Utilizing an Opportunistic Clinical Study and Population-Based Pharmacokinetic Models to Identify Rational Empiric Dosing Regimens for Piperacillin-Tazobactam in Critically Ill Patients.

Determining an effective dosing regimen for piperacillin-tazobactam in critically ill patients is challenging due to substantial pharmacokinetic variability caused by complex pathophysiological changes. To address this need, a prospective clinical study was conducted, which enrolled 112 critically ill patients and employed an opportunistic sampling strategy. Population modeling and simulation were performed to characterize the pharmacokinetics (PK) and probability of target attainment (PTA) of piperacillin-tazobactam under various dosing regimens.

Population pharmacokinetics and target attainment analyses to identify a rational empirical dosing strategy for cefepime in critically ill patients.

Objectives: We aimed to identify rational empirical dosing strategies for cefepime treatment in critically ill patients by utilizing population pharmacokinetics and target attainment analysis.

Patients And Methods: A prospective and opportunistic pharmacokinetic (PK) study was conducted in 130 critically ill patients in two ICU sites. The plasma concentrations of cefepime were determined using a validated LC-MS/MS method.

Evaluation of Empirical Dosing Regimens for Meropenem in Intensive Care Unit Patients Using Population Pharmacokinetic Modeling and Target Attainment Analysis.

In the present study, population pharmacokinetic (PK) analysis was performed based on meropenem data from a prospective study conducted in 114 critically ill patients with a wide range of renal functions and various disease conditions. The final model was a one-compartment model with linear elimination, with creatinine clearance and continuous renal replacement therapy affecting clearance, and total bodyweight impacting the volume of distribution. Our model is a valuable addition to the existing meropenem population PK models, and it could be particularly useful during implementation of a therapeutic drug monitoring program combined with Bayesian forecasting.

Antibodies against biotin-labeled red blood cells can shorten posttransfusion survival.

Background: In hematologic and transfusion medicine research, measurement of red blood cell (RBC) in vivo kinetics must be safe and accurate. Recent reports indicate use of biotin-labeled RBC (BioRBC) to determine red cell survival (RCS) offers substantial advantages over Cr and other labeling methods. Occasional induction of BioRBC antibodies has been reported.

Development and validation of a simple and sensitive LC-MS/MS method for the quantification of cefazolin in human plasma and its application to a clinical pharmacokinetic study.

Cefazolin is widely used during surgery to prevent surgical site infections (SSIs). Although cefazolin redosing is often needed due to its short half-life, the appropriate redosing schedule remains controversial and there is limited information on cefazolin disposition following repeated doses during surgery. In parallel with an ongoing cefazolin redosing clinical study, we have developed and fully validated a simple and robust liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the quantification of cefazolin in human plasma.

Sex-specific cytokine responses and neurocognitive outcome after blood transfusions in preterm infants.

Background: The objective of this study was to determine sex-specific differences in inflammatory cytokine responses to red blood cell (RBC) transfusion in preterm infants in the neonatal period and their relationship to later neurocognitive status.

Methods: Infants with a birth weight <1000 g and gestational age 22-29 weeks were enrolled in the Transfusion of Prematures (TOP) trial. The total number of transfusions was used as a marker of transfusion status.

Development and validation of a simple and sensitive LC-MS/MS method for quantification of ampicillin and sulbactam in human plasma and its application to a clinical pharmacokinetic study.

Ampicillin-sulbactam is a broad-spectrum combination antibiotic used for a variety of clinical applications, including as a prophylactic agent to reduce the risk of surgical site infection. The pharmacokinetics of ampicillin-sulbactam after redosing during prolonged surgeries remains incompletely understood. In anticipation of further studying the intra-operative pharmacokinetics of this drug, we have developed a novel liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the quantification of ampicillin and sulbactam.

Neonatal Umbilical Arterial Catheter Removal Is Accompanied by a Marked Decline in Phlebotomy Blood Loss.

Background: Umbilical arterial catheters (UACs) are frequently used in critically ill neonates. UAC are convenient, reliable, and allow for caregiver convenience in performing painless arterial blood sampling. We hypothesized that UAC removal in extremely low birth weight (ELBW) neonates will result in significantly less phlebotomy blood loss (PBL) after correcting for severity of illness.

Aspects of matrix and analyte effects in clinical pharmacokinetic sample analyses using LC-ESI/MS/MS - Two case examples.

The increasing focus on high throughput sample analysis has led to the common practice of using simplest sample preparation method possible (i.e. protein precipitation) and shortest sample run-time possible.

Anemia induces gut inflammation and injury in an animal model of preterm infants.

