ml/min/1.73m² (IQR 47.1). Male gender and antibiotic treatment were independently associated with the occurrence of ARC. The revised Schwartz formula seems less appropriate for ARC detection.

CONCLUSIONS

A large proportion of critically ill children develop ARC during their stay at the intensive care unit. Clinicians should be cautious when using Schwartz formula to detect ARC. Our findings require confirmation from large study cohorts and investigation of the relationship with clinical outcome.

Pharmacokinetics-pharmacodynamics issues relevant for the clinical use of beta-lactam antibiotics in critically ill patients

Antimicrobials are among the most important and commonly prescribed drugs in the management of critically ill patients and beta-lactams are the most common antibiotic class used. Critically ill patient's pathophysiological factors lead to altered pharmacokinetics and pharmacodynamics of beta-lactams.A comprehensive bibliographic search in PubMed database of all English language articles published from January 2000 to December 2017 was performed, allowing the selection of articles addressing the pharmacokinetics or pharmacodynamics of beta-lactam antibiotics in critically ill patients.In critically ill patients, several factors may increase volume of distribution and enhance renal clearance, inducing high intra- and inter-patient variability in beta-lactam concentration and promoting the risk of antibiotic underdosing. The duration of infusion of beta-lactams has been shown to influence the fT > minimal inhibitory concentration and an improved beta-lactam pharmacodynamics profile may be obtained by longer exposure with more frequent dosing, extended infusions, or continuous infusions.The use of extracorporeal support techniques in the critically ill may further contribute to this problem and we recommend not reducing standard antibiotic dosage since no drug accumulation was found in the available literature and to maintain continuous or prolonged infusion, especially for the treatment of infections caused by multidrug-resistant bacteria.Prediction of outcome based on concentrations in plasma results in overestimation of antimicrobial activity at the site of infection, namely in cerebrospinal fluid and the lung. Therefore, although no studies have assessed clinical outcome, we recommend using higher than standard dosing, preferably with continuous or prolonged infusions, especially when treating less susceptible bacterial strains at these sites, as the pharmacodynamics profile may improve with no apparent increase in toxicity.A therapeutic drug monitoring-guided approach could be particularly useful in critically ill patients in whom achieving target concentrations is more difficult, such as obese patients, immunocompromised patients, those infected by highly resistant bacterial strains, patients with augmented renal clearance, and those undergoing extracorporeal support techniques.

An evaluation of risk factors to predict target concentration non-attainment in critically ill patients prior to empiric β-lactam therapy

To determine whether target concentration non-attainment can be anticipated in critically ill patients prior to initiating empiric β-lactam antibiotic therapy based on readily available clinical factors. Retrospective review of consecutive patients treated with piperacillin or meropenem and who underwent therapeutic drug monitoring (TDM) at St Vincent's Hospital (Sydney, Australia) between January 2013 and December 2015 was performed. Predefined subgroups were patients who received continuous renal replacement therapy (CRRT) and those who did not (non-CRRT). Potential risk factors were evaluated by correlation with β-lactam antibiotic trough concentrations (C_min) lower than or equal to targeted minimum inhibitory concentration (MIC). Only the first drug concentration after initiation of the antibiotic treatment was included to reflect empirical dose selection. A total of n = 249 patients (piperacillin, n = 169; meropenem, n = 80) were investigated. For non-CRRT patients (n = 210), multivariate analysis demonstrated the following: male gender (p = 0.006); younger age (p = 0.015); prescribed daily antibiotic dose less than 1.5 times the product information recommendations (p = 0.004); lack of positive microbiology (p = 0.006); lower overall illness severity (p = 0.005); and estimated glomerular filtration rate (eGFR) ≥ 90 mL/min/1.73 m² (p < 0.001), to be associated with C_min ≤ MIC. No predictor variable was found to be significantly associated with C_min ≤ MIC for the CRRT cohort. Evaluating the risk of target concentration non-attainment using simple clinical factors is possible at the bedside for non-CRRT patients prior to empiric antibiotic initiation. Clinicians should be wary of selecting doses based on the product information especially when treating younger male patients with apparently 'normal' renal function.

Target attainment with continuous dosing of piperacillin/tazobactam in critical illness: a prospective observational study

Optimal dosing of β-lactam antibiotics in critically ill patients is a challenge given the unpredictable pharmacokinetic profile of this patient population. Several studies have shown intermittent dosing to often yield inadequate drug concentrations. Continuous dosing is an attractive alternative from a pharmacodynamic point of view. This study evaluated whether, during continuous dosing, piperacillin concentrations reached and maintained a pre-defined target in critically ill patients. Adult patients treated with piperacillin by continuous dosing in the intensive care unit of a university medical centre in The Netherlands were prospectively studied. Total and unbound piperacillin concentrations drawn at fixed time points throughout the entire treatment course were determined by liquid chromatography-tandem mass spectrometry. A pharmacokinetic combined target of a piperacillin concentration ≥80 mg/L, reached within 1 h of starting study treatment and maintained throughout the treatment course, was set. Eighteen patients were analysed. The median duration of monitored piperacillin treatment was 60 h (interquartile range, 33-96 h). Of the 18 patients, 5 (27.8%) reached the combined target; 15 (83.3%) reached and maintained a less strict target of >16 mg/L. In this patient cohort, this dosing schedule was insufficient to reach the pre-defined target. Depending on which target is to be met, a larger initial cumulative dose is desirable, combined with therapeutic drug monitoring.

