Pharmacokinetics of meropenem in children receiving continuous renal replacement therapy: Validation of clinical trial simulations

The impact of extracorporeal support on antimicrobial pharmacokinetics in critically ill neonatal and paediatric patients: A systematic review

OBJECTIVES

Infections represent a major risk for critically ill neonatal and paediatric patients requiring extracorporeal life-saving support such as extracorporeal membrane oxygenation (ECMO) and/or continuous renal replacement therapies (CRRT). Patient outcomes rely on achieving target antimicrobial concentrations. In critically ill adults on extracorporeal support, suboptimal antimicrobial concentrations have been shown to be common. Our objective was to systematically review antimicrobial pharmacokinetic studies in critically ill term neonatal and paediatric patients receiving ECMO and/or CRRT and compare them to similar cohorts of patients not receiving ECMO or CRRT.

METHODS

Studies published between 1990 and 2022 were identified through systematic searches in PUBMED, Embase, Web of Science, Medline, Google Scholar and CINAHL. Studies were included which provided antimicrobial pharmacokinetic parameters (volume of distribution and clearance) in the neonatal and paediatric patients receiving ECMO and/or CRRT. Studies were excluded if no antimicrobial pharmacokinetic parameters were described or could be calculated.

RESULTS

Forty-four pharmacokinetic studies were identified describing 737 patients, with neonatal patients recruited in 70% of the ECMO studies and <1% of the CRRT studies. Of all the studies, 50% were case reports or case series. The pharmacokinetics were altered for gentamicin, daptomycin, ceftolozane, micafungin, voriconazole, cefepime, fluconazole, piperacillin, and vancomycin, although considerable patient variability was described.

CONCLUSION

Significant gaps remain in our understanding of the pharmacokinetic alterations in neonatal and paediatric patients receiving ECMO and CRRT support.

Can capillary microsampling facilitate a clinical pharmacokinetics study of cefazolin in critically ill children?

Aim: Pharmacokinetic studies in children are limited, in part due to challenges in blood sampling. We compare the use of capillary microsampling and conventional sampling techniques in pediatric patients to show results that can be used in the pharmacokinetic analysis of Cefazolin.Patients & Methods: Paired blood samples (n = 48) were collected from 12 patients (median age/weight 49 months/18 kg).Results: The United States Federal Drug Administration incurred sample reanalysis acceptance criteria was used and identified 79% of paired samples achieved a difference of less than 20% in magnitude with a capillary microsampling bias of -10% (SD 20%). With exclusion of PK outliers, this rose to 88%.Conclusion: Capillary microsampling is reliable, meets acceptance criteria and can be used in pharmacokinetic studies.ACTRN: 12618001469202.

Meropenem Clearance in a Child With End-stage Renal Disease Undergoing Prolonged Intermittent Renal Replacement Therapy: A Case Report and Literature Review

BACKGROUND

Meropenem is frequently used to treat severe infections in critically ill children. However, pharmacokinetic data on meropenem in children with end-stage renal disease (ESRD) undergoing prolonged intermittent renal replacement therapy (PIRRT) is limited. Our objectives were to evaluate meropenem clearance in a child with ESRD with and without PIRRT, compare the results to previous continuous renal replacement therapy studies in children, toddlers and neonates, and assess whether the currently used dose of meropenem is sufficient.

CASE DESCRIPTION

A 5-year-old girl with an estimated glomerular filtration rate of 12.8 mL/min/1.73 m 2 was diagnosed with pulmonary infection and treated with 300 mg meropenem once a day. PIRRT was performed for 8 hours every 2 days. We used WinNonlin to evaluate meropenem clearance with and without PIRRT.

RESULTS

Our case showed that PIRRT increased the clearance of meropenem from 1.39 (1.3) to 2.42 L/h (2.3 mL/kg/min) and caught up 42.6% of the total clearance. This result is in accordance with previous studies in children but slightly less than seen in toddlers and neonates under continuous renal replacement therapy. The current dose of 300 mg once a day is not sufficient to reach the therapeutic target.

