Population Pharmacokinetic Modeling and Simulations of Imipenem in Burn Patients With and Without Continuous Venovenous Hemofiltration in the Military Health System

An Appraisal of Pharmacotherapy-Pertinent Literature Published in 2021 and 2022 for Clinicians Caring for Patients With Thermal or Inhalation Injury

Studies focusing on pharmacotherapy interventions to aid patients after thermal injury are a minor focus in burn injury-centered studies and published across a wide array of journals, which challenges those with limited resources to keep their knowledge current. This review is a renewal of previous years' work to facilitate extraction and review of the most recent pharmacotherapy-centric studies in patients with thermal and inhalation injury. Twenty-three geographically dispersed, board-certified pharmacists participated in the review. A Medical Subject Heading-based, filtered search returned 2336 manuscripts over the previous 2-year period. After manual review, 98 (4%) manuscripts were determined to have a potential impact on current pharmacotherapy practice. The top 10 scored manuscripts are discussed. Only 17% of those reviewed were assessed to likely have little effect on current practice. The overall impact of the current cohort was higher than previous editions of this review, which is encouraging. There remains a need for investment in well-designed, high-impact, pharmacotherapy-pertinent research for patients sustaining thermal or inhalation injuries.

Which Are the Best Regimens of Broad-Spectrum Beta-Lactam Antibiotics in Burn Patients? A Systematic Review of Evidence from Pharmacology Studies

BACKGROUND

Burn injury causes profound pathophysiological changes in the pharmacokinetic/pharmacodynamic (PK/PD) properties of antibiotics. Infections are among the principal complications after burn injuries, and broad-spectrum beta-lactams are the cornerstone of treatment. The aim of this study was to review the evidence for the best regimens of these antibiotics in the burn patient population.

METHODS

We performed a systematic review of evidence available on MEDLINE (from its inception to 2023) of pharmacology studies that focused on the use of 13 broad-spectrum beta-lactams in burn patients. We extracted and synthetized data on drug regimens and their ability to attain adequate PK/PD targets.

RESULTS

We selected 35 studies for analysis. Overall, studies showed that both high doses and the continuous infusion (CI) of broad-spectrum beta-lactams were needed to achieve internationally-recognized PK/PD targets, ideally with therapeutic drug monitoring guidance. The most extensive evidence concerned meropenem, but similar conclusions could be drawn about piperacillin-tazobactam, ceftazidime, cefepime, imipenem-clinastatin and aztreonam. Insufficient data were available about new beta-lactam-beta-lactamase inhibitor combinations, ceftaroline, ceftobiprole and cefiderocol.

CONCLUSIONS

Both high doses and CI of broad-spectrum beta-lactams are needed when treating burn patients due to the peculiar changes in the PK/PD of antibiotics in this population. Further studies are needed, particularly about newer antibiotics.

Individualized antibiotic dosage regimens for patients with augmented renal clearance

Objectives: Augmented renal clearance (ARC) is a state of enhanced renal function commonly observed in 30%-65% of critically ill patients despite normal serum creatinine levels. Using unadjusted standard dosing regimens of renally eliminated drugs in ARC patients often leads to subtherapeutic concentrations, poor clinical outcomes, and the emergence of multidrug-resistant bacteria. We summarized pharmaceutical, pharmacokinetic, and pharmacodynamic research on the definition, underlying mechanisms, and risk factors of ARC to guide individualized dosing of antibiotics and various strategies for optimizing outcomes. Methods: We searched for articles between 2010 and 2022 in the MEDLINE database about ARC patients and antibiotics and further provided individualized antibiotic dosage regimens for patients with ARC. Results: 25 antibiotic dosage regimens for patients with ARC and various strategies for optimization of outcomes, such as extended infusion time, continuous infusion, increased dosage, and combination regimens, were summarized according to previous research. Conclusion: ARC patients, especially critically ill patients, need to make individualized adjustments to antibiotics, including dose, frequency, and method of administration. Further comprehensive research is required to determine ARC staging, expand the range of recommended antibiotics, and establish individualized dosing guidelines for ARC patients.

The Role of Serum Albumin Level during Hospitalization as a Predictor of Complications and Mortality in Children with Burns

Background

Serum albumin can function as a potential biomarker to determine the severity of the injury and clinical staging of children with burns. Therefore, in this study, we investigated the association between serum albumin level and complications and mortality rate in children with burns.

