David A. Wampler

Pathway for H2O2 and O2 detoxification in Clostridium acetobutylicum.

An unusual non-haem diiron protein, reverse rubrerythrin (revRbr), is known to be massively upregulated in response to oxidative stress in the strictly anaerobic bacterium Clostridium acetobutylicum. In the present study both in vivo and in vitro results demonstrate an H2O2 and O2 detoxification pathway in C. acetobutylicum involving revRbr, rubredoxin (Rd) and NADH : rubredoxin oxidoreductase (NROR). RevRbr exhibited both NADH peroxidase (NADH : H2O2 oxidoreductase) and NADH oxidase (NADH : O2 oxidoreductase) activities in in vitro assays using NROR as the electron-transfer intermediary from NADH to revRbr. Rd increased the NADH consumption rate by serving as an intermediary electron-transfer shuttle between NROR and revRbr. While H2O2 was found to be the preferred substrate for revRbr, its relative oxidase activity was found to be significantly higher than that reported for other Rbrs. A revRbr-overexpressing strain of C. acetobutylicum showed significantly increased tolerance to H2O2 and O2 exposure. RevRbr thus appears to protect C. acetobutylicum against oxidative stress by functioning as the terminal component of an NADH peroxidase and NADH oxidase.

No Deaths Associated with Patient Refusal of Transport After Naloxone-Reversed Opioid Overdose

Abstract Introduction. Naloxone is widely used in the treatment and reversal of opioid overdose. Most emergency medical services (EMS) systems administer naloxone by standing order, and titrate only to reverse respiratory depression without fully reversing sedation. Some EMS systems routinely administer sufficient naloxone to fully reverse the effects of opioid overdose. Frequently patients refuse further medical evaluation or intervention, including transport. Objectives. The purpose of this study was to evaluate the safety of this practice and determine whether increased mortality is associated with full reversal of opioids. As a component of a comprehensive quality assurance initiative, we assessed mortality during the 48 hours after patients received naloxone to reverse opioid overdose followed by patient-initiated refusal of transportation. Methods. The setting was a large urban fire-based EMS system. Investigators provided the Bexar County Medical Examiners Office (MEO) with a list of patients who were treated by the San Antonio Fire Department with naloxone, and not transported. Inclusion criteria were administration of naloxone and patient-initiated refusal. Patient dispositions also included aid only, referral to the MEO, or referral to law enforcement. The list was then compared with the MEO database. A chart review was completed on all patients treated and subsequently presented to the MEO within two days. A secondary time period of 30 days was also assessed. Results. The list identified 592 patients treated with naloxone and not transported to the emergency department. Five-hundred fifty-two patients received naloxone and refused transport or were not transported. The remaining 40 patients all presented to EMS in cardiac arrest, naloxone was administered during the course of resuscitation, and subsequent efforts were terminated in the field. None of the patients receiving naloxone with a subsequent patient-initiated refusal were examined at the MEO within the two-day end point. The 30-day assessment revealed that nine individuals were treated with naloxone and subsequently died, but the shortest time interval between date of service and date of death was four days. Conclusion. The primary outcome was that no patients who were treated with naloxone for opioid overdose and then refused care were examined by the MEO within a 48-hour time frame.

Cardiac Arrest Survival Is Rare Without Prehospital Return of Spontaneous Circulation

Abstract Background. Emergency medical services (EMS) are crucial in the management of out-of-hospital cardiac arrest (OHCA). Despite accepted termination-of-resuscitation criteria, many patients are transported to the hospital without achieving field return of spontaneous circulation (ROSC). Objective. We examine field ROSC influence on OHCA survival to hospital discharge in two large urban EMS systems. Methods. A retrospective analysis of prospectively collected data was conducted. Data collection is a component of San Antonio Fire Departments comprehensive quality assurance/quality improvement program and Cincinnati Fire Departments participation in the Cardiac Arrest Registry to Enhance Survival (CARES) project. Attempted resuscitations of medical OHCA and cardiac OHCA for San Antonio and Cincinnati, respectively, from 2008 to 2010 were analyzed by city and in aggregate. Results. A total of 2,483 resuscitation attempts were evaluated. Age and gender distributions were similar between cities, but ethnic profiles differed. Cincinnati had 17% (p = 0.002) more patients with an initial shockable rhythm and was more likely to initiate transport before field ROSC. Overall survival to hospital discharge was 165 of 2,483 (6.6%). More than one-third (894 of 2,483, 36%) achieved field ROSC. Survival with field ROSC was 17.2% (154 of 894) and without field ROSC was 0.69% (11 of 1,589). Of the 11 survivors transported prior to field ROSC, nine received defibrillation by EMS. No asystolic patient survived to hospital discharge without field ROSC. Conclusion. Survival to hospital discharge after OHCA is rare without field ROSC. Resuscitation efforts should focus on achieving field ROSC. Transport should be reserved for patients with field ROSC or a shockable rhythm.