Association between augmented renal clearance and clinical outcomes in patients receiving β-lactam antibiotic therapy by continuous or intermittent infusion: a nested cohort study of the BLING-II randomised, placebo-controlled, clinical trial

Augmented renal clearance (ARC) is known to influence β-lactam antibiotic pharmacokinetics. This substudy of the BLING-II trial aimed to explore the association between ARC and patient outcomes in a large randomised clinical trial. BLING-II enrolled 432 participants with severe sepsis randomised to receive β-lactam therapy by continuous or intermittent infusion. An 8-h creatinine clearance (CL_Cr) measured on Day 1 was used to identify ARC, defined as CL_Cr ≥ 130 mL/min. Patients receiving any form of renal replacement therapy were excluded. Primary outcome was alive ICU-free days at Day 28. Secondary outcomes included 90-day mortality and clinical cure at 14 days following antibiotic cessation. A total of 254 patients were included, among which 45 (17.7%) manifested ARC [median (IQR) CL_Cr 165 (144-198) mL/min]. ARC patients were younger (P <0.001), more commonly male (P = 0.04) and had less organ dysfunction (P <0.001). There was no difference in ICU-free days at Day 28 [ARC, 21 (12-24) days; no ARC, 21 (11-25) days; P = 0.89], although clinical cure was significantly greater in the unadjusted analysis in those manifesting ARC [33/45 (73.3%) vs. 115/209 (55.0%) P = 0.02]. This was attenuated in the multivariable analysis. No difference was noted in 90-day mortality. There were no statistically significant differences in clinical outcomes in ARC patients according to the dosing strategy employed. In this substudy of a large clinical trial of β-lactam antibiotics in severe sepsis, ARC was not associated with any differences in outcomes, regardless of dosing strategy.

The use of liquid chromatography-tandem mass spectrometry for therapeutic drug monitoring of antibiotics in cancer patients

Cancer remains a leading cause of mortality and morbidity worldwide. In addition to organ failure, the most frequent reasons for admission of cancer patients to intensive care units (ICU) are: infections and sepsis. As critically ill, the complexity of the health situation of cancer patients renders the standard antimicrobial regimen more complex and even inadequate which results in increased mortality rates. This is due to pathophysiological changes in the volume of distribution, increased clearance, as well as to organ dysfunction. While in the former cases a decrease in drug efficacy is observed, the hallmark of the latter one is overdosing leading to increased toxicity at the expense of efficacy. Furthermore, an additional risk factor is the potential drug-drug interaction between antibiotics and antineoplastic agents. Therefore, therapeutic drug monitoring (TDM) is a necessity to improve the clinical outcome of antimicrobial therapy in cancer patients. To be applied in routine analysis the method used for TDM should be cheap, fast and highly accurate/sensitive. Furthermore, as ICU patients are treated with a cocktail of antibiotics the method has to cover the simultaneous analysis of antibiotics used as a first/second line of treatment. The aim of the current review is to briefly survey the pitfalls in the current antimicrobial therapy and the central role of TDM in dose adjustment and drug-drug interaction’s evaluation. A major section is dedicated to summarize the currently published analytical methods and to shed light on the difficulties and potential problems that can be encountered during method development.

Standard dosing of piperacillin and meropenem fail to achieve adequate plasma concentrations in ICU patients

BACKGROUND

Controversies remain regarding optimal dosing and the need for plasma concentration measurements when treating intensive care patients with beta-lactam antibiotics.

METHODS

We studied ICU patients treated with either antibiotic, excluding patients on renal replacement therapy. Antibiotic concentrations were measured at the mid and end of the dosing interval, and repeated after 2-3 days when feasible. Glomerular filtration rate (GFR) was estimated from plasma creatinine and cystatin C, GFR calculated from cystatin C (eGFR) and measured creatinine clearance (CrCl). Measured concentrations were compared to the clinical susceptible breakpoints for Pseudomonas aeruginosa, 16 and 2 mg/l for piperacillin and meropenem respectively.

RESULTS

We analysed 33 and 31 paired samples from 20 and 19 patients treated with piperacillin-tazobactam and meropenem respectively. Antibiotic concentrations at the mid and end of the dosing interval were for piperacillin, 27.0 (14.7-52.9) and 8.6 (2.7-30.3); and for meropenem, 7.5 (4.7-10.2) and 2.4 (1.0-3.5). All values median (interquartile range) and concentrations in mg/l. The percentage of measured concentrations below the breakpoint at the mid and end of the dosing interval were for piperacillin, 27% and 61%; and for meropenem, 6% and 48%. Lower estimates of GFR were associated with higher concentrations but concentrations varied greatly between patients with similar GFR. The correlation with terminal concentration half-life was similar for eGFR and CrCl.

CONCLUSIONS

With standard doses of meropenem and piperacillin-tazobactam, plasma concentrations in ICU patients vary > 10-fold and are suboptimal in a significant percentage of patients. The variation is large also between patients with similar renal function.

Cerebrospinal fluid penetration of meropenem in neurocritical care patients with proven or suspected ventriculitis: a prospective observational study

BACKGROUND

Ventriculitis is a complication of temporary intraventricular drains. The limited penetration of meropenem into the cerebrospinal fluid (CSF) is well known. However, ventricular CSF pharmacokinetic data in patients with ventriculitis are lacking. The aim of this study was to evaluate meropenem pharmacokinetics in the serum and CSF of neurocritical care patients with proven or suspected ventriculitis.

METHODS

We conducted an observational pharmacokinetic study of neurocritical care patients with proven or suspected ventriculitis receiving meropenem. Multiple blood and CSF samples were taken and were described using nonparametric pharmacokinetic modelling with Pmetrics.

RESULTS

In total, 21 patients (median age 52 years, median weight 76 kg) were included. The median (range) of peak and trough concentrations in serum were 20.16 (4.40-69.00) mg/L and 2.54 (0.00-31.40) mg/L, respectively. The corresponding peak and trough concentrations in CSF were 1.20 (0.00-6.20) mg/L and 1.28 (0.00-4.10) mg/L, respectively, with a median CSF/serum ratio (range) of 0.09 (0.03-0.16). Median creatinine clearance ranged from 60.7 to 217.6 ml/minute (median 122.5 ml/minute). A three-compartment linear population pharmacokinetic model was most appropriate. No covariate relationships could be supported for any of the model parameters. Meropenem demonstrated poor penetration into CSF, with a median CSF/serum ratio of 9 % and high interindividual pharmacokinetic variability.

