Population pharmacokinetics of cefazolin in critically ill children infected with methicillin-sensitive Staphylococcus aureus.

OBJECTIVES: Cefazolin is one of curative treatments for infections due to methicillin-sensitive Staphylococcus aureus (MSSA). Both growth and critical illness may impact the pharmacokinetic (PK) parameters. We aimed to build a population PK model for cefazolin in critically ill children in order to optimize individual dosing regimens. METHODS: We included all children (age < 18 years, body weight (BW) > 2.5 kg) receiving cefazolin for MSSA infection. Cefazolin total plasma concentrations were quantified by high-performance liquid chromatography. A data modelling process was performed with the software MONOLIX. Monte Carlo simulations were used in order to attain the PK target of 100% fT > 4 ×MIC. RESULTS: Thirty-nine patients with a median (range) age of 7 (0.1-17) years and a BW of 21 (2.8-79) kg were included. The PK was ascribed to a one-compartment model, where typical clearance and volume of distribution estimations were 1.4 L/h and 3.3 L respectively. BW, according to the allometric rules, and estimated glomerular filtration rate (eGFR) on clearance were the two influential covariates. Continuous infusion with a dosing of 100 mg/kg/day to increase to 150 mg/kg/day for children with a BW < 10 kg or eGFR >200 mL/min/1.73m2 were the best schemes to reach the PK target of 100% fT> 4 ×MIC. CONCLUSIONS: In critically ill children infected with MSSA, continuous infusion seems to be the most appropriate scheme to reach the PK target of 100 % fT > 4 ×MIC in children with normal and augmented renal function.

Population pharmacokinetics of cefazolin before, during and after cardiopulmonary bypass in adult patients undergoing cardiac surgery.

PURPOSE: The aims of the present study were to establish a population pharmacokinetic (PPK) model of cefazolin for adult patients undergoing cardiac surgery with cardiopulmonary bypass (CPB) and to assess the probability of target attainment (PTA) for the prophylaxis of surgical site infection (SSI) using cefazolin. METHODS: Adult patients who underwent cardiac surgery with CPB were enrolled in the prospective study. Blood samples for plasma cefazolin assay were collected, and total and unbound drug concentrations were measured and analysed using the nonlinear mixed-effects modelling (NONMEM) software considering saturable plasma protein binding. Using the PPK model, plasma unbound cefazolin concentration-time courses with current prophylaxis protocols were simulated, and the PTA for common SSI pathogens was estimated. RESULTS: A total of 199 blood samples were obtained from 27 patients. A one-compartment model with first-order elimination plus an on/off CPB compartment best described the data. The population mean for systemic drug clearance (CL) was reduced and that for the volume of distribution (V) was increased during CPB compared with the pre-CPB values. CPB-induced hypoalbuminemia was associated with reduced maximum protein binding (Bmax). The simulation studies suggested that the current dosing protocols are insufficient for attaining PTA > 0.9 throughout surgery against pathogens with minimum inhibitory concentrations (MICs) >8 mg/L. A new dosing protocol that achieves a PTA > 0.9 for pathogens with a MIC of 16 mg/L was proposed. CONCLUSION: PPK modelling with simulation may be valuable for devising a cefazolin prophylaxis protocol for patients undergoing cardiac surgery with CPB.

Pregnancy-related pharmacokinetics and antimicrobial prophylaxis during fetal surgery, cefazolin and clindamycin as examples.

