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Academic Appointments


Research & Scholarship

Current Research and Scholarly Interests


1) ICU Outcomes Research: glycemic control, sedation scoring, ICU device related infections, database analysis; 2) Clinical Pharmacology (i.e., pharmacokinetics, pharmacodynamics) of sedatives (eg, midazolam, lorazepam, propofol, dexemedetomidine) administered to ICU patients.

Teaching

2013-14 Courses


Publications

Journal Articles


  • The use of clinical simulation systems to train critical care physicians. Journal of intensive care medicine Lighthall, G. K., Barr, J. 2007; 22 (5): 257-269

    Abstract

    Intensive care units are complex and dynamic clinical environments in which the delivery of appropriate and timely care to critically ill patients depends on the integrated and efficient actions of providers with specialized training. The use of realistic clinical simulator systems can help to facilitate and standardize the training of critical-care physicians, nurses, respiratory therapists, and pharmacists without having the training process jeopardize the well-being of patients. In this article, we review the current state of the art of patient simulator systems and their applications to critical-care medicine, and we offer some examples and recommendations on how to integrate simulator systems into critical-care training.

    View details for PubMedID 17895484

  • Literature and medical interventions: An experiential course for undergraduates FAMILY MEDICINE Shafer, A., Borkovi, T., Barr, J. 2005; 37 (7): 469-471

    View details for Web of Science ID 000230468400007

    View details for PubMedID 15988641

  • Methicillin-resistant Staphylococcus aureus infections in ICU patients. Anesthesiology clinics of North America Sista, R. R., Oda, G., Barr, J. 2004; 22 (3): 405-?

    Abstract

    The incidence of methicillin-resistant Staphylococcus aureus (MRSA) infections in patients admitted to the intensive care unit has dramatically increased in recent years, with an associated increase in morbidity and mortality and the costs of caring for patients with MRSA infections. Although indiscriminate and inappropriate use of antibiotics has contributed to this phenomenon, horizontal transmission of MRSA between patients and health care providers is the principal cause of this observed increase. This article discusses the pathogenesis, epidemiology, treatment, and prevention of MRSA infections in critically ill patients.

    View details for PubMedID 15325711

  • Outcomes in critically ill patients before and after the implementation of an evidence-based nutritional management protocol CHEST Barr, J., Hecht, M., Flavin, K. E., Khorana, A., Gould, M. K. 2004; 125 (4): 1446-1457

    Abstract

    To determine whether the implementation of a nutritional management protocol in the ICU leads to the increased use of enteral nutrition, earlier feeding, and improved clinical outcomes in patients.Prospective evaluation of critically ill patients before and after the introduction of an evidence-based guideline for providing nutritional support in the ICU.The medical-surgical ICUs of two teaching hospitals.Two hundred critically ill adult patients who remained npo > 48 h after their admission to the ICU. One hundred patients were enrolled into the preimplementation group, and 100 patients were enrolled in the postimplementation group.Implementation of an evidence-based ICU nutritional management protocol.Nutritional outcome measures included the number of patients who received enteral nutrition, the time to initiate nutritional support, and the percent caloric target administered on day 4 of nutritional support. Clinical outcomes included the duration of mechanical ventilation, ICU and in-hospital length of stay (LOS), and in-hospital mortality rates. Patients in the postimplementation group were fed more frequently via the enteral route (78% vs 68%, respectively; p = 0.08), and this difference was statistically significant after adjusting for severity of illness, baseline nutritional status, and other factors (odds ratio, 2.4; 95% confidence interval [CI], 1.2 to 5.0; p = 0.009). The time to feeding and the caloric intake on day 4 of nutritional support were not different between the groups. The mean (+/- SD) duration of mechanical ventilation was shorter in the postimplementation group (17.9 +/- 31.3 vs 11.2 +/- 19.5 days, respectively; p = 0.11), and this difference was statistically significant after adjusting for age, gender, severity of illness, type of admission, baseline nutritional status, and type of nutritional support (p = 0.03). There was no difference in ICU or hospital LOS between the two groups. The risk of death was 56% lower in patients who received enteral nutrition (hazard ratio, 0.44; 95% CI, 0.24 to 0.80; p = 0.007).An evidence-based nutritional management protocol increased the likelihood that ICU patients would receive enteral nutrition, and shortened their duration of mechanical ventilation. Enteral nutrition was associated with a reduced risk of death in those patients studied.