Methods

In this descriptive-analytic cross-sectional study, 85 patients younger than 18 years with burns who were admitted to Shahid Motahari hospital between 2021 and 2022 were studied. Demographic information, including patients' age, sex, weight, underlying diseases, medical information, albumin level, and C-reactive protein (CRP), was obtained from patient records. Patients were observed until discharge. The independent t-test, chi-square, Pearson correlation, and logistic regression were used for analysis and to examine the predictive role of albumin.

Results

Out of 85 patients, 47 and 38 were boys and girls, respectively. The mean age of the participants was 3.69 ± 3.09 years. The mean length of hospital stay was 2.3 days, with a median of 1.5 days. The mean percentage of burns was 23.44 ± 16.50, and burn grade 2 was the most common. A total of 25 patients (29.41%) were admitted to the intensive care unit (ICU), and 13 deaths (15.29%) were observed among the patients. The mean albumin level was significantly lower than in other patients with outcomes of pulmonary infection, sepsis, renal failure, ICU admission, and death (P < 0.001).

Conclusion

Serum Albumin has a significant predictive value in death, pulmonary infection, sepsis, admission to the ICU, and renal failure. Serum albumin may be a good prognostic marker associated with morbidity and mortality.

Beta-Lactam Probability of Target Attainment Success: Cefepime as a Case Study

Introduction: Probability of target attainment (PTA) analysis using Monte Carlo simulations has become a mainstay of dose optimization. We highlight the technical and clinical factors that may affect PTA for beta-lactams. Methods: We performed a mini review in adults to explore factors relating to cefepime PTA success and how researchers incorporate PTA into dosing decisions. In addition, we investigated, via simulations with a population pharmacokinetic (PK) model, factors that may affect cefepime PTA success. Results: The mini review included 14 articles. PTA results were generally consistent, given the differences in patient populations. However, dosing recommendations were more varied and appeared to depend on the definition of pharmacodynamic (PD) target, definition of PTA success and specific clinical considerations. Only 3 of 14 articles performed formal toxicological analysis. Simulations demonstrated that the largest determinants of cefepime PTA were the choice of PD target, continuous vs. intermittent infusion and creatinine clearance. Assumptions for protein binding, steady state vs. first dose, and simulating different sampling schemes may impact PTA success under certain conditions. The choice of one or two compartments had a minimal effect on PTA. Conclusions: PTA results may be similar with different assumptions and techniques. However, dose recommendation may differ significantly based on the selection of PD target, definition of PTA success and considerations specific to a patient population. Demographics and the PK parameters used to simulate time-concentration profiles should be derived from patient data applicable to the purpose of the PTA. There should be strong clinical rationale for dose selection. When possible, safety and toxicity should be considered in addition to PTA success.

Hemoperfusion with Seraph 100 Microbind Affinity Blood Filter Unlikely to Require Increased Antibiotic Dosing: A Simulations Study Using a Pharmacokinetic/Pharmacodynamic Approach

INTRODUCTION

The Seraph® 100 Microbind® Affinity Blood Filter (Seraph 100) is a hemoperfusion device that can remove pathogens from central circulation. However, the effect of Seraph 100 on achieving pharmacodynamic (PD) targets is not well described. We sought to determine the impact of Seraph 100 on ability to achieve PD targets for commonly used antibiotics.

METHODS

Estimates of Seraph 100 antibiotic clearance were obtained via literature. For vancomycin and gentamicin, published pharmacokinetic models were used to explore the effect of Seraph 100 on ability to achieve probability of target attainment (PTA). For meropenem and imipenem, the reported effect of continuous kidney replacement therapy (CKRT) on achieving PTA was used to extrapolate decisions for Seraph 100.

RESULTS

Seraph 100 antibiotic clearance is likely less than 0.5 L/h for most antibiotics. Theoretical Seraph 100 clearance up to 0.5 L/h and 2 L/h had a negligible effect on vancomycin PTA in virtual patients with creatinine clearance (CrCl) = 14 mL/min and CrCl >14 mL/min, respectively. Theoretical Seraph 100 clearance up to 0.5 L/h and 2 L/h had a negligible effect on gentamicin PTA in virtual patients with CrCl = 120 mL/min and CrCl <60 mL/min, respectively. CKRT intensity resulting in antibiotic clearance up to 2 L/h generally does not require dose increases for meropenem or imipenem. As Seraph 100 is prescribed intermittently and likely contributes far less to antibiotic clearance, dose increases would also not be required.

