Decreasing the time to achieve therapeutic vancomycin concentrations in critically ill patients: developing and testing of a dosing nomogram

The Impact of Augmented Renal Clearance on Vancomycin Pharmacokinetics and Pharmacodynamics in Critically Ill Patients

Augmented renal clearance (ARC), defined as a creatinine clearance (CrCl) > 130 mL/min/1.73 m2, is observed in 30-65% of critically ill patients. When following standard dosage guidelines, patients with ARC often experience subtherapeutic vancomycin levels, resulting in treatment failure due to accelerated drug elimination. This review aims to explore ARC's impact on vancomycin pharmacokinetics and pharmacodynamics (PK/PD) indices in ARC patients, seeking to identify an accurate dose adjustment method for this patient population. In September 2023, a comprehensive literature search was conducted on the MEDLINE and EMBASE databases to include all available studies providing information on the impact of ARC on vancomycin therapy in critically ill adults. Articles that studied the pediatric population and those with insufficient PK data were excluded. A total of 21 articles met the inclusion criteria. The findings revealed a positive correlation between CrCl and vancomycin clearance, indicating low serum concentrations. Therefore, upward dosing adjustments are necessary to improve treatment success. Younger age consistently emerged as a major contributor to ARC and vancomycin PK/PD alterations. This study summarizes the PK/PD alterations, current dosage recommendations and proposes preliminary recommendations on possible dosing approaches to decrease the risk of subtherapeutic exposure in this patient population.

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

In silico Evaluation of a Vancomycin Dosing Guideline Among Adults with Serious Infections

BACKGROUND

This study aimed to compare the achievement of pharmacokinetic-pharmacodynamic (PK-PD) exposure targets for vancomycin using a newly developed dosing guideline with product-information-based dosing in the treatment of adult patients with serious infections.

METHODS

In silico product-information- and guideline-based dosing simulations for vancomycin were performed across a range of doses and patient characteristics, including body weight, age, and renal function at 36-48 and 96 hours, using a pharmacokinetic model derived from a seriously ill patient population. The median simulated concentration and area under the 24-hour concentration-time curve (AUC 0-24 ) were used to measure predefined therapeutic, subtherapeutic, and toxicity PK-PD targets.

RESULTS

Ninety-six dosing simulations were performed. The pooled median trough concentration target with guideline-based dosing at 36 and 96 hours was achieved in 27.1% (13/48) and 8.3% (7/48) of simulations, respectively. The pooled median AUC 0-24 /minimum inhibitory concentration ratio with guideline-based dosing at 48 and 96 hours was attained in 39.6% (19/48) and 27.1% (13/48) of simulations, respectively. Guideline-based dosing simulations yielded improved trough target attainment compared with product-information-based dosing at 36 hours and significantly less subtherapeutic drug exposure. The toxicity threshold was exceeded in 52.1% (25/48) and 0% (0/48) for guideline- and product-information-information-based dosing, respectively ( P < 0.001).

CONCLUSIONS

A Critical care vancomycin dosing guideline appeared slightly more effective than standard dosing, as per product information, in achieving PK-PD exposure associated with an increased likelihood of effectiveness. In addition, this guideline significantly reduced the risk of subtherapeutic exposure. The risk of exceeding toxicity thresholds, however, was greater with the guideline, and further investigation is suggested to improve dosing accuracy and sensitivity.

Development of a Predictive Dosing Nomogram to Achieve PK/PD Targets of Amikacin Initial Dose in Critically Ill Patients: A Non-Parametric Approach

French guidelines recommend reaching an amikacin concentration of ≥8 × MIC 1 h after beginning infusion (C_1h), with MIC = 8 mg/L for probabilistic therapy. We aimed to elaborate a nomogram guiding clinicians in choosing the right first amikacin dose for ICU patients in septic shock. A total of 138 patients with 407 observations were prospectively recruited. A population pharmacokinetic model was built using a non-parametric, non-linear mixed-effects approach. The total body weight (TBW) influenced the central compartment volume, and the glomerular filtration rate (according to the CKD-EPI formula) influenced its clearance. A dosing nomogram was produced using Monte Carlo simulations of the amikacin amount needed to achieve a C_1h ≥ 8 × MIC. The dosing nomogram recommended amikacin doses from 1700 mg to 4200 mg and from 28 mg/kg to 49 mg/kg depending on the patient's TBW and renal clearance. However, a C_through ≤ 2.5 mg/L 24 h and 48 h after an optimal dose of amikacin was obtained with probabilities of 0.20 and 0.81, respectively. Doses ≥ 30 mg/kg are required to achieve a C_1h ≥ 8 × MIC with MIC = 8 mg/L. Targeting a MIC = 8 mg/L should depend on local ecology.

Critically Ill Patients with Renal Hyperfiltration: Optimizing Antibiotic Dose

Renal hyperfiltration (RHF) is a prevalent phenomenon in critically ill patients characterized by augmented renal clearance (ARC) and increased of elimination of renally eliminated medications. Multiple risk factors had been described and potential mechanisms may contribute to the occurrence of this condition. RHF and ARC are associated with the risk of suboptimal exposure to antibiotics increasing the risk of treatment failure and unfavorable patient outcomes. The current review discusses the available evidence related to the RHF phenomenon, including definition, epidemiology, risk factors, pathophysiology, pharmacokinetic variability, and considerations for optimizing the dosage of antibiotics in critically ill patients.

Risk factors associated with augmented renal clearance in a mixed intensive care unit population: a retrospective study

BACKGROUND

Augmented renal clearance is increasingly recognized in critically ill patients. This condition may lead to suboptimal dosing of renally excreted medications.

AIM

Our primary objective was to identify demographic and clinical factors associated with augmented renal clearance in a mixed critically ill population.

METHOD

This retrospective single center observational cohort study evaluated patients admitted in a mixed adult intensive care unit for augmented renal clearance, defined as a creatinine clearance of ≥ 130 ml/min/1.73m²_, through weekly 24-h urine collection. Variables associated with augmented renal clearance were identified using univariate analysis, then served as covariates in a backward stepwise logistic regression. Goodness-of-fit of the model was assessed and receiver operating characteristic curve was generated.

RESULTS

Augmented renal clearance was observed in 25.3% of the study cohort (n = 324). Age below 50 years (adjusted odds ratio 7.32; 95% CI 4.03-13.29, p < 0.001), lower serum creatinine at intensive care admission (adjusted odds ratio 0.97; 95% CI 0.96-0.99, p < 0.001) and trauma admission (adjusted odds ratio 2.26; 95% CI 1.12-4.54, p = 0.022) were identified as independent risk factors. Our model showed acceptable discrimination in predicting augmented renal clearance (Area under receiver operating characteristic curve (0.810; 95% CI 0.756-0.864, p < 0.001)).

