A Practical Integration of Automatic Generation Control and Demand Response

For a power grid to operate properly, electrical frequency must be continuously maintained close to its nominal value. Increasing penetration of distributed generation, such as solar and wind generation, introduces fluctuations in active power while also reducing the natural inertial response of the electricity grid, creating reliability concerns. While frequency regulation has traditionally been achieved by controlling generators, the control of Demand Response resources has been recognized in recent smart grid literature as an efficient means for providing additional regulation capability. To this end, several control methodologies have been proposed recently, but various features of these proposals make their practical implementations difficult. In this paper, we propose a new control algorithm that facilitates optimal frequency regulation through direct control of both generators and Demand Response, while addressing several issues that prevent practical implementation of other proposals. In particular, i) our algorithm is ideal for control over a large, low-bandwidth network as communication and measurement is only required every 2 seconds, ii) it enables Demand Response resources to recover energy lost during system transients, and iii) it accommodates both measured disturbances and unmeasured disturbances. We demonstrate the viability of our approach through dynamic simulations on a 118-bus grid model.NSF initiative, Award no. EFRI-144130

A Retrospective Comparison of Daptomycin Thrice-Weekly Versus Q48H Dosing in Hemodialysis Patients with Vancomycin-Resistant Enterococcus (VRE) or Methicillin-Resistant Staphylococcus Aureus (MRSA) Bacteremia

Background. Multi-drug resistant bacteria are a growing concern in healthcare. Daptomycin is being used with increasing frequency in the treatment of vancomycin-resistant enterococci (VRE) and methicillin-resistant Staphylococcus aureus (MRSA) bacteremias in hemodialysis (HD) patients. Thrice-weekly dosing of daptomycin in this population would allow for coordination of dosing with common outpatient HD schedules. The aim of this study is to determine if thrice-weekly dosing of daptomycin is equivalent to dosing every 48 hours in patients receiving chronic intermittent hemodialysis. Equivalence will be assessed with regard to microbiological cure, clinical cure, hospital length of stay, and mortality. Methods. All patients with positive blood cultures who received at least one dose of daptomycin between January 1st 2009 and December 31st 2010 at Indiana University Health Methodist and University Hospitals were identified. Adult patients with end-stage renal disease on a stable thrice-weekly hemodialysis regimen, confirmed VRE or MRSA bacteremia, and at least three doses of inpatient daptomycin therapy were enrolled in the study. Results. Twelve patients met criteria for inclusion in this study. Nine received daptomycin every 48 hours for the treatment of bacteremia, and three received daptomycin thrice-weekly after dialysis. There was no difference in time to clearance of blood cultures between the Q48H and thrice-weekly groups (2.11±2.15 days vs. 4.33±4.16 days; p=0.241).Length of hospital stay was not statistically significantly different between the two groups (22.8 days vs. 14.9 days; p=0.065).Conclusions. Thrice-weekly dosing of daptomycin may be effective for the treatment of bacteremia in hemodialysis patients

Hemopericardium and Cardiac Tamponade Associated with Dabigatran Use

OBJECTIVE: To describe 2 cases of hemopericardium following treatment with dabigatran. CASE SUMMARIES: A 70-year-old male with a history of dabigatran use presented with cough, fatigue, and bloody stools. The patient had a large hyperdense pericardial effusion caused by accumulation of bloody fluid, leading to hypotension and shock. Approximately 1000 mL of hemorrhagic fluid was drained from the pericardial space. A 77-year-old female was admitted for treatment of pneumonia and atrial fibrillation. Dabigatran was initiated and, after 6 doses, the patient developed abdominal pain, respiratory distress, and shock. She was diagnosed with pericardial effusion leading to cardiac tamponade. Pericardiocentesis and thoracentesis procedures removed a cumulative total of 2000 mL of bloody fluid. DISCUSSION: Dabigatran is an oral direct thrombin inhibitor approved for the reduction of stroke and systemic embolism risk in patients with nonvalvular atrial fibrillation. In December 2011, the Food and Drug Administration released a statement describing serious bleeding events associated with dabigatran use. According to the Naranjo scale, the cases presented here had probable associations between hemopericardium and dabigatran. While there is no known literature supporting this relationship, there are documented cases of warfarin-induced hemopericardium. CONCLUSIONS: These case reports highlight the potential for dabigatran to cause hemopericardium and cardiac tamponade. Additional reports may better elucidate (or characterize) the risk of dabigatran-induced hemopericardium and cardiac tamponade

Use of Cilostazol for Secondary Stroke Prevention: An Old Dog with New Tricks?

