Reproducible Quantification of Unbound Fractions of Four Beta-Lactam Antibiotics: Ultrafiltration Versus Microdialysis of Spiked Healthy Donor Plasma.

BACKGROUND: Ultrafiltration (UF) is a conventional method for isolating the protein-unbound plasma fractions of therapeutic drugs. However, the ideal UF conditions for specific compounds remain largely unexplored. By comparing UF-derived unbound concentrations with the corresponding results obtained using a reference method, the authors sought to identify appropriate UF conditions for cefotaxime, cloxacillin, flucloxacillin, and piperacillin. METHODS: In vitro microdialysis (MD) with a no-net-flux approach was used as a reference method for plasma protein separation, for which UF performance was assessed. Four levels of relative centrifugal force (2500-11,290 g ) and 2 levels of temperature (37 vs. 22°C) during 10 minutes of UF centrifugation were evaluated. Ultrafiltrates and reference microdialysates were analyzed using liquid chromatography-tandem mass spectrometry to obtain unbound concentrations. After identifying the appropriate UF conditions in the spiked plasma samples, exploratory analyses of clinical samples (n = 10 per analyte) were performed. RESULTS: Of the evaluated UF alternatives, the best overall agreement with the MD-derived reference concentrations was obtained with 11,290 g UF performed at 22°C. For cloxacillin specifically, 37°C UF yielded better agreement than 22°C UF at 11,290 g. Clinical sample analyses indicated minimal differences between 22°C and 37°C at 11,290 g UF for cefotaxime and piperacillin. However, consistently lower levels of unbound cloxacillin (median: -23%, IQR: -19% to -24%) and flucloxacillin (median: -27%, IQR: -21 to -34%) were observed after UF at 22°C versus 37°C. CONCLUSIONS: For the evaluated UF device, 10 minutes of 11,290 g UF at 22°C is appropriate for flucloxacillin, cefotaxime, and piperacillin, and can arguably be justified for cloxacillin as well for laboratory practice purposes. Maintenance of 37°C during high-centrifugal UF may lead to overestimation, particularly for unbound flucloxacillin.

Photographic assessment of burn wounds: a simple strategy in a resource-poor setting.

OBJECTIVE: To validate the use of photographic burn wound assessment in evaluation of burn size and wound characteristics. METHODS: Feasibility study of agreement between methods of measurement of burn size and characteristics, in patients admitted to the burn unit at Kamuzu Central Hospital (KCH), Malawi, over two months in 2011. Burn wounds were photographed and assessed clinically, concurrently, by an experienced clinician. Photographs reviewed by two blinded burn clinicians after 4-6 weeks. Correlation between clinical assessment and photographic evaluation was calculated using kappa score and Pearson's correlation coefficient. RESULTS: Thirty-nine patients were included in evaluation of TBSA, and fifty wounds assessed for their characteristics. Pearson's correlation coefficient for agreement of TBSA between clinical exam and photograph review by expert#1, and #2, was 0.96, 0.93 (p<0.001), respectively. Pearson's correlation coefficients comparing expert#1 and #2 to the gold standard were: proportion of full-thickness burn (0.88 and 0.81, p<0.001), and epithelialized superficial burn (0.89 and 0.55, p<0.001). Kappa scores were significant for wound evolution (expert#1 0.57, expert#2 0.64, p<0.001), and prognosis (expert#1 0.80, expert#2 0.80, p<0.001). CONCLUSIONS: Burn assessment with digital photography is a valid and affordable alternative to direct clinical exam, alleviating access issues to burn care in developing countries.