Adjustment of Antimicrobial Dosages for Continuous Venovenous Hemofiltration Based on Patient-Specific Information

Rationale and evidence for the use of new beta-lactam/beta-lactamase inhibitor combinations and cefiderocol in critically ill patients

BACKGROUND

Healthcare-associated infections involving Gram-negative bacteria (GNB) with difficult-to-treat resistance (DTR) phenotype are associated with impaired patient-centered outcomes and poses daily therapeutic challenges in most of intensive care units worldwide. Over the recent years, four innovative β-lactam/β-lactamase inhibitor (BL/BLI) combinations (ceftolozane-tazobactam, ceftazidime-avibactam, imipenem-relebactam and meropenem-vaborbactam) and a new siderophore cephalosporin (cefiderocol) have been approved for the treatment of certain DTR-GNB infections. The literature addressing their microbiological spectrum, pharmacokinetics, clinical efficacy and safety was exhaustively audited by our group to support the recent guidelines of the French Intensive Care Society on their utilization in critically ill patients. This narrative review summarizes the available evidence and unanswered questions on these issues.

METHODS

A systematic search for English-language publications in PUBMED and the Cochrane Library database from inception to November 15, 2022.

RESULTS

These drugs have demonstrated relevant clinical success rates and a reduced renal risk in most of severe infections for whom polymyxin- and/or aminoglycoside-based regimen were historically used as last-resort strategies-namely, ceftazidime-avibactam for infections due to Klebsiella pneumoniae carbapenemase (KPC)- or OXA-48-like-producing Enterobacterales, meropenem-vaborbactam for KPC-producing Enterobacterales, ceftazidime-avibactam/aztreonam combination or cefiderocol for metallo-β-lactamase (MBL)-producing Enterobacterales, and ceftolozane-tazobactam, ceftazidime-avibactam and imipenem-relebactam for non-MBL-producing DTR Pseudomonas aeruginosa. However, limited clinical evidence exists in critically ill patients. Extended-infusion scheme (except for imipenem-relebactam) may be indicated for DTR-GNB with high minimal inhibitory concentrations and/or in case of augmented renal clearance. The potential benefit of combining these agents with other antimicrobials remains under-investigated, notably for the most severe presentations. Other important knowledge gaps include pharmacokinetic information in particular situations (e.g., pneumonia, other deep-seated infections, and renal replacement therapy), the hazard of treatment-emergent resistance and possible preventive measures, the safety of high-dose regimen, the potential usefulness of rapid molecular diagnostic tools to rationalize their empirical utilization, and optimal treatment durations. Comparative clinical, ecological, and medico-economic data are needed for infections in whom two or more of these agents exhibit in vitro activity against the causative pathogen.

CONCLUSIONS

New BL/BLI combinations and cefiderocol represent long-awaited options for improving the management of DTR-GNB infections. Several research axes must be explored to better define the positioning and appropriate administration scheme of these drugs in critically ill patients.

Pharmacokinetics of zanamivir in critically ill patients undergoing continuous venovenous hemofiltration

BACKGROUND

Limited data exist for dosing of zanamivir in the setting of CVVH in the intensive care unit (ICU). Our objective is to report the pharmacokinetics and sieving coefficient (S_v) of zanamivir in patients receiving continuous venovenous hemofiltration (CVVH).

METHODS

In this prospective observational study, patients of ≥18 years admitted to the ICU with a life-threatening Influenza A or B infection, treated with zanamivir i.v. undergoing CVVH were included. Patients received a zanamivir loading dose of 600 mg i.v., 12 h later followed by maintenance dosages two times daily according to the treating physician. Per patient, nine CFT plasma and nine ultrafiltrate samples were drawn on day 2 of treatment and analysed with a validated HPLC-MS/MS method.

RESULTS

Four patients were included in the study. The zanamivir elimination half-life was prolonged with 5.6-9.9 h, compared to patients with normal renal function. A S_v of approximately 1.0 was identified, with unrestricted transport of zanamivir to the ultrafiltrate.

CONCLUSIONS

Zanamivir is well cleared by CVVH. In absence of the possibility for therapeutic drug monitoring, the ultrafiltration rate seems as a good surrogate parameter to estimate the CL_CVVH and may help guide the dosing of zanamivir.

Target attainment and pharmacokinetics of cefotaxime in critically ill patients undergoing continuous kidney replacement therapy

OBJECTIVES

Limited data exist about the antimicrobial target attainment and pharmacokinetics of cefotaxime in critically ill patients in the ICU undergoing continuous kidney replacement therapy (CKRT). We conducted a prospective observational study in two large teaching hospitals [Isala Hospital (IH) and Zwolle and Maasstad Hospital (MH)] to investigate target attainment and pharmacokinetics of cefotaxime in patients undergoing CKRT.

PATIENTS AND METHODS

Patients aged ≥18 years admitted to the ICU treated with IV cefotaxime 1000 mg three times daily (IH) or 4 times daily (MH) were included. Fifteen patients were enrolled in total. Per patient eight cefotaxime plasma and eight ultrafiltrate samples were drawn in IH and four plasma samples in MH on Day 2 of treatment. In ICU patients the recommended antimicrobial target of cefotaxime is a plasma concentration 100% of the time above the MIC.