Photoheterotrophic Metabolism of Acrylamide by a Newly Isolated Strain of Rhodopseudomonas palustris

ABSTRACT Acrylamide, a neurotoxin and suspected carcinogen, is produced by industrial processes and during the heating of foods. In this study, the microbial diversity of acrylamide metabolism has been expanded through the isolation and characterization of a new strain of Rhodopseudomonas palustris capable of growth with acrylamide under photoheterotrophic conditions. The newly isolated strain grew rapidly with acrylamide under photoheterotrophic conditions (doubling time of 10 to 12 h) but poorly under anaerobic dark or aerobic conditions. Acrylamide was rapidly deamidated to acrylate by strain Ac1, and the subsequent degradation of acrylate was the rate-limiting reaction in cell growth. Acrylamide metabolism by succinate-grown cultures occurred only after a lag period, and the induction of acrylamide-degrading activity was prevented by the presence of protein or RNA synthesis inhibitors. 13C nuclear magnetic resonance studies of [1,2,3-13C]acrylamide metabolism by actively growing cultures confirmed the rapid conversion of acrylamide to acrylate but failed to detect any subsequent intermediates of acrylate degradation. Using concentrated cell suspensions containing natural abundance succinate as an additional carbon source, [13C]acrylate consumption occurred with the production and then degradation of [13C]propionate. Although R. palustris strain Ac1 grew well and with comparable doubling times for each of acrylamide, acrylate, and propionate, R. palustris strain CGA009 was incapable of significant acrylamide- or acrylate-dependent growth over the same time course, but grew comparably with propionate. These results provide the first demonstration of anaerobic photoheterotrophic bacterial acrylamide catabolism and provide evidence for a new pathway for acrylate catabolism involving propionate as an intermediate.

Dual defibrillation in out-of-hospital cardiac arrest: A retrospective cohort analysis

STUDY OBJECTIVES The goal of our study is to determine if prehospital dual defibrillation (DD) is associated with better neurologically intact survival in out-of-hospital cardiac arrest. METHODS This study is a retrospective cohort analysis of prospectively collected Quality Assurance/Quality Improvement data from a large urban fire based EMS system out-of-hospital cardiac arrest (OHCA) database between Jan 2013 and Dec 2015. Our inclusion criteria were administration of DD or at least four conventional 200J defibrillations for cases of recurrent and refractory ventricular fibrillation (VF). We excluded any case with incomplete data. The primary outcome for our study was neurologically intact survival (defined as Cerebral Performance Category 1 and 2). RESULTS A total of 3470 cases of OHCA were treated during the time period of Jan 2013 to Dec 2015. There were 302 cases of recurrent and refractory VF identified. Twenty-three cases had incomplete data. Of the remaining 279 cases, 50 were treated with DD and 229 received standard single shock 200J defibrillations. There was no statistically significant difference in the primary outcome of neurologically intact survival between the DD group (6%) and the standard defibrillation group (11.4%) (p=0.317) (OR 0.50, 95% CI 0.15-1.72). CONCLUSION Our retrospective cohort analysis on the prehospital use of DD in OHCA found no association with neurologically intact survival. Case-control studies are needed to further evaluate the efficacy of DD in the prehospital setting.

