Burn Injury and Augmented Renal Clearance: A Case for Optimized Piperacillin-Tazobactam Dosing

Pharmacokinetic Analysis of Intravenous Push Cefepime in Burn Patients with Augmented Renal Clearance

Patients with augmented renal clearance (ARC) are a subset of critically ill patients including burn patients that exhibit increased renal elimination of medications beyond that of similarly injured patients. Currently approved maximum regimens of medications primarily eliminated by the kidney, such as cefepime (>90% unchanged in the urine), may be inadequate (eg, compromising the bactericidal activity of cefepime) in patients with ARC. Due to recent resource limitations, centers have changed infusion practices of commonly prescribed medications to intravenous push (IVP), potentially exacerbating the problem of maintaining bactericidal cefepime concentrations. The hypothesis of the study was patients with ARC are not currently achieving adequate target attainment, when receiving cefepime 2 g every 8 h IVP. Eight blood samples were collected from each patient, and concentrations measured via LC-MS/MS. WinNonlin (version 8.3) was used to estimate the pharmacokinetic parameters of cefepime and simulate plasma concentrations of cefepime in each of the ten subjects. Simulations of cefepime plasma concentrations produced by a 2 g dose given every 8 h and a 1 g dose given every 4 h were performed and the time above a MIC of 4 mg/L, 8 mg/L, and 16 mg/L compared. The 2 g every 8 h regimen remained above the breakpoints for 92%, 85%, and 71% of the dosing interval, respectively. The 1 g every 4 h regimen remained above the same breakpoints at a frequency of 100%, 99%, and 92% of the dosing interval. Giving cefepime 1 g every 4 h is a simple approach to increase the likelihood of maintaining the optimal bactericidal activity of cefepime in patients with ARC.

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.

Augmented Renal Function in Burn Patients: Occurrence and Discordance With Commonly Used Methods to Assess Renal Function

Augmented renal clearance (ARC) is defined by supraphysiologic renal function and is associated with drug failure due to subtherapeutic drug exposure. Burn patients are cited as being at high risk for ARC, yet rates of ARC have not been well described. This retrospective study described the prevalence and incidence of ARC, and compared 12-hour urine collection values (CrCl-12) vs. common estimates of renal function in assessed patients at an American Burn Association-verified burn center. All thermally injured burn patients with a CrCl-12 result were included. ARC was defined as a CrCl-12 >130 ml/min. Cockcroft-Gault, modification of diet in renal disease (MDRD), and CKD-EPI-2021 estimates were calculated. Over 13 months, 163 CrCl-12 results were collected in 68 patients at a median of 9 days from admission with an average value of 160 ml/min. The median total body surface area (total body surface area [TBSA]%) was 17.25%. ARC prevalence was 70.6% with an incidence of 66.3% in all CrCl-12 assessments. Those with ARC were less likely to have heart failure, P = .007. Age, TBSA%, and trauma were not different between those with or without ARC. ARC incidences in those with TBSAs of ≥20%, <20%, or <10%, were 70.5%, 58.6%, and 76.7%, respectively. Agreement of Cockcroft-Gault, MDRD, and CKD-EPI-2021 to CrCl-12 was moderate to weak and frequently failed to identify ARC. ARC is common in burn patients, regardless of TBSA%. Widely accepted estimations of renal function may be incorrect resulting in under-dosing of medications. Additional research is required to identify burn patients at greatest risk for ARC and subsequent dosing strategies to maintain pharmacologic efficacy without unduetoxicity.

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

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