Augmented creatinine clearance in traumatic brain injury

Validation of Two Scoring Tools to Predict Risk of Augmented Renal Clearance in Trauma Patients

INTRODUCTION

Augmented renal clearance (ARC) is prevalent in trauma populations. Identification is underrecognized by calculated creatinine clearance or estimated glomerular filtration rate equations. Predictive scores may assist with ARC identification. The goal of this study was to evaluate validity of the ARCTIC score and ARC Predictor to predict ARC in critically ill trauma patients.

METHODS

This single center, retrospective study was performed at an academic level 1 trauma center. Critically ill adult trauma patients undergoing 24-h urine-collection were included. Patients with serum creatinine >1.5 mg/dL, kidney replacement therapy, suspected rhabdomyolysis, chronic kidney disease, or inaccurate urine collection were excluded. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) for ARCTIC Score and ARC Predictor were calculated. Receiver operating characteristic curves were created for ARCTIC score and ARC Predictor models.

RESULTS

One-hundred and twenty-two patients with ARC and 78 patients without ARC were included. The ARCTIC score sensitivity, specificity, PPV, and NPV were 89%, 54%, 75%, and 75%, respectively. The ARC Predictor demonstrated sensitivity, specificity, PPV, and NPV of 77%, 88%, 91%, and 71%, respectively. Regression analyses revealed both ARCTIC score ≥6 and ARC Predictor threshold >0.5 as significant risk factors for ARC in presence of traumatic brain injury, obesity, injury severity score, and negative nitrogen balance (ARCTIC ≥6: odds ratio 8.59 [95% confidence interval 3.90-18.92], P < 0.001; ARC Predictor >0.5: odds ratio 20.07 [95% confidence interval 8.53-47.19], P < 0.001).

CONCLUSIONS

These findings corroborate validity of two pragmatic prediction tools to identify patients at high risk of ARC. Future studies evaluating correlations between ARCTIC score, ARC Predictor, and clinical outcomes are warranted.

A descriptive pharmacokinetic/pharmacodynamic analysis of ceftazidime-avibactam in a case series of critically ill patients with augmented renal clearance

To describe the pharmacokinetics/pharmacodynamics (PK/PD) of a 2 h infusion of ceftazidime-avibactam (CAZ-AVI) in critically ill patients with augmented renal clearance (ARC). A retrospective review of all critically ill patients with ARC who were treated with CAZ-AVI between August 2020 and May 2023 was conducted. Patients whose 12-h creatinine clearance prior to CAZ-AVI treatment and steady-state concentration (Css) of CAZ-AVI were both monitored were enrolled. The free fraction (fCss) of CAZ-AVI was calculated from Css. The joint PK/PD targets of CAZ-AVI were considered optimal when a Css/minimum inhibitory concentration (MIC) ratio for CAZ ≥4 (equivalent to 100% fT > 4 MIC) and a Css/CT ratio of AVI >1 (equivalent to 100% fT > CT 4.0 mg/L) were reached simultaneously, quasioptimal when only one of the two targets was reached, and suboptimal when neither target was reached. The relationship between PK/PD goal achievement, microbial eradication and the clinical efficacy of CAZ-AVI was evaluated. Four patients were included. Only one patient achieved optimal joint PK/PD targets, while the other three reached suboptimal targets. The patient with optimal PK/PD targets achieved microbiological eradication, while the other three patients did not, but all four patients achieved good clinical efficacy. Standard dosages may not enable most critically ill patients with ARC to reach the optimal joint PK/PD targets of CAZ-AVI. Optimal drug dose adjustment of CAZ-AVI in ARC patients requires dynamic drug concentration monitoring.

Enhanced renal clearance impacts levetiracetam concentrations in patients with traumatic brain injury with and without augmented renal clearance

BACKGROUND

The purpose of this study was to examine the impact of ARC on levetiracetam concentrations during the first week following acute TBI. The hypothesis was levetiracetam concentrations are significantly lower in TBI patients with augmented renal clearance (ARC) compared to those with normal renal clearance.

METHODS

This is a prospective cohort pharmacokinetic study of adults with moderate to severe TBI treated with levetiracetam during the first week after injury. Serial blood collections were performed daily for analysis of levetiracetam, cystatin C, and 12-hr creatinine clearance (CrCl) determinations. Patients were divided into two cohorts: with (CrCl ≥130 ml/min/1.73 m2) and without ARC.

RESULTS

Twenty-two patients with moderate to severe TBI were included. The population consisted primarily of young male patients with severe TBI (mean age 40 years old, 68% male, median admission GCS 4). Each received levetiracetam 1000 mg IV every 12 h for the study period. ARC was present in 77.3% of patients, with significantly lower levetiracetam concentrations in ARC patients and below the conservative therapeutic range (< 6mcg/mL) for all study days. In patients without ARC, the serum concentrations were also below the expected range on all but two study days (Days 4 and 5). Four of the 22 (18.2%) patients exhibited seizure activity during the study period (two of these patients exhibited ARC). Cystatin C concentrations were significantly lower in patients with ARC, though the mean for all patients was within the typical normal range.

CONCLUSIONS

ARC has a high prevalence in patients with moderate to severe TBI. Levetiracetam concentrations after standard dosing were low in all TBI patients, but significantly lower in patients with ARC. This study highlights the need to consider personalized drug dosing in TBI patients irrespective of the presence of ARC.

CLINICAL TRIAL REGISTRATION

This study was registered at cliicaltrials.gov (NCT02437838) Registered on 08/05/2015, https://clinicaltrials.gov/ct2/show/NCT02437838 .

Creatinine Clearance in Acute Brain Injury: A Comparison of Methods

BACKGROUND

Currently, the measurement of glomerular filtration rate is very complex and costly, so its daily evaluation is performed using endogenous markers, of which creatinine is the most frequently used. It allows the estimation of glomerular filtration rate by means of its clearance or by formulas based on its serum and urine concentration. Augmented renal clearance (ARC) is frequent among critically ill patients and is defined as creatinine clearance (CrCl) > 130 ml/min/1.73 m2. The aim of this study was to compare measured CrCl (MCC) and estimated CrCl obtained with the Cockcroft-Gault formula (CG), the Modification of Diet in Renal Disease Study equation (MDRD), and the Chronic Kidney Disease Epidemiology Collaboration formula (CKD-EPI) in patients with severe traumatic brain injury and nontraumatic subarachnoid hemorrhage. The second aim was to assess the incidence of ARC in this population of neurocritical patients.

METHODS

This was a prospective, observational, single center study from a cohort of 74 patients admitted to the neurocritical intensive care unit due to traumatic brain injury or subarachnoid hemorrhage. Serum creatinine (at 7 a.m.) and a 6-h urine collection were analyzed, and CrCl was measured and estimated by using CG, MDRD, and CKD-EPI. The intraclass correlation coefficient (ICC) was evaluated for each pair, and Bland-Altman plots were used to assess clinical significance.

RESULTS

Among 74 patients, the median age was 53 (interquartile range [IQR] 36-65), and the median Glasgow Coma Scale score at admission was 6. The median MCC at admission was 176 (IQR 135-214). The medians of CG, MDRD and CKD-EPI were, respectively, 129 ml/min/1.73 m2 (IQR 95-176), 158 (IQR 115-202), and 116 (97-132). An ICC was applied to evaluate the correlation between MCC and estimated methods and showed a weak correlation between MCC and estimated CrCl obtained with the three different methods. The strongest ICC statistical correlation was found between MCC and MDRD, and the weakest correlation was found between MCC and CKD-EPI. Bland-Altman plots showed that differences between each pair were not clinically acceptable. ARC was present in 78% of measurements, using MCC. A weak correlation was observed between MCC and calculated CrCl. CG, MDRD, and CKD-EPI overestimated MCC when MCC ≤ 130 ml/min/1.73 m2 and underestimated it when MCC > 130 ml/min/1.73 m2.

CONCLUSIONS

In this population, there was a weak statistical correlation between measured and estimated methods. In patients with ARC, formulas underestimated MCC. MCC should probably be the preferred methodology for renal function assessment in the clinical setting to better adjust drug dosage and guarantee drug effectiveness.