CONCLUSION

We identified age below 50 years, lower serum creatinine upon intensive care admission and trauma as independent risk factors for augmented renal clearance, consistent with the literature suggesting that patients with low serum creatinine upon admission could have a higher risk of developing augmented renal clearance.

Drug Dosing in Critically Ill Adult Patients with Augmented Renal Clearance

Augmented renal clearance (ARC) is a phenomenon of enhanced renal function seen in critically ill patients. ARC alters the disposition of renally eliminated medications currently used in the intensive care unit, resulting in underdosing and potential therapy failure. Our review addresses the rising concern of inadequate dosing in patients with ARC by summarizing the currently available evidence. To our knowledge, this guide is the first to provide clinicians with dose recommendation insights for renally eliminated agents in adult critically ill patients with ARC. A comprehensive literature search using MEDLINE, Embase, Cochrane Library, CINAHL, Scopus, and ProQuest Dissertations and Theses Global was conducted until 3 November 2021. Screening and data extraction were conducted in two steps: title and abstract screening followed by full-text review. Full text review resulted in a total of 51 studies included in this review. The results demonstrated the need for higher-than-standard doses for meropenem, imipenem, and vancomycin and reduced dosing intervals for ceftriaxone in patients with ARC. The potential need for increased dosing frequency in patients with ARC was also found for both enoxaparin and levetiracetam. In conclusion, ARC has been shown to influence the probability of target attainment in several medications requiring dosing changes to mitigate the risk of therapeutic failure.

Validation of the Augmented Renal Clearance in Trauma Intensive Care scoring system for augmented renal clearance prediction in a trauma subgroup of a mixed ICU population

WHAT IS KNOWN AND OBJECTIVE

Augmented renal clearance is prevalent in trauma patients and leads to subtherapeutic levels of renally eliminated medications with potentially unfavourable clinical outcomes. The Augmented Renal Clearance of Trauma in Intensive Care (ARCTIC) score has been developed to predict augmented renal clearance in critically ill trauma patients. Our primary objective was to validate this score among the trauma subgroup of a mixed intensive care patient cohort.

METHODS

This single-centre, retrospective, observational cohort study assessed augmented renal clearance using a timed 24-h urine collection performed weekly. ARC was defined as a measured creatinine clearance of ≥130 ml/min/1.73 m² . ARCTIC score performance was evaluated through a receiver operator characteristic curves and analysis of sensitivities and specificities for the trauma subgroup, the medical/surgical subgroup and the pooled cohort.

RESULTS AND DISCUSSION

Augmented renal clearance was observed in 33.9% (n = 58) of trauma patients (n = 171) and 15.7% (n = 24) of medical/surgical patients (n = 153). Examination of different cutoffs for the ARCTIC score in our trauma population confirmed that the optimal cutoff score was ≥6. Comparison between ROC curves for ARCTIC score and for regression model based upon our data in trauma patients indicated validation of the score in this subgroup. Comparison of sensitivities and specificities for ARCTIC score between trauma (93.1% and 41.6%, respectively) and medical/surgical subjects (87.5% and 49.6%, respectively) showed no clinical nor statistical difference, suggesting validation for the medical/surgical subgroup as well.

WHAT IS NEW AND CONCLUSION

In our mixed ICU population, the ARCTIC score was validated in the trauma subgroup. We also found that the score performed well in the medical/surgical population. Future studies should assess the performance of the ARCTIC score prospectively.

Augmented Renal Clearance in Severe Infections-An Important Consideration in Vancomycin Dosing: A Narrative Review

Vancomycin is a hydrophilic antibiotic widely used in severe infections, including bacteremia and central nervous system (CNS) infections caused by Gram-positive bacteria such as methicillin-resistant Staphylococcus aureus (MRSA), coagulase-negative staphylococci and enterococci. Appropriate antimicrobial dosage regimens can help achieve the target exposure and improve clinical outcomes. However, vancomycin exposure in serum and cerebrospinal fluid (CSF) is challenging to predict due to rapidly changing pathophysiological processes and patient-specific factors. Vancomycin concentrations may be decreased for peripheral infections due to augmented renal clearance (ARC) and increased distribution caused by systemic inflammatory response syndrome (SIRS), increased capillary permeability, and aggressive fluid resuscitation. Additionally, few studies on vancomycin’s pharmacokinetics (PK) in CSF for CNS infections. The relationship between exposure and clinical response is unclear, challenging for adequate antimicrobial therapy. Accurate prediction of vancomycin pharmacokinetics/pharmacodynamics (PK/PD) in patients with high interindividual variation is critical to increase the likelihood of achieving therapeutic targets. In this review, we describe the interaction between ARC and vancomycin PK/PD, patient-specific factors that influence the achievement of target exposure, and recent advances in optimizing vancomycin dosing schedules for severe infective patients with ARC.

Predictive performance of reported vancomycin population pharmacokinetic model in patients with different renal function status, especially those with augmented renal clearance

BACKGROUND

There is a significant correlation between augmented renal clearance (ARC) and lower serum trough concentrations of vancomycin (VCM) during therapy. There is a need to evaluate the predictive performance of the population pharmacokinetic (PPK) model used for individual calculation of dosage regimens in ARC patients.

OBJECTIVE

Our study aimed to estimate the predictive performance differences of the reported VCM PPK software JPKD-vancomycin and SmartDose in patients with varying renal function status, especially those with ARC.

METHODS

Patients receiving VCM treatment from May 2014 to December 2019 were enrolled, and divided into the ARC group, the normal renal function (NRF) group, and the impaired renal function (IRF) group. VCM dosage, trough concentration, area under the curve (AUC) and pharmacokinetic parameters were compared among the three groups. The predictive performance of PPK software was expressed using absolute prediction error (APE), sensitivity, specificity, and regression coefficient (r²) of linear regression analysis between the measured VCM trough concentration and the predicted trough concentration.

