Comparison of Enk Fibreoptic Atomizer with translaryngeal injection for topical anaesthesia for awake fibreoptic intubation in patients at risk of secondary cervical injury: A randomised controlled trial.

BACKGROUND: Two methods of topical anaesthesia for awake fibreoptic intubation (FOI) in patients at risk of secondary cervical injury were compared: the translaryngeal injection (TLI) technique and the Enk Fibreoptic Atomizer. OBJECTIVE: The objective of this study was to determine which system of topical anaesthesia provides the fastest and most comfortable awake FOI, using the oral approach. DESIGN: A randomised controlled study. SETTING: A single centre trial between 2009 and 2011. PATIENTS: One hundred and twenty patients (63 women, 57 men) who underwent neurosurgery of the spine at Klinikum St. Georg Leipzig were randomly allocated into two groups (group TLI, 61 patients; group ENK-ATOMIZER, 59 patients). Inclusion criteria were an American Society of Anesthesiology (ASA) physical status of 1 to 3, age 18 to 80 years, and those who met any one of three indications for FOI - cervical instability, predicted difficult airway, a BMI greater than 40 kg m(-2), and who gave written informed consent.Exclusion criteria were emergency awake FOI, mental disability/delirium, polytrauma and contraindication to TLI. INTERVENTIONS: Two anaesthesiologists experienced in both techniques performed all anaesthesia procedures within the study. MAIN OUTCOME MEASURES: The primary outcome was the timing sequence of awake FOI. The incidence of coughing/gagging, ease of tracheal tube placement, mucosal bleeding, cardiopulmonary stability and postoperative outcomes were also investigated. RESULTS: Awake FOI was significantly faster using the TLI technique (mean, 191 s; range, 123 to 447 s; SD, 83.5) than the Enk Fibreoptic Atomizer [mean, 430 s; range, 275 to 773 s; SD, 124.9; (P = 0.0001)]. Patients in group TLI exhibited significantly less gagging (P = 0.047) but more mucosal bleeding (P <  .001). CONCLUSION: Awake FOI using the TLI technique was faster and provided better topical anaesthesia with less gagging during endoscopic intubation. However, the TLI technique was also more invasive. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT00948350.

Determining incremental coulombic efficiency and physiological parameters of early stage Geobacter spp. enrichment biofilms.

Geobacter spp. enrichment biofilms were cultivated in batch using one-chamber and two-chamber bioelectrochemical reactors. Time-resolved substrate quantification was performed to derive physiological parameters as well as incremental coulombic efficiency (i.e., coulombic efficiency during one batch cycle, here every 6h) during early stage biofilm development. The results of one-chamber reactors revealed an intermediate acetate increase putatively due to the presence of acetogens. Total coulombic efficiencies of two-chamber reactors were considerable lower (19.6±8.3% and 49.3±13.2% for 1st and 2nd batch cycle, respectively) compared to usually reported values of mature Geobacter spp. enrichment biofilms presumably reflecting energetic requirements for biomass production (i.e., cells and extracellular polymeric substances) during early stages of biofilm development. The incremental coulombic efficiency exhibits considerable changes during batch cycles indicating shifts between phases of maximizing metabolic rates and maximizing biomass yield. Analysis based on Michaelis-Menten kinetics yielded maximum substrate uptake rates (vmax,Ac, vmax,I) and half-saturation concentration coefficients (KM,Ac,KM,I) based on acetate uptake or current production, respectively. The latter is usually reported in literature but neglects energy demands for biofilm growth and maintenance as well as acetate and electron storage. From 1st to 2nd batch cycle, vmax,Ac and KM,Ac, decreased from 0.0042-0.0051 mmol Ac- h-1 cm-2 to 0.0031-0.0037 mmol Ac- h-1 cm-2 and 1.02-2.61 mM Ac- to 0.28-0.42 mM Ac-, respectively. Furthermore, differences between KM,Ac/KM,I and vmax,Ac/vmax,I were observed providing insights into the physiology of Geobacter spp. enrichment biofilms. Notably, KM,I considerably scattered while vmax,Ac/vmax,I and KM,Ac remained rather stable indicating that acetate transport within biofilm only marginally affects reaction rates. The observed data variation mandates the requirement of a more detailed analysis with an improved experimental system, e.g., using flow conditions and a comparison with Geobacter spp. pure cultures.

Novel 96-well quantitative bioelectrocatalytic analysis platform reveals highly efficient direct electrode regeneration of cytochrome P450 BM3 on indium tin oxide.

Enzymes are the most effective catalysts for a broad range of difficult chemical reactions e.g. hydroxylation of non-activated C-H Bonds and stereoselective synthesis. Nevertheless, a lot of enzymes are not accessible for the biotechnological applications or industrial use. One reason is the prerequisite of expensive cofactors. In this context, we developed a bioelectrocatalytic analysis platform for the electrochemical and photonic quantification of the direct electron transfer from the electrode to redox enzymes and therefore, bypass the need of soluble cofactors that had to be continuously exchanged or regenerated. As reference enzyme, we chose cytochrome P450 BM3 that is restricted by NADPH dependence. We optimized the substrate spectrum for aromatic compounds by introduction of the triple mutation A74G/F87V/L188Q and established a sensitive fluorimetric product formation assay to monitor the enzymatic conversion of 7-ethoxycoumarine to 7-hydroxycoumarine. Gold and indium tin oxide electrodes were characterized with respect to surface morphology, charge-transfer resistance and P450 BM3 immobilization as well as activity. Using gold electrodes, no significant product formation by electrode mediated direct electron transfer could be detected. In contrast, P450 BM3 adsorbed on unmodified indium tin oxide electrodes revealed 36% activity by electrode mediated direct electron transfer in comparison to enzyme regeneration by NADPH. Since the reaction volumes are in the microliter range and upscaling of the measurement system is easily possible, our analysis platform is a useful tool for bioelectrocatalytic enzyme characterization and library screening based optimization for applications in the field of enzyme catalyzed chemical synthesis but also enzyme based fuel cells.