Jeremy Clain

Distinct Molecular Mechanisms for Agonist Peptide Binding to Types A and B Cholecystokinin Receptors Demonstrated Using Fluorescence Spectroscopy

Fluorescence spectroscopy provides a direct method for evaluating the environment of a fluorescent ligand bound to its receptor. We utilized this methodology to determine the environment of Alexa within a cholecystokinin (CCK)-like probe (Alexa488-Gly-[(Nle28,31)CCK-26–33]; CCK-8 probe) bound to the type A CCK receptor (Harikumar, K. G., Pinon, D. L., Wessels, W. S., Prendergast, F. G., and Miller, L. J. (2002) J. Biol. Chem. 277, 18552–18560). Here, we study this probe at the type B CCK receptor and develop another probe with its fluorophore closer to the carboxyl-terminal pharmacophore of type B receptor ligands (Alexa488-Trp-Nle-Asp-Phe-NH2; CCK-4 probe). Both probes bound to type B CCK receptors in a saturable and specific manner and represented full agonists. Similar to the type A receptor, at the type B receptor these probes exhibited shorter lifetimes and lower anisotropy when the receptor was in the active conformation than when it was shifted to its inactive, G protein-uncoupled state using guanosine 5′-[β,γ-imido]-triphosphate trisodium salt. Absolute values for lifetime and anisotropy were lower for the CCK-8 probe bound to the type B receptor than for this probe bound to the type A receptor, and Alexa fluorescence was more easily quenched by iodide at the type B receptor. This represents the first direct evidence that, despite having identical affinities for binding and potencies for activating type A and B receptors, CCK is docked via distinct mechanisms, with the amino terminus more exposed to the aqueous milieu when bound to the type B CCK receptor than to the type A CCK receptor. Of interest, despite this difference in binding, activation of both receptors results in analogous direction of movement of the fluorescent indicator probes.

Experience with rituximab in the treatment of antineutrophil cytoplasmic antibody associated vasculitis

Prior to the 1970s, severe cases of antineutrophil cytoplasmic antibody associated vasculitis (AAV) were thought to be invariably fatal. However, the use of cyclophosphamide-based treatment regimens fundamentally altered disease outcomes, transforming AAV into a manageable, chronic illness. Despite the tremendous success of cyclophosphamide in the treatment of AAV, there remained a need for alternative therapies, due to high rates of treatment failures and significant toxicities. In recent years, with the introduction of targeted biologic response modifiers into clinical practice, many have hoped that the treatment options for AAV could be expanded. Rituximab, a chimeric monoclonal antibody directed against the B-lymphocyte protein CD20, has been the most successful biologic response modifier to be used in AAV. Following the first report of its use in AAV in 2001, experience with rituximab for treatment of AAV has rapidly expanded. Rituximab, in combination with glucocorticosteroids, is now well established as a safe and effective alternative to cyclophosphamide for remission induction for severe manifestations of granulomatosis with polyangiitis and microscopic polyangiitis. In addition, initial experiences with rituximab for remission maintenance in these diseases have been favorable, as have experiences for remission induction in eosinophilic granulomatosis with polyangiitis.

CARDIAC TAMPONADE OR SOMETHING MORE: WHEN HEMODYNAMICS DON’T IMPROVE WITH PERICARDIOCENTESIS

Hemodynamic instability is a common reason for medical ICU admission. Early identification of shock etiology is essential for optimal management. A 20 year-old woman was admitted to our medical ICU with profound hypotension occurring in the midst of a workup for protracted fatigue, dyspnea, and

Novel Treatments for Drug-Resistant Tuberculosis

Drug resistance has emerged as a major obstacle to global control of tuberculosis (TB). Treatment with currently available medications requires prolonged courses of numerous drugs, many of which are associated with significant adverse effects. New drugs are urgently needed to meet the challenge posed by drug-resistant TB, in order to relieve the burden that drug resistance has placed on individual patients and health systems. Fortunately, many new drugs have been developed for the treatment of drug-resistant TB in recent years. The new antimycobacterial agents are derived from various medication classes, work by means of an assortment of mechanisms of action, and are at differing phases of development. This review provides a survey of the most promising new agents, in order to promote familiarity with these emerging drugs and compounds.

Diagnosis of NTM Disease: Pulmonary and Extrapulmonary

Making a diagnosis of nontuberculous (NTM) disease is fraught with practical difficulties. For NTM pulmonary disease, there is rarely one piece of data that establishes or eliminates the diagnosis. In the case of NTM extrapulmonary disease, a high index of suspicion is required, and technical challenges can preclude rapid diagnostic certainty. In all instances, a measured and judicious approach is required when considering the possibility of NTM disease, and careful consideration of the individual patient, while adhering to general guiding principles, is necessary.

Non-antimicrobial airway management of non-cystic fibrosis bronchiectasis

Bronchiectasis are often encountered in clinical practice, and are characterized by abnormal airway dilatation and distortion associated with impaired mucociliary clearance and mucous plugging, which are frequently associated with recurrent infections. Numerous etiologies can underlie the development of bronchiectasis, but the most important distinction in research and clinical practice is between bronchiectasis due to cystic fibrosis (CF) and bronchiectasis due to all other reasons (non-CF bronchiectasis). The causes of non-CF bronchiectasis are varied and often unclear. Patients disease severity and phenotypes of non-CF bronchiectasis also varied, which can influence disease trajectory, frequency of exacerbations and mortality. This article reviews the published evidence and suggests interventions to enhance airways clearance in patients with non-CF bronchiectasis, which are key components of an individualized therapeutic program in order to achieve symptomatic relief and prevention of exacerbations and functional decline.

