Continuous versus intermittent infusion of cefepime in neurosurgical patients with post-operative intracranial infections

Optimizing Betalactam Clinical Response by Using a Continuous Infusion: A Comprehensive Review

INTRODUCTION

Antimicrobial resistance is a major healthcare issue responsible for a large number of deaths. Many reviews identified that PKPD data are in favor of the use of continuous infusion, and we wanted to review clinical data results in order to optimize our clinical practice.

METHODOLOGY

We reviewed Medline for existing literature comparing continuous or extended infusion to intermittent infusion of betalactams.

RESULTS

In clinical studies, continuous infusion is as good as intermittent infusion. In the subset group of critically ill patients or those with an infection due to an organism with high MIC, a continuous infusion was associated with better clinical response.

CONCLUSIONS

Clinical data appear to confirm those of PK/PD to use a continuous infusion in severely ill patients or those infected by an organism with an elevated MIC, as it is associated with higher survival rates. In other cases, it may allow for a decrease in antibiotic daily dosage, thereby contributing to a decrease in overall costs.

The Blood-Brain Barrier and Pharmacokinetic/Pharmacodynamic Optimization of Antibiotics for the Treatment of Central Nervous System Infections in Adults

Bacterial central nervous system (CNS) infections are serious and carry significant morbidity and mortality. They encompass many syndromes, the most common being meningitis, which may occur spontaneously or as a consequence of neurosurgical procedures. Many classes of antimicrobials are in clinical use for therapy of CNS infections, some with established roles and indications, others with experimental reporting based on case studies or small series. This review delves into the specifics of the commonly utilized antibacterial agents, updating their therapeutic use in CNS infections from the pharmacokinetic and pharmacodynamic perspectives, with a focus on the optimization of dosing and route of administration that have been described to achieve good clinical outcomes. We also provide a concise synopsis regarding the most focused, clinically relevant information as pertains to each class and subclass of antimicrobial therapeutics. CNS infection morbidity and mortality remain high, and aggressive management is critical in ensuring favorable patient outcomes while averting toxicity and upholding patient safety.

Beta-Lactams Dosing in Critically Ill Patients with Gram-Negative Bacterial Infections: A PK/PD Approach

Beta-lactam antibiotics are often the backbone of treatment for Gram-negative infections in the critically ill. Beta-lactams exhibit time-dependent killing, and their efficacy depends on the percentage of dosing interval that the concentration remains above the minimum inhibitory concentration. The Gram-negative resistance rates of pathogens are increasing in the intensive care unit (ICU), and critically ill patients often possess physiology that makes dosing more challenging. The volume of distribution is usually increased, and drug clearance is variable. Augmented renal clearance and hypermetabolic states increase the clearance of beta-lactams, while acute kidney injury reduces the clearance. To overcome the factors affecting ICU patients and decreasing susceptibilities, dosing strategies involving higher doses, and extended or continuous infusions may be required. In this review, we specifically examined pharmacokinetic models in ICU patients, to determine the desired beta-lactam regimens for clinical breakpoints of Enterobacterales and Pseudomonas aeruginosa, as determined by the European Committee on Antimicrobial Susceptibility Testing. The beta-lactams evaluated included penicillins, cephalosporins, carbapenems, and monobactams. We found that when treating less-susceptible pathogens, especially P. aeruginosa, continuous infusions are frequently needed to achieve the desired pharmacokinetic/pharmacodynamic targets. More studies are needed to determine optimal dosing strategies in the novel beta-lactams.

Brain Exposure to Piperacillin in Acute Hemorrhagic Stroke Patients Assessed by Cerebral Microdialysis and Population Pharmacokinetics

BACKGROUND

The broad antibacterial spectrum of piperacillin/tazobactam makes the combination suitable for the treatment of nosocomial bacterial central nervous system (CNS) infections. As limited data are available regarding piperacillin CNS exposure in patients without or with low-grade inflammation, a clinical study was conducted (1) to quantify CNS exposure of piperacillin by cerebral microdialysis and (2) to evaluate different dosing regimens in order to improve probability of target attainment (PTA) in brain.

METHODS

Ten acute hemorrhagic stroke patients (subarachnoid hemorrhage, n = 6; intracerebral hemorrhage, n = 4) undergoing multimodality neuromonitoring received 4 g piperacillin/0.5 g tazobactam every 8 h by 30-min infusions for the management of healthcare-associated pneumonia. Cerebral microdialysis was performed as part of the clinical neuromonitoring routine, and brain interstitial fluid samples were retrospectively analyzed for piperacillin concentrations after the first and after multiple doses for at least 5 days and quantified by high-performance liquid chromatography. Population pharmacokinetic modeling and Monte Carlo simulations with various doses and types of infusions were performed to predict exposure. A T_>MIC of 50% was selected as pharmacokinetic/pharmacodynamic target parameter.