Onset timing and duration of augmented renal clearance in a mixed intensive care unit

BACKGROUND

Augmented renal clearance (ARC) is associated with lower blood plasma concentrations of renally excreted drugs; however, its time course is unknown. The current study aimed to determine the onset timing/duration of ARC, its risk factors, and its association with clinical outcomes by continuous monitoring of urinary creatinine clearance (CrCl) in critically ill patients.

METHODS

Data were retrospectively obtained from the medical records of 2592 critically ill patients admitted to the intensive care unit (ICU) from January 2019 to June 2022 at a tertiary emergency hospital. Among these, patients with continuously measured urinary CrCl were selected and observed over time. We evaluated the onset timing and duration of ARC by plotting Kaplan-Meier curves. Furthermore, by multivariate analyses, factors associated with the onset and persistence of ARC were analyzed, and the association between the ARC time course and clinical outcomes was evaluated.

RESULTS

The prevalence of ARC was 33.4% (245/734). ARC onset was within 3 days of admission in approximately half of the cases, and within 1 week in most of the other cases. In contrast, the persistence duration of ARC varied widely (median, 5 days), and lasted for more than a month in some cases. Multivariate analysis identified younger age, male sex, lower serum creatinine at admission, admission with central nervous system disease, no medical history, use of mechanically assisted ventilation, and vasopressor use as onset factors for ARC. Furthermore, factors associated with ARC persistence such as younger age and higher urinary CrCl on ARC day 1 were detected. The onset of ARC was significantly associated with reduced mortality, but persistent of ARC was significantly associated with fewer ICU-free days.

CONCLUSIONS

Despite the early onset of ARC, its duration varied widely and ARC persisted longer in younger patients with higher urinary CrCl. Since the duration of ARC was associated with fewer ICU-free days, it may be necessary to consider a long-term increased-dose regimen of renally excreted drugs beginning early in patients who are predicted to have a persistent ARC.

Augmented Renal Clearance in Patients with Acute Ischemic Stroke: A Prospective Observational Study

BACKGROUND

Augmented renal clearance (ARC) is a phenomenon that has been demonstrated in many subsets of critically ill patients and is characterized by a creatinine clearance (CrCl) > 130 mL/min. Prior research has examined ARC prevalence in the presence of sepsis, traumatic brain injury, subarachnoid hemorrhage, and intracranial hemorrhage. However, to our knowledge, no studies have examined whether this phenomenon occurs in patients suffering from an acute ischemic stroke (AIS). The objective of this study was to evaluate whether patients experiencing an AIS exhibit ARC, identify potential contributing factors, and examine the precision of current renal clearance estimation methods in patients with AIS experiencing ARC.

METHODS

This was a single-center prospective observational study conducted in adult patients admitted to a neurocritical intensive care unit (ICU) at a community hospital. Once consent was gained, patients with an admitting diagnosis of an AIS underwent a 24-h urine collection to assess measured CrCl. The primary end point assessed for ARC, defined as a measured CrCl > 130 mL/min. The secondary end point evaluated length of stay in the neurocritical ICU.

RESULTS

Twenty-eight patients met enrollment criteria, and data was analyzed for 20 patients. ARC was present in 35% of enrolled patients. Mathematical estimations of renal function were inadequate in detecting ARC manifestation. Patients experiencing ARC were associated with nonsignificantly shorter ICU length of stay.

CONCLUSIONS

ARC appears to manifest in patients with AIS inconsistently. Patients experiencing ARC were associated with nonsignificantly shorter ICU length of stay.

Evaluation of vancomycin pharmacokinetics in patients with augmented renal clearances: A randomized clinical trial

Purpose: Vancomycin is a narrow therapeutic window glycopeptide antibiotic that acts against Gram-positive bacteria. As it is renally eliminated, therapeutic drug monitoring is recommended for vancomycin, especially in case of kidney function alteration. Augmented renal clearance (ARC), defined as a creatinine clearance of more than 130 ml/min, is a risk factor for sub-therapeutic concentrations of vancomycin. This study aimed to evaluate the vancomycin pharmacokinetics following the administration of two different regimens in ARC patients.

Methods: A randomized clinical trial (IRCT20180802040665N1) was conducted on patients in need of vancomycin therapy. Eight hours of urine was collected and 56 patients divided into two groups with creatinine clearance of more than 130 ml/min were included in the study. The first group received 15 mg/kg of vancomycin every 12 h and the second group 15 mg/kg every 8 h. After four doses, the peak and trough concentrations were measured from two blood samples. The primary outcome was the percentage of patients who attainted AUC more than 400. The occurrence of acute kidney injury also was evaluated after seven days.

Results: The mean age of patients in the every 12 h and every 8 h groups was 44.04 ± 16.55 and 42.86 ± 11.83 years, respectively. While neurosurgical issues were the most common causes of hospitalization, central nervous infections were the most common indications for vancomycin initiation. Urinary creatinine clearance was 166.94 ± 41.32 ml/min in the every 12 h group and 171.78 ± 48.56 ml/min in the every 8 h group. 46.42% of patients in the every 12 h group and 82.14% of patients in the every 8 h group attained AUC/MIC of more than 400 mg × hr/L. None of the patients in the every 12 h group reached more than 15 mcg/ml concentration. At the 7-day follow-up, 10.7% patients in the BD group and 28.6% patients in the TDS group developed acute kidney injury (p = 0.089).

Conclusion: Administration of vancomycin at a dose of 15 mg/kg every 8 h is associated with higher pharmacokinetic attainment in ARC patients. The occurrence of acute kidney injury also was not significantly higher in this therapeutic regimen. AUC/MIC monitoring is necessary in this population.

The Prescription of Oral Mucosal Mesenchymal Stem Cells post-Traumatic Brain Injury Improved the Kidney and Heart Inflammation and Oxidative Stress

Background

In the last years, mesenchymal stem cells (MSCs) have been considered as a useful strategy to treat many diseases such as traumatic brain injury (TBI). The production of inflammatory agents by TBI elicits an inflammatory response directed to other systems of body, such as the heart and the kidneys. In this study, the efficacy of oral mucosal mesenchymal stem cells (OMSCs) prescription after TBI in inflammation and oxidative stress of the heart and kidneys was evaluated.

Methods

Twenty-four male rats were located in groups as follows: sham, TBI, vehicle (Veh), and stem cell (SC). OMSCs were injected intravenously 1 and 24 hours after TBI. Inflammatory, oxidative stress, and histopathological outcomes of the heart and kidney tissues were investigated 48 hours after TBI.

Results

TBI caused an increase in the level of interleukin-1β (IL-1β), interleukin-6 (IL-6), malondialdehyde (MDA), and carbonyl protein (PC) of the heart and kidney compared to the sham group. Superoxide dismutase (SOD), total antioxidant capacity (TAC), catalase (CAT), and interleukin-10 (IL-10) of the heart and kidney decreased after TBI. The use of OMSCs after TBI reduced the changes of these factors in both the heart and the kidney.

Conclusion

Application of OMSCs after TBI can decrease inflammation and oxidative stress of the heart and kidney tissues leading to the reduction of damage. Therefore, this method can be evaluated in the TBI patients in future studies.

Population pharmacokinetic model of vancomycin in postoperative neurosurgical patients

Objective: Vancomycin is commonly used in postoperative neurosurgical patients for empirical anti-infective treatment due to the low success rate of bacterial culture in cerebrospinal fluid (about 20%) and the high mortality of intracranial infection. At conventional doses, the rate of target achievement for vancomycin trough concentration is low and the pharmacokinetics of vancomycin varies greatly in these patients, which often leads to treatment failure. The objective of this study was to establish a population pharmacokinetic (PPK) model of vancomycin in postoperative neurosurgical patients for precision medicine.

Method: A total of 895 vancomycin plasma concentrations from 560 patients (497 postoperative neurosurgical patients) were retrospectively collected. The model was analyzed by nonlinear mixed effects modeling method. One-compartment model and mixed residual model was employed. The influence of covariates on model parameters was tested by forward addition and backward elimination. Goodness-of-fit, bootstrap and visual predictive check were used for model evaluation. Monte Carlo simulations were employed for dosing strategies with AUC₂₄ targets 400–600.