Antimicrobial prophylaxis during surgery aims to prevent post-operative site infections. For fetal surgery, this includes the fetal and amniotic compartments. Both are deep compartments as drug equilibrium with maternal blood is achieved relatively late. Despite prophylaxis, chorio-amnionitis or endometritis following ex utero intrapartum treatment or fetoscopy occur in 4.13% and 1.45% respectively of the interventions. This review summarizes the observations on two commonly administered antimicrobials (cefazolin, clindamycin) for surgical prophylaxis during pregnancy, with emphasis on the deep compartments. For both compounds, antimicrobial exposure is on target when we consider the maternal and fetal plasma compartment. In contrast, amniotic fluid concentrations-time profiles display a delayed and much more blunted pattern, behaving as deep compartment. For cefazolin, there are data that document further dilution in the setting of polyhydramnios. Along this deep compartment concept, there is some accumulation during repeated administration, modeled for cefazolin and observed for clindamycin. The relative underexposure to antimicrobials in amniotic fluid may be reflected in the pattern of maternal-fetal complications after fetal surgery, and suggest that antimicrobial prophylaxis practices for fetal surgery should be reconsidered. Further studies should be designed by a multidisciplinary team (fetal surgeons, clinical pharmacologists and microbiologists) to facilitate efficient evaluation of antimicrobial prophylaxis.

Prophylactic Cefazolin Dosing in Women With Body Mass Index >35 kg·m-2 Undergoing Cesarean Delivery: A Pharmacokinetic Study of Plasma and Interstitial Fluid.

BACKGROUND: Obesity is a risk factor for surgical site infection after cesarean delivery. There is inadequate pharmacokinetic data available regarding prophylactic cefazolin dosing in obese pregnant women. We aimed to describe the plasma and interstitial fluid (ISF) pharmacokinetics of cefazolin in obese women undergoing elective cesarean delivery and use dosing simulations to predict optimal dosing regimens. METHODS: Eligible women were scheduled for elective cesarean delivery at term, with a body mass index (BMI) of >35 kg·m. Plasma and ISF samples were collected following 2 g of intravenous cefazolin. Concentrations were determined using liquid chromatography-mass spectrometry. Population pharmacokinetic modeling and Monte Carlo dosing simulations were performed using Pmetrics. Total and unbound cefazolin concentrations in plasma and ISF were compared with the minimum inhibitory concentration at which 90% of isolates are inhibited (MIC90) of cefazolin for Staphylococcus aureus, 2 mg·L. The fractional target attainment (FTA) of dosing regimens to achieve a pre-established target of 95% unbound ISF concentrations >2 mg·L throughout a 3-hour duration of the surgery was calculated. RESULTS: The 12 women recruited had a median (interquartile range [IQR]) BMI of 41.5 (39.7-46.6) kg·m and a median (IQR) gestation of 38.7 weeks (37.9-39.0). For each timepoint up to 180 minutes, the median across subjects of total and unbound plasma concentration of cefazolin remained above 2 mg·L. The minimum observed total plasma concentration was 31.7 mg·L and plasma unbound concentration was 7.7 mg·L (observed in the same participant). For each timepoint up to 150 minutes, the median across subjects of unbound ISF concentrations remained above 2 mg·L. The minimum observed unbound ISF concentration was 0.7 mg·L (observed in 1 participant). In 2 participants, the ISF concentration of cefazolin was not maintained above 2 mg·L. The mean (± standard error [SE]) penetration of cefazolin (calculated as area under the concentration-time curve for the unbound fraction of drug [fAUC]tissue/fAUCplasma) into the ISF was 0.884 ± 1.11. Simulations demonstrated that FTA >95% was achieved in patients weighing 90-150 kg by an initial 2 g dose with redosing of 2 g at 2 hours. FTA was improved to >99% when an initial 3 g dose was repeated at 2 hours. CONCLUSIONS: To maintain adequate ISF antibiotic concentrations in obese pregnant women, our results suggest that redosing of cefazolin may be required. When wound closure has not occurred within 2 hours, redosing is suggested, following either a 2 or 3 g initial bolus. These preliminary results require validation in a larger population.

Evaluation of Blast Overpressure Exposure Effects on Concentration of Antibiotics in Mice.