    View details for Web of Science ID 000221793700042

    View details for PubMedID 15078758

  • Use of a fully simulated intensive care unit environment for critical event management training for internal medicine residents CRITICAL CARE MEDICINE Lighthall, G. K., Barr, J., Howard, S. K., Gellar, E., Sowb, Y., Bertacini, E., Gaba, D. 2003; 31 (10): 2437-2443
  • Variability in antibiotic prescribing patterns and outcomes in patients with clinically suspected ventilator-associated pneumonia CHEST Fowler, R. A., Flavin, K. E., Barr, J., Weinacker, A. B., Parsonnet, J., Gould, M. K. 2003; 123 (3): 835-844

    Abstract

    To describe the variation in clinical practice strategies for the treatment of suspected ventilator-associated pneumonia (VAP) in a population of critically ill patients, and to determine whether initial empiric treatment with certain antibiotics, monotherapy vs combination antibiotic therapy, or appropriate vs inappropriate antibiotic therapy is associated with survival, length of hospital stay, or days free of antibiotics.Prospective, observational cohort study.Medical-surgical ICUs of two university-affiliated tertiary medical centers.Between May 1, 1998, and August 1, 2000, we screened 7,030 ICU patients and identified 156 patients with clinically suspected VAP. Patients were followed up until death or discharge from the hospital.The mean age was 62 years, mean APACHE (acute physiology and chronic health evaluation) II score was 14, and mortality was 34%. Combination antibiotic therapy was used in 53% of patients. Piperacillin-tazobactam, fluoroquinolones, vancomycin, cephalosporins, and aminoglycosides were the most commonly employed antibiotics. Initial empiric antibiotics were deemed appropriate in 92% of patients. The predominant organisms isolated from respiratory secretions included Pseudomonas aeruginosa and Staphylococcus aureus. Patients had lower in-hospital mortality rates if their initial treatment regimen included an antipseudomonal penicillin plus beta-lactamase inhibitor (hazard ratio [HR], 0.41; 95% confidence interval [CI], 0.21 to 0.80; p = 0.009). There was also a strong trend toward reduced mortality rates in patients treated with aminoglycosides (HR, 0.43; 95% CI, 0.16 to 1.11; p = 0.08). Specific antibiotic therapy was not associated with length of hospital stay or days free of antibiotics. Outcomes were similar for patients treated with monotherapy vs combination therapy, and for patients who received initial appropriate vs inappropriate therapy.Patients with clinically suspected VAP who receive initial empiric therapy with antipseudomonal penicillins plus beta-lactamase inhibitors, and possibly aminoglycosides, have lower in-hospital mortality rates when compared with those who are not treated with these antibiotics. These agents should be considered for the initial empiric therapy of VAP.

    View details for Web of Science ID 000181536500035

    View details for PubMedID 12628886

  • Propofol dosing regimens for ICU sedation based upon an integrated pharmacokinetic-pharmacodynamic model ANESTHESIOLOGY Barr, J., Egan, T. D., Sandoval, N. F., Zomorodi, K., Cohane, C., Gambus, P. L., Shafer, S. L. 2001; 95 (2): 324-333

    Abstract

    The pharmacology of propofol infusions administered for long-term sedation of intensive care unit (ICU) patients has not been fully characterized. The aim of the study was to develop propofol dosing guidelines for ICU sedation based on an integrated pharmacokinetic-pharmacodynamic model of propofol infusions in ICU patients.With Institutional Review Board approval, 30 adult male medical and surgical ICU patients were given target-controlled infusions of propofol for sedation, adjusted to maintain a Ramsay sedation scale score of 2-5. Propofol administration in the first 20 subjects was based on a previously derived pharmacokinetic model for propofol. The last 10 subjects were given propofol based on a pharmacokinetic model derived from the first 20 subjects. Plasma propofol concentrations were measured, together with sedation score. Population pharmacokinetic and pharmacodynamic parameters were estimated by means of nonlinear regression analysis in the first 20 subjects, then prospectively tested in the last 10 subjects. An integrated pharmacokinetic-pharmacodynamic model was used to construct dosing regimens for light and deep sedation with propofol in ICU patients.The pharmacokinetics of propofol were described by a three-compartment model with lean body mass and fat body mass as covariates. The pharmacodynamics of propofol were described by a sigmoid model, relating the probability of sedation to plasma propofol concentration. The pharmacodynamic model for propofol predicted light and deep levels of sedation with 73% accuracy. Plasma propofol concentrations corresponding to the probability modes for sedation scores of 2, 3, 4, and 5 were 0.25, 0.6, 1.0, and 2.0 microg/ml. Predicted emergence times in a typical subject after 24 h, 72 h, 7 days, and 14 days of light sedation (sedation score = 3 --> 2) with propofol were 13, 34, 198, and 203 min, respectively. Corresponding emergence times from deep sedation (sedation score = 5 --> 2) with propofol were 25, 59, 71, and 74 h.Emergence time from sedation with propofol in ICU patients varies with the depth of sedation, the duration of sedation, and the patient's body habitus. Maintaining a light level of sedation ensures a rapid emergence from sedation with long-term propofol administration.