Result: Estimated glomerular filtration rate (eGFR), body weight (BW) and mannitol had significant influence on vancomycin clearance (CL). eGFR(mL/min)=144×(Scr/a)b×0.993age, for female, a = 0.7, Scr ≤ 0.7 mg/dl, b = −0.329, Scr > 0.7 mg/dl, b = −1.209; for male, a = 0.9, Scr ≤ 0.9 mg/dl, b = −0.411, Scr > 0.9 mg/dl, b = −1.210. Vancomycin clearance was accelerated when co-medicated with mannitol and increased with eGFR and BW. In the final model, the population typical value is 7.98 L/h for CL and 60.2 L for apparent distribution volume, CL (L/h)=7.98×(eGFR/115.2)0.8×(BW/70)0.3×eA, where A = 0.13 when co-medicated with mannitol, otherwise A = 0. The model is stable and effective, with good predictability.

Conclusion: In postoperative neurosurgical patients, a higher dose of vancomycin may be required due to the augmented renal function and the commonly used mannitol, especially in those with high body weight. Our vancomycin PPK model could be used for individualized treatment in postoperative neurosurgical 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.

Optimization of levetiracetam dosing regimen in critically ill patients with augmented renal clearance: a Monte Carlo simulation study

Background

Levetiracetam pharmacokinetics is extensively altered in critically ill patients with augmented renal clearance (ARC). Consequently, the dosage regimens commonly used in clinical practice may not be sufficient to achieve target plasma concentrations. The aim of this study is to propose alternative dosage regimens able to achieve target concentrations in this population. Furthermore, the feasibility of the proposed dosing regimens will be discussed from a clinical point of view.

Methods

Different dosage regimens for levetiracetam were evaluated in critically ill patients with ARC. Monte Carlo simulations were conducted with extended or continuous infusions and/or high drug doses using a previously developed population pharmacokinetic model. To assess the clinical feasibility of the proposed dosages, we carried out a literature search to evaluate the information on toxicity and efficacy of continuous administration or high doses, as well as the post-dilution stability of levetiracetam.

Results

According to the simulations, target concentrations in patients with CrCl of 160 or 200 mL/min can be achieved with the 3000 mg daily dose by prolonging the infusion time of levetiracetam. For patients with CrCl of 240 mL/min, it would be necessary to administer doses higher than the maximum recommended. Available evidence suggests that levetiracetam administration in continuous infusion or at higher doses than those approved seems to be safe. It would be desirable to re-examinate the current recommendations about drug stability and to achieve a consensus in this issue.

Conclusions

Conventional dosage regimens of levetiracetam (500–1500 mg twice daily in a short infusion) do not allow obtaining drug plasma concentrations among the defined target in critically ill patients with ARC. Therefore, new dosing guidelines with specific recommendations for patients in this subpopulation are needed. This study proposes new dosages for levetiracetam, including extended (4 or 6 h) infusions, continuous infusions or the administration of doses higher than the recommended in the summary of product characteristics (> 3000 mg). These new dosage recommendations take into account biopharmaceutical and pharmacokinetic aspects and meet feasibility criteria, which allow them to be transferred to the clinical environment with safety and efficacy. Nevertheless, further clinical studies are needed to confirm these results.

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.

Pediatric severe traumatic brain injury mortality prediction determined with machine learning-based modeling

INTRODUCTION

Severe traumatic brain injury (sTBI) is a leading cause of mortality in children. As clinical prognostication is important in guiding optimal care and decision making, our goal was to create a highly discriminative sTBI outcome prediction model for mortality.

METHODS

Machine learning and advanced analytics were applied to the patient admission variables obtained from a comprehensive pediatric sTBI database. Demographic and clinical data, head CT imaging abnormalities and blood biochemical data from 196 children and adolescents admitted to a tertiary pediatric intensive care unit (PICU) with sTBI were integrated using feature ranking by way of a forest of randomized decision trees, and a model was generated from a reduced number of admission variables with maximal ability to discriminate outcome.

RESULTS

In total, 36 admission variables were analyzed using feature ranking with variable weighting to determine their predictive importance for mortality following sTBI. Reduction analysis utilizing Borata feature selection resulted in a parsimonious six-variable model with a mortality classification accuracy of 82%. The final admission variables that predicted mortality were: partial thromboplastin time (22%); motor Glasgow Coma Scale (21%); serum glucose (16%); fixed pupil(s) (16%); platelet count (13%) and creatinine (12%). Using only these six admission variables, a t-distributed stochastic nearest neighbor embedding algorithm plot demonstrated visual separation of sTBI patients that lived or died, with high mortality predictive ability of this model on the validation dataset (AUC = 0.90) which was confirmed with a conventional area-under-the-curve statistical approach on the total dataset (AUC = 0.91; P < 0.001).

CONCLUSIONS

Machine learning-based modeling identified the most clinically important prognostic factors resulting in a pragmatic, high performing prognostic tool for pediatric sTBI with excellent discriminative ability to predict mortality risk with 82% classification accuracy (AUC = 0.90). After external multicenter validation, our prognostic model might help to guide treatment decisions, aggressiveness of therapy and prepare family members and caregivers for timely end-of-life discussions and decision making.

LEVEL OF EVIDENCE

III; Prognostic.

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).

Cerebrospinal Fluid Concentrations of Meropenem and Vancomycin in Ventriculitis Patients Obtained by TDM-Guided Continuous Infusion

Effective antibiotic therapy of cerebral infections such as meningitis or ventriculitis is hindered by low penetration into the cerebrospinal fluid (CSF). Because continuous infusion of meropenem and vancomycin and routine therapeutic drug monitoring (TDM) have been proposed to optimize antimicrobial exposure in ventriculitis patients, an individualized dosing strategy was implemented in our department. We present a retrospective analysis of meropenem and vancomycin concentrations in serum and CSF in the first nine ventriculitis patients treated with continuous infusion and TDM-guided dose optimization aiming at 20–30 mg/L. Median initial dosing was 8.8 g/24 h meropenem and 4.25 g/24 h vancomycin, respectively, resulting in median serum concentrations of 21.3 mg/L for meropenem and 24.5 mg/L for vancomycin and CSF concentrations of 3.4 mg/L for meropenem and 1.7 mg/L for vancomycin. Median CSF penetration was 15% for meropenem and 7% for vancomycin. With initial dosing, all but one patient achieved CSF concentrations above 1 mg/L. Dose adjustment according to TDM ensured sufficient CSF concentrations in all patients within 48 h of treatment. Given the limited penetration, continuous infusion of meropenem and vancomycin based on renal function and TDM-guided dose optimization appears a reasonable approach to attain sufficient CSF concentrations in ventriculitis patients.

Acute Kidney Injury at the Neurocritical Care Unit

Neurocritical care has advanced substantially in recent decades, allowing doctors to treat patients with more complicated conditions who require a multidisciplinary approach to achieve better clinical outcomes. In neurocritical patients, nonneurological complications such as acute kidney injury (AKI) are independent predictors of worse clinical outcomes. Different research groups have reported an AKI incidence of 11.6% and an incidence of stage 3 AKI, according to the Kidney Disease: Improving Global Outcomes, that requires dialysis of 3% to 12% in neurocritical patients. These patients tend to be younger, have less comorbidity, and have a different risk profile, given the diagnostic and therapeutic procedures they undergo. Trauma-induced AKI, sepsis, sympathetic overstimulation, tubular epitheliopathy, hyperchloremia, use of nephrotoxic drugs, and renal hypoperfusion are some of the causes of AKI in neurocritical patients. AKI is the result of a sum of events, although the mechanisms underlying many of them remain uncertain; however, two important causes that merit mention are direct alteration of the physiological brain-kidney connection and exposure to injury as a result of the specific medical management and well-established therapies that neurocritical patients are subjected to. This review will focus on AKI in neurocritical care patients. Specifically, it will discuss its epidemiology, causes, associated mechanisms, and relationship to the brain-kidney axis. Additionally, the use and risks of extracorporeal therapies in this group of patients will be reviewed.