OBJECTIVE: Infection as sequelae to explosion-related injury is an enduring threat to our troops. There are limited data on the effects of blast on antibiotic pharmacokinetics (PK), pharmacodynamics (PD), and efficacy. The observational study presented here is our Institute's first attempt to address this issue by combining our existing interdepartmental blast, infection modeling, and in vivo PK/PD capabilities and was designed to determine the PK effects of blast on the first-line antibiotic, cefazolin, in an in vivo mouse model. METHODS: A total of 160 male BALB/c mice were divided to sham and blast (exposed to blast overpressure of 19 psi) in two biological replicates. At 1 hour after blast/sham exposure, the animals received IV injection of cefazolin (328 mg/kg). Animals were euthanized at 3 minutes, 10 minutes, 15 minutes, 30 minutes, 1 hour, 3 hours, 6 hours, or 10 hours after the injection. Plasma and liver were analyzed for concentration of cefazolin using mass-spectrometry. RESULTS: We observed increases in the concentration of cefazolin in the plasma and liver of blast exposed animals at later time points and increase in elimination half-life. CONCLUSION: Our results indicate that blast-induced physiologic changes significantly influence cefazolin PK and suggest that efficacy could be affected in the context of the blast; assessment of efficacy and PD effects require further investigation. Metabolic changes resulting from blast may influence other classes of antibiotics and other therapeutics used with these injuries. Therefore, this may have important treatment considerations in other areas of military medicine.

Pharmacokinetics of Total and Unbound Cefazolin during Veno-Arterial Extracorporeal Membrane Oxygenation: A Case Report.

Extra-corporeal membrane oxygenation (ECMO) therapy could affect effective drug concentrations via adsorption onto the oxygenator or associated circuit. We describe a case of a 25-year-old female who required a veno-arterial ECMO therapy for refractory cardiac arrest due to massive pulmonary embolism. She had mild renal dysfunction as a result of the cardiac arrest. A total of 2 g of intravenous cefazolin 8-hourly was administered. Pre- and post-oxygenator blood samples were collected at 0, 1, 4, and 8 h post antibiotic administration. Samples were analyzed for total and unbound cefazolin concentrations. Protein binding was ∼60%. Clearance was reduced due to impaired renal function. The pharmacokinetics of cefazolin appear to not be affected by ECMO therapy and dosing adjustment may not be required.

Determination of total or free cefazolin and metronidazole in human plasma or interstitial fluid by HPLC-UV for pharmacokinetic studies in man.

Cefazolin (CFZ) plus metronidazole (MTZ) is commonly used for perioperative antibiotic prophylaxis. An HPLC-UV method is described for the simultaneous determination of total or free cefazolin and metronidazole in human plasma or in microdialysate of subcutaneous tissue. Separation was performed isocratically using a reversed phase column and phosphate buffer/acetonitrile as mobile phase. The validation characteristics were similar for both drugs. Linearity has been shown down to 0.1 mg/L (R > 0.9990). Intra- and inter-assay precision (CV) and in-accuracy were < 5%. The method was applied to the determination of cefazolin and metronidazole in plasma and microdialysate of surgical patients following 30-min intravenous infusion of cefazolin/metronidazole 2.0/0.5 g.

Pharmacokinetics of cefazolin delivery via the cardiopulmonary bypass circuit priming solution in infants and children.