OBJECTIVE: To evaluate the safety and efficacy of cilostazol for secondary prevention of non-cardioembolic ischemic stroke. DATA SOURCES: PubMed and MEDLINE searches were performed (January 1970-September 2011) using the key words cilostazol, antiplatelet, aspirin, acetylsalicylic acid, secondary stroke prevention, ischemic stroke, intracerebral hemorrhage, intracranial, cerebrovascular accident, and transient ischemic attack. Additionally, reference citations from publications identified were reviewed. STUDY SELECTION AND DATA EXTRACTION: Articles published in English and relevant primary literature evaluating the efficacy and safety of cilostazol in the secondary prevention of atherosclerotic ischemic stroke were included. DATA SYNTHESIS: Antiplatelet therapy plays a vital role in the multifaceted approach to secondary stroke prevention. Current American Heart Association/American Stroke Association clinical guidelines for secondary stroke prevention support the use of aspirin, clopidogrel, and combination aspirin/extended-release dipyridamole. The antiplatelet, antithrombotic, and vasodilatory effects of cilostazol make it a potential alternative agent for atherosclerotic stroke prevention. Recent literature has demonstrated superior efficacy of cilostazol 100 mg twice daily for secondary stroke prevention compared to placebo and aspirin. Three clinical trials were reviewed (1 placebo-controlled, 2 aspirin-controlled), all of which were conducted in Japan or China. Cilostazol reduced the primary outcome of recurrence of stroke, with significantly fewer major bleeding events when compared to aspirin. CONCLUSIONS: Available literature suggests that cilostazol may be safer and more effective than aspirin in the secondary prevention of stroke in Asian patients. Further large-scale studies in more heterogeneous study populations are warranted to determine whether cilostazol is a viable therapeutic option for patients with a history of non-cardioembolic ischemic stroke

Back Talk: The Medicine Cabinet

Presenation to pharmacists at Butler CE Symposium, June 2012, Indianapolis, Indiana

Analysis of Anti-Xa Concentrations in Patients on Treatment Dose Enoxaparin: a Retrospective Chart Review

The purpose of this retrospective chart review was to determine the correlation between full weight-based enoxaparin use and the frequency of anti-Xa concentrations within the defined therapeutic range; to ascertain if anti-Xa monitoring is being appropriately ordered in relation to the timing of enoxaparin dose (after 3 consistent therapeutic doses and 3-5 hours post-dose); to establish if the evidence-based recommended dose adjustment protocol that was studied in the pediatric population was utilized; and if this yielded anti-Xa concentrations within the target range (0.6 – 1.1 IU/mL) for an adult population. The data may suggest a lack of correlation between BMI and whether or not the anti-Xa concentration is within the therapeutic range. Further prospective studies are needed to confirm this finding, and to determine the utility of the available dose adjustment nomogram

Medication Utilization Evaluation of Dabigatran and Rivaroxaban within a Large, Multicenter Health System.

Objective. The objective of this medication utilization evaluation (MUE) was to determine the appropriateness of dabigatran and rivaroxaban while also reviewing outcomes for safety and effectiveness within a large, multi-center health system. Methods. A retrospective chart review was performed using the system’s electronic medical record. A data inquiry was requested and generated for dabigatran usage from July 28, 2011 through July 28, 2012 and for rivaroxaban from March 1, 2012 to July 31, 2012 at eight health system hospitals. All patients receiving at least one dose were eligible for inclusion in the MUE. Results. For dabigatran, 78 of 390 unique patient encounters were analyzed (20%). All 62 rivaroxaban encounters were included in the analysis. Dabigatran was used for appropriate indications in 94% of encounters and 82% for rivaroxaban. Based on indication and renal function, 87% of dabigatran patients and 92% of rivaroxaban patients received correct dosing. For patients transitioning to or from another anticoagulant, appropriate transitions occurred in 44% of dabigatran transitions and 48% of rivaroxaban transitions. At discharge, 83% of dabigatran and 86% of rivaroxaban therapy was continued. There were no reported strokes or systemic embolism with dabigatran, but one reported deep vein thrombosis occurred during hospitalization with rivaroxaban therapy. Documented bleeds in 5% of dabigatran and 3% of rivaroxaban patients. Patient education was documented for 37% of dabigatran and 26% of rivaroxaban patients receiving therapeutic anticoagulation. Conclusion. This MUE revealed the appropriate use of dabigatran and rivaroxaban therapy with few safety outcomes within a large, multi-center health system

Correlation of Treatment Dose Enoxaparin with Anti-Xa Concentrations in Adult Hemodialysis Inpatients

Enoxaparin, a low-molecular-weight-heparin, is being used in hemodialysis patients despite a lack of guideline or manufacturer dose recommendations. Due to enoxaparin’s renal excretion, the possibility of accumulating anti-Xa concentrations in hemodialysis patients using enoxaparin creates a hemorrhagic risk, calling for more research. The objectives of this study are to determine the correlation between treatment dose enoxaparin use and anti-Xa concentrations within the defined therapeutic range in patients receiving chronic, scheduled hemodialysis to determine the degree of change in anti-Xa concentrations in those cases where a concentration was obtained before and after a specific hemodialysis session, and to determine if there is evidence of enoxaparin accumulation over the course of treatment. This was a retrospective cohort study. Patients that were admitted to Indiana University Health facilities in a two-year period were identified from a Cerner query for inclusion eligibility. Inclusion criteria involved patients that received therapeutic dose enoxaparin based on actual body weight on a once daily basis, maintained a scheduled hemodialysis regimen, and had an anti-Xa concentration obtained after at least one enoxaparin dose. Despite lacking statistical significance, the data collected from this study depicts trends which can be utilized to guide future studies. The results of this study suggest that hemodialysis does not effectively remove enoxaparin