Evaluation of the Accuracy of Standard Renal Function Equations in Critically Ill Patients with Subarachnoid Hemorrhage

BACKGROUND

Obtaining an accurate estimation of renal function is germane to optimizing care in critically ill patients. However, there is no consensus on the most accurate renal function assessment to utilize in this patient population, particularly in aneurysmal subarachnoid hemorrhage (aSAH) patients. Thus, the objective of this observational study was to determine the comparability of renal function equations to body surface area (BSA)-adjusted 8-h creatinine clearance (CrCl) in aSAH patients.

METHODS

A PubMed search investigated the applicability of various renal function equations in critically ill patient populations. A subset of these equations was compared to BSA-adjusted 8-h CrCl from a previous study with aSAH patients with no evidence of renal dysfunction (admission serum creatinine < 1.5 mg/dL) and no history of chronic kidney disease. Area-under-the-curve (AUC) calculations were completed using serial laboratory measurements to validate preliminary findings.

RESULTS

A total of 14 renal function equations were identified with seven carried forward for further analysis based upon a priori criteria. Seven equations were excluded for various reasons, including lack of available clinical data, redundancy with other equations, and dissimilar patient populations to this study. When directly compared to the BSA-adjusted 8-h CrCl, only the Cockcroft-Gault and BSA-adjusted Cockcroft-Gault equations were not statistically significantly different (P = 0.0886 and P = 0.4805, respectively); all other equations were statistically significantly different (P < 0.0001). Additionally, only 52% and 44% of patients had average values within 20% of the BSA-adjusted 8-h CrCl using the Cockcroft-Gault and BSA-adjusted Cockcroft-Gault equations, respectively. Finally, the AUC calculations corroborated the preliminary findings with similar results in statistical testing for the Cockcroft-Gault and BSA-adjusted Cockcroft-Gault (P = 0.6300 and P = 0.1513, respectively).

CONCLUSIONS

The Cockcroft-Gault equation may be the best renal function equation to assess in critically ill patients diagnosed with aSAH. However, accuracy and consistency in assessing renal function when compared to the BSA-adjusted 8-h CrCl were lacking. Thus, this study suggests the BSA-adjusted 8-h CrCl may be the most appropriate assessment of renal function in patients with aSAH.

Multipotential and systemic effects of traumatic brain injury

Traumatic brain injury (TBI) is one of the leading causes of disability and mortality of people at all ages. Biochemical, cellular and physiological events that occur during primary injury lead to a delayed and long-term secondary damage that can last from hours to years. Secondary brain injury causes tissue damage in the central nervous system and a subsequent strong and rapid inflammatory response that may lead to persistent inflammation. However, this inflammatory response is not limited to the brain. Inflammatory mediators are transferred from damaged brain tissue to the bloodstream and produce a systemic inflammatory response in peripheral organs, including the cardiovascular, pulmonary, gastrointestinal, renal and endocrine systems. Complications of TBI are associated with its multiple and systemic effects that should be considered in the treatment of TBI patients. Therefore, in this review, an attempt was made to examine the systemic effects of TBI in detail. It is hoped that this review will identify the mechanisms of injury and complications of TBI, and open a window for promising treatment in TBI complications.

The Performance of Equations That Estimate Glomerular Filtration Rate against Measured Urinary Creatinine Clearance in Critically Ill Patients

The performance of glomerular filtration rate- (GFR-) estimating equations was studied against creatinine clearance measured by 24-hour urine collection (CrCl_24h-urine) in critically ill patients. Methods. In this substudy of the PermiT trial (https://clinicaltrials.gov/ct2/show/ISRCTN68144998), patients from King Abdulaziz Medical City-Riyadh who had CrCl_24h-urine were included. We estimated GFR using Cockroft–Gault (CG), modification of diet in renal disease study (MDRD), chronic kidney disease epidemiology collaboration (CKD-EPI), and Jelliffe equations. For the CG equation, we entered the actual weight in one calculation (CG_actual-wt), and if BMI ≥30 kg/m², we entered the ideal body weight (CG_ideal-wt) and the adjusted body weight (CG_adjusted-wt) in two calculations. We calculated the MDRD equation based on 4 (MDRD-4) and 6 variables (MDRD-6). The performance of these equations was assessed by different ways including Spearman correlation, bias (difference between estimated GFR and CrCl_24h-urine), precision (standard deviation of bias), and Bland–Altman plot analysis. Results. The cohort consisted of 237 patients (age 45 ± 20 years, males 75%, mechanically ventilated 99% with serum creatinine 101 ± 94 µmol/L and CrCl_24h-urine 108 ± 69 ml/min/1.73 m²). The correlations between the different equations and CrCl_24h-urine were modest (r: 0.62 to 0.79; p < 0.0001). Bias was statistically significant for CG_actual-wt (21 ml/min), CG_adjusted-wt (12 ml/min), and MDRD-6 (-10 ml/min) equations. Precision ranged from 46 to 54 ml/min. The sensitivity of equations to correctly classify CrCl_24h-urine 30–59.9 ml/min/1.73 m² was 17.2% for CG_actual-wt, 30.0% for CG_ideal-wt, 31.0% for CG_adjusted-wt, 31.0% for MDRD-4, 39.1% for MDRD-6, 13.8% for CKD-EPI, and 34.5% for Jelliffe equation. Conclusions. Commonly used GFR-estimating equations had limited ability to properly estimate CrCl_24h-urine and to correctly classify GFR into clinically relevant ranges that usually determine dosing of medications.

Augmented Renal Clearance Following Traumatic Injury in Critically Ill Patients Requiring Nutrition Therapy

The intent of this study was to ascertain the prevalence of augmented renal clearance (ARC) in patients with traumatic injuries who require nutrition therapy and identify factors associated with ARC. Adult patients admitted to the trauma intensive care unit from January 2015 to September 2016 who received enteral or parenteral nutrition therapy and had a 24 h urine collection within 4 to 14 days after injury were retrospectively evaluated. Patients with a serum creatinine concentration > 1.5 mg/dL, required dialysis, or had an incomplete urine collection were excluded. ARC was defined as a measured creatinine clearance > 149 mL/min/1.73 m². Two hundred and three patients were evaluated. One hundred and two (50%) exhibited ARC. A greater proportion of patients with ARC were male (86% vs. 67%; p = 0.004), had traumatic brain injury (33% vs. 9%; p = 0.001), a higher injury severity score (30 ± 11 vs. 26 ± 12; p = 0.015), were younger (36 ± 15 vs. 54 ± 17 years; p = 0.001), had a lower serum creatinine concentration (0.7 ± 2 vs. 0.9 ± 0.2 mg/dL; p = 0.001) and were more catabolic (nitrogen balance of −10.8 ± 13.0 vs. −6.2 ± 9.2 g/d; p = 0.004). The multivariate analysis revealed African American race and protein intake were also associated with ARC. Half of critically ill patients with traumatic injuries experience ARC. Patients with multiple risk factors for ARC should be closely evaluated for dosing of renally-eliminated electrolytes, nutrients, and medications.

Population Pharmacokinetics of Levetiracetam in Patients with Traumatic Brain Injury and Subarachnoid Hemorrhage Exhibiting Augmented Renal Clearance

BACKGROUND AND OBJECTIVE

Patients with severe trauma exhibit augmented renal clearance, which can alter the dosing requirement of renally eliminated drugs. This study aimed to develop a population pharmacokinetic model for levetiracetam in patients with severe traumatic brain injury and aneurysmal subarachnoid hemorrhage, and use it to describe optimal dosing regimens.

METHODS

This was a prospective open-label observational study. Critically ill adult patients with severe traumatic brain injury or aneurysmal subarachnoid hemorrhage without renal dysfunction and receiving levetiracetam were eligible. Serial levetiracetam plasma concentrations were analyzed to develop a population pharmacokinetic model and perform dosing simulations.

RESULTS

A two-compartment model best described the concentration-time data from 30 patients. The mean ± standard deviation parameter estimates were bioavailability (F) of 0.8 ± 0.2, absorption rate constant of 2.4 ± 2 h^-1, clearance 2.5 ± 1.1 L/h, central volume of distribution 8.9 ± 3.0 L/h, and transfer rate constraints of 1.8 ± 1.1 h^-1 from central to peripheral compartments and 0.7 ± 0.3 h^-1 from peripheral to central compartments. For the simulated intermittent dosing regimens, on average, the median trough concentration reduced by 50% for every 40-mL/min/1.73 m² increase in urinary creatinine clearance. Simulated doses of at least 6 g/day were required for some levels of augmented renal clearance.