RESULTS

A total of 388 patients were included: 86 patients in the ARC group, 241 patients in the NRF group, and 61 patients in the IRF group. The daily dose of the adjusted regimen in the ARC group was higher than in the NRF group, but the trough concentration was significantly lower than in the NRF group (2.8±0.6 g vs 1.9±0.6 g, p<0.001; 10.5±5.1 mg/L vs 12.9±6.8 mg/L, p=0.030). The percentage of trough concentrations lower than 10 mg/L was 84.9% in the ARC group. Compared with the APE of the initial dosage regimen, the APE of the adjusted regimen calculated by JPKD was lower in the ARC group (p=0.041) and the NRF group (p＜0.001). Specificity of JPKD and SmartDose in the ARC group was higher than in the NRF group (p<0.001; p<0.001). According to the linear regression analysis, the coefficients of determination (r²) were all >0.6 for the initial regimen and adjusted regimen of VCM in the ARC and NRF groups, and the r² of the adjusted regimen of JPKD was >0.8 in the ARC and NRF groups. In the IRF group, 31.1% of patients had a change in serum creatinine (Scr) level of >50%. The r² increased from 0.527 to 0.7347 in SmartDose and from 0.55 to 0.7802 in JPKD when using Scr at the sampling time. The ARC group showed a significant decrease in AUC (p<0.001) and an increase in clearance rate (p<0.001) when compared to the NRF group.

CONCLUSION

ARC was significantly associated with subtherapeutic serum VCM concentration. The pharmacokinetic parameters of VCM were diverse in patients with different renal function status. The PPK model JPKD and SmartDose had a good predictive performance for predicting VCM trough concentrations of the ARC and NRF patients, especially using JPKD for prediction of the adjusted regimen. The change of Scr is a main factor affecting the accuracy of software prediction.

Prevalence and Risk Factors of Augmented Renal Clearance: A Systematic Review and Meta-Analysis

Kidney function assessment in the critically ill overlooks the possibility for hyperfunctioning kidneys, known as augmented renal clearance (ARC), which could contribute to therapeutic failures in the intensive care unit (ICU). The aim of this research is to conduct a systematic review and meta-analysis of prevalence and risk factors of ARC in the critically ill. MEDLINE, Embase, Cochrane Library, CINAHL, Scopus, ProQuest Dissertations and Theses Global databases were searched on 27 October 2020. We included studies conducted in critically ill adults who reported the prevalence and/or risk factors of ARC. We evaluated study quality using the Joanna Briggs Institute appraisal tool. Case reports, reviews, editorials and commentaries were excluded. We generated a random-effects meta-analytic model using the inverse variance method and visualized the pooled estimates using forest plots. Seventy studies were included. The pooled prevalence (95% CI) was 39% (34.9–43.3). Prevalence for neuro, trauma, mixed and sepsis ICUs were 74 (55–87), 58 (48–67), 36 (31–41) and 33 (21–48), respectively. Age, male sex and trauma were associated with ARC with pooled OR (95% CI) of 0.95 (0.93–0.96), 2.36 (1.28–4.36), 2.60 (1.21–5.58), respectively. Limitations included variations in ARC definition, inclusion and exclusion criteria and studies design. In conclusion, ARC is prevalent in critically ill patients, especially those in the neurocritical care and trauma ICU population. Young age, male sex and trauma are risk factors for ARC in those with apparently normal renal function. Further research on optimal dosing of drugs in the setting of ARC is warranted. (Prospero registration: CRD42021246417).

Are Antibiotics Appropriately Dosed in Critically Ill Patients with Augmented Renal Clearance? A Narrative Review

AIMS

Augmented renal clearance (ARC), which is commonly defined as increased renal clearance above 130 ml/min/1.73 m², is a common phenomenon among critically ill patients. The increased elimination rate of drugs through the kidneys in patients with ARC can increase the risk of treatment failure due to the exposure to subtherapeutic serum concentrations of medications and affect the optimal management of infections, length of hospital stay, and outcomes. The main goal of this review article is to summarize the recommendations for appropriate dosing of antibiotics in patients with ARC.

METHODS

This article is a narrative review of the articles that evaluated different dosing regimens of antibiotics in patients with ARC. The keywords "Augmented Renal Clearance," "Critically ill patients," "Drug dosing," "Serum concentration," "Beta-lactams," "Meropenem," "Imipenem," "Glycopeptide," "Vancomycin," "Teicoplanin," "Linezolid," "Colistin," "Aminoglycosides," "Amikacin," "Gentamycin," "Fluoroquinolones," "Ciprofloxacin," and "Levofloxacin" were searched in Scopus, Medline, PubMed, and Google Scholar databases, and pediatric, nonhuman, and non-English studies were excluded.

RESULTS

PK properties of antibiotics including lipophilicity or hydrophilicity, protein binding, the volume of distribution, and elimination rate that affect drug concentration should be considered along with PD parameters for drug dosing in critically ill patients with ARC.

CONCLUSION

This review recommends a dosing protocol for some antibiotics to help the appropriate dosing of antibiotics in ARC and decrease the risk of subtherapeutic exposure that may be observed while receiving conventional dosing regimens in critically ill patients with ARC.

Augmented renal clearance of aminoglycosides using population-based pharmacokinetic modelling with Bayesian estimation in the paediatric ICU

OBJECTIVE

To evaluate augmented renal clearance (ARC) using aminoglycoside clearance (CLAMINO24h) derived from pharmacokinetic (PK) modelling.

METHODS

A retrospective study at two paediatric hospitals of patients who received tobramycin or gentamicin from 1999 to 2016 was conducted. Compartmental PK models were constructed using the Pmetrics package, and Bayesian posteriors were used to estimate CLAMINO24h. ARC was defined as a CLAMINO24h of ≥130 mL/min/1.73 m2. Risk factors for ARC were identified using multivariate logistic regression.

RESULTS

The final population model was fitted to 275 aminoglycoside serum concentrations. Overall clearance (L/h) was=CL0×(TBW/70)0.75×AGEH/(TMH + AGEH) + CL1 (0.5/SCr), where TBW is total body weight, H is the Hill coefficient, TM is a maturation term and SCr is serum creatinine. Median CLAMINO24h in those with versus without ARC was 157.36 and 93.42 mL/min/1.73 m2, respectively (P<0.001). ARC was identified in 19.5% of 118 patients. For patients with ARC, median baseline SCr was lower than for those without ARC (0.38 versus 0.41 mg/dL, P=0.073). Risk factors for ARC included sepsis [adjusted OR (aOR) 3.77, 95% CI 1.01-14.07, P=0.048], increasing age (aOR 1.11, 95% CI 1-1.23, P=0.04) and low log-transformed SCr (aOR 0.16, 95% CI 0.05-0.52, P=0.002). Median 24 h AUC (AUC24h) was significantly lower in patients with ARC at 45.27 versus 56.95 mg·h/L, P<0.01.

CONCLUSIONS

ARC was observed in one of every five patients. Sepsis, increasing age and low SCr were associated with ARC. Increased clearance was associated with an attenuation of AUC24h in this population. Future studies are needed to define optimal dosing in paediatric patients with ARC.