OBJECTIVES: Our aim was to describe the pharmacokinetics of cefazolin in paediatric patients undergoing cardiac surgery with cardiopulmonary bypass (CPB) who received cefazolin for peri-operative surgical prophylaxis in addition to having cefazolin added to the CPB circuit priming solution. Secondary aims were to determine the pharmacodynamic exposure associated with the addition of cefazolin to the CPB priming solution and to assess whether a target cefazolin concentration range for the CPB priming solution could be identified. METHODS: A multicentre, prospective, open-label pharmacokinetic study was carried out in children from birth to 16 years of age undergoing cardiac surgery. RESULTS: Forty-one patients met the inclusion criteria and accounted for 492 samples for analysis. Cefazolin concentrations were best described by a one-compartment model with weight as a covariate on the volume of distribution (Vd) with allometric scaling. The mean ± standard deviation (SD) total body CL for the birth-6 month cohort was 0.009 ± 0.006 mL/min/kg with a mean ± SD Vd of 0.59 ± 0.26 L/kg, the mean ± SD total body CL for the 7 month-3 year cohort was 0.01 ± 0.005 mL/min/kg with a mean ± SD Vd of 0.79 ± 0.15 L/kg, and the mean ± SD total body CL for the 4-16 year cohort was 0.007 ± 0.004 mL/min/kg with a mean ± SD Vd of 3.4 ± 0.94 L/kg. The median cefazolin loss in the CPB circuit ranged from 78% to 95% and the median patient cefazolin concentration after CPB circuit detachment ranged from 92 to 197 mg/L. CONCLUSIONS: These data demonstrate that mixing cefazolin in the CPB circuit priming solution was effective in maintaining cefazolin serum concentrations during surgery. If this practice is utilized, re-dosing of cefazolin during the CPB run and upon CPB circuit detachment is most probably not needed. Larger pharmacokinetic studies are warranted.

The Effect of Blood Loss on Cefazolin Levels in Women Undergoing Cesarean Delivery.

OBJECTIVE: To quantify the effects of operative blood loss during cesarean on tissue and plasma cefazolin concentrations. STUDY DESIGN: This was a prospective observational study of singleton pregnancies undergoing scheduled cesarean between 34 and 40 weeks. Cefazolin administered prior to skin incision. Maternal plasma samples were obtained (Time 1[T1]: immediately, T2: 20 minutes, T3: 40 minutes, and T4: 60 minutes after cefazolin infusion). Subcutaneous adipose tissue sampled before and after fascia. Primary outcome was subcutaneous adipose cefazolin level after fascial closure. Formal quantitative blood loss (QBL) performed. Women with higher QBL, those at/above 75% of QBL in this population, were compared with those with lower QBL (QBL below 75%). Data analyzed using bivariable statistics. RESULTS: Ninety-two women were screened, 32 were eligible, and 20 enrolled. Median QBL was 630 mL (interquartile range [IQR]: 473-818) and 1,160 mL (IQR: 1,000-1,560) in the low and high QBL groups, respectively. Demographics and operative characteristics were similar. Median adipose cefazolin level after fascial closure did not differ between the groups (3.5 vs. 3.9 µg/g, p = 0.75). No differences in maternal plasma cefazolin concentrations between the groups at any time point or in pharmacokinetic parameters were seen. CONCLUSION: Intraoperative maternal plasma concentrations and adipose levels of cefazolin are similar between women with high and low blood loss at the time of cesarean delivery.

Pharmacokinetic Study of Cefazolin in Short Daily Hemodialysis.

BACKGROUND: A number of centers across the world offer short daily hemodialysis (SDHD) treatments. To date, cefazolin pharmacokinetics have not been described in patients undergoing SDHD. OBJECTIVE: The purpose of this study was to investigate the effect of SDHD on the pharmacokinetics of cefazolin. METHODS: This was a prospective, open-label, pharmacokinetic study of cefazolin during SDHD in 10 noninfected patients. Participants received a 1-g intravenous (IV) infusion of cefazolin after SDHD on study day 1 and a second dose after SDHD on study day 2. To determine the concentration of cefazolin, 6 blood samples were drawn at 0, 1, 2, 2.3, 4, and 24 hours after initiation of dialysis on day 2, and 2 dialysate samples were drawn at 1 and 2 hours after initiation of dialysis on day 2. Samples were analyzed using high-performance liquid chromatography, and pharmacokinetic parameters were determined. RESULTS: Median interdialysis clearance was 0.16 L/h (interquartile range [IQR]: 0.11-0.21 L/h), and median intradialysis clearance was 1.95 L/h (IQR: 1.66-2.45 L/h). Median interdialysis half-life was 28.2 hours (IQR: 23.5-59.3 hours) as compared with a median intradialysis half-life of 2.3 hours (IQR: 1.7-2.7 hours). The median percentage removal of cefazolin during dialysis was 41% (IQR: 35%-53%). Conclusion and Relevance: Estimated cefazolin dialysis clearance is similar to previous estimates with conventional thrice-weekly regimens. Current dosing recommendations of 1 g IV post-SDHD achieve total serum drug concentrations greater than 40 mg/L in all patients, which is the total drug concentration required for bactericidal activity against Staphylococcus species.