RESULTS

In IH 10/11 patients had higher plasma trough concentrations than the MIC breakpoint of Enterobacterales of 1 mg/L (clinical breakpoint for susceptible strains) and 9/11 patients had concentrations above 2 mg/L (clinical breakpoint for resistant strains). All patients (4/4) in MH had higher plasma trough concentrations than 2 mg/L. A sieving coefficient of 0.74 was identified, with a median amount of 40% of cefotaxime eliminated by CKRT.

CONCLUSIONS

We conclude that cefotaxime 1000 mg 3-4 times daily gives adequate plasma concentrations in patients with anuria or oliguria undergoing CKRT. The 1000 mg four times daily dosage is recommended in patients undergoing CKRT with partially preserved renal function to achieve the target.

Clinical Pharmacokinetics and Pharmacodynamics of Cefepime

Cefepime is a broad-spectrum fourth-generation cephalosporin with activity against Gram-positive and Gram-negative pathogens. It is generally administered as an infusion over 30-60 min or as a prolonged infusion with infusion times from 3 h to continuous administration. Cefepime is widely distributed in biological fluids and tissues with an average volume of distribution of ~ 0.2 L/kg in healthy adults with normal renal function. Protein binding is relatively low (20%), and elimination is mainly renal. About 85% of the dose is excreted unchanged in the urine, with an elimination half-life of 2-2.3 h. The pharmacokinetics of cefepime is altered under certain pathophysiological conditions, resulting in high inter-individual variability in cefepime volume of distribution and clearance, which poses challenges for population dosing approaches. Consequently, therapeutic drug monitoring of cefepime may be beneficial in certain patients including those who are critically ill, have life-threatening infections, or are infected with more resistant pathogens. Cefepime is generally safe and efficacious, with a goal exposure target of 70% time of the free drug concentration over the minimum inhibitory concentration for clinical efficacy. In recent years, reports of neurotoxicity have increased, specifically in patients with impaired renal function. This review summarizes the pharmacokinetics, pharmacodynamics, and toxicodynamics of cefepime contemporarily in the setting of increasing cefepime exposures. We explore the potential benefits of extended or continuous infusions and therapeutic drug monitoring in special populations.

Management of digoxin therapy using pharmacokinetics in a patient undergoing continuous venovenous hemofiltration

PURPOSE

The management of digoxin therapy using pharmacokinetics in a patient undergoing continuous venovenous hemofiltration (CVVH) is reported.

SUMMARY

A 46-year-old African-American woman with New York Heart Association class IV, American College of Cardiology- American Heart Association stage D heart failure arrived from an outside facility with complaints of dyspnea after minimal exertion, orthopnea, and lower-extremity edema. A transthoracic echocardiogram revealed an estimated left ventricular ejection fraction of 15%. The patient subsequently required left ventricular assist device placement on hospital day 5 as a potential bridge to transplantation. A total digoxin loading dose of 500 μg i.v. (8.2 μg/kg) was given in two divided doses six hours apart. The next morning, the serum digoxin concentration was 1.9 ng/mL, and the patient was started on a maintenance digoxin dosage of 125 μg i.v. daily. On postoperative day (POD) 20, the patient developed acute kidney injury, and CVVH was initiated. The sieving coefficient (Sc), transmembrane clearance (CLtm), digoxin concentration in ultrafiltration fluid (Cuf), and need for supplemental digoxin were determined to account for CVVH- associated digoxin loss. After 14 days of CVVH, the patient's clinical condition improved, and CVVH was transitioned to intermittent hemodialysis. On POD 66, the patient was discharged to an extended-care facility without adverse reactions related to digoxin therapy.

CONCLUSION

Analysis of serum digoxin concentration and digoxin Cuf values suggested that digoxin was cleared by CVVH, allowed calculation of Sc and CLtm values, and facilitated determination of digoxin requirements in a critically ill patient requiring CVVH.

Vancomycin clearance in high-volume venovenous hemofiltration

OBJECTIVE

To report the pharmacokinetic and pharmacodynamic properties of vancomycin in 4 patients undergoing high-volume continuous venovenous hemofiltration (CVVH).

CASE SUMMARY

Data from 4 patients prescribed high-volume CVVH for acute renal failure treated with vancomycin were analyzed. Vancomycin plasma concentrations were measured 4 and 24 hours after the end of a 1-hour vancomycin infusion. The mean therapy fluid rate on initiation of vancomycin was 56.2 mL/kg/h (range 48.0-65.5). The mean loading dose of vancomycin was 18.3 mg/kg (range 14.7-19.7). Median vancomycin concentration 4 hours after the dose was 18.1 mg/L (range 13.1-30.0). At 24 hours after the dose, only 1 patient had a detectable vancomycin concentration (5.2 mg/L).

DISCUSSION

There was a large variability in the clearance of vancomycin in this patient population. Current strategies for dosing vancomycin may lead to subtherapeutic trough concentrations. Vancomycin dosing in this patient population should be based on a detailed assessment of the CVVH prescription, vancomycin concentrations, and clinical needs and response.

CONCLUSIONS

An initial vancomycin dose of 20-25 mg/kg with frequent monitoring and adjustment is recommended for patients receiving high-volume CVVH.