Gouty arthritis of the spine in a renal transplant patient : a clinical case report: an unusual presentation of a common disease

Axial gout is a well-documented but uncommon manifestation of gout. Its mimicking nature and the impracticality of axial joint aspiration might considerably delay its diagnosis. We report a case in a normouricemic renal transplant recipient, whereby the primary symptom of severe neck pain suggested pyogenic spondylodiscitis as an initial tentative diagnosis. Clinical findings included a high C-reactive protein concentration and elevated body temperature. The patient did not respond to empiric antibiotic treatment and suffered consecutive attacks of severe wrist and ankle pain in conjunction with a persistent fever. Blood and joint cultures were negative, but analysis of aspirated ankle joint fluid revealed monosodium urate crystals. A dual-energy computed tomography scan confirmed the presence of monosodium urate crystals in the costovertebral joints. Colchicine treatment dramatically improved the patient's clinical condition. Axial gout should be considered in transplant recipients with severe neck or back pain, fever, and increased inflammatory parameters with a high likelihood of an infectious etiology, despite the presence of paradoxically normal or even decreased serum urate concentrations. Dual-energy computed tomography is a noninvasive technique of possible benefit in the detection of axial gout when joint fluid aspiration is not deemed safe

Early target attainment of continuous infusion piperacillin/tazobactam and meropenem in critically ill patients : a prospective observational study

To evaluate target attainment of empirically dosed continuous infusion piperacillin/tazobactam (TZP) and meropenem (MER) in critically ill patients.Patients were sampled on a daily basis. TZP or MER concentrations were evaluated during the first two days antibiotic therapy. The lower limit of the target range was defined as unbound concentrations equaling 4 times the epidemiological cutoff value of P. aeruginosa. The upper limit of the target range was based on the risk of toxicity, i.e. unbound concentrations >160 mg/L for TZP and > 45 mg/L for MER. Multivariable logistic regression was used to evaluate factors associated with target attainment.Data from 253 patients were analyzed. Overall, 76/205 (37.1%) and 36/48 (75%) of the patients receiving TZP or MER respectively, attained target concentrations. In multivariable analysis, estimated creatinine clearance was identified as a risk factor for target non-attainment (OR 0.988, 95%CI [0.982;0.994]). Patients receiving MER were more likely to attain target concentrations compared with patients receiving TZP (OR 6.02, 95%CI [2.12;18.4]).Target attainment of empiric antibiotic therapy in critically ill patients was low (37%) for TZP and moderate (75%) for MER, despite the use of a loading dose and despite optimization of the mode of infusion

Development and evaluation of uncertainty quantifying machine learning models to predict piperacillin plasma concentrations in critically ill patients

Background: Beta-lactam antimicrobial concentrations are frequently suboptimal in critically ill patients. Population pharmacokinetic (PopPK) modeling is the golden standard to predict drug concentrations. However, currently available PopPK models often lack predictive accuracy, making them less suited to guide dosing regimen adaptations. Furthermore, many currently developed models for clinical applications often lack uncertainty quantification. We, therefore, aimed to develop machine learning (ML) models for the prediction of piperacillin plasma concentrations while also providing uncertainty quantification with the aim of clinical practice. Methods: Blood samples for piperacillin analysis were prospectively collected from critically ill patients receiving continuous infusion of piperacillin/tazobactam. Interpretable ML models for the prediction of piperacillin concentrations were designed using CatBoost and Gaussian processes. Distribution-based Uncertainty Quantification was added to the CatBoost model using a proposed Quantile Ensemble method, useable for any model optimizing a quantile function. These models are subsequently evaluated using the distribution coverage error, a proposed interpretable uncertainty quantification calibration metric. Development and internal evaluation of the ML models were performed on the Ghent University Hospital database (752 piperacillin concentrations from 282 patients). Ensuing, ML models were compared with a published PopPK model on a database from the University Medical Centre of Groningen where a different dosing regimen is used (46 piperacillin concentrations from 15 patients.). Results: The best performing model was the Catboost model with an RMSE and R-2 of 31.94-0.64 and 33.53-0.60 for internal evaluation with and without previous concentration. Furthermore, the results prove the added value of the proposed Quantile Ensemble model in providing clinically useful individualized uncertainty predictions and show the limits of homoscedastic methods like Gaussian Processes in clinical applications. Conclusions: Our results show that ML models can consistently estimate piperacillin concentrations with acceptable and high predictive accuracy when identical dosing regimens as in the training data are used while providing highly relevant uncertainty predictions. However, generalization capabilities to other dosing schemes are limited. Notwithstanding, incorporating ML models in therapeutic drug monitoring programs seems definitely promising and the current work provides a basis for validating the model in clinical practice

Antibiotic stewardship in sepsis management : toward a balanced use of antibiotics for the severely ill patient