CONCLUSIONS

Administration of higher-than-standard doses of meropenem and therapeutic drug monitoring in both serum and CSF should be considered to individualise meropenem dosing in neurocritical care patients with ventriculitis.

Augmented renal clearance in Japanese intensive care unit patients: a prospective study

Background

Augmented renal clearance (ARC) of circulating solutes and drugs has been recently often reported in intensive care unit (ICU) patients. However, only few studies on ARC have been reported in Japan. The aims of this pilot study were to determine the prevalence and risk factors for ARC in Japanese ICU patients with normal serum creatinine levels and to evaluate the association between ARC and estimated glomerular filtration rate (eGFR) calculated using the Japanese equation.

Methods

We conducted a prospective observational study from May 2015 to April 2016 at the emergency ICU of a tertiary university hospital; 111 patients were enrolled (mean age, 67 years; interquartile range, 53–77 years). We measured 8-h creatinine clearance (CL_CR) within 24 h after admission, and ARC was defined as body surface area-adjusted CL_CR ≥ 130 mL/min/1.73 m². Multiple logistic regression analysis was performed to identify the risk factors for ARC. Moreover, a receiver operating curve (ROC) analysis, including area under the receiver operating curve (AUROC) was performed to examine eGFR accuracy and other significant variables in predicting ARC.

Results

In total, 43 patients (38.7 %) manifested ARC. Multiple logistic regression analysis was performed for age, body weight, body height, history of diabetes mellitus, Acute Physiology and Chronic Health Evaluation II scores, admission categories of post-operative patients without sepsis and trauma, and serum albumin, and only age was identified as an independent risk factor for ARC (odds ratio, 0.95; 95 % confidence interval [CI], 0.91–0.98). Moreover, the AUROC of ARC for age and eGFR was 0.81 (95 % CI, 0.72–0.89) and 0.81 (95 % CI, 0.73–0.89), respectively. The optimal cutoff values for detecting ARC were age and eGFR of ≤63 years (sensitivity, 72.1 %; specificity, 82.4 %) and ≥76 mL/min/1.73 m² (sensitivity, 81.4 %; specificity, 72.1 %), respectively.

Conclusions

ARC is common in Japanese ICU patients, and age was an independent risk factor for ARC. In addition, age and eGFR calculated using the Japanese equation were suggested to be useful screening tools for identifying Japanese patients with ARC.

Assessment of Modification of Diet in Renal Disease Equation to Predict Reference Serum Creatinine Value in Severe Trauma Patients: Lessons From an Observational Study of 775 Cases

OBJECTIVE

We assessed the Modification of Diet in Renal Disease (MDRD) performance to predict serum creatinine (SCr) in severe trauma population and determined the best theoretical glomerular filtration rate (GFR) to use in this estimation.

BACKGROUND

Baseline SCr may be misestimated in severe trauma patients because of their specific demographic characteristics including renal hyperfiltration. However, the back-calculated MDRD equation is supposed to estimate SCr using a predetermined GFR of 75 mL/min/1.73 m.

METHODS

All severe trauma patients with a normal SCr were retrospectively included between January 2005 and January 2011. For each patient, the lowest SCr (oSCr) observed during the first week was used to estimate the GFR. The median GFR in period 1 (2005-2006) was determined. The back-calculated MDRD performance was assessed in period 2 (2007-2011) to predict oSCr by agreement, precision, and accuracy using a GFR of 75 mL/min/1.73 m (eSCr75-MDRD) or the median GFR observed in period 1 (eSCrTRAUMA-MDRD).

RESULTS

A total of 775 patients were studied: mean age, 37.7 ± 17 years; mean Injury Severity Score, 19 ± 11; 75% of male. In period 1 (n = 243), median GFR was 121 mL/min/1.73 m. In period 2 (n = 532), eSCrTRAUMA-MDRD demonstrated better agreement in predicting oSCr than eSCr75-MDRD (mean bias 2 vs 35 μmol/L; P < 0.001). Both precision (14 vs 39 μmol/L, respectively) and accuracy were significantly improved with eSCrTRAUMA-MDRD. Proportion of estimated SCr values that deviated less than 15%, 30%, or 50% was also higher with eSCrTRAUMA-MDRD (P < 0.001).

CONCLUSIONS

The eSCr75-MDRD equation systematically overestimates oSCr of severe trauma patients. The eSCrTRAUMA-MDRD equation determined was statistically superior allowing more accurate qualification of acute kidney injury.

Piperacillin concentration in relation to therapeutic range in critically ill patients--a prospective observational study

BACKGROUND

Piperacillin levels after standard dosing have been shown frequently to be subtherapeutic, especially when renal clearance was augmented. Here, we aimed to determine if piperacillin was in its therapeutic range in a typically heterogeneous intensive care unit patient group, and also to describe target attainment dependent on daily dosage, creatinine clearance, and renal replacement therapy (RRT).

METHODS

Sixty patients with severe infections were included in this monocentric prospective observational study. Patients received 4.5 g of piperacillin-tazobactam two to three times daily by intermittent infusion depending on renal function according to clinical guidelines. Over 4 days, multiple serum samples (median per patient, 29; in total, 1627) were obtained to determine total piperacillin concentrations using ultra-high-performance liquid chromatography/tandem mass spectrometry.

