Population pharmacokinetics of fluconazole in critically ill patients receiving extracorporeal membrane oxygenation and continuous renal replacement therapy: an ASAP ECMO study.

This multicenter study describes the population pharmacokinetics (PK) of fluconazole in critically ill patients receiving concomitant extracorporeal membrane oxygenation (ECMO) and continuous renal replacement therapy (CRRT) and includes an evaluation of different fluconazole dosing regimens for achievement of target exposure associated with maximal efficacy. Serial blood samples were obtained from critically ill patients on ECMO and CRRT receiving fluconazole. Total fluconazole concentrations were measured in plasma using a validated chromatographic assay. A population PK model was developed and Monte Carlo dosing simulations were performed using Pmetrics in R. The probability of target attainment (PTA) of various dosing regimens to achieve fluconazole area under the curve to minimal inhibitory concentration ratio (AUC0-24/MIC) >100 was estimated. Eight critically ill patients receiving concomitant ECMO and CRRT were included. A two-compartment model including total body weight as a covariate on clearance adequately described the data. The mean (±standard deviation, SD) clearance and volume of distribution were 2.87 ± 0.63 L/h and 15.90 ± 13.29 L, respectively. Dosing simulations showed that current guidelines (initial loading dose of 12 mg/kg then 6 mg/kg q24h) achieved >90% of PTA for a MIC up to 1 mg/L. None of the tested dosing regimens achieved 90% of PTA for MIC above 2 mg/L. Current fluconazole dosing regimen guidelines achieved >90% PTA only for Candida species with MIC <1 mg/L and thus should be only used for Candida-documented infections in critically ill patients receiving concomitant ECMO and CRRT. Total body weight should be considered for fluconazole dose.

It cuts both ways: A single-center retrospective review describing a three-way interaction between flucloxacillin, voriconazole and tacrolimus.

AIM: Tacrolimus is a CYP3A4 substrate with a narrow therapeutic index that requires dose adjustment when used with voriconazole, a recognized CYP3A4 inhibitor. Interactions involving flucloxacillin and tacrolimus or voriconazole individually have been shown to result in decreased concentrations of the latter two drugs. Tacrolimus concentrations have been reported to be unaffected by flucloxacillin when voriconazole is administered; however, this has not been extensively investigated. METHODS: Retrospective review of voriconazole and tacrolimus concentrations and subsequent dose adjustment following flucloxacillin administration. RESULTS: Eight transplant recipients (five lung, two re-do lung, one heart) received concurrent flucloxacillin, voriconazole and tacrolimus. Voriconazole trough concentrations were measured before flucloxacillin initiation in three of eight patients and all trough concentrations were therapeutic. Following flucloxacillin initiation, all eight patients exhibited subtherapeutic concentrations of voriconazole (median concentration 0.15 mg/L [interquartile range (IQR) 0.10-0.28]). In five patients, voriconazole concentrations remained subtherapeutic despite dose increases, and treatment for two patients was changed to alternative antifungal agents. All eight patients required tacrolimus dose increases to maintain therapeutic concentrations after flucloxacillin initiation. Median total daily dose prior to flucloxacillin treatment was 3.5 mg [IQR 2.0-4.3] and this increased to 13.5 mg [IQR 9.5-20] (P=0.0026) during flucloxacillin treatment. When flucloxacillin was ceased, the median tacrolimus total daily dose reduced to 2.2 mg [IQR 1.9-4.7]. Supra-therapeutic tacrolimus concentrations were observed in seven patients after flucloxacillin discontinuation (median concentration 19.7 µg/L [IQR 17.9-28.0]). CONCLUSION: A significant three-way interaction was shown between flucloxacillin, voriconazole and tacrolimus, resulting in subtherapeutic voriconazole concentrations, and requiring substantial tacrolimus dose increases. Administration of flucloxacillin to patients receiving voriconazole should be avoided. Tacrolimus concentrations should be closely monitored, and dosing adjusted during and after flucloxacillin administration.

Conventional and Novel Approaches to Immunosuppression in Lung Transplantation.