CONCLUSIONS

Predicting meropenem clearance in children with ESRD undergoing PIRRT is difficult as clearance will be affected by renal function, PIRRT settings and other factors. Further studies are needed to explore the individual variability of meropenem clearance and optimize the dosing regimen.

β-lactam precision dosing in critically ill children: Current state and knowledge gaps

There has been emerging interest in implementing therapeutic drug monitoring and model-informed precision dosing of β-lactam antibiotics in critically ill patients, including children. Despite a position paper endorsed by multiple international societies that support these efforts in critically ill adults, implementation of β-lactam precision dosing has not been widely adopted. In this review, we highlight what is known about β-lactam antibiotic pharmacokinetics and pharmacodynamics in critically ill children. We also define the knowledge gaps that present barriers to acceptance and implementation of precision dosing of β-lactam antibiotics in critically ill children: a lack of consensus on which subpopulations would benefit most from precision dosing and the uncertainty of how precision dosing changes outcomes. We conclude with opportunities for further research to close these knowledge gaps.

Pharmacokinetics of Commonly Used Medications in Children Receiving Continuous Renal Replacement Therapy: A Systematic Review of Current Literature

BACKGROUND AND OBJECTIVE

The use of continuous renal replacement therapy (CRRT) for renal support has increased substantially in critically ill children compared with intermittent modalities owing to its preferential effects on hemodynamic stability. With the expanding role of CRRT, the quantification of extracorporeal clearance and the effect on primary pharmacokinetic parameters is of the utmost importance. Within this review, we aimed to summarize the current state of the literature and compare published pharmacokinetic analyses of commonly used medications in children receiving CRRT to those who are not.

METHODS

A systematic search of the literature within electronic databases PubMed, EMBASE, Cochrane Library, and Web of Science was conducted. Published studies that were included contained relevant information on the use of commonly administered medications to children, from neonates to adolescents, receiving CRRT. Pharmacokinetic parameters that were analyzed included volume of distribution, total clearance, extracorporeal clearance, area under the curve, and elimination half-life. Information regarding CRRT circuit, flow rates, and membrane components was analyzed to investigate differences in pharmacokinetics between each modality.

RESULTS

Forty-five studies met the final inclusion criteria within this systematic review, totaling 833 pediatric patients, with 586 receiving CRRT. Antimicrobials were the most common pharmacological class represented within the literature, representing 81% (35/43) of studies analyzed. Children receiving CRRT largely had similar volume of distribution and total clearance to critically ill children not receiving CRRT, suggesting reno-protective dose adjustments may lead to subtherapeutic dosing regimens in these patients. Overall, there was a tendency for hydrophilic agents, with a low protein binding to undergo elevated total clearance in these children. However, results should be interpreted with caution because of the large variability amongst patient populations and heterogeneity with CRRT modalities, flow rates, and use of extracorporeal membrane oxygenation within studies. This review was able to identify that variation in solute removal, or CRRT modalities, properties (i.e., flow rates), and membrane composition, may have differing effects on the pharmacokinetics of commonly administered medications.

CONCLUSIONS

The current state of the literature regarding medications administered to children receiving CRRT largely focuses on antimicrobials. Significant gaps remain with other commonly used medications such as sedatives and analgesics. Overall reporting of patient clinical characteristics, CRRT settings, and circuit composition was poor, with only 10% of articles including all relevant information to assess the impact of CRRT on total clearance. Changes in pharmacokinetics because of CRRT often required higher than labeled doses, suggesting renally adjusted or reno-protective doses may lead to subtherapeutic dosing regimens. A thorough understanding of the interplay between patient, drug, and CRRT-circuit factors are required to ensure adequate delivery of dosing regimens to this vulnerable population.

Antimicrobial Dosing Recommendations in Pediatric Continuous Renal Replacement Therapy: A Critical Appraisal of Current Evidence

OBJECTIVES

Continuous renal replacement therapy (CRRT) is commonly employed in critically ill children and is known to affect antimicrobial pharmacokinetics. There is a lack of readily available, evidence-based antimicrobial dosing recommendations in pediatric CRRT. This study aims to quantify commonly used antimicrobial drugs in pediatric CRRT and identify gaps between contemporary literature-based dosing recommendations and those presented in a frequently used dosing reference.

