Simultaneous determination of stable carbon, oxygen, and hydrogen isotopes in cellulose.

A technological development is described through which the stable carbon-, oxygen-, and nonexchangeable hydrogen-isotopic ratios (δ(13)C, δ(18)O, δ(2)H) are determined on a single carbohydrate (cellulose) sample with precision equivalent to conventional techniques (δ(13)C 0.15‰, δ(18)O 0.30‰, δ(2)H 3.0‰). This triple-isotope approach offers significant new research opportunities, most notably in physiology and medicine, isotope biogeochemistry, forensic science, and palaeoclimatology, when isotopic analysis of a common sample is desirable or when sample material is limited.

Influence of Al(2)O(3) nanoparticles on the isothermal cure of an epoxy resin.

The influence of Al(2)O(3) nanoparticles on the curing of an epoxy thermoset based on diglycidyl ether of bisphenol A was investigated using temperature-modulated differential scanning calorimetry (TMDSC) and rheology. Diethylene triamine was used as a hardener. TMDSC not only allows for a systematic study of the kinetics of cure but simultaneously gives access to the evolution of the specific heat capacities of the thermosets. The technique thus provides insight into the glass transition behaviour of the nanocomposites and hence makes it possible to shed some light on the interaction between the nanoparticles and the polymer matrix. The Al(2)O(3) fillers are shown to accelerate the growth of macromolecules upon isothermal curing. Several mechanisms which possibly could be responsible for the acceleration are described. As a result of the faster network growth chemical vitrification occurs at earlier times in the filled thermosets and the specific reaction heat decreases with increasing nanoparticle concentration. Rheologic measurements of the zero-shear viscosity confirm the faster growth of the macromolecules in the presence of the nanoparticles.

Cardiac output and liver blood flow in humans: effect of the volatile anesthetic halothane.

In 40 men with normal circulatory and liver function, from whom 10 were undergoing general anesthesia with halothane for minor orthopedic surgery, the relationship between hemodynamic parameters and total hepatic blood flow (HBF) was investigated. Cardiac output (CO) was measured noninvasively by means of the thoracic electrical bioimpedance method, systemic arterial blood pressure (BPsys, BPdia, mean arterial pressure) by an automated oscillometric device and HBF by indocyanine green clearance. In the subjects without halothane anesthesia no relationship was found between BP and HBF, but a significant correlation could be seen between CO and HBF, whereby the fraction of HBF decreased with increasing CO. In contrast, in the presence of halothane the systemic arterial blood pressure correlated with the HBF, indicating a loss of autoregulation of the liver circulation.

[Comparative effectiveness and tolerance study of a new galenic etomidate formula]. / Vergleichende Wirksamkeits- und Verträglichkeitsuntersuchung einer neuen galenischen Zubereitung von Etomidat.

OBJECTIVE AND STUDY DESIGN: One of the major disadvantages of etomidate is the high frequency of pain on injection. A new galenic formulation based on a lipid emulsion for etomidate (Etomidat-Lipuro) was compared with the commercial standard (etomidate in propylene glycol, Hypnomidate) in a prospective, randomised, double-blind clinical evaluation in 232 patients undergoing elective surgery in general anaesthesia. The patients were premedicated with flunitrazepam 2 hours before the investigation. Two intravenous cannulas were inserted in veins of forearm or back of the hand. One cannula was only used for the application of etomidate and removed immediately after injection. General anaesthesia was induced with 0.3 mg/kg etomidate at an injection rate of 20 mg/30 s. If the patient did not complain of pain or other sensations during injection spontaneously, he was questioned for 15 s after beginning of injection. The arm used for application of etomidate was kept free of any manipulation during the operation and the following five postoperative days. RESULTS: There were marked differences between the two etomidate preparations concerning venous irritation. About 20% of the patients receiving the hypnotic in propylene glycol complained spontaneously of pain on injection, whereas none with the lipid emulsion. No difference was found in the incidence of myoclonic movements. The time interval between the beginning of injection and loss of eyelid closure reflex was about 50 s and not different for the two galenic formulations. Blood pressure during and after induction of anaesthesia did not differ. The heart rate in the group of patients with etomidate in lipid emulsion was slightly increased before and immediately after intubation compared to the propylene glycol group. 4% of the patients in the propylene glycol group suffered from postoperative venous complications as reddening, swelling, induration or pain. These complications could not be seen in the lipid emulsion group.

[Effect of the volatile anesthetics halothane, enflurane and isoflurane on liver circulation in the human]. / Einfluss der volatilen Anästhetika Halothan, Enfluran und Isofluran auf die Leberdurchblutung beim Menschen.

In 40 patients with normal liver function total hepatic blood flow (HBF) was determined by the indocyanine-green clearance method simultaneously with haemodynamic parameters, including cardiac output by means of the noninvasive thoracic electrical bioimpedance method. Furthermore, the influence of halothane, enflurane or isoflurane on HBF and the interaction with haemodynamic parameters was studied. HBF and the cardiocirculatory parameters were determined under normal conditions (waking state) and the 40 patients were then divided into 4 groups (each n = 10). After standardised induction of anaesthesia (0.3 mg/kg etomidate and 2 micrograms/kg fentanyl) and tracheal intubation (1.5 mg/kg suxamethonium chloride) an inhalation anaesthesia in O2/air under control of normal end tidal carbon dioxide concentration was performed by intermittent positive pressure ventilation. Anaesthesia was maintained in the 4 groups either with 1 MAC halothane, 1 MAC enflurane, 1 MAC isoflurane or 1.3 MAC isoflurane. The measurements were repeated at a steady of the desired end expiratory concentration of the respective volatile anaesthetic. All three anaesthetics produced a significant and comparable decrease of cardiac output and arterial blood pressure. Differences between halothane, enflurane and isoflurane in respect of haemodynamic parameters were only minimal. Contrariwise, marked differences could be seen in the effects of the anaesthetics on HBF. In the presence of halothane and enflurane HBF dropped to 58% and 56% resp. of the control value, whereas during isoflurane anaesthesia HBF remained unchanged. Furthermore, only during halothane anaesthesia a significant correlation between arterial blood pressure and HBF could be observed indicating a loss of autoregulation of the hepatic blood flow.