Der Anaesthesist
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Randomized Controlled Trial Comparative Study Clinical Trial
[Premedication in retrobulbar anesthesia. A blood gas analysis comparison of sublingual flunitrazepam and intravenous midazolam].
Benzodiazepines for sedation may decrease the PaO2, the arterial O2 saturation (SaO2), and the CO2 response more in the elderly than in the young. The purpose of this study was to assess changes in blood gases due to i.v. midazolam or sublingual flunitrazepam given as premedication in elderly patients for unilateral cataract surgery. METHODS. ⋯ The results of the study show the potential hazards of i.v. midazolam in the elderly. If sedation is required for cataract surgery under local anaesthesia, we recommend sublingual flunitrazepam or the use of benzodiazepines with lower hypnogenic effects in the elderly. A thorough preoperative discussion of anaesthesia and the operation might be an adequate substitute for any premedication in high-risk patients; the best blood gas analysis results were obtained in the control group.
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Randomized Controlled Trial Comparative Study Clinical Trial
[Ketamine racemate or S-(+)-ketamine and midazolam. The effect on vigilance, efficacy and subjective findings].
Ketamine is a racemic mixture containing equal amounts of optical isomers that have almost identical pharmacokinetic properties but different pharmacodynamic effects. The S-(+)-isomer of ketamine has about twice the anaesthetic and analgesic potency of the racemic ketamine preparation and is judged to induce less psychic emergence reactions and to be followed by a more rapid recovery of vigilance. The present study was designed to assess whether the S-(+)-isomer of ketamine is superior to the racemic mixture in cardiovascular characteristics, emergence reactions and cognitive functions, and whether side effects may be reduced or prevented by administration of midazolam prior to injection of S-(+)-ketamine. ⋯ The clinical use of S-(+)-ketamine therefore seems to be justified. Premedication with benzodiazepines, e.g. midazolam, is essential. The dose to be administered, however, should be carefully selected in order not to abolish the positive effect of S-(+)-ketamine on vigilance by the sedative effects of the benzodiazepine.
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Randomized Controlled Trial Comparative Study Clinical Trial
[Studies using S-(+)-ketamine on probands. Computerized EEG-analysis and transcranial Doppler ultrasonography].
It has been shown in the recent literature that the anaesthetic potency of the ketamine isomer S(+)-ketamine is twice that of the racemic mixture used in clinical practice. METHODS. With approval of the local ethics committee, we investigated the effects of a bolus injection of 2 mg/kg racemic ketamine or 1 mg/kg S(+)-ketamine, respectively, on the electroencephalogram (EEG) and transcranial Doppler sonography (TCD) of the middle cerebral artery in ten healthy volunteers by means of a randomised, double-blind, cross-over design. ⋯ However, the relative lower proportion of slow EEG activity at the end of the study might indicate a better recovery of cortical function following S(+)-ketamine than after racemic ketamine. Assuming a close relationship between cerebral blood flow velocity and cerebral blood flow, our TCD results suggest that both racemic ketamine and S(+)-ketamine will considerably increase cerebral blood flow in spontaneously breathing volunteers. Such an effect has been observed by others and, at least partly, can be explained by a concomitant increase in arterial carbon dioxide partial pressure.
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Randomized Controlled Trial Clinical Trial
[Cerebral effects of ketanserin. The influence on hemodynamics and brain metabolism].
Ketanserin, a 5HT2- and alpha 1-receptor antagonist, decreases blood pressure by decreasing systemic vascular resistance without causing reflex cardiac stimulation, while cardiac output remains unchanged. To date, little is known about the effects of ketanserin on cerebral haemodynamics and cerebral metabolism. According to a recently published study, ketanserin seems not to impair cerebral blood flow autoregulation in man. ⋯ As CO2-responsiveness with ketanserin was higher in group 1 but lower in group 2 than without ketanserin, the direction in which ventilation was changed rather than ketanserin was responsible for these changes in CO2-responsiveness. Neither during normocapnia nor during hypocapnia did ketanserin have any effects on cerebral metabolic activity. Thus, it can be concluded that ketanserin does not impair CBF regulation and metabolism and that cerebral vascular responsiveness to hypocapnia is preserved.
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Randomized Controlled Trial Clinical Trial
[The effect of adding clonidine to mepivacaine. Axillary brachial plexus blockade].
Clonidine (Cl) added to local anaesthetics (LA) prolongs the duration of both anaesthesia and analgesia after peripheral nerve blocks. In this study, we investigated the dose-dependent effect of Cl added to mepivacaine (M) on clinical efficacy, onset, and regression time of brachial plexus block. METHODS. ⋯ Neither the onset time nor the number of patients with adequate surgical anaesthesia was influenced by Cl. Considering the M plasma levels, it is unlikely that the prolongation of the block is caused by local vasoconstriction, which is proposed to be the mechanism of action of epinephrine. The mean differences in haemodynamic parameters were not of clinical relevance, but the two dramatic drops in BP and HR, probably caused by Cl, were significant.