METHODS

The Pediatric Health Information System (PHIS) database was queried from July 1, 2018 through June 30, 2021 to identify admissions in which antimicrobials were billed on the same day as CRRT. Drugs of interest were selected if at least 10% of admission involved administration on at least one CRRT day, with additional clinically important antimicrobials selected by the authors. A comprehensive literature search was performed to identify antimicrobial pharmacokinetic (PK) studies in children for each selected drug. For identified articles, dosing recommendations were extracted and compared to those in a popular tertiary dosing reference (Lexi-Comp Online database). The level of agreement of the dosing recommendations was assessed.

RESULTS

77 unique antimicrobial agents were identified amongst 812 admissions from 20 different PHIS hospitals. Fifteen antimicrobials were billed on the same day as CRRT in ≥10% of admissions, with 4 additional drugs deemed clinically relevant by the authors. Twenty PK studies were identified for these 19 drugs, and dosing recommendations were included in 8 (42.1%) of them. Seventeen agents (89.5%) had some type of CRRT-specific dosing guidance in Lexi-Comp, with only 1 directly based on a pediatric CRRT study. For the 8 agents with PK data available, Lexi-Comp recommendations matched primary literature dosing guidance in 3 (37.5%). Two (25%) lacked agreement between the Lexi-Comp and primary literature, and the remaining 3 (37.5%) had partial agreement with multiple dosing regimens suggested in the primary literature and at least one of these regimens recommended by Lexi-Comp.

CONCLUSION

Significant gaps exist in the data supporting antimicrobial dosing recommendations for children receiving CRRT. Future studies should focus on antimicrobial dosing in pediatric CRRT, emphasizing provision of robust data from which dosing recommendations can be promptly incorporated into tertiary dosing references.

Patient-centered outcomes in pediatric continuous kidney replacement therapy: new morbidity and worsened functional status in survivors

BACKGROUND

Ongoing measures to improve pediatric continuous kidney replacement therapy (CKRT) have lowered mortality rates, shifting the focus to survivor functional status. While septic acute kidney injury generates new morbidity in pediatric critically ill patients, acquired morbidities and functional status of CKRT population are unknown. We predicted that CKRT survivors are at risk for new morbidity and would have worse functional status at PICU discharge compared to baseline, and aimed to describe associated factors.

METHODS

Retrospective cohort study over 24 months of CKRT patients surviving to PICU discharge in a quaternary children's hospital. Functional outcome was determined by Functional Status Scale (FSS).

RESULTS

FSS scores were higher at PICU and hospital discharge compared to baseline. Of 45 CKRT survivors, 31 (69%) had worse FSS score at PICU discharge and 51% had new morbidity (≥3 increase in FSS); majority qualified as moderate to severe disability (FSS ≥10). Four patients (9%) had new tracheostomy, 3 (7%) were ventilator dependent, and 10 (22%) were dialysis dependent. Most (23/45, 51%) required outpatient rehabilitation. Cumulative days on sedation, controlled for illness severity, were independently associated with worse FSS at PICU discharge (aOR 25.18 (3.73, 169.92)). In adjusted analyses, duration of sedation was associated with new morbidity, while neurologic comorbidity, percent fluid overload at CKRT start, and nonrenal comorbidity were associated with moderate to severe disability at PICU discharge when controlled for baseline FSS.

CONCLUSIONS

CKRT survivors, with new morbidity and worse functional outcomes at PICU discharge, are a newly described vulnerable population requiring targeted follow-up. Deliberate decrease of sedation exposure in patients with decreased clearance due to organ dysfunction needs to be studied as a modifiable risk factor.