Background: While very low birth weight (VLBW) infants often require multiple red blood cell transfusions, efforts to minimize transfusion-associated risks have resulted in more restrictive neonatal transfusion practices. However, whether restrictive transfusion strategies limit transfusions without increasing morbidity and mortality in this population remains unclear. Recent epidemiologic studies suggest that severe anemia may be an important risk factor for the development of necrotizing enterocolitis (NEC).

Quantification of Cefepime, Meropenem, Piperacillin, and Tazobactam in Human Plasma Using a Sensitive and Robust Liquid Chromatography-Tandem Mass Spectrometry Method, Part 1: Assay Development and Validation.

The highly variable pharmacokinetics of β-lactam antibiotics and β-lactamase inhibitors poses a significant challenge to clinicians in ensuring appropriate antibiotic doses in critically ill patients. Therefore, routine monitoring of plasma concentrations is important for individualization of antimicrobial therapy. Accordingly, a simple and robust analytical method for the simultaneous measurement of multiple β-lactam antibiotics and β-lactamase inhibitors is highly desirable to ensure quick decisions on dose adjustments.

Quantification of Cefepime, Meropenem, Piperacillin, and Tazobactam in Human Plasma Using a Sensitive and Robust Liquid Chromatography-Tandem Mass Spectrometry Method, Part 2: Stability Evaluation.

Although the stability of β-lactam antibiotics is a known issue, none of the previously reported bioanalytical methods had an adequate evaluation of the stability of these drugs. In the current study, the stability of cefepime, meropenem, piperacillin, and tazobactam under various conditions was comprehensively evaluated. The evaluated parameters included stock solution stability, short-term stability, long-term stability, freeze-thaw stability, processed sample stability, and whole-blood stability.

Development, validation, and potential applications of biotinylated red blood cells for posttransfusion kinetics and other physiological studies: evidenced-based analysis and recommendations.

The current reference method in the United States for measuring in vivo population red blood cell (RBC) kinetics utilizes chromium-51 ( Cr) RBC labeling for determining RBC volume, 24-hour posttransfusion RBC recovery, and long-term RBC survival. Here we provide evidence supporting adoption of a method for kinetics that uses the biotin-labeled RBCs (BioRBCs) as a superior, versatile method for both regulatory and investigational purposes. RBC kinetic analysis using BioRBCs has important methodologic, analytical, and safety advantages over Cr-labeled RBCs.

In premature infants there is no decrease in 24-hour posttransfusion allogeneic red blood cell recovery after 42 days of storage.

Background: Critically ill preterm very-low-birthweight (VLBW) neonates (birthweight ≤ 1.5 kg) frequently develop anemia that is treated with red blood cell (RBC) transfusions. Although RBCs transfused to adults demonstrate progressive decreases in posttransfusion 24-hour RBC recovery (PTR ) during storage-to a mean of approximately 85% of the Food and Drug Administration-allowed 42-day storage-limited data in infants indicate no decrease in PTR with storage.

Antibodies to biotinylated red blood cells in adults and infants: improved detection, partial characterization, and dependence on red blood cell-biotin dose.

Background: Biotin-labeled red blood cells (BioRBCs) are used for in vivo kinetic studies. Because BioRBC dosing occasionally induces antibodies, a sensitive and specific anti-BioRBC detection assay is needed.

Study Design And Methods: Aims were to 1) develop a gel card assay to evaluate existing, naturally occurring and BioRBC-induced plasma antibodies, 2) compare gel card and tube agglutination detection results, and 3) test for a relationship of antibody induction and BioRBC dose.

Estimation of adult and neonatal RBC lifespans in anemic neonates using RBCs labeled at several discrete biotin densities.

Background: Prior conclusions that autologous neonatal red blood cells (RBC) have substantially shorter lifespans than allogeneic adult RBCs were not based on direct comparison of autologous neonatal vs. allogeneic adult RBCs performed concurrently in the same infant. Biotin labeling of autologous neonatal RBCs and allogeneic adult donor RBCs permits concurrent direct comparison of autologous vs.

A Mass Balance-Based Semiparametric Approach to Evaluate Neonatal Erythropoiesis.

Postnatal hemoglobin (Hb) production in anemic preterm infants is determined by several factors including the endogenous erythropoietin levels, allogeneic RBC transfusions administered to treat anemia, and developmental age. As a result, their postnatal Hb production rate can vary considerably. This work introduces a novel Hb mass balance-based semiparametric approach that utilizes infant blood concentrations of Hb from the first 30 postnatal days to estimate the amount of Hb produced and the erythropoiesis rate in newborn infants.

Autologous Infant and Allogeneic Adult Red Cells Demonstrate Similar Concurrent Post-Transfusion Survival in Very Low Birth Weight Neonates.

Objective: Based on the hypothesis that neonatal autologous red blood cell (RBC) survival (RCS) is substantially shorter than adult RBC, we concurrently tracked the survival of transfused biotin-labeled autologous neonatal and allogeneic adult RBC into ventilated, very low birth weight infants.