RESULTS

A high heterogeneity of patient characteristics was observed (e.g., on day 1: creatinine clearance 2-233 mL/min and ten patients on RRT). Piperacillin trough levels showed inter-individual variation from 123 to >1785-fold on different study days. Each day, approximately 50% and 60% of the patients had piperacillin levels below the target ranges 1 and 2, respectively [defined for the calculated unbound piperacillin fraction according to the literature as 100% time above MIC (100%fT > MIC) (target range 1) and ≥ 50%fT > 4 × MIC (target range 2); MIC = 16 mg/L]. Whereas only the minority of patients who received piperacillin-tazobactam three times daily (TID) reached target 1 (38% on day 1), most patients who received piperacillin-tazobactam only twice daily (BID) because of severely impaired renal function reached this target (100% on day 1). Patients with RRT had significant higher percentages of fT > MIC. Zero percent, 55% and 100% of patients without RRT who received antibiotics TID reached target 1 when creatinine clearance was > 65 mL/min, 30-65 mL/min and < 30 mL/min, respectively. In patients with causative strains only sensitive to piperacillin-tazobactam of all antibiotics given to the patient, piperacillin levels negatively correlated with CRP concentrations of day 4 (p < 0.05).

CONCLUSIONS

A dosage of 4.5 g piperacillin-tazobactam TID seems to be frequently insufficient in critically ill patients, and also in patients where renal function is mildly to moderately impaired. For these patients, prescription of 4.5 g piperacillin-tazobactam four times daily could be considered.

TRIAL REGISTRATION

Clinicaltrials.gov NCT01793012. Registered 24 January 2013.

Screening of patients with augmented renal clearance in ICU: taking into account the CKD-EPI equation, the age, and the cause of admission

Background

In ICU patients with normal serum creatinine (SCr), a state of increased renal drug excretion has been described (creatinine clearance ≥130 ml/min/1.73 m²), and named augmented renal clearance (ARC). In ICU patients, the accuracy of GFR estimates is insufficient. However, in clinical practice, the physician has not at one’s disposal patient measured creatinine clearance (CrCl) when prescribing. The primary objective of this study was to assess the accuracy of 4 formulas to estimate GFR (Cockcroft-Gault (CG), Robert, sMDRD, and CKD-EPI formulas) with other covariates to detect ARC in ICU patients.

Methods

We enroled 360 consecutive ICU patients with normal SCr in this prospective observational study conducted in a primary teaching hospital. Comparisons between CrCl values and 4 estimated GFR (eGFR) formulas were estimated.

Results

In these 360 patients, ARC was observed in 33 % of patients most of them trauma. Individual predictive values of equations were poor and the phenomenon increased in ARC subgroup. CG and CKD-EPI were more accurate to detect an ARC. Multivariable analysis showed that the best-fitting model included 3 factors independently correlated to ARC: trauma patients, cut-off values of age ≤58 years, and CKD-EPI more than 108 ml/min/1.73 m².

Conclusions

In ICU patients with normal SCr, eGFR formulas are imprecise in assessing CrCl. If measured CrCl must be ideally used to detect modifications of the renal function, in clinical practice, age, reason for admission, and CKD-EPI could be used as screening tool to identify ARC.

[Augmented renal clearance in critically ill patients: incidence, associated factors and effects on vancomycin treatment]

OBJECTIVE

An augmented renal clearance has been described in some groups of critically ill patients, and it might induce sub-optimal concentrations of drugs eliminated by glomerular filtration, mainly antibiotics. Studies on its occurrence and determinants are lacking. Our goals were to determine the incidence and associated factors of augmented renal clearance and the effects on vancomycin concentrations and dosing in a series of intensive care unit patients.

METHODS

We prospectively studied 363 patients admitted during 1 year to a clinical-surgical intensive care unit. Patients with serum creatinine >1.3 mg/dL were excluded. Creatinine clearance was calculated from a 24-hour urine collection. Patients were grouped according to the presence of augmented renal clearance (creatinine clearance >120 mL/min/1.73 m²), and possible risk factors were analyzed with bivariate and logistic regression analysis. In patients treated with vancomycin, dosage and plasma concentrations were registered.

RESULTS

Augmented renal clearance was present in 103 patients (28%); they were younger (48±15 versus 65±17 years, p<0.0001), had more frequent obstetric (16 versus 7%, p=0.0006) and trauma admissions (10 versus 3%, p=0.016) and fewer comorbidities. The only independent determinants for the development of augmented renal clearance were age (OR 0.95; p<0.0001; 95%CI 0.93-0.96) and absence of diabetes (OR 0.34; p=0.03; 95%CI 0.12-0.92). Twelve of the 46 patients who received vancomycin had augmented renal clearance and despite higher doses, had lower concentrations.

CONCLUSIONS

In this cohort of critically ill patients, augmented renal clearance was a common finding. Age and absence of diabetes were the only independent determinants. Therefore, younger and previously healthy patients might require larger vancomycin dosing.

Population Pharmacokinetics of Doripenem in Critically Ill Patients with Sepsis in a Malaysian Intensive Care Unit

Doripenem has been recently introduced in Malaysia and is used for severe infections in the intensive care unit. However, limited data currently exist to guide optimal dosing in this scenario. We aimed to describe the population pharmacokinetics of doripenem in Malaysian critically ill patients with sepsis and use Monte Carlo dosing simulations to develop clinically relevant dosing guidelines for these patients. In this pharmacokinetic study, 12 critically ill adult patients with sepsis receiving 500 mg of doripenem every 8 h as a 1-hour infusion were enrolled. Serial blood samples were collected on 2 different days, and population pharmacokinetic analysis was performed using a nonlinear mixed-effects modeling approach. A two-compartment linear model with between-subject and between-occasion variability on clearance was adequate in describing the data. The typical volume of distribution and clearance of doripenem in this cohort were 0.47 liters/kg and 0.14 liters/kg/h, respectively. Doripenem clearance was significantly influenced by patients' creatinine clearance (CL(CR)), such that a 30-ml/min increase in the estimated CL(CR) would increase doripenem CL by 52%. Monte Carlo dosing simulations suggested that, for pathogens with a MIC of 8 mg/liter, a dose of 1,000 mg every 8 h as a 4-h infusion is optimal for patients with a CL(CR) of 30 to 100 ml/min, while a dose of 2,000 mg every 8 h as a 4-h infusion is best for patients manifesting a CL(CR) of >100 ml/min. Findings from this study suggest that, for doripenem usage in Malaysian critically ill patients, an alternative dosing approach may be meritorious, particularly when multidrug resistance pathogens are involved.

