Principles of Drug Dosing in Sustained Low Efficiency Dialysis (SLED) and Review of Antimicrobial Dosing Literature

Characterization of Ganciclovir Dosing for the Management of Cytomegalovirus in Solid Organ Transplant Recipients Receiving Sustained Low-Efficiency Dialysis

BACKGROUND

The optimal dosing of intravenous ganciclovir in patients receiving sustained low-efficiency dialysis (SLED) remains unclear.

OBJECTIVE

The primary objective is to characterize the dosing of ganciclovir for treating and preventing cytomegalovirus (CMV) in Solid Organ Transplant Recipients receiving SLED. The secondary objective is to evaluate the safety and efficacy of the dosing practices described in this study.

METHODS

Retrospective review of electronic medical records from solid organ transplant recipients (SOTRs) admitted to the Medical Surgical Intensive Care Unit at the Toronto General Hospital (TGH) between November 28, 2016, and September 1, 2021, was conducted. Patients concurrently receiving ganciclovir and SLED were included.

RESULTS

Among the 27 encounters for CMV prevention, 18 patients underwent 8-hour SLED, 6 underwent 24-hour SLED, and 3 received other SLED durations. Most patients (80%) on 8-hour SLED began ganciclovir at 2.5 mg/kg/d, whereas 80% of those on 24-hour SLED started at 5 mg/kg/d. No breakthrough viremia occurred at 5 mg/kg/d, with 1 instance at 2.5 mg/kg/d. Cytopenia rates were higher at 5 mg/kg/d (33% vs 20%). For treatment (n = 20), 16 patients underwent 8-hour SLED, 2 underwent 24-hour SLED, and 2 underwent 12-hour SLED. Most (75%) on 8-hour SLED started at 2.5 mg/kg/d, whereas all on 24-hour SLED began at 5 mg/kg/d. Viral eradication rates were 75% and 60% at 2.5 and 5 mg/kg/d, respectively, with higher cytopenia rates at 5 mg/kg/d (37.5% vs 0%). Dose adjustments were primarily in response to refractory disease or cytopenia.

CONCLUSION AND RELEVANCE

At our institution, ganciclovir dosing patterns suggest that for patients requiring 8-hour SLED, there is clinician comfort in using 2.5 mg/kg/d for prevention and 5 mg/kg/d for treatment. In 24-hour SLED, 5 mg/kg/d may be considered for prevention. Higher doses may be considered for CMV treatment; however, we found greater variability in the dosing practices for these patients. Further research with larger sample sizes and ganciclovir drug-level assessments is needed to optimize dosing strategies for CMV treatment.

Model-informed identification of optimised dosing strategies for meropenem in critically ill patients receiving SLEDD: an observational study

PURPOSE

An increasing number of critically ill patients receive slow extended daily dialysis (SLEDD) due to their pathophysiology while suffering from sepsis, necessitating effective and safe antibiotic therapy. Although SLEDD reduces meropenem exposure and increases treatment failure risk, effective and safe dosing regimens are unclear. We aimed to identify optimised meropenem dosing strategies for critically ill SLEDD patients through population pharmacokinetic (PK) modelling and PK/pharmacodynamic (PD)-based probability of target attainment (PTA) analysis.

METHODS

Clinical data from a prospective study involving critically ill SLEDD patients receiving meropenem were monitored through routine therapeutic drug monitoring. A total of 178 blood samples from 13 patients (median 14 samples per patient) were analysed. A PK model was developed and utilised to evaluate 24 clinically relevant dosing regimens during SLEDD therapy (7-h on-SLEDD periods q24h) in PTA analyses. The PK/PD target window of minimum meropenem concentration between 8 mg/L (P. aeruginosa; R-breakpoint) and 44.45 mg/L (toxicity threshold) was used.

RESULTS

A one-compartment PK model with linear elimination and total clearance (CL) split into renal (CLREN; 45%) and SLEDD-associated (55%) CL well characterised the SLEDD data. Creatinine clearance (urine-collected; CLCRurine) was identified as significant factor on CLREN. Continuous infusions, specifically 2 g q24h for CLCRurine 0-25 mL/min and 3 g q24h for CLCRurine 25-40 mL/min, showed the highest PTA being effective and safe during SLEDD therapy. A comprehensive dosing nomogram was developed.

CONCLUSION

Our easy-to-use dosing nomogram presents a promising tool in optimising meropenem dosing regimens for critically ill SLEDD patients considering their kidney function in clinical practice.

TRIAL REGISTRATION

Clinicaltrials.gov NCT03985605. Registered 14 June 2019. https://classic.

CLINICALTRIALS

gov/ct2/show/study/NCT03985605.