Effects of cardiopulmonary bypass on the disposition of cefazolin in patients undergoing cardiothoracic surgery.

The aim of the study was to evaluate the disposition of plasma unbound cefazolin in patients undergoing cardiothoracic surgery with cardiopulmonary bypass (CPB). Adult patients undergoing cardiothoracic surgery with CPB were enrolled in the study. Cefazolin sodium was given intravenously before skin incision (1 g) and at the beginning of CPB (2 g). Thereafter, an additional dose (1 g) was given every 4 hours. Seven to ten blood samples were collected before and during surgery. Plasma total and unbound (ultrafiltrated) cefazolin concentrations were analyzed using an HPLC-UV method. Plasma protein binding was analyzed with the Langmuir model. Twenty-seven patients (aged 70 ± 12 years, body weight 62 ± 12 kg, mean ± SD) with GFR >30 mL min-1 completed the study. There was a significant (P < 0.001) increase in median plasma unbound fraction of cefazolin from 21% before skin incision to 45% during CPB (P < 0.001), which was accompanied by a significant (P < 0.001) reduction in median plasma albumin concentration from 36 to 27 g L-1. Plasma concentrations of unbound cefazolin exceeded the assumed target thresholds of 2 µg mL-1 in all samples and of 8 µg mL-1 in all but one of 199 samples. The increased plasma unbound fraction of cefazolin would be attributable to dilutional reduction of serum albumin at the beginning of CPB and to saturable plasma protein binding of cefazolin. These data reveal CPB may alter the plasma protein binding and possibly distribution of cefazolin. Further studies are warranted to reappraise the protocol of antimicrobial prophylaxis with cefazolin in patients undergoing surgery with CPB.

Potentially clinically relevant concentrations of Cefazolin, Midazolam, Propofol, and Sufentanil in auto-transfused blood in congenital cardiac surgery.

BACKGROUND: Use of donor blood in congenital cardiac surgery increases the risk for post-operative morbidity and mortality. To reduce the need for allogenic blood transfusion a technique for peri-operative mechanical red cell salvage is applied. Blood from the operation site is collected in a reservoir, processed, passed through a lipophilic filter and returned to the patient. Influence of this cellsaver system on coagulation, fibrinolysis and inflammatory markers is known. To our knowledge no studies have been performed on the effects of autotransfusion on drug concentrations. A clinically relevant drug dose could potentially be returned to the patient through the auto-transfused blood, leading to unwanted drug reactions post-operatively. We aimed to measure drug concentrations in blood salvaged from the operation site and in the auto-transfused blood to determine if a clinically relevant drug dose is returned to the patient. METHODS: The study was performed at the Department of Cardiothoracic Surgery of a tertiary university hospital. Blood samples were taken from the reservoir, after processing before the lipophilic filter, the auto-transfused blood, and the waste fluid. Samples were stored at - 80 C and drug concentration for sufentanil, propofol, midazolam and cefazolin were measured using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Drug concentrations measured in the reservoir and the auto-transfused blood were compared and the relative reduction was calculated for each patient. RESULTS: Blood samples were taken from 18 cellsaver runs in 18 patients, age 0-13 years. Drug concentrations in the reservoir were comparable to concomitant concentrations in the patient. For sufentanil 34% (median, IQR 27-50) of drug concentration was retained from the reservoir in the auto-transfused blood, for midazolam 6% (median, IQR 4-10), for cefazolin 5% (median, IQR 2-6) and for propofol 0% (median, IQR 0-0) respectively. CONCLUSION: Depending on the drug, up to 34% of the drug concentration salvaged from the operation site is returned to the patient through autotransfusion, potentially causing unwanted drug reactions post-operatively. Additionally, influence of a cellsaver system should be considered in pharmacological research during and after congenital cardiac surgery and could result in dose adjustments in the postoperative phase. TRIAL REGISTRATION: Registration at the Dutch Trial Registry ( NTR3579 ) at August 14 2012.