CONCLUSIONS

Patients with severe traumatic brain injury and aneurysmal subarachnoid hemorrhage with augmented renal clearance are at risk of not achieving target levetiracetam plasma concentrations. We suggest dose titration guided by measured creatinine clearance, and/or, therapeutic drug monitoring if available, to minimize the risk of seizures.

Distant Organ Damage in Acute Brain Injury

Acute brain injuries pose a great threat to global health, having significant impact on mortality and disability. Patients with acute brain injury may develop distant organ failure, even if no systemic diseases or infection is present. The severity of non-neurologic organs' dysfunction depends on the extremity of the insult to the brain. In this comprehensive review we sought to describe the organ-related consequences of acute brain injuries. The clinician should always be aware of the interplay between central nervous system and non-neurological organs, that is constantly present. Cerebral injury is not only a brain disease, but also affects the body as whole, and thus requires holistic therapeutical approach.

Population pharmacokinetics of vancomycin in patients with external ventricular drain-associated ventriculitis

BACKGROUND

To determine the distribution of vancomycin into the cerebrospinal fluid (CSF) in patients with external ventricular drain (EVD)-associated ventriculitis, the pharmacokinetics of vancomycin were evaluated and covariate relationships explored.

METHODS

For the population pharmacokinetic model patients were recruited in a neurocritical care unit at the University Hospital of Muenster in the period between January 2014 and June 2015. All patients had a clinical evidence of EVD-associated ventriculitis. Population pharmacokinetic analysis of vancomycin was performed using NONMEM.

RESULTS

A total of 184 blood and 133 CSF samples were collected from 29 patients. The final population pharmacokinetic model is a three-compartment model with linear elimination. Creatinine clearance (Cl_Cr ) and CSF-lactate were detected as significant covariates, showing that the total vancomycin plasma clearance (Cl) depends on Cl_Cr and furthermore the clearance (Cl_dif ) between the central and CSF compartment correlates with CSF lactate concentration. Based on the final model, the following values were estimated by NONMEM: Cl = 5.15 L/h, Q (intercompartmental clearance) = 3.31 L/h, Cl_dif  = 0.0031 L/h, V_central  = 42.1 L, V_CSF  = 0.32 L and the value of V_peripheral was fixed to 86.2 L. With the developed pharmacokinetic model, area under the curve (AUC) values as well as CSF trough levels were simulated.

CONCLUSION

Based on our analysis, the dosing of vancomycin should be referred to the degree of inflammation (derived from the CSF lactate concentration) and renal function (derived from Cl_Cr ).

Predictors of Augmented Renal Clearance in a Heterogeneous ICU Population as Defined by Creatinine and Cystatin C

INTRODUCTION

The incidence of augmented renal clearance (ARC) in the intensive care unit (ICU) is highly variable, and identification of these patients remains challenging.

OBJECTIVE

The objective of this study was to define the incidence of ARC in a cohort of critically ill adults, using serum Cr and cystatin C, and to identify factors associated with its development.

METHODS

This is a retrospective cohort study of critically ill patients without stage 2 or 3 acute kidney injury with both serum Cr and cystatin C available. The incidence of ARC was defined as a Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI)Cr-cystatin C-estimated glomerular filtration rate >130 mL/min. A multivariable logistic regression model using a penalized Lasso method was fit to identify independent predictors of ARC.

RESULTS

Among the 368 patients included in the study, indication for ICU admission was nonoperative in 55% of patients, and 9% of patients were admitted for major trauma. The overall incidence of ARC was low at 4.1%. In a multivariable logistic regression model, Charlson comorbidity index, major trauma, intracerebral hemorrhage, age, and Sequential Organ Failure Assessment score were found to predict ARC.

CONCLUSION

The incidence of ARC in this study was low, but prediction models identified several factors for early identification of patients with risk factors for or who develop ARC, particularly in a cohort with a low baseline risk of ARC. These factors could be used to help identify patients who may develop ARC.

Increased Vancomycin Clearance in Patients with Solid Malignancies

Vancomycin (VAN) is an anti-microbial agent used to treat a number of bacterial infections, which has a high incidence of nephrotoxicity. We examined the pharmacokinetics of VAN retrospectively based on trough concentrations at large scale and identified pharmacokinetic differences between Japanese patients having solid malignancy and non-malignancy patients. Data were analyzed from 162 solid malignancy patients and 261 non-malignancy patients, including the patient's background, VAN dose, and pharmacokinetics of VAN. We failed to detect differences in values for VAN clearance or shorter elimination half-lives between these two groups. In contrast, multiple regression analysis under adjusting for confounding factors by propensity score, showed that VAN clearance significantly increased in relation to solid malignancies in each stage. We conclude that VAN clearance in solid malignancy patients is increased and that the blood concentration of VAN becomes lower than expected. These results suggest that early monitoring of VAN levels in solid malignancy patients might be essential for maintaining desired effects without side-effects.

VISSA-PLS-DA-Based Metabolomics Reveals a Multitargeted Mechanism of Traditional Chinese Medicine for Traumatic Brain Injury

Metabolomics is an emerging tool to uncover the complex pathogenesis of disease, as well as the multitargets of traditional Chinese medicines, with chemometric analysis being a key step. However, conventional algorithms are not suitable for directly analyzing data at all times. The variable iterative space shrinkage approach-partial least squares-discriminant analysis, a novel algorithm for data mining, was first explored to screen metabolic varieties to reveal the multitargets of Xuefu Zhuyu decoction (XFZY) against traumatic brain injury (TBI) by the 7th day. Rat plasma from Sham, Vehicle, and XFZY groups was used for gas chromatography/mass spectrometry-based metabolomics. This method showed an improved discrimination ability (area under the curve = 93.64%). Threonine, trans-4-hydroxyproline, and creatinine were identified as the direct metabolic targets of XFZY against TBI. Five metabolic pathways affected by XFZY in TBI rats, were enriched using Metabolic Pathway Analysis web tool (i.e., phenylalanine, tyrosine, and tryptophan biosynthesis; phenylalanine metabolism; galactose metabolism; alanine, aspartate, and glutamate metabolism; and tryptophan metabolism). In conclusion, metabolomics coupled with variable iterative space shrinkage approach-partial least squares-discriminant analysis model may be a valuable tool for identifying the holistic molecular mechanisms involved in the effects of traditional Chinese medicine, such as XFZY.

Enhanced Renal Clearance in Patients With Hemorrhagic Stroke

OBJECTIVES

To evaluate enhanced renal clearance over time in patients with aneurysmal subarachnoid hemorrhage or intracerebral hemorrhage via measured creatinine clearance and to compare measured creatinine clearance to creatinine clearance calculated by the Cockcroft-Gault equation and estimated glomerular filtration rate calculated by the Modification of Diet in Renal Diseases equation.

DESIGN

Prospective, observational study.

SETTING

Neurosciences ICU in a tertiary care academic medical center.

PATIENTS

Study participants had an admission diagnosis of aneurysmal subarachnoid hemorrhage or intracerebral hemorrhage, an expected neurosciences ICU length of stay greater than 48 hours, no evidence of renal dysfunction (admission serum creatinine < 1.5 mg/dL), and no history of chronic kidney disease.

INTERVENTIONS

Eight-hour urine collections to measure creatinine clearance were collected daily as the primary method of measuring renal function. Creatinine clearance was also calculated using the Cockcroft-Gault equation and estimated glomerular filtration rate was calculated using the Modification of Diet in Renal Disease equation. Enhanced renal clearance was defined as a measured creatinine clearance greater than the calculated creatinine clearance via Cockcroft-Gault and estimated glomerular filtration rate via Modification of Diet in Renal Disease. Augmented renal clearance was defined by a measured creatinine clearance greater than or equal to 130 mL/min/1.73 m. Relevant demographic, clinical, and outcome data were recorded.