Optimized Dosing Regimens of Meropenem in Septic Children Receiving Extracorporeal Life Support

Objectives: To develop a population pharmacokinetic model of meropenem in children with sepsis receiving extracorporeal life support (ECLS) and optimize the dosage regimen based on investigating the probability of target attainment (PTA). Methods: The children with sepsis were prospectively enrolled in a pediatric intensive care unit from January 2018 to December 2019. The concentration-time data were fitted using nonlinear mixed effect model approach by NONMEM program. The stochastic simulation considering various scenarios based on proposed population pharmacokinetics model were conducted, and the PTAs were calculated to optimize the dosage regimens. Results: A total of 25 children with sepsis were enrolled, of whom13 received ECMO, 9 received CRRT, and 4 received ECMO combined with CRRT. 12 children received a two-step 3-h infusion and 13 children received 1-h infusion. Bodyweight and creatinine clearance had significant impacts on the PK parameters. ECMO intervention was not related to the PK properties. If 100%T > MIC was chosen as target, children receiving 40 mg/kg q8h over a 3 h-infusion only reached the PTA up to 77.4%. If bacteria with MIC 2 mg/L were to be treated with meropenem and the PTA target was 50%T > MIC, a dose of 40 mg/kg q8h for 1 h infusion would be necessary. Conclusions: The PK properties of meropenem in septic children receiving extracorporeal life support were best described. We recommended the opitimized dosing regimens for septic children receiving ECLS depending on the PTA of PK target 50%T > MIC and 100%T > MIC, for children with sepsis during ECLS with different body weight, estimated creatinine clearance (eCRCL) and MIC of bacteria.

Optimal Dosing of Meropenem in a Small Cohort of Critically Ill Children Receiving Continuous Renal Replacement Therapy

Severe sepsis is an important cause of mortality and morbidity in critically ill children. Meropenem is a broad-spectrum antibiotic commonly used to treat sepsis. Current meropenem dosage recommendations for children on continuous renal replacement therapy are extrapolated from pharmacokinetic (PK) studies done in adults. Our study aims to determine the optimal dosing in critically ill septic children receiving continuous renal replacement therapy. A prospective single-center PK study was performed in 9 children in the intensive care unit on continuous renal replacement therapy. Meropenem concentrations were measured from blood and effluent fluid samples. A population PK model was developed using nonlinear mixed-effects modeling software (NONMEM, AstraZeneca UK Ltd, Cheshire, UK). Monte Carlo simulations were performed. The PK/pharmacodynamic target aimed for plasma concentrations above minimum inhibitory concentration of 4 mg/L for 100% of dosing interval (100%ƒT>MIC ). A 2-compartment model best characterized meropenem PK. Mean (range) clearance and elimination half-life was 0.091 L/h/kg (0.04-0.157) and 3.9 hours (2.1-7.5), respectively. Dosing of 40 mg/kg/dose every 12 hours over 30 minutes achieved PK/PD target in only 32% while 20 mg/kg every 8 hours over 4 hours or 40 mg/kg every 8 hours over 2 hours achieved 100% ƒT>MIC target for at least 90% of simulated patients.

Optimizing the Use of Antibiotic Agents in the Pediatric Intensive Care Unit: A Narrative Review

Antibiotics are one of the most prescribed drug classes in the pediatric intensive care unit, yet the incidence of inappropriate antibiotic prescribing remains high in critically ill children. Optimizing the use of antibiotics in this population is imperative to guarantee adequate treatment, avoid toxicity and the occurrence of antibiotic resistance, both on a patient level and on a population level. Antibiotic stewardship encompasses all initiatives to promote responsible antibiotic usage and the PICU represents a major target environment for antibiotic stewardship programs. This narrative review provides a summary of the available knowledge on the optimal selection, duration, dosage, and route of administration of antibiotic treatment in critically ill children. Overall, more scientific evidence on how to optimize antibiotic treatment is warranted in this population. We also give our personal expert opinion on research priorities.