Prediction of vancomycin dose on high-dimensional data using machine learning techniques

OBJECTIVES

Despite therapeutic vancomycin is regularly monitored, its dose requirements vary considerably between individuals. Various innovative vancomycin dosing strategies have been developed for dose optimization; however, the utilization of individual factors and extensibility is insufficient. We aimed to develop an optimal dosing algorithm for vancomycin based on the high-dimensional data using the proposed variable engineering and machine-learning methods.

METHODS

This study proposed a variable engineering process that automatically generates second-order variable interactions. We performed an initial examination of independent variables and interactive variables using eXtreme Gradient Boosting. The vancomycin dose prediction model was established based on the derived variables.

RESULTS

Based on the evaluation of the model performance in the validation cohort, our algorithm accounted for 67.5% of variations in the vancomycin doses. Subgroup analysis showed better performance in patients with medium and high body weight (with the ideal predictive percentage of 72.7% and 73.7%), and low and medium levels of serum creatinine (with the ideal predictive percentage of 77.8% and 73.1%) than in other groups.

CONCLUSION

The new vancomycin dose prediction model is potentially useful for patients whose population profiles are similar to those of our patients and yielded desired reference of clinical indicators with specific breakpoints.

Augmented renal clearance. An unnoticed relevant event

Augmented renal clearance (ARC) is a phenomenon that can lead to a therapeutic failure of those drugs of renal clearance. The purpose of the study was to ascertain the prevalence of ARC in the critically ill patient, to study the glomerular filtration rate (GFR) throughout the follow-up and analyze the concordance between the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) estimation formula and measured GFR. Observational, prospective, multicenter study. ARC was defined as a creatinine clearance greater than 130 ml/min/1.73 m2. Eighteen hospitals were recruited. GFR measurements carried out twice weekly during a 2-month follow-up period. A total of 561 patients were included. ARC was found to have a non-negligible prevalence of 30%. More even, up to 10.7% already had ARC at intensive care unit (ICU) admission. No specific pattern of GFR was found during the follow-up. Patients in the ARC group were younger 56.5 (53.5-58.5) versus 66 (63.5-68.5) years than in the non-ARC group, p < 0.001. ICU mortality was lower in the ARC group, 6.9% versus 14.5%, p = 0.003. There was no concordance between the estimation of GFR by the CKD-EPI formula and GFR calculated from the 4-h urine. ARC is found in up to 30% of ICU patients, so renal removal drugs could be under dosed by up to 30%. And ARC is already detected on admission in 10%. It is a dynamic phenomenon without an established pattern that usually occurs in younger patients that can last for several weeks. And the CKD-EPI formula does not work to estimate the real creatinine clearance of these patients.

Area under the Curve-Based Dosing of Vancomycin in Critically Ill Patients Using 6-Hour Urine Creatinine Clearance Measurement

BACKGROUND

The area under the curve- (AUC-) guided vancomycin dosing is the best strategy for individualized therapy in critical illnesses. Since AUC can be calculated directly using drug clearance (CLvan), any parameter estimating CLvan will be able to achieve the goal of 24-hour AUC (AUC24 h). The present study was aimed to determine CLvan based on 6-hour urine creatinine clearance measurement in critically ill patients with normal renal function.

METHOD

23 adult critically ill patients with an estimated glomerular filtration rate (eGFR) ≥60 mL/min who received vancomycin infusion were enrolled in this pilot study. Vancomycin pharmacokinetic parameters were determined for each patient using serum concentration data and a one-compartment model provided by MONOLIX software using stochastic approximation expectation-maximization (SAEM) algorithm. Correlation of CLvan with the measured creatinine clearance in 6-hour urine collection (CL6 h) and estimated creatinine clearance by the Cockcroft-Gault formula (CLCG) was investigated.

RESULTS

Data analysis revealed that CL6 h had a stronger correlation with CLvan rather than CLCG (r = 0.823 vs. 0.594; p < 0.001 vs. 0.003). The relationship between CLvan and CL6 h was utilized to develop the following equation for estimating CLvan: CLvan (mL/min) = ─137.4 + CL6 h (mL/min) + 2.5 IBW (kg) (R 2  = 0.826, p < 0.001). Regarding the described model, the following equation can be used to calculate the empirical dose of vancomycin for achieving the therapeutic goals in critically ill patients without renal impairment: total daily dose of vancomycin (mg) = (─137.4CL6-h (mL/min) + 2.5 IBW (kg)) × 0.06 AUC24 h (mg.hr/L).

CONCLUSION

For AUC estimation, CLvan can be obtained by collecting urine in a 6-hour period with good approximation in critically ill patients with normal renal function.

Vancomycin Serum Concentration after 48 h of Administration: A 3-Years Survey in an Intensive Care Unit

The present study assessed the proportion of intensive care unit (ICU) patients who had a vancomycin serum concentration between 20 and 25 mg/L after 24–48 h of intravenous vancomycin administration. From 2016 to 2018, adult ICU patients with vancomycin continuous infusion (CI) for any indication were included. The primary outcome was the proportion of patients with a first-available vancomycin serum concentration between 20–25 mg/L at 24 h (D2) or 48 h (D3). Of 3894 admitted ICU patients, 179 were included. A median loading dose of 15.6 (interquartile range (IQR) = (12.5–20.8) mg/kg) was given in 151/179 patients (84%). The median daily doses of vancomycin infusion for D1 and D2 were 2000 [(IQR (1600–2000)) and 2000 (IQR (2000–2500)) mg/d], respectively. The median duration of treatment was 4 (2–7) days. At D2 or D3, the median value of first serum vancomycin concentration was 19.8 (IQR (16.0–25.1)) with serum vancomycin concentration between 20–25 mg/L reported in 43 patients (24%). Time spent in the ICU before vancomycin initiation was the only risk factor of non-therapeutic concentration at D2 or D3. Acute kidney injury occurred significantly more when vancomycin concentration was supra therapeutic at D2 or D3. At D28, 44 (26%) patients had died. These results emphasize the need of appropriate loading dose and regular monitoring to improve vancomycin efficacy and avoid renal toxicity.

A Meta-Analysis on the Performance of Cystatin C- versus Creatinine-based eGFR Equations in Predicting Vancomycin Clearance

BACKGROUND

The objective of this study was to compare the performance of cystatin C- and creatinine-based estimated glomerular filtration rate (eGFR) equations in predicting the clearance of vancomycin.