MEASUREMENTS AND MAIN RESULTS

Fifty aneurysmal subarachnoid hemorrhage patients and 30 intracerebral hemorrhage patients were enrolled, contributing 590 individual measurements. Patients with aneurysmal subarachnoid hemorrhage had a higher mean measured creatinine clearance compared with the mean calculated creatinine clearance based on the Cockcroft-Gault equation (147.9 ± 50.2 vs 109.1 ± 32.7 mL/min/1.73 m; p < 0.0001) and higher mean measured creatinine clearance compared with the mean calculated estimated glomerular filtration rate based on the Modification of Diet in Renal Disease equation (147.9 ± 50.2 vs 126.0 ± 41.9 mL/min/1.73 m; p = 0.04). Ninety-four percent of participants with aneurysmal subarachnoid hemorrhage experienced augmented renal clearance on at least 1 day. In patients with intracerebral hemorrhage, there was a higher mean measured creatinine clearance over the study period compared with the mean calculated creatinine clearance (119.5 ± 57.2 vs 77.8 ± 27.6 mL/min/1.73 m; p < 0.0001) and higher mean measured creatinine clearance compared with the mean calculated estimated glomerular filtration rate based on the Modification of Diet in Renal Disease equation (119.5 ± 57.2 vs 93.0.0 ± 32.8 mL/min/1.73 m; p = 0.02). Fifty percent of participants with intracerebral hemorrhage experienced augmented renal clearance on at least 1 day.

CONCLUSIONS

A substantial group of patients with aneurysmal subarachnoid hemorrhage or intracerebral hemorrhage experienced enhanced renal clearance, which may be otherwise unknown to clinicians. Enhanced renal clearance may lead to increased renal solute elimination over what is expected, resulting in subtherapeutic renally eliminated drug concentrations. This may result in underexposure to critical medications, leading to treatment failure and other medical complications.

Alterations in Peripheral Organs following Combined Hypoxemia and Hemorrhagic Shock in a Rat Model of Penetrating Ballistic-Like Brain Injury

Polytrauma, with combined traumatic brain injury (TBI) and systemic damage are common among military and civilians. However, the pathophysiology of peripheral organs following polytrauma is poorly understood. Using a rat model of TBI combined with hypoxemia and hemorrhagic shock, we studied the status of peripheral redox systems, liver glycogen content, creatinine clearance, and systemic inflammation. Male Sprague-Dawley rats were subjected to hypoxemia and hemorrhagic shock insults (HH), penetrating ballistic-like brain injury (PBBI) alone, or PBBI followed by hypoxemia and hemorrhagic shock (PHH). Sham rats received craniotomy only. Biofluids and liver, kidney, and heart tissues were collected at 1 day, 2 days, 7 days, 14 days, and 28 days post-injury (DPI). Creatinine levels were measured in both serum and urine. Glutathione levels, glycogen content, and superoxide dismutase (SOD) and cytochrome C oxidase enzyme activities were quantified in the peripheral organs. Acute inflammation marker serum amyloid A-1 (SAA-1) level was quantified using western blot analysis. Urine to serum creatinine ratio in PHH group was significantly elevated on 7-28 DPI. Polytrauma induced a delayed disruption of the hepatic GSH/GSSG ratio, which resolved within 2 weeks post-injury. A modest decrease in kidney SOD activity was observed at 2 weeks after polytrauma. However, neither PBBI alone nor polytrauma changed the mitochondrial cytochrome C oxidase activity. Hepatic glycogen levels were reduced acutely following polytrauma. Acute inflammation marker SAA-1 showed a significant increase at early time-points following both systemic and brain injury. Overall, our findings demonstrate temporal cytological/tissue level damage to the peripheral organs due to combined PBBI and systemic injury.

Autonomic dysfunction following traumatic brain injury: translational insights

Although there is a substantial amount of research on the neurological consequences of traumatic brain injury (TBI), there is a knowledge gap regarding the relationship between TBI and the pathophysiology of organ system dysfunction and autonomic dysregulation. In particular, the mechanisms or incidences of renal or cardiac complications after TBI are mostly unknown. Autonomic dysfunction following TBI exacerbates secondary injury and may contribute to nonneurologial complications that prolong hospital length of stay. Gaining insights into the mechanisms of autonomic dysfunction can guide advancements in monitoring and treatment paradigms to improve acute survival and long-term prognosis of TBI patients. In this paper, the authors will review the literature on autonomic dysfunction after TBI and possible mechanisms of paroxysmal sympathetic hyperactivity. Specifically, they will discuss the link among the brain, heart, and kidneys and review data to direct future research on and interventions for TBI-induced autonomic dysfunction.

Augmented Renal Clearance of Vancomycin in Hematologic Malignancy Patients

The pharmacokinetics of vancomycin (VAN) was retrospectively examined based on trough concentrations at large scale to identify pharmacokinetic differences between Japanese hematologic malignancy and non-malignancy patients. Data from 261 hematologic malignancy patients and 261 non-malignancy patients, including the patient's background, VAN dose, and pharmacokinetics of VAN estimated by an empirical Bayesian method, were collected and analyzed. Our results showed significantly higher values for VAN clearance and shorter elimination half-lives in patients with hematologic malignancies than non-malignancy patients. In addition, multiple regression analysis under adjusting for confounding factors by propensity score, showed that VAN clearance significantly increased in relation to hematologic malignancies. In conclusion, since in hematologic cancer patients VAN clearance is increased, the blood concentration of VAN becomes lower than expected and this may contribute to the survival of resistant bacteria when VAN is administered at low doses. These results suggest that early monitoring of VAN levels in hematologic cancer patients might be recommended to maintain desired effects without side-effects.

Subtherapeutic piperacillin concentrations in neurocritical patients

PURPOSE

Increased renal elimination is the leading cause for subtherapeutic concentrations of renally cleared antibiotics and it has been hypothesized that brain damaged patients in the intensive care unit (ICU) are particularly at risk. The objective of this study is to determine the prevalence of subtherapeutic piperacillin concentrations in neurocritical patients and to investigate if having a neurocritical diagnosis is a risk factor for this.

MATERIALS AND METHODS

Single center retrospective analysis of a prospective cohort study of adult ICU patients receiving continuous infusion piperacillin/tazobactam. Patients were categorized as either having a neurocritical diagnosis or not. An unbound piperacillin concentration > 4× the epidemiologic cut-off value (ECOFF) of Pseudomonas aeruginosa was selected as the PKPD target of choice. Multivariable logistic regression was performed to identify risk factors for subtherapeutic piperacillin concentrations.

RESULTS

356 patients had a measured creatinine clearance (mCrCl) and matched piperacillin concentration, 52 of which had a neurocritical diagnosis. Subtherapeutic piperacillin concentrations were reported significantly more frequent in neurocritical patients. In multivariate analysis, the only risk factor identified for subtherapeutic piperacillin concentration was an increasing mCrCl.

CONCLUSION

Subtherapeutic piperacillin concentrations are common in neurocritical patients yet having a neurocritical admission diagnosis was not identified as an independent risk factor.

Augmented Renal Clearance

Augmented renal clearance (ARC) is a phenomenon in critically ill patients characterized by increased creatinine clearance and elimination of renally eliminated medications. Patients with severe neurologic injury, sepsis, trauma, and burns have been consistently identified as at risk of ARC, with mean creatinine clearances ranging from 170 ml/minute to more than 300 ml/minute. Several potential mechanisms may contribute to the occurrence of ARC including endogenous responses to increased metabolism and solute production, alterations in neurohormonal balance, and therapeutic maneuvers such as fluid resuscitation. Augmented renal clearance is associated with suboptimal exposure to critical medications, including β-lactams and vancomycin, increasing the risk of treatment failure. Although definitive screening tools are not yet known, critical care pharmacists must be vigilant in recognizing when ARC may be a contributing factor affecting expected treatment outcomes in individual patients. Optimizing dosing strategies in critically ill patients with ARC remains a goal of continued research. The current review discusses the clinical characteristics and methods of identifying patients at risk of ARC, potential mechanisms for ARC, and describes pharmacotherapy dosing considerations in patients with ARC.

