A. Koehler

Bio: A. Koehler is an academic researcher from Dresden University of Technology. The author has contributed to research in topics: Mepivacaine & Ropivacaine. The author has an hindex of 1, co-authored 1 publications receiving 42 citations.

The effects of lipid infusion on myocardial function and bioenergetics in l-bupivacaine toxicity in the isolated rat heart.

Abstract: BACKGROUND: It is unclear whether improved metabolism or a “lipid sink” effect of lipid infusion is responsible for the positive effects in local anesthetic-induced myocardial depression. METHODS: We used an isolated rat heart, constant-pressure perfused, nonrecirculating Langendorff preparation and exposed hearts to 5 g/mL l-bupivacaine and 9 L/mL lipid emulsion. Hearts were freeze-clamped and energy was charge measured by HPLC. In a second experiment the effects of pacing hearts was evaluated. The effects of lipid addition on local anesthetic concentrations in Krebs–Henseleit buffer and human plasma were examined by using a mass spectrometer. RESULTS: With spontaneously beating hearts l-bupivacaine led to a significant decrease in heart rate (to 74% 7% of baseline), dP/dt (69% 7%), systolic pressure (78% 6%), coronary flow (61% 8%), and to an increase in PR (177% 52%) and QRS intervals (166% 36%). Lipid infusion exerted a positive inotropic effect, significantly augmenting dP/dt and systolic pressure back to 94% 11% and 102% 16% of baseline in l-bupivacaine-treated hearts. Heart rate, coronary flow, PR, and QRS intervals remained unchanged after lipid intervention. Lipid infusion in paced hearts had a significant effect on dP/dt, systolic pressure, and Mvo2. Neither l-bupivacaine nor lipids had an effect on energy charge. A lipid concentration of 500 L/mL plasma was necessary to effect changes in the plasma concentration of local anesthetics. CONCLUSION: Lipid application in l-bupivacaine-induced cardiac depression had a significant positive inotropic effect, which we would attribute to a direct inotropic effect. However, in an isolated heart model, indirect, local anesthetic plasma-binding effect of lipids cannot be excluded. (Anesth Analg 2007;104:186‐92)

Fragmentation of toxicologically relevant drugs in positive‐ion liquid chromatography–tandem mass spectrometry

Abstract: The identification of drugs and related compounds by LC-MS-MS is an important analytical challenge in several application areas, including clinical and forensic toxicology, doping control analysis, and environmental analysis. Although target-compound based analytical strategies are most frequently applied, at some point the information content of the MS-MS spectra becomes relevant. In this article, the positive-ion MS-MS spectra of a wide variety of drugs and related substances are discussed. Starting point was an MS-MS mass spectral library of toxicologically relevant compounds, available on the internet. The positive-ion MS-MS spectra of ∼570 compounds were interpreted by chemical and therapeutic class, thus involving a wide variety of drug compound classes, such benzodiazepines, beta-blockers, angiotensin-converting enzyme inhibitors, phenothiazines, dihydropyridine calcium channel blockers, diuretics, local anesthetics, vasodilators, as well as various subclasses of anti-diabetic, antidepressant, analgesic, and antihistaminic drugs. In addition, the scientific literature was searched for available MS-MS data of these compound classes and the interpretation thereof. The results of this elaborate study are presented in this article. For each individual compound class, the emphasis is on class-specific fragmentation, as discussing fragmentation of all individual compounds would take far too much space. The recognition of class-specific fragmentation may be quite informative in determining the compound class of a specific unknown, which may further help in the identification. In addition, knowledge on (class-specific) fragmentation may further help in the optimization of the selectivity in targeted analytical approaches of compounds of one particular class.

A novel one-step and green synthesis of highly fluorescent carbon dots from saffron for cell imaging and sensing of prilocaine

Abstract: For the first time, a novel and green strategy have been successfully established to synthesize carbon dots from saffron. In this synthesis, a simple method based on hydrothermal treatment was used to synthesis carbon dots with a quantum yield of 23.6%. The as-synthesized carbon dots exhibited many advantages including high fluorescence intensity, water solubility, stability, non-toxic, eco-friendly and importantly using in sensing drugs and cell imaging. Also, the carbon dots were used to assay prilocaine based on quenching assay, without any labeling or using chemical reagents. The influence of several experimental parameters affecting the optical signal, were studied. Under the optimal conditions, prilocaine was measured in a linear range of 2.3–400 nmol L −1 (0.5–90 ng mL −1 ). The sensor enables to detect prilocaine as low as 1.8 nmol L −1 . Finally, the carbon dots were applied for cell imaging of bone marrow cells and Olfactory mucosa cells from rats to illustrate their potential in various applications, with satisfactory results.