Most therapeutic advances in immunosuppression have occurred over the past few decades. Although modern strategies have been effective in reducing acute cellular rejection, excess immunosuppression comes at the price of toxicity, opportunistic infection, and malignancy. As our understanding of the immune system and allograft rejection becomes more nuanced, there is an opportunity to evolve immunosuppression protocols to optimize longer term outcomes while mitigating the deleterious effects of traditional protocols.

Antimicrobial Exposures in Critically Ill Patients Receiving Extracorporeal Membrane Oxygenation.

Rationale: Data suggest that altered antimicrobial concentrations are likely during extracorporeal membrane oxygenation (ECMO). Objectives: The primary aim of this analysis was to describe the pharmacokinetics (PKs) of antimicrobials in critically ill adult patients receiving ECMO. Our secondary aim was to determine whether current antimicrobial dosing regimens achieve effective and safe exposure. Methods: This study was a prospective, open-labeled, PK study in six ICUs in Australia, New Zealand, South Korea, and Switzerland. Serial blood samples were collected over a single dosing interval during ECMO for 11 antimicrobials. PK parameters were estimated using noncompartmental methods. Adequacy of antimicrobial dosing regimens were evaluated using predefined concentration exposures associated with maximal clinical outcomes and minimal toxicity risks. Measurements and Main Results: We included 993 blood samples from 85 patients. The mean age was 44.7 ± 14.4 years, and 61.2% were male. Thirty-eight patients (44.7%) were receiving renal replacement therapy during the first PK sampling. Large variations (coefficient of variation of ⩾30%) in antimicrobial concentrations were seen leading to more than fivefold variations in all PK parameters across all study antimicrobials. Overall, 70 (56.5%) concentration profiles achieved the predefined target concentration and exposure range. Target attainment rates were not significantly different between modes of ECMO and renal replacement therapy. Poor target attainment was observed across the most frequently used antimicrobials for ECMO recipients, including for oseltamivir (33.3%), piperacillin (44.4%), and vancomycin (27.3%). Conclusions: Antimicrobial PKs were highly variable in critically ill patients receiving ECMO, leading to poor target attainment rates. Clinical trial registered with the Australian New Zealand Clinical Trials Registry (ACTRN12612000559819).

Multispecies Outbreak of Nocardia Infections in Heart Transplant Recipients and Association with Climate Conditions, Australia.

A multispecies outbreak of Nocardia occurred among heart transplant recipients (HTR), but not lung transplant recipients (LTR), in Sydney, New South Wales, Australia, during 2018-2019. We performed a retrospective review of 23 HTR and LTR who had Nocardia spp. infections during June 2015-March 2021, compared risk factors for Nocardia infection, and evaluated climate conditions before, during, and after the period of the 2018-2019 outbreak. Compared with LTR, HTR had a shorter median time from transplant to Nocardia diagnosis, higher prevalence of diabetes, greater use of induction immunosuppression with basiliximab, and increased rates of cellular rejection before Nocardia diagnosis. During the outbreak, Sydney experienced the lowest monthly precipitation and driest surface levels compared with time periods directly before and after the outbreak. Increased immunosuppression of HTR compared with LTR, coupled with extreme weather conditions during 2018-2019, may explain this outbreak of Nocardia infections in HTR.

Population pharmacokinetics of ciprofloxacin in critically ill patients receiving extracorporeal membrane oxygenation (an ASAP ECMO study).