Simultaneous quantification of fentanyl, sufentanil, cefazolin, doxapram and keto-doxapram in plasma using liquid chromatography-tandem mass spectrometry.

A simple and specific UPLC-MS/MS method was developed and validated for simultaneous quantification of fentanyl, sufentanil, cefazolin, doxapram and its active metabolite keto-doxapram. The internal standard was fentanyl-d5 for all analytes. Chromatographic separation was achieved with a reversed-phase Acquity UPLC HSS T3 column with a run-time of only 5.0 min per injected sample. Gradient elution was performed with a mobile phase consisting of ammonium acetate or formic acid in Milli-Q ultrapure water or in methanol with a total flow rate of 0.4 mL min-1 . A plasma volume of only 50 µL was required to achieve adequate accuracy and precision. Calibration curves of all five analytes were linear. All analytes were stable for at least 48 h in the autosampler. The method was validated according to US Food and Drug Administration guidelines. This method allows quantification of fentanyl, sufentanil, cefazolin, doxapram and keto-doxapram, which is useful for research as well as therapeutic drug monitoring, if applicable. The strength of this method is the combination of a small sample volume, a short run-time, a deuterated internal standard, an easy sample preparation method and the ability to simultaneously quantify all analytes in one run.

Fast and sensitive HPLC/UV method for cefazolin quantification in plasma and subcutaneous tissue microdialysate of humans and rodents applied to pharmacokinetic studies in obese individuals.

Antimicrobial prophylactic dosing of morbidly obese patients may differ from normal weighted individuals owing to alterations in drug tissue distribution. Drug subcutaneous tissue distribution can be investigated by microdialysis patients and animals. The need for cefazolin prophylactic dose adjustment in obese patients remains under discussion. The paper describes the validation of an HPLC-UV method for cefazolin quantification in plasma and microdialysate samples from clinical and pre-clinical studies. A C18 column with an isocratic mobile phase was used for drug separation, with detection at 272 nm. Total and unbound cefazolin lower limit of quantitation was 5 µg/mL in human plasma, 2 µg/mL in rat plasma, and 0.5 and 0.025 µg/mL in human and rat microdialysate samples, respectively. The maximum intra- and inter-day imprecisions were 10.7 and 8.1%, respectively. The inaccuracy was <9.7%. The limit of quantitation imprecision and inaccuracy were < 15%. Cefazolin stability in the experimental conditions was confirmed. Cefazolin plasma concentrations and subcutaneous tissue penetration were determined by microdialysis in morbidly obese patients (2 g i.v. bolus) and diet-induced obese rats (30 mg/kg i.v. bolus) using the method. This method has the main advantages of easy plasma clean-up and practicability and has proven to be useful in cefazolin clinical and pre-clinical pharmacokinetic investigations.

Factors that affect the duration of antimicrobial therapy for cellulitis.

