European journal of anaesthesiology
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The molecular effects of droperidol (C22H22FN3O2) on single sodium channels from the human brain were investigated using the electrophysiological planar lipid-bilayer technique. Droperidol (0.05-0.8mM) induced a concentration dependent and voltage independent reduction in the time averaged single channel conductance by two mechanisms: a reduction in the fractional channel open time (major effect, approximately 90%) and a decrease in the channel amplitude (minor effect). ⋯ These blocking effects of droperidol on CNS sodium channels occurred at a concentration range comparable with other specific anaesthetic compounds but far beyond clinical serum levels (up to 0.002 mM). Therefore in contrast with animal preparations (frog peripheral nerve, sodium channel) the human brain sodium channel is not a major target site for droperidol during clinical anaesthesia.
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Case Reports
Neurological complaints after unsuccessful spinal anaesthesia as a manifestation of incipient syringomyelia.
The medical literature sometimes reports neurological complications after spinal or epidural anaesthesia. In a few cases, the onset of symptoms can be a sign of a pre-existing disease without a primary connection with regional anaesthesia. In the following case report, the patient complained of paraesthesias in both legs after a failed spinal anaesthesia, even though the needle had been placed intrathecally. Only neurological examination and nuclear magnetic resonance imaging revealed the presence of syringomyelia.
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Besides the fast tetrodotoxin-sensitive Na+ current, small dorsal root ganglion neurones of rats also possess a slower tetrodotoxin-resistant Na+ current. The blocking effect of commonly used local anaesthetics upon the tetrodotoxin-resistant Na+ current was investigated in the present paper. Dorsal root ganglia were dissected from adult rats and cells were enzymatically isolated. ⋯ High concentrations of tetrodotoxin also blocked the tetrodotoxin-resistant Na+ current with a half-maximal blocking concentration of 115 microM. The block by high tetrodotoxin concentrations did not compete with the lignocaine block, suggesting that there were two independent blocking mechanisms for the two substances. The tetrodotoxin-resistant Na+ currents also showed a marked sensitivity to phasic (use-dependent) block by local anaesthetics.
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Calcium-channel blockers reduce the in vitro effects of hypothermia and benzodiazepines have been reported to reduce inward calcium flow through L-type cardiac-calcium channels. Thus, this study was designed to determine if diazepam could reduce hypothermia-induced changes in ventricular papillary muscle electromechanical activity. Conventional microelectrode techniques were used while force was recorded using a miniature force transducer. ⋯ Nisoldipine reduced both APD90 and inotropy. At 27 degrees C, 100 microM diazepam and nisoldipine (1.0 microM) reduced the hypothermia-induced lengthening of APD and the increase in force. Although diazepam reduced the hypothermia-induced alterations, the concentration required to do so (100 microM) suggests that this effect has little role in clinical use.