METHODS

MEDLINE and Embase databases were searched from inception up to September 2019 to identify all studies that compared the predictive performance of cystatin C- and/or creatinine-based eGFR in predicting the clearance of vancomycin. The prediction errors (PEs) (the value of eGFR equations minus vancomycin clearance) were quantified for each equation and were pooled using a random-effects model. The root mean squared errors were also quantified to provide a metric for imprecision.

RESULTS

This meta-analysis included evaluations of seven different cystatin C- and creatinine-based eGFR equations in total from 26 studies and 1,234 patients. The mean PE (MPE) for cystatin C-based eGFR was 4.378 mL min^-1 (95% confidence interval [CI], -29.425, 38.181), while the creatinine-based eGFR provided an MPE of 27.617 mL min^-1 (95% CI, 8.675, 46.560) in predicting clearance of vancomycin. This indicates the presence of unbiased results in vancomycin clearance prediction by the cystatin C-based eGFR equations. Meanwhile, creatinine-based eGFR equations demonstrated a statistically significant positive bias in vancomycin clearance prediction.

CONCLUSION

Cystatin C-based eGFR equations are better than creatinine-based eGFR equations in predicting the clearance of vancomycin. This suggests that utilising cystatin C-based eGFR equations could result in better accuracy and precision to predict vancomycin pharmacokinetic parameters.

What Are the Current Approaches to Optimising Antimicrobial Dosing in the Intensive Care Unit?

Antimicrobial dosing in the intensive care unit (ICU) can be problematic due to various challenges including unique physiological changes observed in critically ill patients and the presence of pathogens with reduced susceptibility. These challenges result in reduced likelihood of standard antimicrobial dosing regimens achieving target exposures associated with optimal patient outcomes. Therefore, the aim of this review is to explore the various methods for optimisation of antimicrobial dosing in ICU patients. Dosing nomograms developed from pharmacokinetic/statistical models and therapeutic drug monitoring are commonly used. However, recent advances in mathematical and statistical modelling have resulted in the development of novel dosing software that utilise Bayesian forecasting and/or artificial intelligence. These programs utilise therapeutic drug monitoring results to further personalise antimicrobial therapy based on each patient’s clinical characteristics. Studies quantifying the clinical and cost benefits associated with dosing software are required before widespread use as a point-of-care system can be justified.

Genetic Algorithms as a Tool for Dosing Guideline Optimization: Application to Intermittent Infusion Dosing for Vancomycin in Adults

This paper demonstrates the use of a genetic algorithm (GA) for the optimization of a dosing guideline. GAs are well‐suited to derive combinations of doses and dosing intervals that go into a dosing guideline when the number of possible combinations rule out the calculation of all possible outcomes. GAs also allow for different constraints to be imposed on the optimization process to safeguard the clinical feasibility of the dosing guideline. In this work, we demonstrate the use of a GA for the optimization of intermittent vancomycin administration in adult patients. Constraints were placed on the dose strengths, the length of the dosing intervals, and the maximum infusion rate. In addition, flexibility with respect to the timing of the first maintenance dose was included in the optimization process. The GA‐based optimal solution is compared with the Scottish Antimicrobial Prescribing Group vancomycin guideline.

Augmented renal clearance in pediatric intensive care: are we undertreating our sickest patients?

Many critically ill patients display a supraphysiological renal function with enhanced renal perfusion and glomerular hyperfiltration. This phenomenon described as augmented renal clearance (ARC) may result in enhanced drug elimination through renal excretion mechanisms. Augmented renal clearance seems to be triggered by systemic inflammation and therapeutic interventions in intensive care. There is growing evidence that ARC is not restricted to the adult intensive care population, but is also prevalent in critically ill children. Augmented renal clearance is often overlooked due to the lack of reliable methods to assess renal function in critically ill children. Standard equations to calculate glomerular filtration rate (GFR) are developed for patients who have a steady-state creatinine production and a stable renal function. Those formulas are not reliable in critically ill patients with acutely changing GFR and tend to underestimate true GFR in patients with ARC. Tools for real-time, continuous, and non-invasive measurement of fluctuating GFR are most needed to identify changes in kidney function during critical illness and therapeutic interventions. Such devices are currently being validated and hold a strong potential to become the standard of practice. In the meantime, urinary creatinine clearance is considered the most reliable method to detect ARC in critically ill patients. Augmented renal clearance is clearly associated with subtherapeutic antimicrobial concentrations and subsequent therapeutic failure. This warrants the need for adjusted dosing regimens to optimize pharmacokinetic and pharmacodynamic target attainment. This review aims to summarize current knowledge on ARC in critically ill children, to give insight into its possible pathophysiological mechanism, to evaluate screening methods for ARC in the pediatric intensive care population, and to illustrate the effect of ARC on drug exposure, therapeutic efficacy, and clinical outcome.

[Effect of augmented renal clearance on plasma concentration of vancomycin and treatment outcome in children with methicillin-resistant Staphylococcus aureus infection]

OBJECTIVE

To investigate the effect of augmented renal clearance (ARC) on plasma concentration of vancomycin, bacteriological outcome, and clinical outcome in children with methicillin-resistant Staphylococcus aureus (MRSA) infection treated by vancomycin.

METHODS

A retrospective analysis was performed for the clinical data of 60 critically ill children who were treated with vancomycin due to MRSA infection from January 2013 to July 2017 and underwent plasma concentration monitoring. According to estimated glomerular filtration rate, these children were divided into an ARC group with 19 children and a normal renal function group with 41 children. The two groups were compared in terms of the use of vancomycin, plasma concentration of vancomycin, and treatment outcome.

RESULTS

The children in the ARC group had an age of 1-12 years, and the ARC group had significantly higher body weight and body surface area than the normal renal function group (P<0.05). Compared with the normal renal function group, the ARC group had a significantly lower initial trough concentration of vancomycin and a significantly lower proportion of children who achieved the effective trough concentration of vancomycin (10-20 mg/L) (P<0.05). There were no significant differences in bacteriological outcome and clinical outcome between the two groups (P>0.05), but the ARC group had significantly longer length of stay in the pediatric intensive care unit (PICU) and length of hospital stay than the normal renal function group (P<0.05).

CONCLUSIONS

ARC can significantly reduce the trough concentration of vancomycin and prolong the length of PICU stay and the length of hospital stay in children with MRSA infection. Idividualized medication should be administered to children with ARC.

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.