Reappraisal of the Optimal Dose of Meropenem in Critically Ill Infants and Children: a Developmental Pharmacokinetic-Pharmacodynamic Analysis

Data of developmental pharmacokinetics (PK) of meropenem in critically ill infants and children with severe infections are limited. We assessed the population PK and defined the appropriate regimen to optimize treatment in this population based on developmental PK-pharmacodynamic (PD) analysis. Blood samples were collected from pediatric intensive care unit patients with severe infection treated with standard dosage regimens for meropenem. Population PK data were analyzed using NONMEM software. Fifty-seven patients (mean age, 2.96 years [range, 0.101 to 14.4]; mean body weight, 15.8 kg [range, 5.0 to 65.0]) were included. A total of 135 meropenem concentrations were obtainable for population PK modeling. The median number of samples per patients was 2 (range, 1 to 4). A two-compartment model with first-order elimination was optimal for PK modeling. Weight and creatinine clearance (estimated by the Schwartz formula) were significantly correlated with the PK parameters of meropenem. The probabilities of target attainment for pathogens with low MICs of 1 and 2 μg/ml were 87.5% and 68.6% following administration of 40 mg/kg/dose (every 8 h [q8h]) as a 4-h infusion and 98.0% and 73.3% with high MICs of 4 and 8 μg/ml following administration of 110 mg/kg/day as a continuous infusion in critically ill infants and children under 70% fT _>MIC (the free time during which the plasma concentration of meropenem exceeds the MIC), respectively. The standard dosage regimens for meropenem did not meet an appropriate PD target, and an optimal dosing regimen was established in critically ill infants and children. (This study has been registered at ClinicalTrials.gov under identifier NCT03643497.).

Meropenem pharmacokinetics during extracorporeal membrane oxygenation and continuous haemodialysis: a case report

OBJECTIVES

Pharmacokinetic (PK) parameters can change significantly during extracorporeal membrane oxygenation (ECMO) and continuous haemodialysis. This case report describes the pharmacokinetics of a 3-h meropenem infusion in an infantile anuric patient on ECMO with continuous haemodialysis.

CASE

A 19-month-old female patient with asplenia syndrome was admitted to the paediatric intensive care unit for postoperative management of an extracardiac total cavopulmonary connection procedure. Veno-arterial ECMO and continuous haemodialysis were initiated on postoperative Day 2 for circulatory insufficiency due to septic shock and thrombosis of the inferior vena cava extending to the pulmonary artery. Blood and ascites cultures were positive for extended-spectrum β-lactamase-producing Escherichia coli, and 3-h meropenem infusions [120-300 mg/kg/day divided every 8 h (q8h)] were commenced. Following dose escalation to 300 mg/kg/day q8h, sustained negative blood cultures were confirmed. The estimated meropenem clearance and volume of distribution (V_d) were 2.21 mL/kg/min and 0.59 L/kg, respectively. These patient-specific PK parameters were used to predict the PK profile of various dosing regimens. Both 1-h and 3-h infusions of meropenem at 60, 120 and 200 mg/kg/day q8h predicted that the free drug concentration would remain above the minimum inhibitory concentration (fT_>MIC) at an MIC of 1 μg/mL for >40% of the dosing interval. However, when the target was set at 100% fT_>MIC, only a 3-h infusion of 200 mg/kg/day q8h could achieve the target in this patient despite the presence of anuria.

CONCLUSION

To optimise meropenem dosing in paediatric patients on ECMO and continuous haemodialysis, further study and PK monitoring are warranted.

Comparative review of imipenem/cilastatin versus meropenem

INTRODUCTION

Carbapenems are broad-spectrum antibacterial molecules. Imipenem-cilastatin and meropenem are the two main molecules used in French healthcare services.

OBJECTIVE

We aimed to evaluate the relative strengths and weaknesses of these two molecules by considering their pharmacokinetic, pharmacodynamic, microbiological, and clinical properties. We demonstrated that imipenem-cilastatin and meropenem are not alike.

METHOD

Review of the literature by querying the MEDLINE network.

RESULTS

Imipenem-cilastatin is the first marketed molecule of the carbapenem class. It is more effective against Gram-positive cocci. Its stability does not allow for long infusions and its main adverse effect on the central nervous system limits its use. Meropenem is more effective against Gram-negative bacilli. Its stability and its milder adverse effects distinguish it from imipenem-cilastatin.