    View details for Web of Science ID 000170237800007

    View details for PubMedID 11506101

  • Population pharmacokinetics of midazolam administered by target controlled infusion for sedation following coronary artery bypass grafting ANESTHESIOLOGY Zomorodi, K., Donner, A., Somma, J., Barr, J., Sladen, R., Ramsay, J., Geller, E., Shafer, S. L. 1998; 89 (6): 1418-1429

    Abstract

    Midazolam is commonly used for short-term postoperative sedation of patients undergoing cardiac surgery. The purpose of this multicenter study was to characterize the pharmacokinetics and intersubject variability of midazolam in patients undergoing coronary artery bypass grafting.With institutional review board approval, 90 consenting patients undergoing coronary artery bypass grafting were enrolled at three study centers. All subjects received sufentanil and midazolam via target-controlled infusions. After operation, midazolam was titrated to maintain deep sedation for at least 2 h. It was then titrated downward to decrease sedation for a minimum of 4 h more and was discontinued before tracheal extubation. Arterial blood samples were taken throughout the study and were assayed for midazolam and 1-hydroxymidazolam. Midazolam population pharmacokinetic parameters were estimated using NONMEM. Cross-validation was used to estimate the performance of the model.The pharmacokinetics of midazolam were best described by a simple three-compartment mammillary model. Typical pharmacokinetic parameters were V1 = 32.2 l, V2 = 53 l, V3 = 245 l, Cl1 = 0.43 l/min, Cl2 = 0.56 l/min, and Cl3 = 0.39 l/min. The calculated elimination half-life was 15 h. The median absolute prediction error was 25%, with a bias of 1.4%. The performance in the cross-validation was similar. Midazolam metabolites were clinically insignificant in all patients.The intersubject variability and predictability of the three-compartment pharmacokinetic model are similar to those of other intravenous anesthetic drugs. This multicenter study did not confirm previous studies of exceptionally large variability of midazolam pharmacokinetics when used for sedation in intensive care settings.

    View details for Web of Science ID 000077376100019

    View details for PubMedID 9856717

  • PROPOFOL - A NEW DRUG FOR SEDATION IN THE INTENSIVE-CARE UNIT INTERNATIONAL ANESTHESIOLOGY CLINICS Barr, J. 1995; 33 (1): 131-154

    Abstract

    Patients in the ICU who require intubation and mechanical ventilation benefit from adequate sedation and analgesia. Traditionally, this has been achieved using benzodiazepines and opioids. Alternatively, propofol is being administered for sedation of patients in the ICU with increasing frequency. Propofol has a number of properties that make it a potentially superior choice for sedation of intubated ICU patients. The rapid onset and offset of sedation with propofol, even after prolonged administration, allow for greater control over the level of sedation and more rapid weaning from mechanical ventilation. In addition, long-term administration of propofol does not appear to be associated with the development of tolerance, addiction, or withdrawal following discontinuation. Propofol suppresses cellular oxygen consumption and carbon dioxide production without increasing anaerobic metabolism. This may be beneficial in patients with severe hypoxemia, hypercarbia, or myocardial ischemia. Finally, the use of propofol may reduce or eliminate the need for other medications in these patients such as muscle relaxants, antihypertensives, lipid nutritional supplements, and analgesics, thereby simplifying their medication regimens and reducing the overall cost of their care while in the ICU. Propofol can be administered to critically ill patients for sedation with a high degree of safety and efficacy. Propofol causes systemic vasodilatation which may result in unwanted hypotension, especially in patients who are already hemodynamically compromised. Propofol also causes ventilatory depression, so its use should be restricted in the ICU to patients whose airway is protected by an endotracheal tube and whose ventilation is closely monitored. Finally, continuous administration of propofol may cause clinically significant hypertriglyceridemia in patients with disordered triglyceride metabolism, or in patients receiving excessive doses of propofol or parenteral lipid supplements. Although propofol is more expensive than equipotent doses of other sedative agents, the additional cost of using propofol for sedation of critically ill patients in the ICU may be more than offset by the savings accrued from faster times to extubation, shorter ICU stays, and the use of fewer medications to manage these patients. Further research needs to be done to determine the potential clinical and cost benefits of using propofol for sedation of patients in the ICU.