Plasma and interstitial fluid population pharmacokinetics of vancomycin in critically ill patients with sepsis

Vancomycin is a commonly prescribed antibiotic in the intensive care unit. However, there are limited data describing its distribution into the interstitial fluid (ISF) of tissues. The aim of this study was to describe the plasma and tissue ISF population pharmacokinetics of vancomycin in critically ill patients with sepsis. Serial vancomycin blood and ISF samples were collected at pre-specified time intervals in critically ill patients with sepsis. ISF sampling occurred using a subcutaneously inserted microdialysis catheter. Bioanalysis was undertaken using a validated spectrometric assay method. Population pharmacokinetic analysis was performed using Pmetrics^®. Seven patients were recruited and pharmacokinetic data were available for six of them. The median (interquartile range) age, weight, Acute Physiology and Chronic Health Evaluation (APACHE) II score, Sequential Organ Failure Assessment (SOFA) score and measured creatinine clearance (CL_Cr) were 55 (44-67) years, 85 (81-102) kg, 20 (16-29), 5 (4-8) and 90 (83-98) mL/min, respectively. Vancomycin pharmacokinetics was best described by a three-compartment linear model. Measured CL_Cr (on vancomycin clearance) and weight (on volume of distribution of the central compartment) were the only patient covariates that improved the model fit. Coefficients of variation for the vancomycin rate constants into and out of the peripheral and tissue ISF compartments were also high, ranging from 47% to 134%. There is significant variability of vancomycin distribution into tissue ISF, which it was not possible to explain with patient characteristics.

Prospective evaluation of a continuous infusion vancomycin dosing nomogram in critically ill patients undergoing continuous venovenous haemofiltration

Objectives

The most optimal method of attaining therapeutic vancomycin concentrations during continuous venovenous haemofiltration (CVVH) remains unclear. Studies have shown continuous infusion vancomycin (CIV) achieves target concentrations more rapidly and consistently when compared with intermittent infusion. Positive correlations between CVVH intensity and vancomycin clearance (CLvanc) have been noted. This study is the first to evaluate a CIV regimen in patients undergoing CVVH that incorporates weight-based CVVH intensity (mL/kg/h) into the dosing nomogram.

Methods

This was a prospective, observational study of patients undergoing CVVH and receiving CIV based on the nomogram. The primary outcome was achievement of a therapeutic vancomycin concentration (15-25 mg/L) at 24 h. Secondary outcomes included the achievement of therapeutic concentrations at 48 and 72 h.

Results

The nomogram was analysed in 52 critically ill adults. Vancomycin concentrations were therapeutic in 43/52 patients (82.7%) at 24 h. Of the nine patients who were not therapeutic at 24 h, seven were supratherapeutic and two were subtherapeutic. The mean (SD) concentration was 20.1 (4.2)  mg/L at 24 h, 20.7 (3.7) mg/L at 48 h and 21.9 (3.5)  mg/L at 72 h. Patients with CVVH intensity >20 mL/kg/h experienced higher CLvanc at 24 h compared with patients with CVVH intensity <20 mL/kg/h (3.1 versus 2.6 L/h; P = 0.013).

Conclusions

By incorporating CVVH intensity into the CIV dosing nomogram, the majority of patients achieved therapeutic concentrations at 24 h and maintained them within range at 48 and 72 h. Additional studies are required to validate this nomogram before widespread implementation may be considered.

Reliability of serum creatinine-based formulae estimating renal function in non-critically ill surgery patients: Focus on augmented renal clearance

WHAT IS KNOWN AND OBJECTIVES

Formulae estimating glomerular filtration rate (GFR) are frequently used to guide drug dosing. The objectives of this prospective single-center study were to evaluate agreement between these equations and measured creatinine clearance (CrCl) in non-critically ill surgery patients with normal kidney function and augmented renal clearance (ARC, CrCl ≥ 130 mL/min/1.73 m²), to determine predictors for disagreement, define a GFR estimator cut-off value identifying ARC and determine the ARC prevalence and duration in non-critically ill surgical patients.

METHODS

Hospitalized adult non-critically ill abdominal and trauma surgery patients were eligible for inclusion. Measured CrCl based on an 8-hour urinary collection (CrCl_8h ) was used as the primary method for determining kidney function. Agreement between equations and measured CrCl_8h was assessed in terms of precision, defined as a bias within ±10 mL/min/1.73 m². Predictors for disagreement were identified for the most precise estimator using an ordinal logistic regression model with negative bias, agreement and positive bias as outcome variables. A receiver operating characteristic (ROC) analysis was performed to identify an estimator cut-off predicting ARC, which was subsequently applied for the daily proportion of patients displaying ARC and ARC duration.

RESULTS AND DISCUSSION

During the study period (14/11/2013 - 13/05/2014), in 232 adult non-critically ill abdominal and trauma surgery patients, all estimators tend to underestimate CrCl_8h (mean bias ranging from 17 to 22 mL/min/1.73 m²), especially in patients displaying ARC (mean bias ranging from 44 to 56 mL/min/1.73 m²). eGFR_CKD-EPI performed the best. Younger age and low ASA score independently predicted underestimation of CrCl_8h . Three different eGFR_CKD-EPI cut-offs with decreasing sensitivity and increasing specificity (84, 95 and 112 mL/min/1.73 m²) identified, respectively, 65%, 44% and 14% patients displaying ARC. The median ARC duration was 4, 4 and 3 days, respectively.

WHAT IS NEW AND CONCLUSION

In surgical patients, eGFR frequently underestimates measured CrCl, especially in young patients with low ASA score. eGFR cut-offs predicting ARC were identified.

Assessment of acute kidney injury in neurologically and traumatically injured intensive care patients receiving large vancomycin doses

Background:

Previous reports note that in a mixed patient population, vancomycin doses >4 g/day are associated with increased rates of acute kidney injury (AKI).

Objective:

The objective of the study is to determine if vancomycin regimens >4 g/day are associated with a higher incidence of AKI in neurocritical care unit (NCCU) and trauma/burn Intensive Care Unit (TBICU) patients.

Materials and Methods:

This single-centered, retrospective study enrolled adult patients initiated on vancomycin in the NCCU and TBICU at an academic medical center during 2016. Based on maximum steady-state dose exposure, patients were separated into two groups: ≤4 g/day and >4 g/day. The primary outcome of incidence of AKI was defined by the AKI Network criteria.

Results:

A total of 284 patients were screened for eligibility; 165 patients met inclusion criteria, 98 patients received ≤4 g/day and 67 patients received >4 g/day. The >4 g/day group had a lower mean age (32.6±11.1 vs. 47.8±16.2, P < 0.001), included more male patients (81% vs. 60%, P = 0.008), were more often treated for a central nervous system infection (31% vs. 11%, P = 0.001), had, on average, more concomitant use of nephrotoxic drugs (2.2±1.2 vs. 1.8±0.9, P = 0.02) and had a higher exposure to contrast (94% vs. 79%, P < 0.001). The primary outcome of AKI occurred in 14 patients receiving ≤4 g/day and five patients receiving >4 g/day which was not statistically significant (14% vs. 7%, P = 0.22).