Prevalence and Risk Factors for Augmented Renal Clearance in a Population of Critically Ill Patients

BACKGROUND

Critically ill patients show a high, albeit variable, prevalence of augmented renal clearance (ARC). This condition has relevant consequences on the elimination of hydrophilic drugs. Knowledge of risk factors for ARC helps in the early identification of ARC. The aims of this study were evaluation of (1) risk factors for ARC and (2) the prevalence of ARC in critically ill patients over a period of 1 year.

METHODS

A retrospective cohort study was performed for all consecutive patients admitted to our intensive care unit (ICU). Augmented renal clearance was defined by a creatinine clearance ≥130 mL/min/1.73 m². "Patient with ARC" was defined as a patient with a median of creatinine clearance ≥130 mL/min/1.73 m² over the period of admission. Four variables were tested, Simplified Acute Physiology Score II (SAPS II), male gender, age, and trauma as cause for ICU admission. An analysis (patient based and clearance based) was performed with logistic regression.

RESULTS

Of 475 patients, 446 were included in this study, contributing to 454 ICU admissions and 5586 8-hour creatinine clearance (8h-CL_CR). Overall, the prevalence of patients with ARC was 24.9% (n = 113). In a subset of patients with normal serum creatinine levels, the prevalence was 43.0% (n = 104). Of the set of all 8h-CL_CR measurements, 25.4% (1418) showed ARC. In the patient-based analysis, the adjusted odds ratio was: 2.0 (confidence interval [CI]:1.1-3.7; P < .05), 0.93 (CI: 0.91-0.94; P < .01), 2.7 (CI: 1.4-5.3; P < .01), and 0.98 (CI: 0.96 -1.01; P = .15), respectively, for trauma, age, male sex, and SAPS II. In the clearance-based analysis, the adjusted odds ratio were 1.7 (CI: 1.4-1.9; P < .01), 0.94 (CI: 0.932-0.942; P < .01), and 2.9 (CI: 2.4-3.4; P < .01), respectively, for trauma, age, and male sex.

CONCLUSIONS

Trauma, young age, and male sex were independent risk factors for ARC. This condition occurs in a considerable proportion of critical care patients, which was particularly prevalent in patients without evidence of renal dysfunction.

Validation of a Nomogram for Achieving Target Trough Concentration of Vancomycin: Accuracy in Patients With Augmented Renal Function

BACKGROUND

Adjustment of initial vancomycin (VCM) dosage has been recommended on the basis of the renal function nomogram in therapeutic drug monitoring guidelines in Japan. However, this nomogram has not been clinically validated, and few studies have focused on its usefulness in patients with risk of augmented renal function. Therefore, this study aimed to evaluate the validity of the VCM nomogram and the association between patient conditions related to augmented renal function and its accuracy.

METHODS

In this retrospective study, we screened data of 398 patients who received VCM and had estimated glomerular filtration rates ≥30 mL·min·1.73 m. Patients who met nomogram dosing criteria were categorized into a nomogram group, and the associations of age, renal function, and individual conditions such as febrile neutropenia, solid tumor, blood cancer, and brain injury with subtherapeutic concentrations (<10.0 mcg/mL) of VCM were evaluated.

RESULTS

In total, 177 patients were categorized into the nomogram group, and 83 (47%), 81 (46%), and 13 patients (7%) had VCM trough concentrations of 10-20, <10, and >20 mcg/mL, respectively. Age <50 years was only significantly associated with subtherapeutic trough concentrations. Specific conditions of patients such as febrile neutropenia, solid tumor, and blood cancer were associated with elevated VCM clearance; however, there was no decline in trough VCM concentrations regardless of the presence of the specific conditions.

CONCLUSIONS

The Japanese VCM dosing nomogram was effective in minimizing the number of instances of supratherapeutic VCM serum concentrations; however, it lacked accuracy in achieving target trough concentrations. The accuracy of the nomogram could be enhanced by categorizing patients according to age. Nevertheless, this study provides novel evidence of the usefulness of this nomogram in avoiding subtherapeutic concentrations of VCM in patients with risk factors for augmented renal clearance.

Higher than standard dosing regimen are needed to achieve optimal antibiotic exposure in critically ill patients with augmented renal clearance receiving piperacillin-tazobactam administered by continuous infusion

PURPOSE

To determine whether augmented renal clearance (ARC) impacts negatively on piperacillin-tazobactam unbound concentrations in critically ill patients receiving 16 g/2 g/day administered continuously.

MATERIAL AND METHODS

Fifty nine critically ill patients without renal impairment underwent 24-h creatinine clearance (Cr_CL) measurement and therapeutic drug monitoring during the first three days of antimicrobial therapy by piperacillin-tazobactam. The main outcome was the rate of piperacillin underexposure, defined by at least one of three samples under 16 mg/L. Monte Carlo simulation was performed to predict the distribution of piperacillin concentrations for various Cr_CL and minimal inhibitory concentration (MIC) values.

RESULTS

The rate of piperacillin underexposure was 19%, significantly higher in ARC patients (0 vs. 31%, p = .003). A threshold of Cr_CL ≥ 170 mL/min had a sensitivity and specificity of 1 (95%CI: 0.79-1) and 0.69 (95%CI: 0.61-0.76) to predict piperacillin underexposure. In ARC patients, a 20 g/2.5 g/24 h PTZ dosing regimen was associated with the highest probability to reach the 16 mg/L empirical target, without risk of excessive dosing.

CONCLUSIONS

When targeting a theoretical MIC at the upper limit of the susceptibility range, the desirable target (100%fT_>16) may not be achieved in patients with Cr_CL ≥ 170 mL/min receiving PTZ 16 g/2 g/day administered continuously.

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.

Pharmacokinetics and Pharmacodynamics of Antimicrobials in Critically Ill Patients

Critically ill patients with severe infections often have altered pharmacokinetic and pharmacodynamic variables that lead to challenging treatment decisions. These altered variables can often lead to inadequate dosing and poor treatment outcomes. The pharmacokinetic parameters include absorption, distribution, metabolism, and excretion. Pharmacodynamics is the relationship between drug serum concentrations and pharmacologic and toxicologic properties of the medication. In addition to these altered parameters, these critically ill patients frequently are receiving organ support in the forms of continuous renal replacement therapy or extra-corporeal membrane oxygenation. Altered pharmacodynamics can lead to decreased end-organ perfusion, which can ultimately lead to treatment failure or exposure-related toxicity. The most common antimicrobials utilized in the intensive care unit are classified by the pharmacodynamic principles of time-dependent, concentration-dependent, and concentration dependent with time-dependence. Thus, the aim of this review is to outline pharmacokinetic and pharmacodynamic changes of critically ill patients with severe infections and provide strategies for optimal antibiotic agent dosing in these patients.

Augmented Renal Clearance in Patients With Febrile Neutropenia is Associated With Increased Risk for Subtherapeutic Concentrations of Vancomycin

BACKGROUND

Augmented renal clearance (ARC) has frequently been observed in critically ill patients. The risk factors for ARC in patients, including those in the general ward, and their influences on vancomycin (VCM) treatment remain unclear. The aims of this study were to investigate the risk factors for ARC and to evaluate the influence of ARC on the pharmacokinetic parameters of VCM.

METHODS

This study included a total of 292 patients with VCM treatment who had normal serum creatinine concentrations. ARC was defined by an estimated creatinine clearance ≥130 mL·min·1.73 m. The risk factors for ARC were determined with stepwise logistic regression analysis. The pharmacokinetic parameters of VCM were estimated through the Bayesian method using a 2-compartment model.

RESULTS

ARC was observed in 48 patients (16.4%). Age ≤65 years [odds ratio (OR): 5.77; 95% CI: 2.89-11.97; P < 0.0001], brain injury (OR: 5.11; 95% CI: 1.49-17.57; P = 0.0086), febrile neutropenia (OR: 2.76; 95% CI: 1.11-6.67; P = 0.0254), and a mean volume of infusion fluid ≥1500 mL/d (OR: 2.53; 95% CI: 1.27-5.16; P = 0.0091) were independent risk factors for the occurrence of ARC. The patients with ARC exhibited higher VCM clearance values than the non-ARC patients. The median trough serum concentrations of VCM were 7.4 (interquartile range: 5.2-11.6) mcg/mL in the ARC patients and 12.2 (8.9-16.3) mcg/mL in the non-ARC patients (P < 0.0001). Subtherapeutic trough concentrations of VCM (<10.0 mcg/mL) were found in 68.8% of the ARC patients and in 32.8% of the non-ARC patients (P < 0.0001).

