Protein Solvent Shell Structure Provides Rapid Analysis of Hydration Dynamics.

The solvation layer surrounding a protein is clearly an intrinsic part of protein structure-dynamics-function, and our understanding of how the hydration dynamics influences protein function is emerging. We have recently reported simulations indicating a correlation between regional hydration dynamics and the structure of the solvation layer around different regions of the enzyme Candida antarctica lipase B, wherein the radial distribution function (RDF) was used to calculate the pairwise entropy, providing a link between dynamics (diffusion) and thermodynamics (excess entropy) known as Rosenfeld scaling. Regions with higher RDF values/peaks in the hydration layer (the first peak, within 6 Å of the protein surface) have faster diffusion in the hydration layer. The finding thus hinted at a handle for rapid evaluation of hydration dynamics at different regions on the protein surface in molecular dynamics simulations. Such an approach may move the analysis of hydration dynamics from a specialized venture to routine analysis, enabling an informatics approach to evaluate the role of hydration dynamics in biomolecular function. This paper first confirms that the correlation between regional diffusive dynamics and hydration layer structure (via water center of mass around protein side-chain atom RDF) is observed as a general relationship across a set of proteins. Second, it seeks to devise an approach for rapid analysis of hydration dynamics, determining the minimum amount of information and computational effort required to get a reliable value of hydration dynamics from structural data in MD simulations based on the protein-water RDF. A linear regression model using the integral of the hydration layer in the water-protein RDF was found to provide statistically equivalent apparent diffusion coefficients at the 95% confidence level for a set of 92 regions within five different proteins. In summary, RDF analysis of 10 ns of data after simulation convergence is sufficient to accurately map regions of fast and slow hydration dynamics around a protein surface. Additionally, it is anticipated that a quick look at protein-water RDFs, comparing peak heights, will be useful to provide a qualitative ranking of regions of faster and slower hydration dynamics at the protein surface for rapid analysis when investigating the role of solvent dynamics in protein function.

Implications of Augmented Renal Clearance on Drug Dosing in Critically Ill Patients: A Focus on Antibiotics.

Augmented renal clearance (ARC) has been reported in approximately 30-65% of patients in the intensive care unit (ICU) despite the presence of a normal serum creatinine concentration. In certain ICU patient populations (e.g., patients with sepsis or trauma), the incidence increases to roughly 50-85%. Risk factors for ARC include the following: age younger than 50-55 years, male sex, higher diastolic blood pressure, fewer comorbidities, and a lower Acute Physiology and Chronic Health Evaluation II (APACHE II) or modified Sequential Organ Failure Assessment (SOFA) score at ICU admission. In addition, patient populations with the highest reported incidence of ARC include those with major trauma, sepsis, traumatic brain injury, subarachnoid hemorrhage, and central nervous system infection. Due to the high incidence of ARC in patients with a normal serum creatinine concentration, clinicians should consider screening ICU patients deemed high risk by using the ARC scoring system or the identification and assessment algorithm provided in this review. In addition, an 8-hour continuous urine collection should be considered to assess a measured creatinine clearance for evaluating the necessity of medication dosage adjustments. There is a clear association between ARC and subtherapeutic antibiotic concentrations as well as literature suggesting worse clinical outcomes; thus, the risk of underdosing antibiotics in a patient with ARC could increase the risk of treatment failure. This review examines strategies to overcome ARC and summarizes current pharmacokinetic and pharmacodynamic literature in patients with ARC in an effort to provide dosing guidance for this patient population.

Length of Stay Comparison between Rivaroxaban and Warfarin in the Treatment of Pulmonary Embolism: Results from a Real-World Observational Cohort Study.

Background. Trials have shown that novel oral anticoagulants may decrease length of stay versus warfarin. A comparison of length of stay in the treatment of pulmonary embolism (PE) has not been performed outside post hoc analysis of a large clinical trial. Objective. To evaluate if rivaroxaban decreases length of stay compared to warfarin plus enoxaparin in the treatment of PE. Methods. This was a multicenter, retrospective, observational cohort study. Patients were identified based on discharge diagnosis of PE and were excluded if they received anticoagulants prior to admission and had additional indications for anticoagulation or reduced creatinine clearance. The primary endpoint was length of stay. Secondary endpoints included time from initial dose of oral anticoagulant to discharge and length of stay comparison between subgroups. Results. Inclusion criterion was met by 158 patients (82 warfarin, 76 rivaroxaban). The median length of stay was 4.5 days (interquartile range [IQR], 2.7, 5.9) in the warfarin group and 1.8 days (IQR, 1.2, 3.7) in the rivaroxaban group (P < 0.001). Time interval from first dose of oral anticoagulant to discharge was shorter with rivaroxaban (P < 0.001). Conclusions. Patients given rivaroxaban had decreased length of stay versus those given warfarin plus enoxaparin for the treatment of PE.