Conclusions:

Our results indicate that administering >4 g/day of vancomycin to achieve therapeutic vancomycin troughs does not appear to lead to an increased incidence of AKI in a mixed NCCU and TBICU population.

Influence of Mechanical Ventilation on the Pharmacokinetics of Vancomycin Administered by Continuous Infusion in Critically Ill Patients

Pathophysiological changes involved in drug disposition in critically ill patients should be considered in order to optimize the dosing of vancomycin administered by continuous infusion, and certain strategies must be applied to reach therapeutic targets on the first day of treatment. The aim of this study was to develop a population pharmacokinetic model of vancomycin to determine clinical covariates, including mechanical ventilation, that influence the wide variability of this antimicrobial. Plasma vancomycin concentrations from 54 critically ill patients were analyzed simultaneously by a population pharmacokinetic approach. A nomogram for dosing recommendations was developed and was internally evaluated through stochastic simulations. The plasma vancomycin concentration-versus-time data were best described by a one-compartment open model with exponential interindividual variability associated with vancomycin clearance and the volume of distribution. Residual error followed a homoscedastic trend. Creatinine clearance and body weight significantly dropped the objective function value, showing their influence on vancomycin clearance and the volume of distribution, respectively. Characterization based on the presence of mechanical ventilation demonstrated a 20% decrease in vancomycin clearance. External validation (n = 18) was performed to evaluate the predictive ability of the model; median bias and precision values were 0.7 mg/liter (95% confidence interval [CI], -0.4, 1.7) and 5.9 mg/liter (95% CI, 5.4, 6.4), respectively. A population pharmacokinetic model was developed for the administration of vancomycin by continuous infusion to critically ill patients, demonstrating the influence of creatinine clearance and mechanical ventilation on vancomycin clearance, as well as the implications for targeting dosing rates to reach the therapeutic range (20 to 30 mg/liter).

Augmented Renal Clearance in Critical Illness: An Important Consideration in Drug Dosing

Augmented renal clearance (ARC) is a manifestation of enhanced renal function seen in critically ill patients. The use of regular unadjusted doses of renally eliminated drugs in patients with ARC might lead to therapy failure. The purpose of this scoping review was to provide and up-to-date summary of the available evidence pertaining to the phenomenon of ARC. A literature search of databases of available evidence in humans, with no language restriction, was conducted. Databases searched were MEDLINE (1946 to April 2017), EMBASE (1974 to April 2017) and the Cochrane Library (1999 to April 2017). A total of 57 records were included in the present review: 39 observational studies (25 prospective, 14 retrospective), 6 case reports/series and 12 conference abstracts. ARC has been reported to range from 14-80%. ARC is currently defined as an increased creatinine clearance of greater than 130 mL/min/1.73 m² best measured by 8-24 h urine collection. Patients exhibiting ARC tend to be younger (<50 years old), of male gender, had a recent history of trauma, and had lower critical illness severity scores. Numerous studies have reported antimicrobials treatment failures when using standard dosing regimens in patients with ARC. In conclusion, ARC is an important phenomenon that might have significant impact on outcome in critically ill patients. Identifying patients at risk, using higher doses of renally eliminated drugs or use of non-renally eliminated alternatives might need to be considered in ICU patients with ARC. More research is needed to solidify dosing recommendations of various drugs in patients with ARC.

Augmented Renal Clearance Using Population-Based Pharmacokinetic Modeling in Critically Ill Pediatric Patients

OBJECTIVES

The objectives of this study were to: 1) evaluate the prevalence of augmented renal clearance in critically ill pediatric patients using vancomycin clearance; 2) derive the pharmacokinetic model that best describes vancomycin clearance in critically ill pediatric patients; and 3) correlate vancomycin clearance with creatinine clearance estimated by modified Schwartz or Cockcroft-Gault.

DESIGN

Retrospective, two-center, cohort study from 2003 to 2016.

SETTING

Clinical drug monitoring services in the PICUs at two tertiary care, teaching hospitals.

PATIENTS

Children from 1 to 21 years old.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Identify patients with augmented renal clearance (vancomycin clearance ≥ 130 mL/min/1.73 m used as definition of augmented renal clearance). Derive final population-based pharmacokinetic model and estimate individual patient pharmacokinetic parameters. Compare estimated glomerular filtration rate (modified Schwartz or Cockcroft-Gault depending on age < or ≥ 17 yr) with vancomycin clearance. Augmented renal clearance was identified in 12% of 250 total subjects. The final population-based pharmacokinetic model for vancomycin clearance (L/hr) was 0.118 × weight (e). Median vancomycin clearance in those with versus without augmented renal clearance were 141.3 and 91.7 mL/min/1.73 m, respectively (p < 0.001). By classification and regression tree analysis, patients who were more than 7.9 years old were significantly more likely to experience augmented renal clearance (17% vs 4.6% in those ≤ 7.9 yr old; p = 0.002). In patients with augmented renal clearance, 79% of 29 had vancomycin trough concentrations less than 10 µg/mL, compared with 52% of 221 in those without augmented renal clearance (p < 0.001). Vancomycin clearance was weakly correlated to the glomerular filtration rate estimated by the modified Schwartz or Cockcroft-Gault method (Spearman R = 0.083).

CONCLUSIONS

Augmented renal clearance was identified in one of 10 critically ill pediatric patients using vancomycin clearance, with an increase of approximately 50 mL/min/1.73 m in those with augmented renal clearance. As augmented renal clearance results in subtherapeutic antibiotic concentrations, optimal dosing is essential in those exhibiting augmented renal clearance.