Augmented renal clearance and therapeutic monitoring of β-lactams

Successful application of antibacterial therapy in the critically ill requires an appreciation of the complex interaction between the host, the causative pathogen and the chosen pharmaceutical. A pathophysiological change in the intensive care unit (ICU) patient challenging the 'one dose fits all' concept includes augmented renal clearance (ARC), defined as a creatinine clearance (CL(Cr)) of ≥130 mL/min. Ideally, CL(Cr) values should be obtained by a timed measured collection of urine, with plasma and urine creatinine levels. Increased renal clearance of antibiotics also occurs in the ICU patient and therefore β-lactam antibiotic exposure in the critically ill could easily lead to trough drug concentrations below therapeutic ranges. One way to document and alter drug levels is via therapeutic drug monitoring (TDM). The interactions of ARC and β-lactam TDM are further explored in this article in specific reference to a concomitant article in this issue of the journal.

Determining the mechanisms underlying augmented renal drug clearance in the critically ill: use of exogenous marker compounds

Introduction

The aim of this study was to explore changes in glomerular filtration (GFR) and renal tubular function in critically ill patients at risk of augmented renal clearance (ARC), using exogenous marker compounds.

Methods

This prospective, observational pharmacokinetic (PK) study was performed in a university-affiliated, tertiary-level, adult intensive care unit (ICU). Patients aged less than or equal to 60 years, manifesting a systemic inflammatory response, with an expected ICU length of stay more than 24 hours, no evidence of acute renal impairment (plasma creatinine concentration <120 μmol/L) and no history of chronic kidney disease or renal replacement therapy were eligible for inclusion. The following study markers were administered concurrently: sinistrin 2,500 mg (Inutest; Laevosan, Linz, Austria), p-aminohippuric acid (PAH) 440 mg (4% p-aminohippuric acid sodium salt; CFM Oskar Tropitzsch, Marktredwitz, Germany), rac-pindolol 5 or 15 mg (Barbloc; Alphapharm, Millers Point, NSW, Australia) and fluconazole 100 mg (Diflucan; Pfizer Australia Pty Ltd, West Ryde, NSW, Australia). Plasma concentrations were then measured at 5, 10, 15, 30, 60 and 120 minutes and 4, 6, 12 and 24 hours post-administration. Non-compartmental PK analysis was used to quantify GFR, tubular secretion and tubular reabsorption.

Results

Twenty patients were included in the study. Marker administration was well tolerated, with no adverse events reported. Sinistrin clearance as a marker of GFR was significantly elevated (mean, 180 (95% confidence interval (CI), 141 to 219) ml/min) and correlated well with creatinine clearance (r =0.70, P <0.01). Net tubular secretion of PAH, a marker of tubular anion secretion, was also elevated (mean, 428 (95% CI, 306 to 550) ml/min), as was net tubular reabsorption of fluconazole (mean, 135 (95% CI, 100 to 169) ml/min). Net tubular secretion of (S)- and (R)-pinodolol, a marker of tubular cation secretion, was impaired.

Conclusions

In critically ill patients at risk of ARC, significant alterations in glomerular filtration, renal tubular secretion and tubular reabsorption are apparent. This has implications for accurate dosing of renally eliminated drugs.

Clinical implications of antibiotic pharmacokinetic principles in the critically ill

Successful antibiotic therapy in the critically ill requires sufficient drug concentrations at the site of infection that kill or suppress bacterial growth. The relationship between antibiotic exposure and achieving the above effects is referred to as pharmacokinetics/pharmacodynamics (PK/PD). The associated indices therefore provide logical targets for optimal antibiotic therapy. While dosing regimens to achieve such targets have largely been established from studies in animals and non-critically ill patients, they are often poorly validated in the ICU. Endothelial dysfunction, capillary leak, altered major organ blood flow, deranged plasma protein concentrations, extremes of body habitus, the application of extracorporeal support modalities, and a higher prevalence of intermediate susceptibility, independently, and in combination, significantly confound successful antibiotic treatment in this setting. As such, the prescription of standard doses are likely to result in sub-therapeutic concentrations, which in turn may promote treatment failure or the selection of resistant pathogens. This review article considers these issues in detail, summarizing the key changes in antibiotic PK/PD in the critically ill, and suggesting alternative dosing strategies that may improve antibiotic therapy in these challenging patients.

Can changes in renal function predict variations in β-lactam concentrations in septic patients?

This study investigated whether variations in creatinine clearance (CLCr) are correlated with changes in β-lactam concentrations or pharmacokinetics in septic patients. Data for 56 adult patients admitted to the ICU in whom routine therapeutic drug monitoring (TDM) of broad-spectrum β-lactams (ceftazidime, cefepime, piperacillin or meropenem) was performed were reviewed. Patients were included if they had at least two TDM during their ICU stay for the same antibiotic and were not concomitantly treated with any extracorporeal replacement therapy. Serum drug concentrations were measured by HPLC-UV. Antibiotic pharmacokinetics were calculated using a one-compartment model and the percentage of time spent above four times the MIC (%T>4×MIC) for Pseudomonas aeruginosa and the antibiotic clearance (ATB-CL) were obtained. CLCr was measured on the same day as the TDM using 24-h urine collection. The %T>4×MIC and ATB-CL were significantly correlated with CLCr at the first (r=-0.41, P=0.002; r=0.56, P<0.001, respectively) and second (r=-0.61, P<0.001; r=0.63, P<0.001, respectively) TDM. However, changes in ATB-CL were only weakly correlated with changes in CLCr (r=0.34, P=0.01). The proportion of patients with insufficient β-lactam concentrations at the first and second TDM were 39% and 30%, respectively, and increased proportionally to CLCr. Although CLCr was significantly correlated with concentrations and clearance of broad-spectrum β-lactams, changes in CLCr did not reliably predict variations in drug pharmacokinetics/pharmacodynamics. Routine TDM should be considered to adapt β-lactam doses in this setting.