Scoping review of drug dosing recommendations in sustained low-efficiency dialysis

The objective of this scoping review was to answer the question, "What has been published describing drug dosing in sustained low-efficiency dialysis (SLED)?" PubMed, Embase, and Scopus were searched on November 18, 2022. Methodology followed the Arksey and O'Malley framework for scoping reviews and Preferred Reporting Items for Systematic Reviews and Meta-Analysis Extension for Scoping Reviews guidelines. Two investigators independently screened abstracts and full-texts of citations identified related to drug dosing and SLED. Exclusion criteria included case reports, conference abstracts, pediatrics, treatment dialysis, and non-human subjects. A standardized data extraction sheet was used to collate and summarize data. The quality of evidence was evaluated by two investigators using the Mixed Methods Appraisal Tool. A total of 230 citations were identified for screening. Of these, 29 studies met criteria for inclusion after full-text review. Four drug groups including beta-lactam antibiotics, non-beta-lactam antibiotics, antifungals, and levetiracetam were identified. Dialysate rates, dialysis durations, and medication doses used varied widely across studies. Outcomes and pharmacokinetic parameters that were assessed were also heterogenous. Drug dosing in SLED is challenging and there is minimal evidence available to guide appropriate dosing. Larger studies are needed to more accurately determine how to appropriately dose medications in SLED. Therapeutic drug monitoring should be used in all patients on SLED when available.

Archetypal sustained low-efficiency daily diafiltration (SLEDD-f) for critically ill patients requiring kidney replacement therapy: towards an adequate therapy

Sustained low-efficiency dialysis is a hybrid form of kidney replacement therapy that has gained increasing popularity as an alternative to continuous forms of kidney replacement therapy in intensive care unit settings. During the COVID-19 pandemic, the shortage of continuous kidney replacement therapy equipment led to increasing usage of sustained low-efficiency dialysis as an alternative treatment for acute kidney injury. Sustained low-efficiency dialysis is an efficient method for treating hemodynamically unstable patients and is quite widely available, making it especially useful in resource-limited settings. In this review, we aim to discuss the various attributes of sustained low-efficiency dialysis and how it is comparable to continuous kidney replacement therapy in efficacy, in terms of solute kinetics and urea clearance, and the various formulae used to compare intermittent and continuous forms of kidney replacement therapy, along with hemodynamic stability. During the COVID-19 pandemic, there was increased clotting of continuous kidney replacement therapy circuits, which led to increased use of sustained low-efficiency dialysis alone or together with extra corporeal membrane oxygenation circuits. Although sustained low-efficiency dialysis can be delivered with continuous kidney replacement therapy machines, most centers use standard hemodialysis machines or batch dialysis systems. Even though antibiotic dosing differs between continuous kidney replacement therapy and sustained low-efficiency dialysis, reports of patient survival and renal recovery are similar for continuous kidney replacement therapy and sustained low-efficiency dialysis. Health care studies indicate that sustained low-efficiency dialysis has emerged as a cost-effective alternative to continuous kidney replacement therapy. Although there is considerable data to support sustained low-efficiency dialysis treatments for critically ill adult patients with acute kidney injury, there are fewer pediatric data, even so, currently available studies support the use of sustained low-efficiency dialysis for pediatric patients, particularly in resource-limited settings.

How I prescribe prolonged intermittent renal replacement therapy

Prolonged Intermittent Renal Replacement Therapy (PIRRT) is the term used to define 'hybrid' forms of renal replacement therapy. PIRRT can be provided using an intermittent hemodialysis machine or a continuous renal replacement therapy (CRRT) machine. Treatments are provided for a longer duration than typical intermittent hemodialysis treatments (6-12 h vs. 3-4 h, respectively) but not 24 h per day as is done for continuous renal replacement therapy (CRRT). Usually, PIRRT treatments are provided 4 to 7 times per week. PIRRT is a cost-effective and flexible modality with which to safely provide RRT for critically ill patients. We present a brief review on the use of PIRRT in the ICU with a focus on how we prescribe it in that setting.

Pharmacokinetic Alterations Associated with Critical Illness

Haemodynamic, metabolic, and biochemical derangements in critically ill patients affect drug pharmacokinetics and pharmacodynamics making dose optimisation particularly challenging. Appropriate therapeutic dosing depends on the knowledge of the physiologic changes caused by the patient's comorbidities, underlying disease, resuscitation strategies, and polypharmacy. Critical illness will result in altered drug protein binding, ionisation, and volume of distribution; it will also decrease oral drug absorption, intestinal and hepatic metabolism, and renal clearance. In contrast, the resuscitation strategies and the use of vasoactive drugs may oppose these effects by leading to a hyperdynamic state that will increase blood flow towards the major organs including the brain, heart, kidneys, and liver, with the subsequent increase of drug hepatic metabolism and renal excretion. Metabolism is the main mechanism for drug clearance and is one of the main pharmacokinetic processes affected; it is influenced by patient-specific factors, such as comorbidities and genetics; therapeutic-specific factors, including drug characteristics and interactions; and disease-specific factors, like organ dysfunction. Moreover, organ support such as mechanical ventilation, renal replacement therapy, and extracorporeal membrane oxygenation may contribute to both inter- and intra-patient variability of drug pharmacokinetics. The combination of these competing factors makes it difficult to predict drug response in critically ill patients. Pharmacotherapy targeted to therapeutic goals and therapeutic drug monitoring is currently the best option for the safe care of the critically ill. The aim of this paper is to review the alterations in drug pharmacokinetics associated with critical illness and to summarise the available evidence.