INTRODUCTION: This study aimed to describe the pharmacokinetics (PK) of ciprofloxacin in critically ill patients receiving ECMO and recommend a dosing regimen that provides adequate drug exposure. METHODS: Serial blood samples were taken from ECMO patients receiving ciprofloxacin. Total ciprofloxacin concentrations were measured by chromatographic assay and analysed using a population PK approach with Pmetrics®. Dosing simulations were performed to ascertain the probability of target attainment (PTA) represented by the area under the curve to minimum inhibitory concentration ratio (AUC0-24/MIC) ≥ 125. RESULTS: Eight patients were enrolled, of which three received concurrent continuous venovenous haemodiafiltration (CVVHDF). Ciprofloxacin was best described in a two-compartment model with total body weight and creatinine clearance (CrCL) included as significant predictors of PK. Patients not requiring renal replacement therapy generated a mean clearance of 11.08 L/h while patients receiving CVVHDF had a mean clearance of 1.51 L/h. Central and peripheral volume of distribution was 77.31 L and 90.71 L, respectively. ECMO variables were not found to be significant predictors of ciprofloxacin PK. Dosing simulations reported that a 400 mg 8 -hly regimen achieved > 72% PTA in all simulated patients with CrCL of 30 mL/min, 50 mL/min and 100 mL/min and total body weights of 60 kg and 100 kg at a MIC of 0.5 mg/L. CONCLUSION: Our study reports that established dosing recommendations for critically ill patients not on ECMO provides sufficient drug exposure for maximal ciprofloxacin activity for ECMO patients. In line with non-ECMO critically ill adult PK studies, higher doses and therapeutic drug monitoring may be required for critically ill adult patients on ECMO.

Population Pharmacokinetics and Dosing Simulations of Ceftriaxone in Critically Ill Patients Receiving Extracorporeal Membrane Oxygenation (An ASAP ECMO Study).

BACKGROUND: Despite the surge in use of extracorporeal membrane oxygenation (ECMO) in the adult intensive care unit, little guidance is available on the appropriate dosing of antimicrobials in this setting. Ceftriaxone is an antimicrobial with a high affinity to plasma protein, a property identified in the literature as susceptible to sequestration into extracorporeal circuits and hypothesised to require dosage adjustments in this setting. OBJECTIVE: The aim of this study was to describe the pharmacokinetics of ceftriaxone and identify the best dosing regimen for critically ill adult patients receiving ECMO. METHODS: Serial blood samples were taken from patients receiving both ECMO and ceftriaxone. Total and unbound drug concentrations were measured in plasma by chromatographic assay and analysed using a population pharmacokinetic approach with Pmetrics®. Dosing simulations were performed to identify the optimal dosing strategy: 60 and 100% of time with free (unbound) drug concentration exceeding the minimum inhibitory concentration (fT>MIC). RESULTS: In total, 14 patients were enrolled, of which three were receiving renal replacement therapy (RRT). Total and unbound ceftriaxone was best described in a two-compartment model with total body weight, serum albumin concentrations, creatinine clearance (CrCL), and the presence of RRT included as significant predictors of pharmacokinetics. Patients not on RRT generated a mean renal clearance of 0.90 L/h, non-renal clearance of 0.33 L/h, and central volume of distribution of 7.94 L. Patients on RRT exhibited a mean total clearance of 1.18 L/h. ECMO variables were not significant predictors of ceftriaxone pharmacokinetics. Steady-state dosing simulations found that dosages of 1 g every 12 h and 2 g every 24 h achieved >90% probabilities of target attainment in patients with CrCL of 0 mL/min with RRT and 30 and 100 mL/min and various serum albumin concentrations (17 and 26 g/L). CONCLUSIONS: Dosing recommendations for critically ill adult patients not on ECMO appear to be sufficient for patients on ECMO. Patients exhibiting augmented renal clearance (> 130 mL/min) or treatment of less susceptible pathogens may require higher doses, which requires further investigation.

Population Pharmacokinetics of Vancomycin in Critically Ill Adult Patients Receiving Extracorporeal Membrane Oxygenation (an ASAP ECMO Study).