Capnography for the Nonintubated Patient in the Emergency Setting

BACKGROUND Multiple studies illustrate the benefits of waveform capnography in the nonintubated patient. This type of monitoring is routinely used by anesthesia providers to recognize ventilation issues. Its role in the administration of deep sedation is well defined. Prehospital providers embrace the ease and benefit of monitoring capnography. Currently, few community-based emergency physicians utilize capnography with the nonintubated patient. OBJECTIVE This article will identify clinical areas where monitoring end-tidal carbon dioxide is beneficial to the emergency provider and patient. DISCUSSION Capnography provides real-time data to aid in the diagnosis and patient monitoring for patient states beyond procedural sedation and bronchospasm. Capnographic changes provide valuable information in such processes as diabetic ketoacidosis, seizures, pulmonary embolism, and malignant hyperthermia. CONCLUSIONS Capnography is a quick, low-cost method of enhancing patient safety with the potential to improve the clinicians diagnostic power.

Promoting early diagnosis of hemodynamic instability during simulated hemorrhage with the use of a real-time decision-assist algorithm

BACKGROUND This study aimed to test the hypothesis that the addition of a real-time decision-assist machine learning algorithm by emergency medical system personnel could shorten the time needed to identify an unstable patient during a hemorrhage profile as compared with vital sign information alone. METHODS Fifty emergency medical team-paramedics from a large, urban fire department participated as subjects. Subjects viewed a monitor screen on two occasions as follows: (1) display of standard vital signs alone and (2) with the addition of an index (Compensatory Reserve Index) associated with estimated central blood volume status. The subjects were asked to push a computer key at any point in the sequence they believed the patient had become unstable based on information provided by the monitor screen. The average difference in time to identify hemodynamic instability between experimental and control groups was assessed by paired, two-tailed t test and reported with 95% confidence intervals (95% CI). RESULTS The mean (SD) amount of time required to identify an unstable patient was 18.3 (4.1) minutes (95% CI, 17.2–19.4 minutes) without the algorithm and 10.7 (4.2) minutes (95% CI, 9.5–11.9 minutes) with the algorithm (p < 0.001). CONCLUSION In a simulated patient encounter involving uncontrolled hemorrhage, the use of a monitor that estimates central blood volume loss was associated with early identification of impending hemodynamic instability. Physiologic monitors capable of early identification and estimation of the physiologic capacity to compensate for blood loss during hemorrhage may enable optimal guidance for hypotensive resuscitation. They may also help identify casualties benefitting from forward administration of plasma, antifibrinolytics and procoagulants in a remote damage-control resuscitation model.

The long spine board does not reduce lateral motion during transport—a randomized healthy volunteer crossover trial

OBJECTIVE For thirty years, emergency medical services agencies have emphasized limiting spinal motion during transport of the trauma patient to the emergency department. The long spine board (LSB) has been the mainstay of spinal motion restriction practices, despite the paucity of data to support its use. The purpose of this study was to determine reduction in lateral motion afforded by the LSB in comparison to the stretcher mattress alone. METHODS This was a randomized controlled crossover trial where healthy volunteer subjects were randomly assigned to either LSB or stretcher mattress only. All subjects were fitted with a rigid cervical collar, secured to the assigned device (including foam head blocks), and driven on a closed course with prescribed turns at a low speed (<20 mph). Upon completion, the subjects were then secured to the other device and the course was repeated. Each subject was fitted with 3 graduated-paper disks (head, chest, hip). Lasers were affixed to a scaffold attached to the stretcher bridging over the patient and aimed at the center of the concentric graduations on the disks. During transport, the degree of lateral movement was recorded during each turn. Significance was determined by t test. RESULTS In both groups, the head demonstrated the least motion with 0.46±0.4-cm mattress and 0.97±0.7-cm LSB (P≤ .0001). The chest and hip had lateral movement with chest 1.22±0.9-cm mattress and 2.22±1.4-cm LSB (P≤ .0001), and the hip 1.20±0.9-cm mattress and 1.88±1.2-cm LSB (P≤ .0001), respectively. In addition, lateral movement had a significant direct correlation with body mass index. CONCLUSION The stretcher mattress significantly reduced lateral movement during transport.