BACKGROUND: The recommended duration of antibiotic therapy for patients hospitalized with cellulitis is 5-14 days. However, factors that affect the duration of treatment have rarely been examined. METHODS: We conducted an observation study in a regional hospital in Japan to examine factors that affect the duration of antibiotic therapy for cellulitis. Our study included 102 patients with cellulitis of the lower extremities who were treated with intravenous cefazolin alone. Intravenous cefazolin was terminated when redness, swelling, and tenderness of the lower extremities disappeared, and subsequently the patients were discharged. The relationship between the duration (days) of treatment with intravenous cefazolin (DIVC) and clinical factors were analyzed. RESULTS: The median DIVC was 8 days (interquartile range, 7-10 days). On univariate analysis, DIVC correlated significantly with patient age (P = 0.0071) and with C-reactive protein levels before treatment (P = 0.0053). DIVC in patients with diabetes mellitus was significantly longer than that in patients without diabetes mellitus (P = 0.0033). DIVC in patients with blood stream infection was significantly longer than that in patients without blood stream infection (P = 0.029). On multivariate analysis, variables independently associated with longer DIVC included patient age (P = 0.044), C-reactive protein levels before treatment (P = 0.017), presence of diabetes mellitus (P = 0.0021), and presence of blood stream infection (P = 0.028). CONCLUSIONS: Duration of treatment with intravenous antibiotics for cellulitis is associated with patient age, C-reactive protein levels, coexisting diabetes mellitus, and coexisting blood stream infection. These findings should be considered when treatment plans for cellulitis are devised.

Evaluation of cefazolin antimicrobial prophylaxis during cardiac surgery with cardiopulmonary bypass.

Objectives: Although clinical practice guidelines recommend standard cefazolin antimicrobial prophylaxis (AP) dosing for cardiac surgery, limited data exist as to whether adequate concentrations are achieved in this patient population. The goal of our study was to characterize intraoperative cefazolin concentrations particularly at wound closure with regards to maintaining target cefazolin closure concentrations ≥40 mg/L. Methods: Adults undergoing cardiac surgery with cardiopulmonary bypass (CPB) and receiving cefazolin AP according to protocol were studied. Blood samples were collected after the preoperative cefazolin dose, prior to intraoperative cefazolin doses and at wound closure. Intraoperative trough and closure concentrations were characterized and evaluated against a target threshold of ≥ 40 mg/L (≥8 mg/L unbound, assuming 80% protein binding). Results: Fifty-five subjects (64.9 ±âŸ10.4 years, 89.7 ±âŸ16.5 kg, CLCR >50 mL/min/72 kg) completed the study. Total cefazolin concentrations were <40 mg/L in 40% (12 of 30) of intraoperative trough samples and 9.8% (5 of 51) of closure samples. Below-target concentrations at some time during surgery were documented in 30.9% (17 of 55) of subjects. In multivariate analyses, lower body weight (P = 0.027) and shorter duration of surgery (P = 0.045) were significant predictors of closure concentrations <40 mg/L. A total cefazolin exposure (preoperative and intraoperative doses) of ≥ 7.6 mg/kgdosing weight for every hour of surgery (intermittent dosing) was required to achieve target closure concentrations. Conclusions: The standard cefazolin AP regimen was not reliable in maintaining target closure concentrations ≥40 mg/L in patients with normal renal function undergoing elective cardiac surgery with CPB. The findings supported a cefazolin AP regimen consisting of at least 2 g preoperatively and every 3 h during surgery.

A randomized controlled double blind trial comparing the effects of the prophylactic antibiotic, Cefazolin, administered at caesarean delivery at two different timings (before skin incision and after cord clamping) on both the mother and newborn.