Augmented renal clearance in septic and traumatized patients with normal plasma creatinine concentrations: identifying at-risk patients

Introduction

Improved methods to optimize drug dosing in the critically ill are urgently needed. Traditional prescribing culture involves recognition of factors that mandate dose reduction (such as renal impairment), although optimizing drug exposure, through more frequent or augmented dosing, represents an evolving strategy. Elevated creatinine clearance (CL_CR) has been associated with sub-therapeutic antibacterial concentrations in the critically ill, a concept termed augmented renal clearance (ARC). We aimed to determine the prevalence of ARC in a cohort of septic and traumatized critically ill patients, while also examining demographic, physiological and illness severity characteristics that may help identify this phenomenon.

Methods

This prospective observational study was performed in a 30-bed tertiary level, university affiliated, adult intensive care unit. Consecutive traumatized and septic critically ill patients, receiving antibacterial therapy, with a plasma creatinine concentration ≤110 μmol/L, were eligible for enrolment. Pulse contour analysis (Vigileo / Flo Trac^® system, Edwards Lifesciences, Irvine, CA, USA), was used to provide continuous cardiac index (CI) assessment over a single six-hour dosing interval. Urinary CL_CR measures were obtained concurrently.

Results

Seventy-one patients contributed data (sepsis n = 43, multi-trauma n = 28). Overall, 57.7% of the cohort manifested ARC, although there was a greater prevalence in trauma (85.7% versus 39.5%, P <0.001). In all patients, a weak correlation was noted between CI and CL_CR (r = 0.346, P = 0.003). This was mostly driven by septic patients (r = 0.508, P = 0.001), as no correlation (r = -0.012, P = 0.951) was identified in trauma. Those manifesting ARC were younger (P <0.001), male (P = 0.012), with lower acute physiology and chronic health evaluation (APACHE) II (P= 0.008) and modified sequential organ failure assessment (SOFA) scores (P = 0.013), and higher cardiac indices (P = 0.013). In multivariate analysis, age ≤50 years, trauma, and a modified SOFA score ≤4, were identified as significant risk factors. These had greater utility in predicting ARC, compared with CI assessment alone.

Conclusions

Diagnosis, illness severity and age, are likely to significantly influence renal drug elimination in the critically ill, and must be regularly considered in future study design and daily prescribing practice.

See related commentary by De Waele and Carlier, http://ccforum.com/content/17/2/130

Continuous infusion of piperacillin/tazobactam in septic critically ill patients--a multicenter propensity matched analysis

The clinical efficacy of continuous infusion of piperacillin/tazobactam in critically ill patients with microbiologically documented infections is currently unknown. We conducted a retrospective multicenter cohort study in 7 Portuguese intensive care units (ICU). We included 569 critically ill adult patients with a documented infection and treated with piperacillin/tazobactam admitted to one of the participating ICU between 2006 and 2010. We successfully matched 173 pairs of patients according to whether they received continuous or conventional intermittent dosing of piperacillin/tazobactam, using a propensity score to adjust for confounding variables. The majority of patients received 16g/day of piperacillin plus 2g/day of tazobactam. The 28-day mortality rate was 28.3% in both groups (p = 1.0). The ICU and in-hospital mortality were also similar either in those receiving continuous infusion or intermittent dosing (23.7% vs. 20.2%, p = 0.512 and 41.6% vs. 40.5%, p = 0.913, respectively). In the subgroup of patients with a Simplified Acute Physiology Score (SAPS) II>42, the 28-day mortality rate was lower in the continuous infusion group (31.4% vs. 35.2%) although not reaching significance (p = 0.66). We concluded that the clinical efficacy of piperacillin/tazobactam in this heterogeneous group of critically ill patients infected with susceptible bacteria was independent of its mode of administration, either continuous infusion or intermittent dosing.

High creatinine clearance in critically ill patients with community-acquired acute infectious meningitis

Background

A high dose of anti-infective agents is recommended when treating infectious meningitis. High creatinine clearance (CrCl) may affect the pharmacokinetic / pharmacodynamic relationships of anti-infective drugs eliminated by the kidneys. We recorded the incidence of high CrCl in intensive care unit (ICU) patients admitted with meningitis and assessed the diagnostic accuracy of two common methods used to identify high CrCl.

Methods

Observational study performed in consecutive patients admitted with community-acquired acute infectious meningitis (defined by >7 white blood cells/mm³ in cerebral spinal fluid) between January 2006 and December 2009 to one medical ICU. During the first 7 days following ICU admission, CrCl was measured from 24-hr urine samples (24-hr-UV/P creatinine) and estimated according to Cockcroft-Gault formula and the simplified Modification of Diet in Renal Disease (MDRD) equation. High CrCl was defined as CrCl >140 ml/min/1.73 m² by 24-hr-UV/P creatinine. Diagnostic accuracy was performed with ROC curves analysis.

Results

Thirty two patients were included. High CrCl was present in 8 patients (25%) on ICU admission and in 15 patients (47%) during the first 7 ICU days for a median duration of 3 (1-4) days. For the Cockcroft-Gault formula, the best threshold to predict high CrCl was 101 ml/min/1.73 m² (sensitivity: 0.96, specificity: 0.75, AUC = 0.90 ± 0.03) with a negative likelihood ratio of 0.06. For the simplified MDRD equation, the best threshold to predict high CrCl was 108 ml/min/1.73 m² (sensitivity: 0.91, specificity: 0.80, AUC = 0.88 ± 0.03) with a negative likelihood ratio of 0.11. There was no difference between the estimated methods in the diagnostic accuracy of identifying high CrCl (p = 0.30).