RESULTS

Median peak concentrations of unbound piperacillin in brain interstitial space fluid were 1.16 (range 0.08-3.59) and 2.78 (range 0.47-7.53) mg/L after the first dose and multiple doses, respectively. A one-compartment model with a transit compartment and a lag time (for the first dose) between systemic and brain exposure was appropriate to describe the brain concentrations. Bootstrap median estimates of the parameters were: transfer rate from plasma to brain (0.32 h^-1), transfer rate from brain to plasma (7.31 h^-1), and lag time [2.70 h (coefficient of variation 19.7%)]. The simulations suggested that PTA would exceed 90% for minimum inhibitory concentrations (MICs) up to 0.5 mg/L and 1 mg/L at a dose of 12-16 and 24 g/day, respectively, regardless of type of infusion. For higher MICs, PTA dropped significantly.

CONCLUSION

Limited CNS exposure of piperacillin might be an obstacle in treating patients without general meningeal inflammation except for infections with highly susceptible pathogens. Brain exposure of piperacillin did not improve significantly with a prolongation of infusions.

Improving intraoperative administration of surgical antimicrobial prophylaxis: a quality improvement report

Despite widespread adoption of the Surgical Care Improvement Programme, the incidence of surgical site infections (SSIs) remains high. It is possible that lapses in appropriate administration of antimicrobial prophylaxis may play a role. We noted significant discordance with national guidelines with regards to intraoperative antibiotic administration at our institution, leading to implementation of a quality improvement initiative using multidisciplinary education and reminder-based interventions to improve prescribing practices and increase compliance with national guidelines. We observed a significant improvement in adherence to all aspects of antibiotic administration guidelines as a result of such interventions. Targeted multidisciplinary interventions may help improve prescribing practices of surgical antimicrobial prophylaxis and provide an opportunity to potentially decrease the burden of SSI and the related morbidity and mortality.

Continuous infusion of ceftolozane-tazobactam resulted in high cerebrospinal fluid concentrations of ceftolozane in a patient with multidrug-resistant Pseudomonas aeruginosa meningitis

Multidrug-resistant Pseudomonas aeruginosa has limited treatment options. Treatment of healthcare-associated meningitis requires agents active against the organism in vitro and able to penetrate the cerebrospinal fluid adequately. Ceftolozane-tazobactam has been recently approved to treat various Gram-negative organisms, including Pseudomonas aeruginosa; however, ceftolozane's penetration into human cerebrospinal fluid is unknown. Here, we present a case of a patient with multidrug-resistant Pseudomonas aeruginosa meningitis treated with a continuous infusion of ceftolozane-tazobactam. Samples of both serum and cerebrospinal fluid were analyzed for ceftolozane concentration on continuous infusion. Cerebrospinal fluid concentrations of ceftolozane were 83% of that in serum. Treatment with ceftolozane-tazobactam, along with combinations of other antibiotics, resulted in clearance of organism from the patient's cerebrospinal fluid and marked decrease in inflammatory cells. Studies are warranted to determine the efficacy of ceftolozane-tazobactam for patients with healthcare-associated meningitis.

Antimicrobial Stewardship: From Bedside to Theory. Thirteen Examples of Old and More Recent Strategies from Everyday Clinical Practice

“Antimicrobial stewardship” is a strategy that promotes the responsible use of antimicrobials. The objective of this paper is to focus on consolidated and more recent improvements in clinical strategies that should be adopted in hospitalized patients to ameliorate their infectious diseases’ outcome and to reduce the antibiotic resistance risk through judicious use of antibiotics. We present 13 common clinical scenarios, the respective suggested interventions and the explanations of the supporting evidence, in order to help clinicians in their decision-making process. Strategies including the choice of antibiotic and dose optimization, antibiotic spectrum narrowing (de-escalation), shortening of duration, shift to oral route or outpatient parenteral antibiotic (including elastomeric pumps), and biomarkers are described and discussed.

Continuous infusion of cefepime and neurotoxicity: a retrospective cohort study

OBJECTIVES

Neurotoxicity related to cefepime is increasingly reported in the literature but specific data concerning continuous infusion (CI) of the drug are still lacking. Our primary objective was to evaluate the incidence of neurotoxicity related to CI of cefepime and the associated risk factors. Our secondary objectives were to analyse the plasma cefepime concentrations and to define the threshold above which neurotoxicity occurs.