Our study aimed to describe the population pharmacokinetics (PK) of vancomycin in critically ill patients receiving extracorporeal membrane oxygenation (ECMO), including those receiving concomitant renal replacement therapy (RRT). Dosing simulations were used to recommend maximally effective and safe dosing regimens. Serial vancomycin plasma concentrations were measured and analyzed using a population PK approach on Pmetrics. The final model was used to identify dosing regimens that achieved target exposures of area under the curve (AUC0-24) of 400-700 mg · h/liter at steady state. Twenty-two patients were enrolled, of which 11 patients received concomitant RRT. In the non-RRT patients, the median creatinine clearance (CrCL) was 75 ml/min and the mean daily dose of vancomycin was 25.5 mg/kg. Vancomycin was well described in a two-compartment model with CrCL, the presence of RRT, and total body weight found as significant predictors of clearance and central volume of distribution (Vc). The mean vancomycin renal clearance and Vc were 3.20 liters/h and 29.7 liters respectively, while the clearance for patients on RRT was 0.15 liters/h. ECMO variables did not improve the final covariate model. We found that recommended dosing regimens for critically ill adult patients not on ECMO can be safely and effectively used in those on ECMO. Loading doses of at least 25 mg/kg followed by maintenance doses of 12.5-20 mg/kg every 12 h are associated with a 97-98% probability of efficacy and 11-12% probability of toxicity, in patients with normal renal function. Therapeutic drug monitoring along with reductions in dosing are warranted for patients with renal impairment and those with concomitant RRT. (This study is registered with the Australian New Zealand Clinical Trials Registry [ANZCTR] under number ACTRN12612000559819.).

Population pharmacokinetics of cefepime in critically ill patients receiving extracorporeal membrane oxygenation (an ASAP ECMO study).

OBJECTIVES: This study aimed to describe the population pharmacokinetics (PK) of cefepime during extracorporeal membrane oxygenation (ECMO) and through dosing simulations, identify a maximally effective and safe dosing strategy. METHODS: Serial cefepime plasma concentrations were measured in patients on ECMO, and data were analysed using a population PK approach with Pmetrics®. Dosing simulations were used to identify the optimal dosing strategy that achieved target trough concentrations (Cmin) of 8-20 mg/L. Six patients were enrolled, of which one was receiving renal replacement therapy. Cefepime was best described in a two-compartment model, with total body weight and creatinine clearance (CrCL) as significant predictors of PK parameters. The mean clearance and central volume of distribution were 2.42 L/h and 15.09 L, respectively. RESULTS: Based on simulations, patients with CrCL of 120 mL/min receiving 1 g 8-hourly dosing achieved a 40-44% probability of efficacy (Cmin > 8 mg/L) and 1-6% toxicity (Cmin > 20 mg/L). Patients with CrCL 30 mL/min and 65 mL/min receiving 1 g 12-hourly dosing achieved an 84-92% and 46-53% probability of efficacy and 8-44% and 1-8% probability of toxicity, respectively. Simulations demonstrated a lower probability of efficacy and higher probability of toxicity with decreasing patient weight. CONCLUSION: This study reported reduced cefepime clearance in patients receiving ECMO, resulting in an increased risk of cefepime toxicity. To avoid drug accumulation, modified dosing regimens should be used in critically ill patients on ECMO. Clinicians should adopt therapeutic drug monitoring when treating less susceptible organisms and in patients with reduced renal clearance on ECMO.

Population Pharmacokinetics of Piperacillin and Tazobactam in Critically Ill Patients Receiving Extracorporeal Membrane Oxygenation: an ASAP ECMO Study.

Our study aimed to describe the population pharmacokinetics (PK) of piperacillin and tazobactam in patients on extracorporeal membrane oxygenation (ECMO), with and without renal replacement therapy (RRT). We also aimed to use dosing simulations to identify the optimal dosing strategy for these patient groups. Serial piperacillin and tazobactam plasma concentrations were measured with data analyzed using a population PK approach that included staged testing of patient and treatment covariates. Dosing simulations were conducted to identify the optimal dosing strategy that achieved piperacillin target exposures of 50% and 100% fraction of time free drug concentration is above MIC (%fT>MIC) and toxic exposures of greater than 360 mg/liter. The tazobactam target of percentage of time free concentrations of >2 mg/liter was also assessed. Twenty-seven patients were enrolled, of which 14 patients were receiving concurrent RRT. Piperacillin and tazobactam were both adequately described by two-compartment models, with body mass index, creatinine clearance, and RRT as significant predictors of PK. There were no substantial differences between observed PK parameters and published parameters from non-ECMO patients. Based on dosing simulations, a 4.5-g every 6 hours regimen administered over 4 hours achieves high probabilities of efficacy at a piperacillin MIC of 16 mg/liter while exposing patients to a <3% probability of toxic concentrations. In patients receiving ECMO and RRT, a frequency reduction to every 12 hours dosing lowers the probability of toxic concentrations, although this remains at 7 to 9%. In ECMO patients, piperacillin and tazobactam should be dosed in line with standard recommendations for the critically ill.