Conclusions

High CrCl is frequently observed in ICU patients admitted with community-acquired acute infectious meningitis. The estimated methods of CrCl could be used as a screening tool to identify high CrCl.

Does Beta-lactam Pharmacokinetic Variability in Critically Ill Patients Justify Therapeutic Drug Monitoring? A Systematic Review

The pharmacokinetics of beta-lactam antibiotics in intensive care patients may be profoundly altered due to the dynamic, unpredictable pathophysiological changes that occur in critical illness. For many drugs, significant increases in the volume of distribution and/or variability in drug clearance are common. When “standard” beta-lactam doses are used, such pharmacokinetic changes can result in subtherapeutic plasma concentrations, treatment failure, and the development of antibiotic resistance. Emerging data support the use of beta-lactam therapeutic drug monitoring (TDM) and individualized dosing to ensure the achievement of pharmacodynamic targets associated with rapid bacterial killing and optimal clinical outcomes. The purpose of this work was to describe the pharmacokinetic variability of beta-lactams in the critically ill and to discuss the potential utility of TDM to optimize antibiotic therapy through a structured literature review of all relevant publications between 1946 and October 2011. Only a few studies have reported the utility of TDM as a tool to improve beta-lactam dosing in critically ill patients. Moreover, there is little agreement between studies on the pharmacodynamic targets required to optimize antibiotic therapy. The impact of TDM on important clinical outcomes also remains to be established. Whereas TDM may be theoretically rational, clinical studies to assess utility in the clinical setting are urgently required.

Augmented Renal Clearance in the Critically Ill: How to Assess Kidney Function

BACKGROUND:

Augmented renal clearance in critically ill patients can result in underdosing of life-saving drugs, potentially leading to therapeutic failure. To detect this phenomenon, correct assessment of the kidney function is essential. Currently, little is known about the validity of mathematical formulas to estimate renal function in this subset of patients.

OBJECTIVE:

To evaluate the validity of different methods to estimate kidney function in critically ill patients with augmented renal clearance by comparing measured renal clearance with estimated clearance using different formulas.

METHODS:

An observational, retrospective, single-center study was conducted in a 34-bed surgical intensive care unit (SICU) of the University Hospitals Leuven, Leuven, Belgium. Adults admitted to the SICU in 2010 with a measured creatinine clearance (CrCl) of 120 mL/min or more (based on 24-hour urinary collection) were included. The measured clearance values were compared with estimated clearance values as calculated by the Cockcroft-Gault (CrClCG) method and the re-expressed 4-variable Modification of Diet in Renal Disease estimated glomerular filtration rate (eGFR) formula. Spearman rank order correlation was performed to determine the relationship between measured and estimated clearances. Bland-Altman plots were evaluated to assess bias and limits of agreement between the 2 methods.

RESULTS:

Records on 1317 patients were screened. Augmented renal clearance was present in 390 patients. Spearman correlation showed fair correlation between measured and estimated clearances (rs = 0.343; p < 0.001 [CrClCG] and rs = 0.290; p < 0.001 [eGFR]). Bias was −11.2 mL/min with limits of agreement (–131.7; 109.3 mL/min [CrClCG]) and −19.9 mL/min with limits of agreement (–170.4; 130.7 mL/min [eGFR]).

CONCLUSIONS:

Estimated renal clearances, such as the eGFR estimated by the MDRD formula or CrCl estimated by CG, showed poor agreement with measured CrCl values in our critically ill population displaying augmented renal clearance. Clinicians should be cautious when interpreting kidney function based on estimating equations in this subset of patients. Instead, measured CrCl using urinary collection is recommended in patients suspected of displaying augmented renal clearance.

Population pharmacokinetics of extended-infusion piperacillin-tazobactam in hospitalized patients with nosocomial infections

While extended infusions of piperacillin-tazobactam (TZP) are increasingly used in practice, the effect of infusion on the pharmacokinetic (PK) profile of TZP has not been widely assessed. To assess its effect on the pharmacokinetic profile of TZP, seven serum samples were collected from 11 hospitalized patients who received 3.375 g TZP intravenously for 4 h every 8 h. Population pharmacokinetic models were fit to the PK data utilizing first-order, Michaelis-Menten (MM), and parallel first-order/MM clearance. A population PK model with first-order clearance was fit to the tazobactam PK data. Monte Carlo simulations (MCSs) were used to determine the most effective administration schedule to ensure that free piperacillin concentrations were above the MIC for at least 50% of the dosing interval (50% fT>MIC) and to quantify the extent of the nonlinear clearance. The model incorporating parallel linear/MM clearance best fit the piperacillin PK data. The MCSs demonstrated that approximately 50% of the administered piperacillin is cleared by the nonlinear clearance mechanism. The results of the MCSs also revealed that more intensive TZP extended infusion dosing schemes (3.375 to 4.5 g intravenously [3-h infusion] every 6 h) than those commonly used in clinical practice were needed to maximize the 50% fT>MIC for MICs of ≥8 mg/liter. This study suggests that extended infusion of TZP is the most effective method of administration for patients with nosocomial infections. Due to the hyperclearance nature of the hospitalized patient populations studied, more intensive TZP dosing regimens may be needed to maximize fT>MIC in certain hospitalized populations.

Antibiotics in critically ill patients: a systematic review of the pharmacokinetics of β-lactams

INTRODUCTION

Several reports have shown marked heterogeneity of antibiotic pharmacokinetics (PK) in patients admitted to ICUs, which might potentially affect outcomes. Therefore, the pharmacodynamic (PD) parameter of the efficacy of β-lactam antibiotics, that is, the time that its concentration is above the bacteria minimal inhibitory concentration (T > MIC), cannot be safely extrapolated from data derived from the PK of healthy volunteers.