METHODS

In this single-centre retrospective cohort study, all adult patients who underwent at least one cefepime therapeutic drug monitoring (TDM) and were treated with CI of 4 g/day between January 2017 and June 2019 were included. Neurotoxicity was evaluated according to a strict definition and was correlated with steady-state concentration at the time of toxicity presentation.

RESULTS

Ninety-eight patients with 201 cefepime TDM studies were included, with an incidence of neurotoxicity of 14.3% (14/98). Patients with neurotoxicity had more often underlying brain disease (35.7% (5/14) vs 11.9% (10/84), p = 0.030)) and higher steady-state concentrations (mean ± standard deviation 71.8 ± 32.9 mg/L vs 49.6 ± 30.6, p = 0.036) than the others. A receiver operating characteristic curve analysis yielded a cefepime steady-state concentration of 63.2 mg/L as the best cut-off point between patients with or without neurotoxicity. A mean steady-state concentration of 46.4 mg/L was achieved if the dosages of cefepime were adapted to renal function which was under our threshold concentration but above our highest pharmacokinetic/pharmacodynamic target of 32-40 mg/L.

CONCLUSIONS

Our results suggest that 4 g/day of cefepime adapted to renal function and infused over 24 h is a trade-off for the risk/benefit ratio, when used empirically.

Cerebrospinal fluid pharmacokinetics of ceftaroline in neurosurgical patients with an external ventricular drain

BACKGROUND

Owing to its antibacterial properties, ceftaroline could be attractive for prevention or treatment of bacterial post-neurosurgical meningitis/ventriculitis. However, few data are available concerning its meningeal concentrations.

OBJECTIVES

To investigate ceftaroline CSF pharmacokinetics in ICU patients with an external ventricular drain (EVD).

METHODS

Patients received a single 600 mg dose of ceftaroline as a 1 h intravenous infusion. Blood and CSF samples were collected before and 0.5, 1, 3, 6, 12 and 24 h after the end of the infusion. Concentrations were assayed in plasma and CSF by LC-MS/MS. A two-step compartmental pharmacokinetic analysis was conducted. Ceftaroline plasma data were first analysed, and thereafter plasma parameters estimated and corrected for protein binding of 20% were fixed to fit unbound CSF concentrations. In the final model, parameters for both plasma and CSF data were simultaneously estimated.

RESULTS

Nine patients with an EVD were included. The Cmax was 18.29 ± 3.33 mg/L in plasma (total concentrations) and at 0.22 ± 0.17 mg/L in CSF (unbound concentration). The model-estimated CSF input/CSF output clearance ratio was 9.4%, attesting to extensive efflux transport at the blood-CSF barrier.

CONCLUSIONS

Ceftaroline CSF concentrations are too low to ensure prophylactic protection against most pathogens with MICs between 1 and 2 mg/L, owing to its limited central distribution.

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

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

Optimal infusion rate in antimicrobial therapy explosion of evidence in the last five years

Background

Sporadic studies in antimicrobial therapy have evaluated the effects of infusion rates on therapeutic and economic outcomes, and new findings may challenge the regular infusion regimen.

Methods

Focusing on studies comparing the outcomes of different infusion regimens, the relevant literature was identified by searching PubMed, Web of Science, and Scopus from January 1, 2013 to March 1, 2018. Papers were finally chosen using a PRISMA flowchart.

Results

Antimicrobials with the superiority of prolonged infusion to standard infusion in terms of efficacy and safety include meropenem, doripenem, imipenem, cefepime, ceftazidime, piperacillin/tazobactam, linezolid, and vancomycin. The strategy of concomitantly reducing total daily dose and prolonging infusion time may cause treatment failure (eg, imipenem). Extended infusion of piperacillin/tazobactam has pharmacoeconomic advantage over standard infusion. Prolonged infusion of voriconazole is inferior to standard infusion because of lower efficacy caused by pharmacokinetic changes. Comparable outcomes following standard infusion and continuous infusion were observed with norvancomycin and nafcillin. Factors determining whether prolonged infusion has a benefit over standard infusion include MIC of bacterial pathogens, bacterial density, diagnosis, disease severity, total daily dose, and renal function.