Donor heart and lung procurement: A consensus statement.

Heart and lung procurements are multiphased processes often accompanied by an array of complex logistics. Approaches to donor evaluation and management, organ procurement, and organ preservation vary among individual procurement teams. Because early graft failure remains a major cause of mortality in contemporary thoracic organ transplant recipients, we sought to establish some standardization in the procurement process. This paper, in this vein, represents an international consensus statement on donor heart and lung procurement and is designed to serve as a guide for physicians, surgeons, and other providers who manage donors to best optimize the clinical status for the procurement of both heart and lungs for transplantation. Donation after brain death (DBD) and donation after circulatory determination death (referred to as donation after circulatory death [DCD] for the remainder of the paper) for both heart and lung transplantation will be discussed in this paper. Although the data available on DCD heart donation are limited, information regarding the surgical technique for procurement is included within this consensus statement. Furthermore, this paper will focus on adult DBD and DCD heart and lung procurement. Currently, no certification, which is either recognized and/or endorsed by the transplant community at large, exists for the training of a cardiothoracic procurement surgeon. Nevertheless, establishing a training curriculum and credentialing requirements are beyond the scope of this paper.

Oral ribavirin for respiratory syncytial virus infection after lung transplantation: Efficacy and cost-efficiency.

BACKGROUND: Respiratory syncytial virus (RSV) causes serious respiratory tract infections in lung transplant (LTx) recipients, is associated with development of bronchiolitis obliterans syndrome, and has no proven effective therapy. We evaluated the efficacy, safety, and cost-effectiveness of oral ribavirin for the treatment of RSV infection after LTx. METHODS: Between December 2011 and May 2014, 52 LTx recipients developed 56 episodes of symptomatic RSV infection, which was diagnosed by positive RSV polymerase chain reaction on nasopharyngeal swabs. An intravenous (IV) loading dose of ribavirin (33 mg/kg) was given in 52 of 56 episodes; an equivalent oral loading dose was given in 2 episodes. Oral ribavirin (20 mg/kg/day) was given by day 2 in 53 of 56 episodes. Median duration of therapy was 8 days (range 6-31 days). RESULTS: Mean forced expiratory volume in 1 sec decreased from 2.38 ± 0.78 liters to 2.07 ± 0.85 liters (p < 0.001) at presentation, recovered to 2.26 ± 0.82 liters at cessation of ribavirin, and was maintained at 2.31 ± 0.81 liters within 3 months. New-onset bronchiolitis obliterans syndrome developed in 1 of 38 patients (2.6%) at 3 months. Anemia worsened in 23 episodes, and de novo anemia developed in 5 episodes. Mean hemoglobin decreased from 118 ± 16 g/liter to 113 ± 21 g/liter (p = 0.015). There were 4 late deaths. Compared with IV therapy, mean drug cost saving was US $6,035 per episode, and mean inpatient bed days was reduced by 6.7 days (p < 0.001). CONCLUSIONS: To our knowledge, we report the largest series of LTx recipients treated with oral ribavirin for RSV. Oral ribavirin appears to be an effective, well-tolerated alternative to IV or inhaled ribavirin; provides considerable cost savings and reduces length of hospital stay. Potential long-term benefits in preventing development of chronic lung allograft dysfunction are yet to be determined.

Medication Error Minimization Scheme (MEMS) in an adult tertiary intensive care unit (ICU) 2009-2011.