    View details for Web of Science ID A1995QX08000009

    View details for PubMedID 7635554

  • BIGUANIDE-ASSOCIATED LACTIC-ACIDOSIS - CASE-REPORT AND REVIEW OF THE LITERATURE ARCHIVES OF INTERNAL MEDICINE Gan, S. C., Barr, J., Arieff, A. I., Pearl, R. G. 1992; 152 (11): 2333-2336

    Abstract

    The biguanides are a class of oral hypoglycemic agents that are commonly used in the treatment of diabetes mellitus. Such agents include metformin, phenformin, and buformin. The use of phenformin was discontinued in the United States in 1976 because of probable association with lactic acidosis. However, metformin is currently in common use in many parts of the world. In this report, we describe a patient with severe lactic acidosis secondary to metformin administration, and review the literature relevant to biguanide-associated lactic acidosis.We describe a diabetic man with end-stage renal failure and diabetes mellitus who was hospitalized with life-threatening lactic acidosis (lactate, 10.9 mmol/L). Unbeknownst to the hospital staff, he was being treated with metformin, which had been prescribed in Indonesia.Arterial blood gas analysis revealed a pH of 6.76 and a bicarbonate level of 1.6 mmol/L prior to treatment. Following therapy, which included oxygen, volume expansion, other supportive therapy, and hemodialysis, the patient completely recovered and was discharged from the hospital.Lactic acidosis can complicate biguanide therapy in diabetic patients with renal insufficiency. We review the literature relevant to the pathogenesis and therapy of biguanide-associated lactic acidosis. Physicians who have completed their training after 1976 may not be familiar with metformin and other biguanides, but with the increasing numbers of immigrants to the United States, physicians should be aware of the potential complications of these medications.

    View details for Web of Science ID A1992JX15100023

    View details for PubMedID 1444694

Conference Proceedings


  • A double-blind, randomized comparison of IV lorazepam versus midazolam for sedation of ICU patients via a pharmacologic model Barr, J., Zomorodi, K., Bertaccini, E. J., Shafer, S. L., Geller, E. LIPPINCOTT WILLIAMS & WILKINS. 2001: 286-298

    Abstract

    Benzodiazepines, such as lorazepam and midazolam, are frequently administered to surgical intensive care unit (ICU) patients for postoperative sedation. To date, the pharmacology of lorazepam in critically ill patients has not been described. The aim of the current study was to characterize and compare the pharmacokinetics and pharmacodynamics of lorazepam and midazolam administered as continuous intravenous infusions for postoperative sedation of surgical ICU patients.With Institutional Review Board approval, 24 consenting adult surgical patients were given either lorazepam or midazolam in a double-blind fashion (together with either intravenous fentanyl or epidural morphine for analgesia) through target-controlled intravenous infusions titrated to maintain a moderate level of sedation for 12-72 h postoperatively. Moderate sedation was defined as a Ramsay Sedation Scale score of 3 or 4. Sedation scores were measured, together with benzodiazepine plasma concentrations. Population pharmacokinetic and pharmacodynamic parameters were estimated using nonlinear mixed-effects modeling.A two-compartment model best described the pharmacokinetics of both lorazepam and midazolam. The pharmacodynamic model predicted depth of sedation for both midazolam and lorazepam with 76% accuracy. The estimated sedative potency of lorazepam was twice that of midazolam. The predicted C50,ss (plasma benzodiazepine concentrations where P(Sedation > or = ss) = 50%) values for midazolam (sedation score [SS] > or = n, where n = a Ramsay Sedation Score of 2, 3, ... 6) were 68, 101, 208, 304, and 375 ng/ml. The corresponding predicted C50,ss values for lorazepam were 34, 51, 104, 152, and 188 ng/ml, respectively. Age, fentanyl administration, and the resolving effects of surgery and anesthesia were significant covariates of benzodiazepine sedation. The relative amnestic potency of lorazepam to midazolam was 4 (observed). The predicted emergence times from sedation after a 72-h benzodiazepine infusion for light (SS = 3) and deep (SS = 5) sedation in a typical patient were 3.6 and 14.9 h for midazolam infusions and 11.9 and 31.1 h for lorazepam infusions, respectively.The pharmacology of intravenous infusions of lorazepam differs significantly from that of midazolam in critically ill patients. This results in significant delays in emergence from sedation with lorazepam as compared with midazolam when administered for ICU sedation.

    View details for Web of Science ID 000170237800003

    View details for PubMedID 11506097

  • GUARDIAN - AN EXPERIMENTAL SYSTEM FOR INTELLIGENT ICU MONITORING HAYESROTH, B., Uckun, S., Larsson, J. E., DRAKOPOULOS, J., Gaba, D., Barr, J., Chien, J. BMJ PUBLISHING GROUP. 1994: 1004-1004

    View details for Web of Science ID A1994QF21600211

    View details for PubMedID 7949846

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