Roles of the Redox-Active Disulfide and Histidine Residues Forming a Catalytic Dyad in Reactions Catalyzed by 2-Ketopropyl Coenzyme M Oxidoreductase/Carboxylase

NADPH:2-ketopropyl-coenzyme M oxidoreductase/carboxylase (2-KPCC), an atypical member of the disulfide oxidoreductase (DSOR) family of enzymes, catalyzes the reductive cleavage and carboxylation of 2-ketopropyl-coenzyme M [2-(2-ketopropylthio)ethanesulfonate; 2-KPC] to form acetoacetate and coenzyme M (CoM) in the bacterial pathway of propylene metabolism. Structural studies of 2-KPCC from Xanthobacter autotrophicus strain Py2 have revealed a distinctive active-site architecture that includes a putative catalytic triad consisting of two histidine residues that are hydrogen bonded to an ordered water molecule proposed to stabilize enolacetone formed from dithiol-mediated 2-KPC thioether bond cleavage. Site-directed mutants of 2-KPCC were constructed to test the tenets of the mechanism proposed from studies of the native enzyme. Mutagenesis of the interchange thiol of 2-KPCC (C82A) abolished all redox-dependent reactions of 2-KPCC (2-KPC carboxylation or protonation). The air-oxidized C82A mutant, as well as wild-type 2-KPCC, exhibited the characteristic charge transfer absorbance seen in site-directed variants of other DSOR enzymes but with a pK(a) value for C87 (8.8) four units higher (i.e., four orders of magnitude less acidic) than that for the flavin thiol of canonical DSOR enzymes. The same higher pK(a) value was observed in native 2-KPCC when the interchange thiol was alkylated by the CoM analog 2-bromoethanesulfonate. Mutagenesis of the flavin thiol (C87A) also resulted in an inactive enzyme for steady-state redox-dependent reactions, but this variant catalyzed a single-turnover reaction producing a 0.8:1 ratio of product to enzyme. Mutagenesis of the histidine proximal to the ordered water (H137A) led to nearly complete loss of redox-dependent 2-KPCC reactions, while mutagenesis of the distal histidine (H84A) reduced these activities by 58 to 76%. A redox-independent reaction of 2-KPCC (acetoacetate decarboxylation) was not decreased for any of the aforementioned site-directed mutants. We interpreted and rationalized these results in terms of a mechanism of catalysis for 2-KPCC employing a unique hydrophobic active-site architecture promoting thioether bond cleavage and enolacetone formation not seen for other DSOR enzymes.

No Benefit in Neurologic Outcomes of Survivors of Out-of-Hospital Cardiac Arrest with Mechanical Compression Device

Abstract Introduction: Out-of-hospital cardiac arrest (OHCA) is a major cause of death and morbidity in the United States. Quality cardiopulmonary resuscitation (CPR) has proven to be a key factor in improving survival. The aim of our study was to investigate the outcomes of OHCA when mechanical CPR (LUCAS 2 Chest Compression System™) was utilized compared to conventional CPR. Although controlled trials have not demonstrated a survival benefit to the routine use of mechanical CPR devices, there continues to be an interest for their use in OHCA. Methods: We conducted a retrospective observational study of OHCA comparing the outcomes of mechanical and manual chest compressions in a fire department based EMS system serving a population of 1.4 million residents. Mechanical CPR devices were geographically distributed on 11 of 33 paramedic ambulances. Data were collected over a 36-month period and outcomes were dichotomized based on utilization of mechanical CPR. The primary outcome measure was survival to hospital discharge with a cerebral performance category (CPC) score of 1 or 2. Results: This series had 3,469 OHCA reports, of which 2,999 had outcome data and met the inclusion criteria. Of these 2,236 received only manual CPR and 763 utilized a mechanical CPR device during the resuscitation. Return of spontaneous circulation (ROSC) was attained in 44% (334/763) of the mechanical CPR resuscitations and in 46% (1,020/2,236) of the standard manual CPR resuscitations (p = 0.32). Survival to hospital discharge was observed in 7% (52/763) of the mechanical CPR resuscitations and 9% (191/2,236) of the manual CPR group (p = 0.13). Discharge with a CPC score of 1 or 2 was observed in 4% (29/763) of the mechanical CPR resuscitation group and 6% (129/2,236) of the manual CPR group (p = 0.036). Conclusions: In our study, use of the mechanical CPR device was associated with a poor neurologic outcome at hospital discharge. However, this difference was no longer evident after logistic regression adjusting for confounding variables. Resuscitation management following institution of mechanical CPR, specifically medication and airway management, may account for the poor outcome reported. Further investigation of resuscitation management when a mechanical CPR device is utilized is necessary to optimize survival benefit.