Rear-side resonator architecture for the passive coherent combining of high-brightness laser diodes.

We describe a new coherent beam combining architecture based on passive phase locking of emitters in an extended cavity on the rear facet and their coherent combination on the front facet. This rear-side technique provides strong optical feedback for phase locking while maintaining a high electrical-to-optical efficiency. Two high-brightness high-power tapered laser diodes are coherently combined using a Michelson-based cavity. The combining efficiency is above 82% and results in an output power of 6.7 W in a nearly diffraction-limited beam with an M(4σ)(2)≤1.2. A semi-active automatic adjustment of the current enhances the long-term stability of the combination, while the short-term stability is passively ensured by the extended cavity. This new laser configuration exhibits the simplicity of passive self-organizing architectures while providing a power conversion efficiency of 27% that is comparable to master oscillator power amplifier architectures.

[Asymptomatic aneurysm of the superior mesenteric artery]. / Asymptomatisches Aneurysma der Arteria mesenterica superior.

The aneurysm of the superior mesenteric artery is a rare diagnosis also among the group of the aneurysms of the visceral arteries. Usually it is discovered already in the state of asymptomatic aneurysm. In accordance to size and localisation an elective operation should be performed, respecting the principles of vascular surgery. We report on an own case.

A haemodynamic comparison of epidural versus intrathecal sufentanil to supplement general anaesthesia for abdominal aortic surgery.

The present study was designed to evaluate the influence of epidural sufentanil (ES) and intrathecal sufentanil (IS) on the peri-operative haemodynamic responses during abdominal aortic surgery. Twenty-four ASA Grade II patients without clinical symptoms of coronary artery disease received, randomly, epidural (n = 12) or intrathecal (n = 12) sufentanil combined with light general anaesthesia for elective bifemoral grafting for aorto-iliac occlusive disease. The IS group contained significantly more hypertensive patients than the ES group. This resulted in a significantly higher systolic and mean blood pressure, which remained constant from the start to the end of the study. Following a single bolus injection of 150 micrograms of sufentanil epidurally or intrathecally, there was a significant decrease in heart rate (HR), systolic, mean and diastolic blood pressure, systemic vascular resistance (SVR) and coronary perfusion pressure in both groups. This suggests that IS and ES must be used with caution in patients with cardiovascular disease. The abdominal incision restored the haemodynamic changes produced by sufentanil administration, but these did not exceed pre-sufentanil values. There were no significant changes in filling pressure, cardiac index (CI) and left ventricular work after aortic cross-clamping in the two groups. Revascularization produced significant differences in HR, SVR and CI in both groups in comparison with the pre-declamping period. Notable was the maintenance of systemic blood pressure following revascularization due to preservation of sympathetic activity. It was concluded that both epidural and intrathecal sufentanil produce comparable and stable haemodynamics in this category of patients.

[Studies on the long-term exposure of operating room personnel to 2-bromo-2-chloro-1,1,1-trifluorethane (Halothane)]. / Untersuchungen zur Langzeitexposition von Operationspersonal gegenüber 2-Brom-2-chlor-1,1,1-trifluorethan (Halothan).

Different operation theatres of the county of Gera were examined to quantify the exposition against halothane which is used as an inhalation narcotic, and also against ethanol. Besides the short time exposition (0.5 h) determined with gas sampling tubes the long time exposition (up to 8 h) was monitored personally by means of charcoal passive samplers. The analytical method of choice was gas chromatography, in the second case after thermal desorption of the enriched pollutants. Generally, the concentrations are lower than the MAKD if the workplace is equipped with an exhaust type NAREX 101. Without it the MAKD is reached quickly. A statistical evaluation of the results shows that there exist remarkable differences between as well the degree as the scattering of the individual exposition levels depending from the task in the operating theatre. Obviously the percentage of anesthesia using halothane is increasing.

A study of epidural morphine and sufentanil anesthesia for abdominal aortic surgery.

Thirty six comparable patients, ASA 2, without cardiac disease, underwent aortic disobliteration, 19 under epidural 100 micrograms/kg morphine (EM) and 17 under epidural 2 micrograms/kg sufentanil (ES), combined with general anesthesia. To compare the hemodynamics, measurements were taken pre-operatively, after induction of general anesthesia, during aortic dissection, aortic cross-clamping and 3-5 minutes after the first revascularisation. Plasma and CSF drug levels were measured at intervals in 6 patients in the EM end 5 patients in the ES group. Both drugs provided satisfactory analgesia which persisted for 10.4 hours in the EM and 6.3 hours in the ES group. The fall in systemic pressure and left ventricular work in both groups after induction of general anesthesia suggests that EM and ES must be used with caution in patients with hypovolemic or cardiovascular disease. There was a significant difference in SVR between the two groups during the aortic dissection, due to a rise in SBP in the ES group and a tendency for SVR to fall in the EM group. However significant differences in left ventricular work did not occur. Notable was the absence of significant changes in filling pressure, CI and left ventricular function during aortic cross-clamping. After revascularization a significant decrease in systolic blood pressure occurred in association with an increase in heart rate in the EM group. The influence of the plasma and CSF concentrations of morphine and sufentanil on the hemodynamic changes during surgery were evaluated.

Stress ulcer in normotensive and spontaneously hypertensive rats.

Spontaneously hypertensive rats (SHR) and their normotensive progenitors, the Wistar-Kyoto (WKY) rats, were tested in the open-field arena and subsequently exposed to either cold-restraint stress or activity-stress. SHR rats were more active and judged less fearful in the open-field test. Changes in core body temperature, and adrenal and thymus weights did not differentiate between SHR and WKY rats in the cold-restraint procedure. A significant adrenal hypertrophy was observed for SHR rats in the activity-stress procedure. WKY rats were more susceptible to stress ulcer in both the cold-restraint and the activity-stress procedures. While running-wheel activity had been considered an important etiological variable for activity-stress ulcer, the lower activity demonstrated by the ulcer-prone WKY rats suggested that genetic variables might be more relevant to stress ulcer disease.

Inescapable shock alters mescaline's disruption of active avoidance acquisition.

Rats were tested on a two-way avoidance acquisition with or without inescapable shock given 24 h prior to training. Mescaline given to nonshock rats disrupted acquisition in a dose-dependent fashion and tolerance developed to this disruption. Mescaline given to shock rats had no effect on acquisition even though levels of acquisition were the same for both shock and nonshock rats without drug. Moreover, subchronic treatment (5 days facilitated acquisition. These experiments demonstrate an interaction between shock, which presumably is a stressor, and mescaline. The data are consistent with the observation that when animals are exposed to presumptive stressors (e.g., shock, handling) hallucinogens can facilitate behavior, while in other situations, hallucinogens disrupt behavior.

[The significance of intraoperative bacteriological findings in operations on the gallbladder and biliary tract (author's transl)]. / Die Bedeutung intraoperativer bakterieller Befunde bei Gallenblasen-und Gallenwegs-operationen.

The symptomless bacterial contamination of the biliary tree is apt to be the origin of general or local postoperative complications. The present retrospective study of 369 bilary operations with intraoperative bacteriologica investigations yielded the following results: septic wound complications were found in 9% of the cases with bacteriocholia against 3.5% in the cases with abacterial bile. In geriatric patients with complicated gallstone disease the bacterial contamination of the bile exceeds 50% of all cases. The importance of an adequate antibiotic treatment for this group, starting intraoperatively, is stressed.