CONCLUSION

Meropenem is preferred for daily use in healthcare services when carbapenems are to be used.

Surviving sepsis campaign international guidelines for the management of septic shock and sepsis-associated organ dysfunction in children

OBJECTIVES

To develop evidence-based recommendations for clinicians caring for children (including infants, school-aged children, and adolescents) with septic shock and other sepsis-associated organ dysfunction.

DESIGN

A panel of 49 international experts, representing 12 international organizations, as well as three methodologists and three public members was convened. Panel members assembled at key international meetings (for those panel members attending the conference), and a stand-alone meeting was held for all panel members in November 2018. A formal conflict-of-interest policy was developed at the onset of the process and enforced throughout. Teleconferences and electronic-based discussion among the chairs, co-chairs, methodologists, and group heads, as well as within subgroups, served as an integral part of the guideline development process.

METHODS

The panel consisted of six subgroups: recognition and management of infection, hemodynamics and resuscitation, ventilation, endocrine and metabolic therapies, adjunctive therapies, and research priorities. We conducted a systematic review for each Population, Intervention, Control, and Outcomes question to identify the best available evidence, statistically summarized the evidence, and then assessed the quality of evidence using the Grading of Recommendations Assessment, Development, and Evaluation approach. We used the evidence-to-decision framework to formulate recommendations as strong or weak, or as a best practice statement. In addition, "in our practice" statements were included when evidence was inconclusive to issue a recommendation, but the panel felt that some guidance based on practice patterns may be appropriate.

RESULTS

The panel provided 77 statements on the management and resuscitation of children with septic shock and other sepsis-associated organ dysfunction. Overall, six were strong recommendations, 49 were weak recommendations, and nine were best-practice statements. For 13 questions, no recommendations could be made; but, for 10 of these, "in our practice" statements were provided. In addition, 52 research priorities were identified.

CONCLUSIONS

A large cohort of international experts was able to achieve consensus regarding many recommendations for the best care of children with sepsis, acknowledging that most aspects of care had relatively low quality of evidence resulting in the frequent issuance of weak recommendations. Despite this challenge, these recommendations regarding the management of children with septic shock and other sepsis-associated organ dysfunction provide a foundation for consistent care to improve outcomes and inform future research.

Surviving Sepsis Campaign International Guidelines for the Management of Septic Shock and Sepsis-Associated Organ Dysfunction in Children

OBJECTIVES

To develop evidence-based recommendations for clinicians caring for children (including infants, school-aged children, and adolescents) with septic shock and other sepsis-associated organ dysfunction.

DESIGN

A panel of 49 international experts, representing 12 international organizations, as well as three methodologists and three public members was convened. Panel members assembled at key international meetings (for those panel members attending the conference), and a stand-alone meeting was held for all panel members in November 2018. A formal conflict-of-interest policy was developed at the onset of the process and enforced throughout. Teleconferences and electronic-based discussion among the chairs, co-chairs, methodologists, and group heads, as well as within subgroups, served as an integral part of the guideline development process.

METHODS

The panel consisted of six subgroups: recognition and management of infection, hemodynamics and resuscitation, ventilation, endocrine and metabolic therapies, adjunctive therapies, and research priorities. We conducted a systematic review for each Population, Intervention, Control, and Outcomes question to identify the best available evidence, statistically summarized the evidence, and then assessed the quality of evidence using the Grading of Recommendations Assessment, Development, and Evaluation approach. We used the evidence-to-decision framework to formulate recommendations as strong or weak, or as a best practice statement. In addition, "in our practice" statements were included when evidence was inconclusive to issue a recommendation, but the panel felt that some guidance based on practice patterns may be appropriate.

RESULTS

The panel provided 77 statements on the management and resuscitation of children with septic shock and other sepsis-associated organ dysfunction. Overall, six were strong recommendations, 52 were weak recommendations, and nine were best-practice statements. For 13 questions, no recommendations could be made; but, for 10 of these, "in our practice" statements were provided. In addition, 49 research priorities were identified.