Study Design: RBC aliquots from the first clinically ordered, allogeneic adult RBC transfusion and from autologous infant blood were labeled at separate biotin densities (biotin-labeled RBC [BioRBC]) and transfused. Survival of these BioRBCs populations were concurrently followed over weeks by flow cytometric enumeration using leftover blood.

A Method to Evaluate Fetal Erythropoiesis from Postnatal Survival of Fetal RBCs.

Fetal RBCs are produced during a period of very rapid growth and stimulated erythropoiesis under hypoxic intrauterine conditions. Fetal RBC life span varies with gestational age (GA) and is shorter than that in healthy adults. Due to the special kinetic properties of life span-based survival of human RBCs, a mathematical model-based kinetic analysis of the survival of fetal RBCs shortly after birth provides a unique opportunity to "look backward in time" to evaluate fetal erythropoiesis.

Reticulocyte Hemoglobin Content During the First Month of Life in Critically Ill Very Low Birth Weight Neonates Differs From Term Infants, Children, and Adults.

Background: Reticulocyte hemoglobin content (RET-He)-an established indicator of iron status in children and adults-was determined in very low birth weight (VLBW) infants.

Methods: Longitudinal retrospective RET-He data in 26 VLBW neonates during the first month of age were compared with: (a) concurrent complete blood counts (CBCs), including hemoglobin (Hb) concentration, reticulocyte count, and immature reticulocyte fraction (IRF), and erythropoietin (EPO) levels; (b) clinical variables; and (c) RET-He data from the literature for term infants, children, and adults.

Results: RET-He within 24 hr following birth was 31.

Mean remaining life span: a new clinically relevant parameter to assess the quality of transfused red blood cells.

Background: The quality of transfused red blood cells (RBCs) to treat anemia depends on its potential for oxygen delivery, governed by two properties: 1) initial posttransfusion recovery and 2) life span of initially surviving RBCs. The latter property is poorly evaluated by the traditional mean potential life span (MPL) or mean cell age (MA), because these parameters do not evaluate how long transfused RBCs remain in circulation. Furthermore, evaluation of MPL is based on two problematic assumptions regarding transfused RBCs: 1) they were produced at a constant steady-state rate and 2) they have similar storage life spans.

Pharmacodynamically optimized erythropoietin treatment combined with phlebotomy reduction predicted to eliminate blood transfusions in selected preterm infants.

Background: Preterm very-low-birth-weight (VLBW) infants weighing <1.5 kg at birth develop anemia, often requiring multiple red blood cell transfusions (RBCTx). Because laboratory blood loss is a primary cause of anemia leading to RBCTx in VLBW infants, our purpose was to simulate the extent to which RBCTx can be reduced or eliminated by reducing laboratory blood loss in combination with pharmacodynamically optimized erythropoietin (Epo) treatment.

Tracking donor RBC survival in premature infants: agreement of multiple populations of biotin-labeled RBCs with Kidd antigen-mismatched RBCs.

Background: Anemia, a common condition among critically ill premature infants, is affected by red blood cell (RBC) survival (RCS). We hypothesized that transfused allogeneic Kidd antigen-mismatched RBCs would demonstrate the same concurrent RCS tracking as RBCs multilabeled at separate, discrete low densities with biotin (BioRBCs).

Methods: Allogeneic RBCs from adult donors were labeled at four biotin densities, mixed, and transfused into 17 anemic premature infants.

Comparison of multiple red cell volume methods performed concurrently in premature infants following allogeneic transfusion.

Background: Study of the pathophysiology and treatment of anemia of prematurity is facilitated by direct measurement of red cell volume (RCV) utilizing microliter quantities of blood samples. Our objective was to compare concurrent measurements of multiple direct RCV methods in infants.

Methods: Eighteen preterm infants receiving clinically indicated transfusions had concurrent flow cytometric determinations of RCV and 24-h red blood cell (RBC) recovery based on donor-recipient differences of biotin-labeled RBCs (BioRBCs), Kidd antigen mismatched RBCs, and fetal hemoglobin-positive (HbF(+)) RBCs.

Population pharmacodynamic analysis of erythropoiesis in preterm infants for determining the anemia treatment potential of erythropoietin.

A population pharmacokinetics/pharmacodynamic (PK/PD) model was developed to describe changes in erythropoiesis as a function of plasma erythropoietin (EPO) concentration over the first 30 days of life in preterm infants who developed severe anemia requiring red blood cell (RBC) transfusion. Several covariates were tested as possible factors influencing the responsiveness to EPO. Discarded blood samples in 27 ventilated preterm infants born at 24-29 wk of gestation were used to construct plasma EPO, hemoglobin (Hb), and RBC concentration-time profiles.