BACKGROUND: Caesarean delivery (CD) increases the risk of postpartum infection by 5 to 20 fold. Prevention of surgical site infection (SSI) is the goal of antibiotic prophylaxis. This study was carried out to assess the optimum timing for prophylactic antibiotic administration and to assess the amount of the antibiotic crossing the placental barrier. METHODS: Eligible mothers were recruited, after informed consent, once the decision for CD was made. Each mother received two injections, one prior to skin incision and one after cord clamping, (one being the study drug Cefazolin, and the other, a placebo) based on the randomization code. Demographic, maternal and neonatal monitoring data until discharge from hospital, and at the 6 weeks postpartum visit were collected. Levels of the prophylactic antibiotic were measured from the cord blood in every 8th neonate. The objective of the study was to compare the effects of the prophylactic antibiotic, intravenous Cefazolin 1 g, administered at Caesarean delivery (CD) at two different timings (before skin incision and after cord clamping) on both the mother and newborn. The secondary outcomes that were followed up were the number of maternal and neonatal readmissions. An appropriate test for significance, Fisher's exact test was used to find the association between risk variables and outcome. RESULTS: The total numbers of mothers enrolled were 1106, of whom 553 mothers received antibiotic prior to skin incision (pre-incision) and 543 mothers received antibiotic after cord clamping (post-incision). The pre-incision group had significantly less febrile illness (RR = 0.48, 95% CI: 0.29 - 0.80) and SSI (RR = 0.14, 95% CI: 0.04 - 0.53) when compared with the post- incision group. The post-incision group significantly had >7 days hospital stay when compared to the 4-7 days stay of the pre-incision group (p = 0.005).There were no differences in any of the neonatal outcomes. The quantity of the antibiotic in the cord blood was only 2-3%. CONCLUSIONS: Pre incision prophylactic antibiotic protected the mother from SSI and febrile illness and decreased the hospital stay significantly. TRIAL REGISTRATION: The Clinical Trials Registry India (CTRI) was [ CTRI/2016/03/006710 dated, 04/03/2016].

Clinical on-site monitoring of ß-lactam antibiotics for a personalized antibiotherapy.

An appropriate antibiotherapy is crucial for the safety and recovery of patients. Depending on the clinical conditions of patients, the required dose to effectively eradicate an infection may vary. An inadequate dosing not only reduces the efficacy of the antibiotic, but also promotes the emergence of antimicrobial resistances. Therefore, a personalized therapy is of great interest for improved patients' outcome and will reduce in long-term the prevalence of multidrug-resistances. In this context, on-site monitoring of the antibiotic blood concentration is fundamental to facilitate an individual adjustment of the antibiotherapy. Herein, we present a bioinspired approach for the bedside monitoring of free accessible ß-lactam antibiotics, including penicillins (piperacillin) and cephalosporins (cefuroxime and cefazolin) in untreated plasma samples. The introduced system combines a disposable microfluidic chip with a naturally occurring penicillin-binding protein, resulting in a high-performance platform, capable of gauging very low antibiotic concentrations (less than 6 ng ml-1) from only 1 µl of serum. The system's applicability to a personalized antibiotherapy was successfully demonstrated by monitoring the pharmacokinetics of patients, treated with ß-lactam antibiotics, undergoing surgery.

Population pharmacokinetics of cefazolin before, during and after cardiopulmonary bypass to optimize dosing regimens for children undergoing cardiac surgery.

Objectives: The objective of this study was to characterize cefazolin serum pharmacokinetics in children before, during and after cardiopulmonary bypass (CPB), in order to derive an evidence-based dosing regimen. Patients and methods: This study included children who received cefazolin before surgical incision, before cessation of CPB and after surgery. Blood samples of total and unbound cefazolin concentrations were collected before, during and after CPB. The cefazolin concentration-time profiles were analysed using population pharmacokinetic modelling and predictors for interindividual variability in pharmacokinetic parameters were investigated. Subsequently, optimized dosing regimens were developed using stochastic simulations. Clinicaltrials.gov: NCT02749981. Results: A total of 494 total and unbound cefazolin concentrations obtained from 56 children (aged 6 days to 15 years) were included. A two-compartment model with first-order elimination plus an additional compartment for the effect of CPB best described the data. Clearance (1.56 L/h), central volume (1.93 L) and peripheral volume (2.39 L) were allometrically scaled by body weight. The estimated glomerular filtration rate (eGFR) was identified as a covariate on clearance and the serum albumin concentration was associated with maximum protein binding capacity. Our simulations showed that an additional bolus dose at the start of CPB improves the PTA in typical patients from 59% to >94%. Prolonged surgery and preserved renal function (i.e. drop in eGFR <25%) had a negative impact on PTA. Conclusions: We propose an optimized dosing regimen for cefazolin during cardiac surgery in paediatric patients to avoid treatment failure due to inadequate antibiotic prophylaxis.