British journal of anaesthesia
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Randomized Controlled Trial Clinical Trial
Effect of systemic N-methyl-D-aspartate receptor antagonist (dextromethorphan) on primary and secondary hyperalgesia in humans.
Dextromethorphan is a non-competitive N-methyl-D-aspartate (NMDA) receptor antagonist known to inhibit wind-up and central hyperexcitability of dorsal horn neurones. We studied 24 healthy, unmedicated male volunteers, aged 21-28 yr, in a randomized, double-blind, placebo-controlled, crossover study. Burn injuries were produced on the medial surface of the dominant calf with a 25 x 50 mm rectangular thermode. ⋯ Side effects were frequent but clinically acceptable. The effects of dextromethorphan were in agreement with experimental studies indicating that dextromethorphan is a NMDA receptor antagonist. The effects of dextromethorphan in the burn injury model were similar to those of ketamine and distinct from those of local anaesthetics and opioids.
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Randomized Controlled Trial Comparative Study Clinical Trial
Differential effects of nitrous oxide and propofol on myogenic transcranial motor evoked responses during sufentanil anaesthesia.
We have compared the effects of 50% nitrous oxide and propofol, each administered concurrently with sufentanil, on the amplitudes and latencies of the compound muscle action potential (CMAP) response to transcranial electrical stimulation. Using a crossover design, 12 patients undergoing spinal surgery were exposed to both 50% nitrous oxide and propofol, the latter in a bolus-infusion regimen. Six patients received nitrous oxide first and six received propofol first. ⋯ With single pulse stimulation, median CMAP amplitude was significantly greater during administration of nitrous oxide than propofol (nitrous oxide 335 (10th-90th percentiles 35-849) microV; propofol 36 (0-251) microV) (P < 0.01). With paired stimulation, there was no significant difference in CMAP amplitude during the two regimens (nitrous oxide 1031 (296-1939) microV; propofol 655 (0-1867) microV). The results indicate that propofol caused more depression of transcranial electrical motor evoked responses than 50% nitrous oxide but that the difference was probably clinically unimportant when a paired stimulation paradigm was used.
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Clinical Trial Controlled Clinical Trial
Pharmacokinetics of vecuronium during acute isovolaemic haemodilution.
To evaluate the effect of acute isovolaemic haemodilution on the pharmacokinetics of vecuronium, we studied 13 patients undergoing haemodilution during surgery and 13 control patients. General anaesthesia was induced with thiopentone 4-6 mg kg-1 and fentanyl 2-4 micrograms kg-1, and maintained with enflurane and 60% nitrous oxide in oxygen. The haemodilution patients underwent major elective plastic surgery with an anticipated surgical loss of more than 600 ml. ⋯ The mean volume of the central compartment and volume of distribution at steady state were 42.3 (SD 11.8) ml kg-1 and 168.4 (31.5) ml kg-1, respectively, in control patients, and significantly greater (55.2 (13.4) ml kg-1 and 225.9 (53.3) ml kg-1) in the haemodilution patients (P < 0.05). The elimination half-life was 50.3 (11.5) min in control patients and significantly greater (68.2 (15.1) min) in the haemodilution patients (P < 0.05). The half-lives of fast distribution and distribution, mean residual time, area under the plasma concentration curve and plasma clearance were unchanged in patients who underwent haemodilution compared with the control group.
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Randomized Controlled Trial Clinical Trial
Emergence times from xenon anaesthesia are independent of the duration of anaesthesia.
Xenon (MAC = 71%) has an extremely low blood:gas partition coefficient (0.14). Therefore, we predicted that the rate of emergence from xenon anaesthesia would not be affected greatly by duration of anaesthesia. We studied 54 ASA I-II patients undergoing lower abdominal surgery who received equal MAC anaesthesia with 60% xenon, 60% nitrous oxide with 0.5% isoflurane or 60% nitrous oxide with 0.7% sevoflurane (n = 18 per group), each supplemented with extradural mepivacaine anaesthesia. ⋯ Mean emergence times from xenon anaesthesia were: T1, 3.3 (SD 1.0) min; T2, 3.6 (1.0) min; T3, 5.0 (1.1) min; and T4, 6.2 (1.7) min. These values were approximately 50% of those after nitrous oxide-sevoflurane anaesthesia (T1, 5.6 (1.4) min; T4, 10.5 (2.0) min). We conclude that xenon provided fast emergence from anaesthesia, regardless of the duration of anaesthesia.
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To clarify the anatomy of the extradural space of the thoracic spine, we have compared magnetic resonance (MR) images of the thoracic spine with those of the lumbar spine. In 20 healthy volunteers, T2-weighted axial MR images were obtained at the levels of the C7-T1, T7-8, T11-12 and L2-3 vertebrae. ⋯ At this level, the dura mater seemed to be in direct contact with the ligamentum flavum. Segmentation of the posterior extradural space was commonly observed at the L2-3 and T11-12 levels; however, incomplete segmentation of the posterior extradural space was often present at the T7-8 level.