Comparison of the QuantiFERON-TB Gold Plus and QuantiFERON-TB Gold In-Tube Interferon Gamma Release Assays in Patients at Risk for Tuberculosis and in Health Care Workers

ABSTRACT The QuantiFERON-TB Gold Plus (QFT-Plus; Qiagen, Germantown, MD) interferon gamma release assay (IGRA) received FDA clearance in 2017 and will replace the prior version of the assay, the QFT-Gold In-Tube (QFT-GIT). Here, we compared performances of the QFT-Plus assay and the QFT-GIT version in a diverse patient population, including patients undergoing evaluation for or follow-up of latent tuberculosis infection (LTBI; n = 39) or active TB infection (n = 3), and in health care workers (HCWs; n = 119) at Mayo Clinic (Rochester, MN). Compared to the QFT-GIT, the QFT-Plus assay showed 91.2% (31/34) positive, 98.4% (124/126) negative, and 96.6% (156/161) overall qualitative agreement among the 161 enrolled subjects, with a Cohens kappa value of 0.91 (excellent interrater agreement). Among the 28 patients diagnosed with LTBI at the time of enrollment, the QFT-GIT and QFT-Plus assays agreed in 24 (85.7%) patients; in all four discordant patients, the positivity of the QFT-GIT or QFT-Plus IGRA was associated with low-level interferon gamma (IFN-γ) reactivity, ranging from 0.36 IU/ml to 0.66 IU/ml. Additionally, we document a high degree of correlation between IFN-γ levels in the QFT-GIT TB antigen tube and each of the two QFT-Plus TB antigen tubes, as well as between the QFT-Plus TB1 and TB2 tubes (Pearsons correlation coefficients [R] > 0.95). Overall, we show comparable results between the QFT-GIT and QFT-Plus assays in our study population composed of subjects presenting with a diverse spectrum of TB infections. Our findings suggest that the necessary transition to the QFT-Plus assay will be associated with a minimal difference in assay performance characteristics.

1366: EXTRACORPOREAL ELIMINATION OF BUTALBITAL IN ACUTE ASPIRIN- BUTALBITAL-CAFFEINE-CODEINE POISONING

www.ccmjournal.org Critical Care Medicine • Volume 46 • Number 1 (Supplement) Learning Objectives: Butalbital is a small molecule (approximately 220 Daltons), with 26% protein binding, a 0.8 L/kg volume of distribution, and is eliminated nearly 80% unchanged in the urine. Although hemodialysis (HD) has been used to treat overdoses of other barbiturates, the extracorporeal clearance of butalbital is unknown. The objective of this case is to describe the use of extracorporeal therapy to augment elimination of butalbital after overdose of aspirin-butalbitalcaffeine with codeine (Fiorinal with Codeine). Methods: A 67 year old female was admitted to the medical intensive care unit approximately three hours after ingestion of 40 tablets of Fiorinal with Codeine. Her presentation was notable for a decline in mental status, preserved renal function, and a relatively low peak aspirin concentration at 46.4 mg/dL. Approximately 8-hours after ingestion of nearly 1600mg of butalbital, our patient’s serum concentration was 26.9 mg/L (normal < 10 mg/L). At the end of a four-hour hemodialysis session, the total body elimination of butalbital was approximately 60% which corresponded to an intradialytic clearance of 14-18L/hr. Results: Extracorporeal removal of drug likely explains the majority of this total clearance based on the observed butalbital dialysate concentrations. We believe that timely initiation of intermittent HD in this case averted further cognitive and respiratory depression associated with barbiturate intoxication. Rapid reversal of the patient’s depressed mental status mitigated the respiratory failure risks quite quickly in this case and likely spared a protracted ICU course while intrinsic elimination of the drug occurred. While the inherent risks of the placement of temporary central venous access must be balanced, and the ready availability of dialysis team support must be considered; this objective experience supports the benefit of hemodialysis provision in severe overdoses of Fiorinal with Codeine that fail to respond to standard measures.

Extracorporeal elimination of butalbital in acute aspirin–butalbital–caffeine–codeine (Fiorinal with Codeine) poisoning

Abstract Background: Butalbital is a small molecule (approximately 220 Da), with 26% protein binding, a 0.8 L/kg volume of distribution, and is eliminated nearly 80% unchanged in the urine. Although hemodialysis has been used to treat overdoses of other barbiturates, the extracorporeal clearance of butalbital is unknown. The objective of this case is to describe the use of extracorporeal therapy to augment elimination of butalbital after an overdose of aspirin 325 mg–butalbital 50 mg–caffeine 40 mg with codeine 30 mg (Fiorinal with Codeine). Methods: This is a case report of a single patient. Results: A 67-year-old female was admitted to the medical intensive care unit approximately 3 h after ingestion of 40 tablets of Fiorinal with Codeine. Her presentation was notable for a decline in mental status, preserved renal function and a relatively low peak salicylate concentration at 46.4 mg/dL (3.4 mmol/L). Approximately 8 h after ingestion of 2000 mg of butalbital, our patient’s serum concentration was 26.9 mg/L (normal <10 mg/L). At the end of a four-hour hemodialysis session, the total body elimination of butalbital was approximately 60% which corresponded to an intradialytic clearance of 233–300 mL/min. Conclusions: The extracorporeal clearance of butalbital observed in this case demonstrates the utility of dialysis to augment drug elimination in a Fiorinal with Codeine overdose.