INTRODUCTION: The Medication Error Minimisation Scheme (MEMS) is a locally based ongoing multidisciplinary, multifaceted quality improvement (QI) project within an Australian adult tertiary level Intensive Care Unit (ICU). The project commenced in 2009. Its primary aim is to enhance medication safety within this ICU by utilising existing resources. The aim of this paper is to provide a descriptive account of the various activities, interventions and results of this project within the first three years. METHODS: The research design for this project was based upon Plan-Do-Study-Act (PDSA) cycles associated with QI projects. Medication error rates and audits of: intravenous infusions, incompatible intravenous medications and incorrect documentation of withheld medications were analyzed according to simple statistical techniques. Initial and follow up medication safety surveys were compared using basic statistical analysis. Focus groups exploring barriers and enablers of medication incident reporting were analyzed according to qualitative techniques associated with focus group discussions. Other interventions included: regular education sessions; discussions within other departmental meetings such as nursing staff meetings and Morbidity and Mortality meetings; and bedside discussions and demonstrations. Promotion of medication safety occurred within a number of forums; activities and findings were advertised and displayed; a recognizable Logo for MEMS was employed; and incentives were provided for staff. RESULTS: Reported Medication Incidents (MIs) increased from 6.2 to 14.9 MIs per 1000 patient days. Audits and chart reviews confirmed that more MIs are uncovered by employing a variety of techniques in addition to incident reporting. Staff surveys provided a rich source of information regarding medication safety. Audits of intravenous infusions revealed a reduced error rate from 38/331 (11.5%) to 15/468 (3.2%). Chart review of incorrect documentation of omitted medications decreased from 105/347 (30.3%) to 104/486 (21.4%). Focus groups provided information that was able to be used in a number of hospital forums in order to explain the impact of existing systems upon ICU staff. CONCLUSION: This ongoing QI project was able to achieve its targeted goals. The MI reporting rate was increased. This project demonstrated that measurable, "non-incident report" errors can be reduced by focusing upon and promoting medication safety in the ICU. These activities demonstrated a workplace that values medication safety, the discovery of shortfalls and the benefits of ongoing improvement.

ASAP ECMO: Antibiotic, Sedative and Analgesic Pharmacokinetics during Extracorporeal Membrane Oxygenation: a multi-centre study to optimise drug therapy during ECMO.

BACKGROUND: Given the expanding scope of extracorporeal membrane oxygenation (ECMO) and its variable impact on drug pharmacokinetics as observed in neonatal studies, it is imperative that the effects of the device on the drugs commonly prescribed in the intensive care unit (ICU) are further investigated. Currently, there are no data to confirm the appropriateness of standard drug dosing in adult patients on ECMO. Ineffective drug regimens in these critically ill patients can seriously worsen patient outcomes. This study was designed to describe the pharmacokinetics of the commonly used antibiotic, analgesic and sedative drugs in adult patients receiving ECMO. METHODS/DESIGN: This is a multi-centre, open-label, descriptive pharmacokinetic (PK) study. Eligible patients will be adults treated with ECMO for severe cardiac and/or respiratory failure at five Intensive Care Units in Australia and New Zealand. Patients will receive the study drugs as part of their routine management. Blood samples will be taken from indwelling catheters to investigate plasma concentrations of several antibiotics (ceftriaxone, meropenem, vancomycin, ciprofloxacin, gentamicin, piperacillin-tazobactum, ticarcillin-clavulunate, linezolid, fluconazole, voriconazole, caspofungin, oseltamivir), sedatives and analgesics (midazolam, morphine, fentanyl, propofol, dexmedetomidine, thiopentone). The PK of each drug will be characterised to determine the variability of PK in these patients and to develop dosing guidelines for prescription during ECMO. DISCUSSION: The evidence-based dosing algorithms generated from this analysis can be evaluated in later clinical studies. This knowledge is vitally important for optimising pharmacotherapy in these most severely ill patients to maximise the opportunity for therapeutic success and minimise the risk of therapeutic failure. TRIAL REGISTRATION: ACTRN12612000559819.