Conclusion

To maximally preserve the effectiveness of current antimicrobials, effective interventions should be implemented to enhance the application of optimal infusion strategies. For reducing nephrotoxicity, prolonged infusion of meropenem is better than conventional infusion in neonates with Gram-negative late-onset sepsis, and continuous infusion of vancomycin is superior to intermittent infusion. For increasing efficacy, prolonged or continuous infusion of time-dependent antimicrobials (eg, meropenem, doripenem, imipenem, cefepime, ceftazidime, piperacillin/tazobactam, linezolid, and vancomycin) is an optimal choice. Nevertheless, such advantages may only be demonstrated in special clinical circumstances and special populations (eg, patients with a sequential organ failure assessment (SOFA) score≥9, respiratory tract infections, urinary or intra-abdominal infections, or infections caused by less susceptible pathogens would benefit from prolonged infusion of piperacillin/tazobactam).

Evaluating outcomes of alternative dosing strategies for cefepime: a qualitative systematic review

OBJECTIVE

To perform a qualitative systematic review of the evidence comparing traditional with prolonged intermittent or continuous infusions of cefepime based on clinical and pharmacodynamic outcomes.

DATA SOURCES

PubMed (1946 to October 2014), EMBASE (1980 to October 2014), CENTRAL, Cochrane Database of Systematic Reviews, Web of Science, and International Pharmaceutical Abstracts (1970 to October 2014) were searched using the terms cefepime, pharmacokinetics, pharmacodynamics, drug administration, intravenous infusions, intravenous drug administration, continuous infusion, extended infusion, and intermittent therapy. Reference lists from relevant materials were reviewed.

STUDY SELECTION AND DATA EXTRACTION

Articles evaluating administration regimens of cefepime, one of which included the traditional, manufacturer-recommended 0.5-hour infusion and the other a prolonged or continuous infusion were included. Prespecified clinical outcomes of interest included all-cause mortality, length of hospital stay, clinical cure, and adverse events. The primary pharmacodynamic outcome was percentage time of unbound drug concentration remaining above the minimum inhibitory concentration.

DATA SYNTHESIS

In all, 18 studies were included; 6 studies assessed clinical outcomes, and 12 assessed pharmacodynamic outcomes. Prolonged or continuous infusions of cefepime achieved the pharmacodynamic targets more often than traditional infusions. The association of improved clinical outcomes with prolonged or continuous infusions is unclear. All-cause mortality was significantly decreased with the use of a prolonged cefepime infusion in a retrospective study. Two prospective, randomized studies demonstrated no statistically significant difference in mortality between prolonged and intermittent infusions.

CONCLUSIONS

The available literature on prolonged and continuous infusions of cefepime demonstrated an improved achievement of pharmacodynamic targets; however, the effect on clinical outcomes is inconclusive. Well-designed prospective studies are required to determine optimal dosing and administration strategies.

Low flucloxacillin concentrations in a patient with central nervous system infection: the need for plasma and cerebrospinal fluid drug monitoring in the ICU

OBJECTIVE

To report the difficulty in achieving and maintaining target antibiotic exposure in critically ill patients with deep-seeded infections.

CASE SUMMARY

We present a case of a 36-year-old man who was admitted to the intensive care unit with diffuse central nervous system and peripheral methicillin-sensitive Staphylococcus aureus infection (minimum inhibitory concentration; MIC, 1 µg/mL). Owing to the complicated nature of the infection, sequential concentrations of free flucloxacillin were measured in plasma and cerebrospinal fluid (CSF) and used to direct antibiotic dosing. Unsurprisingly, the trough plasma concentrations of flucloxacillin were below the MIC (0.2-0.4 µg/mL), and the corresponding CSF concentrations were undetectable (<0.1 µg/mL) with standard intermittent bolus dosing of 2 g every 4 hours. By administering flucloxacillin by continuous infusion (CI) and increasing the dose to 20 g daily, the plasma (2.2-5.7 µg/mL) and CSF (0.1 µg/mL) levels were increased, albeit lower than the predefined targets (plasma, 40 µg/mL; CSF, 4 µg/mL).

DISCUSSION

The presence of physiological changes associated with critical illness-namely, hypoalbuminemia and augmented renal clearance-may significantly alter antibiotic pharmacokinetics, and this phenomenon may lead to suboptimal antibiotic exposure if they are not accounted for. This case also highlights the value of applying CI in such patient groups and demonstrates the significance of monitoring plasma and CSF drug concentrations in optimizing antibiotic delivery.

CONCLUSIONS

Future research should aim to evaluate the utility of such drug monitoring with regard to patient outcomes and cost-effectiveness.