Der Anaesthesist
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Comparative Study
[The effect of fresh gas flow on the minute volume of anesthesia ventilators with a gas reservoir].
The tidal volume (TV) delivered by conventional anesthesia ventilators is dependent on fresh gas flow rate (FGF). When FGF is reduced, the TV declines; this must be corrected by increasing the ventilator bellows excursion. In addition, the falling bellows produce a negative pressure during the expiratory phase, which may result in positive negative pressure ventilation (PNPV). ⋯ VI-VOLEC (with the relief valve closed) and AV 1 had a loss of less than 10% of the initial TV. Adding a reservoir bag to anesthesia ventilators is an effective method of guaranteeing a TV independent of FGF. The three ventilators tested here proved suitable for minimal-flow anesthesia.
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Case Reports
[Compression of the trachea by a hematoma caused by an internal jugular vein catheter].
In a patient with thrombocytopenia, respiratory obstruction because of a hematoma occurred following internal jugular vein cannulation. This patient recovered completely after surgical intervention. With the following precautions in mind, puncture of the internal jugular vein in patients with coagulopathies has a high success rate and does not result in severe complications: Internal jugular vein cannulation by an experienced physician; optimal conditions for puncture by increasing venous pressure and diameter with slight Trendelenburg position and Valsalva maneuver in patients with spontaneous breathing, or positive end-expiratory pressure in patients with artificial ventilation; catheter insertion by the Seldinger technique; manual compression of the puncture site for 10-15 min; and vein puncture with ultrasonographic aid if possible.
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Neuropsychological and neurophysiological investigations indicate that a 30-40 Hz oscillatory brain mechanism is necessary for the adequate uptake and processing of elementary successive sensory events. An oscillatory component of that particular frequency range can be observed in the mid-latency auditory evoked potential (MLAEP). It is suppressed under non-specific anesthetic agents (agents not acting on specific structures of the brain or receptors). ⋯ By Fast-Fourier Transform-analysis corresponding power spectra were calculated to analyze energy portions of the AEP frequency components. In the awake state AEP showed an oscillatory component between 20- and 100-ms post-stimulus latency. Corresponding power spectra indicated a dominant 30-40 Hz frequency.(ABSTRACT TRUNCATED AT 250 WORDS)
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Randomized Controlled Trial Comparative Study Clinical Trial
[The hemodynamic effects of a treatment with beta-receptor blockers during coronary surgery. A comparison between acebutolol and esmolol].
Patients undergoing coronary artery bypass grafting are at risk for perioperative myocardial ischemia. Most such ischemic episodes occur without obvious hemodynamic changes. Tachycardia as a predictor for increased myocardial oxygen consumption doubles the incidence of myocardial ischemia when heart rate increases to over 110 beats/min. During the operative procedure for coronary revascularization, some maneuvers, e.g. intubation, sternotomy and mediastinal preparation, may be associated with tachycardia and increases in blood pressure despite an adequate level of anesthesia, so that the administration of beta-receptor blocking agents seems to be indicated. ⋯ Both beta-receptor blockers--acebutolol and the ultrashort-acting esmolol--diminish heart rate sufficiently when tachycardia occurs during coronary artery bypass grafting. Reduction of heart rate is associated with a decrease of cardiac output and an impairment of myocardial contractility. From the hemodynamic point of view there is no major difference between the two beta-receptor blockers investigated, but esmolol may have an advantage over acebutolol because of its short elimination half-life.
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Precise placement of central venous catheters is necessary to prevent complications and assure proper functioning. Chest X-ray is the current standard method of locating the catheter tip. This is usually not feasible in the operating room setting, particularly after the induction of anesthesia. ⋯ The position of every catheter was later confirmed by radiography, and in 159 patients the intraatrial ECG method was subjected to direct comparison with the sonographic method. The turbulences due to the injected fluid were found to cause an increased amplitude at frequencies above 350 Hz. If the catheter tip was positioned correctly there was no discernable time lag between the start of the injection and perception of turbulences.(ABSTRACT TRUNCATED AT 250 WORDS)