CONCLUSIONS

A large cohort of international experts was able to achieve consensus regarding many recommendations for the best care of children with sepsis, acknowledging that most aspects of care had relatively low quality of evidence resulting in the frequent issuance of weak recommendations. Despite this challenge, these recommendations regarding the management of children with septic shock and other sepsis-associated organ dysfunction provide a foundation for consistent care to improve outcomes and inform future research.

Scaling beta-lactam antimicrobial pharmacokinetics from early life to old age

AIMS

Beta-lactam dose optimization in critical care is a current priority. We aimed to review the pharmacokinetics (PK) of three commonly used beta-lactams (amoxicillin ± clavulanate, piperacillin-tazobactam and meropenem) to compare PK parameters reported in critically and noncritically ill neonates, children and adults, and to investigate whether allometric and maturation scaling principles could be applied to describe changes in PK parameters through life.

METHODS

A systematic review of PK studies of the three drugs was undertaken using MEDLINE and EMBASE. PK parameters and summary statistics were extracted and scaled using allometric principles to 70 kg individual for comparison. Pooled data were used to model clearance maturation and decline using a sigmoidal (Hill) function.

RESULTS

A total of 130 papers were identified. Age ranged from 29 weeks to 82 years and weight from 0.9-200 kg. PK parameters from critically ill populations were reported with wider confidence intervals than those in healthy volunteers, indicating greater PK variability in critical illness. The standard allometric size and sigmoidal maturation model adequately described increasing clearance in neonates, and a sigmoidal model was also used to describe decline in older age. Adult weight-adjusted clearance was achieved at approximately 2 years postmenstrual age. Changes in volume of distribution were well described by the standard allometric model, although amoxicillin data suggested a relatively higher volume of distribution in neonates.

CONCLUSIONS

Critical illness is associated with greater PK variability than in healthy volunteers. The maturation models presented will be useful for optimizing beta-lactam dosing, although a prospective, age-inclusive study is warranted for external validation.

Uncertainty in Antibiotic Dosing in Critically Ill Neonate and Pediatric Patients: Can Microsampling Provide the Answers?

PURPOSE

With a decreasing supply of antibiotics that are effective against the pathogens that cause sepsis, it is critical that we learn to use currently available antibiotics optimally. Pharmacokinetic studies provide an evidence base from which we can optimize antibiotic dosing. However, these studies are challenging in critically ill neonate and pediatric patients due to the small blood volumes and associated risks and burden to the patient from taking blood. We investigate whether microsampling, that is, obtaining a biologic sample of low volume (<50 μL), can improve opportunities to conduct pharmacokinetic studies.

METHODS

We performed a literature search to find relevant articles using the following search terms: sepsis, critically ill, severe infection, intensive care AND antibiotic, pharmacokinetic, p(a)ediatric, neonate. For microsampling, we performed a search using antibiotics AND dried blood spots OR dried plasma spots OR volumetric absorptive microsampling OR solid-phase microextraction OR capillary microsampling OR microsampling. Databases searched include Web of Knowledge, PubMed, and EMbase.

FINDINGS

Of the 32 antibiotic pharmacokinetic studies performed on critically ill neonate or pediatric patients in this review, most of the authors identified changes to the pharmacokinetic properties in their patient group and recommended either further investigations into this patient population or therapeutic drug monitoring to ensure antibiotic doses are suitable. There remain considerable gaps in knowledge regarding the pharmacokinetic properties of antibiotics in critically ill pediatric patients. Implementing microsampling in an antibiotic pharmacokinetic study is contingent on the properties of the antibiotic, the pathophysiology of the patient (and how this can affect the microsample), and the location of the patient. A validation of the sampling technique is required before implementation.

IMPLICATIONS

Current antibiotic regimens for critically ill neonate and pediatric patients are frequently suboptimal due to a poor understanding of altered pharmacokinetic properties. An assessment of the suitability of microsampling for pharmacokinetic studies in neonate and pediatric patients is recommended before wider use. The method of sampling, as well as the method of bioanalysis, also requires validation to ensure the data obtained reflect the true result.