Introduction: Severe infections in critically ill patients carry a high morbidity and mortality rate. Given the impact of early and broad-spectrum empirical therapy in several studies and the emphasis on this in international guidelines, there is a low threshold for initiating antibiotics in many patients with suspected infection. This has led to the widespread use of antibiotics in critically ill patients, which is often unnecessary or inappropriate. Areas covered: Antimicrobial stewardship (AMS) attempts to reduce antibiotic exposure while improving outcomes and may intuitively contrast with current antibiotic prescription practices. The challenge for critical care physicians is thus to correctly diagnose infection and improve outcome while reducing antibiotic use. This can be done by adhering to local guidelines for empirical therapy, better risk for multidrug resistance assessment, optimized antibiotic dosing, and integration of rapid diagnostic techniques in the decision-making process. Watchful waiting, or withholding antibiotics until infection is confirmed, is justified in non-severely ill patients in whom the clinical picture is not clear. Expert opinion: Integrating AMS strategies in clinical practice can help upholding the best antibiotic empirical therapy while reducing antibiotic consumption. AMS is a multidisciplinary policy and should be embraced by critical care physicians as a solution for balanced antibiotic use

Subtherapeutic piperacillin concentrations in neurocritical patients

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Why we may need higher doses of beta-lactam antibiotics : introducing the 'maximum tolerable dose'

The surge in antimicrobial resistance and the limited availability of new antimicrobial drugs has fueled the interest in optimizing antibiotic dosing. An ideal dosing regimen leads to maximal bacterial cell kill, whilst minimizing the risk of toxicity or antimicrobial resistance. For beta-lactam antibiotics specifically, PK/PD-based considerations have led to the widespread adoption of prolonged infusion. The rationale behind prolonged infusion is increasing the percentage of time the beta-lactam antibiotic concentration remains above the minimal inhibitory concentration (%fT(>MIC)). The ultimate goal of prolonged infusion of beta-lactam antibiotics is to improve the outcome of infectious diseases. However, merely increasing target attainment (or the %fT(>MIC)) is unlikely to lead to improved clinical outcome for several reasons. First, the PK/PD index and target are dynamic entities. Changing the PK (as is the case if prolonged instead of intermittent infusion is used) will result in different PK/PD targets and even PK/PD indices necessary to obtain the same level of bacterial cell kill. Second, the minimal inhibitory concentration is not a good denominator to describe either the emergence of resistance or toxicity. Therefore, we believe a different approach to antibiotic dosing is necessary. In this perspective, we introduce the concept of the maximum tolerable dose (MTD). This MTD is the highest dose of an antimicrobial drug deemed safe for the patient. The goal of the MTD is to maximize bacterial cell kill and minimize the risk of antimicrobial resistance and toxicity. Unfortunately, data about what beta-lactam antibiotic levels are associated with toxicity and how beta-lactam antibiotic toxicity should be measured are limited. This perspective is, therefore, a plea to invest in research aimed at deciphering the dose-response relationship between beta-lactam antibiotic drug concentrations and toxicity. In this regard, we provide a theoretical approach of how increasing uremic toxin concentrations could be used as a quantifiable marker of beta-lactam antibiotic toxicity

Pilot study of oral fluid and plasma meropenem and piperacillin concentrations in the intensive care unit

Background: Therapeutic drug monitoring (TDM) of beta-lactam antibiotics may be used to optimize dosing for patients in the intensive care unit (ICU). A noninvasive matrix such as oral fluid may be interesting in selected patient groups. We compared the oral fluid concentrations of piperacillin and meropenem with the respective unbound and total concentrations in plasma. A secondary objective was to evaluate feasibility of the collection of oral fluid samples in this specific patient population. Methods: The study included 20 non-intubated ICU patients, age 22 to 77 y, receiving piperacillin or meropenem via continuous intravenous infusion. The standard protocol consisted of collecting a paired plasma-oral fluid sample for 3 consecutive days. Oral fluid was obtained from the patients using a standardized procedure by spitting in a plastic container after 2 min of gathering oral fluid in the mouth. Results: Antibiotic concentrations of piperacillin and meropenem are measurable, albeit very low, in unstimulated oral fluid of ICU patients. For piperacillin, a poor correlation was found between oral fluid and both total and unbound plasma concentrations (Spearman's correlation coefficients (Rs) 0.46 and 0.48 respectively). For meropenem this correlation was better (Rs for oral fluid versus total and unbound plasma meropenem concentration 0.92 and 0.93 respectively). Dispersion of antibiotic concentrations was greater in oral fluid than in blood. Collecting oral fluid samples was difficult in non-intubated ICU patients. Conclusions: Oral fluid from non-intubated ICU patients, obtained through a standardized procedure, cannot be recommended as an alternative matrix for quantitative meropenem or piperacillin TDM

Measuring antibiotics in exhaled air in critically ill, non-ventilated patients : a feasibility and proof of concept study

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