Assessment of Appropriateness of an Initial Dosing Regimen of Vancomycin and Development of a New Dosing Nomogram

Vancomycin is a glycopeptide antibiotic used to treat Gram-positive infections including methicillin-resistant Staphylococcus aureus (MRSA). The objectives of this study were to evaluate the appropriateness of the initial dosing regimen of vancomycin, identify factors to be considered in regimen selection and develop a new dosing nomogram. Therapeutic drug monitoring (TDM) data of vancomycin obtained from Seoul National University Hospital from 2011 to 2013 were included in this analysis. The vancomycin trough concentrations at steady-state were estimated using Abbott's PKS software program and then categorized into three levels: subtherapeutic, therapeutic and toxic. The newly developed nomograms were evaluated by analysing the percentage of patients with target vancomycin trough concentration using the data of 2,570 patients of the first TDM cases. Therapeutic level was achieved only in approximately one-fifth of the cases, while 56.0% and 23.8% of the TDMs were considered subtherapeutic and toxic, respectively. As body-weight and creatinine clearance (CrCL) increased, the proportion of patients with a subtherapeutic level increased. Using the newly developed nomogram increased the proportion of patients who achieved therapeutic levels from 23.1% to 45.0% or 13.8% to 36.2% (target, 10-15 and 15-20 mg/L, respectively). These results suggest that the vancomycin concentrations fail to reach the therapeutic level or exceed the safe upper margin of the therapeutic level depending on age, body-weight and CrCL. Considering these factors, the new nomograms provide a strategy to achieve target concentrations of vancomycin more rapidly than existing regimens.

Currently used dosage regimens of vancomycin fail to achieve therapeutic levels in approximately 40% of intensive care unit patients

Objective:

This study aimed to assess whether currently used dosages of vancomycin for treatment of serious gram-positive bacterial infections in intensive care unit patients provided initial therapeutic vancomycin trough levels and to examine possible factors associated with the presence of adequate initial vancomycin trough levels in these patients.

Methods:

A prospective descriptive study with convenience sampling was performed. Nursing note and medical record data were collected from September 2013 to July 2014 for patients who met inclusion criteria. Eighty-three patients were included. Initial vancomycin trough levels were obtained immediately before vancomycin fourth dose. Acute kidney injury was defined as an increase of at least 0.3mg/dL in serum creatinine within 48 hours.

Results:

Considering vancomycin trough levels recommended for serious gram-positive infection treatment (15 - 20µg/mL), patients were categorized as presenting with low, adequate, and high vancomycin trough levels (35 [42.2%], 18 [21.7%], and 30 [36.1%] patients, respectively). Acute kidney injury patients had significantly greater vancomycin trough levels (p = 0.0055, with significance for a trend, p = 0.0023).

Conclusion:

Surprisingly, more than 40% of the patients did not reach an effective initial vancomycin trough level. Studies on pharmacokinetic and dosage regimens of vancomycin in intensive care unit patients are necessary to circumvent this high proportion of failures to obtain adequate initial vancomycin trough levels. Vancomycin use without trough serum level monitoring in critically ill patients should be discouraged.

Application of vancomycin in patients with varying renal function, especially those with augmented renal clearance

CONTEXT

Augmented renal clearance (ARC) refers to enhanced renal elimination of circulating solute, and has attracted wide attention in recent years.

OBJECTIVE

This study evaluates the effects of ARC on serum vancomycin concentration in patients administered vancomycin.

MATERIALS AND METHODS

This was a retrospective study in patients receiving vancomycin treatment at a dose of 1000 mg in every 12 h and undergoing serum monitoring admitted over a 2-year period (May 2013 to May 2015), in order to estimate the influence of ARC on serum vancomycin concentration. In this study, statistical comparisons were made on the results from patients grouped according to creatinine clearance (CL_cr).

RESULTS

One hundred forty-eight patients were enrolled in our study. The results showed that ARC patients were significantly younger, with a significantly lower S_cr and higher GFR. The CL_cr and steady-state trough concentrations of serum vancomycin exhibited a logarithmic correlation (Rs = -0.699, R²=0.488, p < 0.01) in the patients included in our study. The trough vancomycin concentrations of 62.9% patients in high CL_cr group were under 10 μg/mL.

DISCUSSION AND CONCLUSION

Since ARC was significantly associated with subtherapeutic serum vancomycin concentration, it was necessary to devise adjusted dosage regimens for these patients based on their CL_cr.

Comparison of the pharmacokinetics of vancomycin in neurosurgical and non-neurosurgical patients

Although vancomycin concentrations in neurosurgical patients tend to be lower following standard dosing compared with other patient populations, factors influencing vancomycin pharmacokinetics in neurosurgical patients are poorly understood. In this study, pharmacokinetic (PK) parameters in neurosurgical and non-neurosurgical patients were compared. Furthermore, factors influencing vancomycin PK alterations, including those known to augment renal clearance, were determined. Routine therapeutic drug monitoring data from neurosurgical and non-neurosurgical patients were retrospectively collected. Vancomycin PK parameters were estimated using non-linear mixed-effects modelling (NONMEM v.7.2.0); analyses were performed for the entire population and for neurosurgical patients only. Furthermore, the final models performed a bootstrap, visual predictive check and external validation. A total of 359 serum vancomycin concentration data variables from 132 patients were used to execute the PK modelling. Neurosurgical patient factor, the early phase of treatment, underlying liver cirrhosis, co-administration of a nephrotoxic drug and estimated creatinine clearance influenced vancomycin clearance (CL). However, other factors known to augment renal clearance did not affect vancomycin pharmacokinetics. Vancomycin CL was significantly higher in neurosurgical patients than in controls (0.104 ± 0.036 L/h/kg vs. 0.073 ± 0.042 L/h/kg; P <0.01). Augmented vancomycin CL should be considered when determining vancomycin dosages in neurosurgical patients.

Vancomycin dosing nomograms targeting high serum trough levels in different populations: pros and cons

PURPOSE

Utilization of higher doses of vancomycin to achieve the trough concentrations of 15-20 mg/L for complicated infections has been recommended by the Infectious Diseases Society of America clinical practice guideline in recent years. Concerning this recommendation, several nomograms have been constructed targeting this optimal trough level range in different populations of patients. In this review, we have collected available nomograms targeting high trough serum levels of vancomycin, particularly comparing their advantages and limitations.

METHOD

The data were collected by searching Scopus, PubMed, Google scholar, Medline, and Cochrane database systematic reviews. The key words used as search terms were "vancomycin", "high trough level", "dosing nomogram", "dosing strategy", "neonates", "critically ill", "pediatrics", and "hemodialysis". We have included 17 related human studies published up to the date of this publication.

RESULTS & CONCLUSION

Most of the available nomograms have determined the doses according to body weight and renal function. Their initial predicting success rate were 44-76 % for non-critically ill patients, 42-84 % for critically ill patients, 54 % for one nomogram specially designed for hemodialysis patients, and 71 % for the only nomogram developed for neonates. Based on validation studies, in most of cases, using a vancomycin dosing nomogram significantly improved and accelerated achievement of target trough concentrations. However, it should be noted that there are limited data about patients' clinical and microbiological outcomes and they are only validated in narrow groups of patients. Thus, their widespread application could not be encouraged for all patients before performing adequately powered, prospective randomized studies.