European journal of anaesthesiology
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Randomized Controlled Trial Clinical Trial
The optimal dose of local anaesthetic in the orthogonal two-needle technique. Extent of sensory block after the injection of 20, 30 and 40 mL of anaesthetic solution.
Ninety patients undergoing scheduled upper limb orthopaedic surgery were studied to determine the optimal anaesthetic dose using the 'orthogonal two-needle technique'. The patients were randomly assigned to one of three groups to receive one of three different volumes (20, 30 and 40 mL) (n = 30) of anaesthetic solution (a mixture of equal parts of 0.5% bupivacaine with adrenaline 1:200,000 and 2% lignocaine). A significant correlation was found between the volume injected and the anaesthetic spread for all tested areas. ⋯ The comparisons between the 20 mL group and the other two groups are significant in all the tested areas, as well as the comparisons between 30 and 40 mL groups in the areas innervated by radial and musculocutaneous nerves. Only the area innervated by the axillary nerve showed a weaker volume-analgesia relation, confirming the elusiveness of this area to anaesthesia in the axillary approaches. The improved results observed using greater amounts of anaesthetic solution might result from a higher intrasheath pressure with disruption of sheath septa, or from a greater availability of drug for all the terminal branches of brachial plexus, or both.
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Randomized Controlled Trial Clinical Trial
Nitrous oxide inhalation as an adjunct to intravenous induction of general anaesthesia with propofol for day surgery.
Fifty patients were randomly allocated to receive either a preinduction inhalation with nitrous oxide (50%) in oxygen or fentanyl with preoxygenation, before induction of anaesthesia with propofol. Both groups of patients showed a significant rise in arterial oxygen saturation prior to propofol induction which established similar depths of anaesthesia, determined by the acceptability of the laryngeal mask placement. ⋯ Reduction in arterial blood pressure was also more rapid in the fentanyl group compared with the nitrous oxide group. Preinduction inhalation of nitrous oxide (50%) in oxygen appears to be an effective and acceptable method of preoxygenating the patient and augmenting the propofol induction of anaesthesia.