CONCLUSION

Seraph 100 clearance of vancomycin, gentamicin, meropenem, and imipenem is likely clinically insignificant. There is insufficient evidence to recommend increased doses. For aminoglycosides, we recommend extended interval dosing and initiating Seraph 100 at least 30 min to 1 h after completion of infusion to avoid the possibility of interference with maximum concentrations.

The Dosage Recommendation of Cyclosporin in Children with Hemophagocytic Lymphohistiocytosis based on Population Pharmacokinetic Model

OBJECTIVES

Cyclosporin is one of the therapeutic regimens for hemophagocytic lymphohistiocytosis (HLH); however, the optimal dosage of cyclosporine in children with HLH is unknown. It has been found that piperacillin-tazobactam affects the cyclosporine pharmacokinetic process in pediatric HLH patients. Thus, the purpose of the present study was to recommend cyclosporin dosage for pediatric HLH with and without piperacillin- tazobactam.

METHODS

A previously established cyclosporine population pharmacokinetic model for pediatric HLH patients has been used in this study to recommend optimal dosage based on Monte Carlo simulation. The pediatric HLH patients have been included in eight weight groups (5, 10, 20, 30, 40, 50, 60, 70 kg) for sixteen dosages (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 mg/kg), split into one dose or two doses.

RESULTS

The optimal cyclosporin dosages for children having HLH without piperacillin-tazobactam have been found to be 15, 13, 12, 11, 10, and 9 mg/kg, split into two doses for weights of 5-7, 7-10, 10-20, 20-28, 28-45, and 45-70 kg, respectively. For children with HLH, optimal cyclosporin dosages with piperacillin-tazobactam have been found to be 8 and 7 mg/kg, split into two doses for weights of 5-20 and 20-70 kg, respectively.

CONCLUSION

It is the first time that the cyclosporin dosage regimens for HLH in children have been developed based on Monte Carlo simulation, and the initial dosage optimizations of cyclosporine in pediatric HLH patients have been recommended.

Antibiotic Therapy in the Critically Ill with Acute Renal Failure and Renal Replacement Therapy: A Narrative Review

The outcome for critically ill patients is burdened by a double mortality rate and a longer hospital stay in the case of sepsis or septic shock. The adequate use of antibiotics may impact on the outcome since they may affect the pharmacokinetics (Pk) and pharmacodynamics (Pd) of antibiotics in such patients. Acute renal failure (ARF) occurs in about 50% of septic patients, and the consequent need for continuous renal replacement therapy (CRRT) makes the renal elimination rate of most antibiotics highly variable. Antibiotics doses should be reduced in patients experiencing ARF, in accordance with the glomerular filtration rate (GFR), whereas posology should be increased in the case of CRRT. Since different settings of CRRT may be used, identifying a standard dosage of antibiotics is very difficult, because there is a risk of both oversimplification and failing the therapeutic efficacy. Indeed, it has been seen that, in over 25% of cases, the antibiotic therapy does not reach the necessary concentration target mainly due to lack of the proper minimal inhibitory concentration (MIC) achievement. The aim of this narrative review is to clarify whether shared algorithms exist, allowing them to inform the daily practice in the proper antibiotics posology for critically ill patients undergoing CRRT.

Comparison of Piperacillin and Tazobactam Pharmacokinetics in Critically Ill Patients with Trauma or with Burn

Critical illness caused by burn and sepsis is associated with pathophysiologic changes that may result in the alteration of pharmacokinetics (PK) of antibiotics. However, it is unclear if one mechanism of critical illness alters PK more significantly than another. We developed a population PK model for piperacillin and tazobactam (pip-tazo) using data from 19 critically ill patients (14 non-burn trauma and 5 burn) treated in the Military Health System. A two-compartment model best described pip-tazo data. There were no significant differences found in the volume of distribution or clearance of pip-tazo in burn and non-burn patients. Although exploratory in nature, our data suggest that after accounting for creatinine clearance (CrCl), doses would not need to be increased for burn patients compared to trauma patients on consideration of PK alone. However, there is a high reported incidence of augmented renal clearance (ARC) in burn patients and pharmacodynamic (PD) considerations may lead clinicians to choose higher doses. For critically ill patients with normal kidney function, continuous infusions of 13.5-18 g pip-tazo per day are preferable. If ARC is suspected or the most stringent PD targets are desired, then continuous infusions of 31.5 g pip-tazo or higher may be required. This approach may be reasonable provided that therapeutic drug monitoring is enacted to ensure pip-tazo levels are not supra-therapeutic.