METHODS

We performed a full review of published studies addressing the PK of intravenous β-lactam antibiotics given to infected ICU patients. Study selection comprised a comprehensive bibliographic search of the PubMed database and bibliographic references in relevant reviews from January 1966 to December 2010. We selected only English-language articles reporting studies addressing β-lactam antibiotics that had been described in at least five previously published studies. Studies of the PK of patients undergoing renal replacement therapy were excluded.

RESULTS

A total of 57 studies addressing six different β-lactam antibiotics (meropenem, imipenem, piperacillin, cefpirome, cefepime and ceftazidime) were selected. Significant PK heterogeneity was noted, with a broad, more than twofold variation both of volume of distribution and of drug clearance (Cl). The correlation of antibiotic Cl with creatinine clearance was usually reported. Consequently, in ICU patients, β-lactam antibiotic half-life and T > MIC were virtually unpredictable, especially in those patients with normal renal function. A better PD profile was usually obtained by prolonged or even continuous infusion. Tissue penetration was also found to be compromised in critically ill patients with septic shock.

CONCLUSIONS

The PK of β-lactam antibiotics are heterogeneous and largely unpredictable in ICU patients. Consequently, the dosing of antibiotics should be supported by PK concepts, including data derived from studies of the PK of ICU patients and therapeutic drug monitoring.

Increased creatinine clearance in polytrauma patients with normal serum creatinine: a retrospective observational study

INTRODUCTION

The aim of this study, performed in an intensive care unit (ICU) population with a normal serum creatinine, was to estimate urinary creatinine clearance (CLCR) in a population of polytrauma patients (PT) through a comparison with a population of non trauma patients (NPT).

METHODS

This was a retrospective, observational study in a medical and surgical ICU in a university hospital. A total of 284 patients were consecutively included. Two different groups were studied: PT (n = 144) and NPT (n = 140). Within the second week after admission to the ICU, renal function was assessed using serum creatinine, 24 h urinary CLCR .

RESULTS

Among the 106 patients with a CLCR above 120 mL minute(-1) 1.73 m(-2), 79 were PT and 27 NPT (P < 0.0001). Only 63 patients had a CLCR below 60 mL minute(-1) 1.73 m(-2) with 15 PT and 48 NPT (P < 0.0001). Patients with CLCR greater than 120 mL minute(-1). 1.73 m(-2) were younger, had a lower SAPS II score and a higher male ratio as compared to those having CLCR lower than 120 mL minute(-1). 1.73 m(-2). Through a logistic regression analysis, age and trauma were the only factors independently correlated to CLCR.

CONCLUSIONS

In ICU patients with normal serum creatinine, CLCR, is higher in PT than in NPT. The measure of CLCR should be proposed as routine for PT patients in order to adjust dose regimen, especially for drugs with renal elimination.

Augmented renal clearance: implications for antibacterial dosing in the critically ill

The prescription of pharmaceuticals in the critically ill is complicated by a paucity of knowledge concerning the pharmacokinetic implications of the underlying disease state. Changes in organ function can be dramatic in this population, both as a consequence of the primary pathophysiology and in response to clinical interventions provided. Vascular tone, fluid status, cardiac output and major organ blood flow can be significantly altered from baseline, influencing the volume of distribution and clearance of many commonly prescribed agents. Although measurable endpoints can be used to titrate doses for many drugs in this setting (such as sedatives), for those agents with silent pharmacodynamic indices, enhanced excretory organ function can result in unexpectedly low plasma concentrations, leading to treatment failure. This is particularly relevant to the use of antibacterials in the critically ill, where inadequate, inappropriate and/or delayed prescription can have significant effects on morbidity and mortality. Augmented renal clearance (ARC) refers to enhanced renal elimination of circulating solute and is being described with increasing regularity in the critically ill. However, defining this process in terms of current measures of renal function is problematic, as although the glomerular filtration rate (GFR) is largely considered the best index of renal function, there is no consensus on an upper limit of normal. In addition, the most readily available and accurate estimate of the GFR at the bedside is still widely debated. From a pharmacokinetic point of view, ARC can result in elevated renal elimination and subtherapeutic plasma concentrations of pharmaceuticals, although whether this process solely involves augmented filtration (as opposed to enhanced tubular secretion and/or reabsorption) remains uncertain. The primary contributors to this process are likely to be the innate immune response to infection and inflammation (with its associated systemic and haemodynamic consequences), fluid loading and use of vasoactive medications. The resultant increase in cardiac output and renal blood flow prompts enhanced glomerular filtration and drug elimination. Current evidence suggests that young patients without pre-existing co-morbidity or organ dysfunction who present with trauma are most likely to manifest ARC. As this phenomenon has received little attention in the literature, dose modification has rarely been considered. However, with increasing data supporting the concept, and many investigators demonstrating subtherapeutic concentrations of drugs in the critically ill, consideration of ARC and alternative dosing regimens is now mandatory, both to improve the likelihood of treatment success and to reduce the rate of development of antibacterial resistance.

Bench-to-bedside review: Appropriate antibiotic therapy in severe sepsis and septic shock--does the dose matter?

Appropriate antibiotic therapy in patients with severe sepsis and septic shock should mean prompt achievement and maintenance of optimal exposure at the infection site with broad-spectrum antimicrobial agents administered in a timely manner. Once the causative pathogens have been identified and tested for in vitro susceptibility, subsequent de-escalation of antimicrobial therapy should be applied whenever feasible. The goal of appropriate antibiotic therapy must be pursued resolutely and with continuity, in view of the ongoing explosion of antibiotic-resistant infections that plague the intensive care unit setting and of the continued decrease in new antibiotics emerging. This article provides some principles for the correct handling of antimicrobial dosing regimens in patients with severe sepsis and septic shock, in whom various pathophysiological conditions may significantly alter the pharmacokinetic behaviour of drugs.