CONCLUSIONS

This observational study investigated the influence of febrile neutropenia on the emergency of ARC for the first time. ARC was strongly associated with VCM pharmacokinetics, and two-thirds of the ARC patients had subtherapeutic VCM concentrations. In patients with ARC, individualized dosing regimens are required to achieve the target trough concentration.

Association between augmented renal clearance, antibiotic exposure and clinical outcome in critically ill septic patients receiving high doses of β-lactams administered by continuous infusion: a prospective observational study

This study assessed whether augmented renal clearance (ARC) impacts negatively on antibiotic concentrations and clinical outcomes in patients treated by high-dose β-lactams administered continuously. Over a 9-month period, all critically ill patients without renal impairment treated by one of the monitored β-lactams for a documented infection were eligible. During the first 3 days of antibiotic therapy, every patient underwent 24-h CL_Cr measurements and therapeutic drug monitoring. The main outcome was the rate of β-lactam underdosing, defined as a free drug concentration <4 × MIC of the known pathogen. Secondary outcomes were rates of subexposure for β-lactams and therapeutic failure. The performance of CL_Cr in predicting underdosing was assessed by a ROC curve, and multivariable logistic regression was performed to determine risk factors for subexposure and therapeutic failure. A total of 79 patients were included and 235 samples were analysed. The rate of underdosing_<4×MIC was 12%, with a significant association with CL_Cr (P <0.0001). A threshold of CL_Cr ≥ 170 mL/min had a sensitivity and specificity of 0.93 (95% CI 0.77-0.99) and 0.65 (95% CI 0.58-0.71) for predicting β-lactam underdosing_<4×MIC. Mean CL_Cr values ≥170 mL/min were significantly associated with subexposure_<4xMIC [OR = 10.1 (2.4-41.6); P = 0.001]. Patients with subexposure_<4×MIC presented higher rates of therapeutic failure [OR = 6.3 (1.2-33.2); P = 0.03]. Mean CL_Cr values ≥170 mL/min remain a risk factor for subexposure to β-lactams despite high doses of β-lactams administered continuously. β-Lactam subexposure was associated with higher rates of therapeutic failure in septic critically ill patients.

Evaluation of Intravenous Vancomycin Pharmacokinetic Parameters in Patients With Acute Brain Injury

BACKGROUND

Vancomycin is a glycopeptide antibiotic that is primarily cleared by renal elimination. Patients with acute brain injury often exhibit augmented renal clearance which has been associated with subtherapeutic vancomycin concentrations.

OBJECTIVE

To determine whether population pharmacokinetics accurately predict vancomycin empiric dose frequency in patients with acute brain injury.

METHODS

This was a single-center, retrospective cohort study conducted following institutional review board approval at Virginia Commonwealth University Health System. Data were collected from patients 18 years of age or older admitted with acute brain injury. The primary outcome was the difference in the elimination rate constant of vancomycin between population predicted pharmacokinetics and patient-specific pharmacokinetics.

RESULTS

A total of 158 patients were included in the analysis. A test of the paired differences between the mean population predicted and patient-specific elimination rate constants showed that the mean population predicted elimination rate constant was larger by 0.0211 h^-1 (95% confidence interval [CI]: -0.028 to -0.015). The difference between the mean population predicted and patient-specific half-lives showed that the mean population predicted half-life was shorter by 1.01 hours (95% CI: 0.7-1.3). Vancomycin was administered at a mean initial dose of 15.4 mg/kg (standard deviation [SD] = 2.2), with an average frequency of 12 hours (SD = 1.1). The average trough concentration at steady state was 9.9 µg/mL (SD = 4.9).

CONCLUSIONS

The small clinical difference in population and patient-specific elimination rate constants demonstrates that population pharmacokinetics may be an accurate empiric dosing strategy for determining vancomycin dose frequency in patients with acute brain injury.

Association between augmented renal clearance and clinical failure of antibiotic treatment in brain-injured patients with ventilator-acquired pneumonia: A preliminary study

OBJECTIVES

This preliminary study aimed to determine whether augmented renal clearance (ARC) impacts negatively on the clinical outcome in traumatic brain-injured patients (TBI) treated for a first episode of ventilator-acquired pneumonia (VAP).

METHODS

During a 5-year period, all TBI patients who had developed VAP were retrospectively reviewed to assess variables associated with clinical failure in multivariate analysis. Clinical failure was defined as an impaired clinical response with a need for escalating antibiotics during treatment and/or within 15 days after the end-of-treatment. Recurrence was considered if at least one of the initial causative bacterial strains was growing at a significant concentration from a second sample. Augmented renal clearance (ARC) was defined by an enhanced creatinine clearance exceeding 130mL/min/1.73m² calculated from a urinary sample during the first three days of antimicrobial therapy.

MAIN RESULTS

During the study period, 223 TBI patients with VAP were included and 59 (26%) presented a clinical failure. Factors statistically associated with clinical failure were GSC≤7 (OR=2.2 [1.1-4.4], P=0.03), early VAP (OR=3.9 [1.9-7.8], P=0.0001), bacteraemia (OR=11 [2.2-54], P=0.003) and antimicrobial therapy≤7 days (OR=3.7 [1.8-7.4], P=0.0003). ARC was statistically associated with recurrent infections with an OR of 4.4 [1.2-16], P=0.03.

CONCLUSION

ARC was associated with recurrent infection after a first episode of VAP in TBI patients. The optimal administration and dosing of the antimicrobial agents in this context remain to be determined.

Identifying augmented renal clearance in trauma patients: Validation of the Augmented Renal Clearance in Trauma Intensive Care scoring system

BACKGROUND

Augmented renal clearance (ARC) is common in trauma patients and associated with subtherapeutic antimicrobial concentrations. This study reported the incidence of ARC, identified ARC risk factors, and described a model to predict ARC (i.e., ARCTIC) that is specific to trauma patients.

METHODS

Consecutive trauma patients who were admitted to the intensive care unit between March 2015 and January 2016 and had a measured creatinine clearance (CrCl) were considered for inclusion. Patients were excluded if their serum creatinine (SCr) was greater than 1.3 mg/dL. ARC was defined as a measured CrCl of 130 mL/min or greater. Demographic and trauma-specific variables were then compared, and multivariate analysis was performed. Using these results, a weighted scoring system was constructed and evaluated using receiver operating characteristic curve analysis. ARCTIC score cutoffs were chosen based on sensitivity, specificity, positive predictive value, and negative predictive value. The derived scoring system was then compared to a previously published scoring system for accuracy.

RESULTS

There were 133 patients with a mean age of 48 ± 19 years and SCr of 0.8 ± 0.2 mg/dL. The mean measured CrCl was 168 ± 65 mL/min, and the incidence of ARC was 67%. Multivariate analysis revealed the following risk factors for ARC (age, <56: odds ratios [OR], 58.3; 95% confidence interval [CI], 5.2-658.9; age, 56 to 75: OR, 13.5; 95% CI, 1.2-151.7), SCr less than 0.7 mg/dL (OR, 12.5; 95% CI, 3-52.6), and male sex (OR, 6.9; 95% CI, 1.9-24.9). Using these results, the ARCTIC scoring system was: 4 points if younger than 56 years, 3 points if aged 56 years to 75 years, 3 points if SCr less than 0.7 mg/dL, and 2 points if male sex. Receiver operating characteristic curve analysis revealed an area (95% CI) of 0.813 (0.735-0.892) (p < 0.001). An ARCTIC score of 6 or higher had a sensitivity, specificity, positive predictive value, and negative predictive value of 0.843, 0.682, 0.843, and 0.682, respectively.

CONCLUSION

The incidence of ARC in trauma patients is high. The ARCTIC score represents a practical, pragmatic system that can be easily applied at the bedside. An ARCTIC score of 6 or higher represents an appropriate cutoff to screen for ARC where antimicrobial adjustments should be considered.

LEVEL OF EVIDENCE

Prognostic/epidemiologic study, level III.