British journal of anaesthesia
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Sevoflurane uptake (Vsevo) can be predicted by the square root of time model or the four-compartment model. However, Vsevo and the effect of cardiac output on anaesthetic uptake have not been quantified clinically. After obtaining IRB approval and informed consent, 34 adult patients received closed-circuit anaesthesia with sevoflurane for 1 h. ⋯ The rate of sevoflurane uptake decreased less than predicted by the square root of time and four-compartment models, even when measured cardiac output was used in the formulae. These findings confirm that the square root of time and four-compartment models do not accurately predict anaesthetic uptake. In addition, uptake of sevoflurane cannot be predicted by patient characteristics but was higher in patients with a higher cardiac output.
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Randomized Controlled Trial Comparative Study Clinical Trial
Differential onset of median nerve block: randomized, double-blind comparison of mepivacaine and bupivacaine in healthy volunteers.
We have compared the delay in onset of 1% mepivacaine and 0.33% bupivacaine in different nerve fibre types in 10 volunteers undergoing median nerve blocks, in a randomized, double-blind, crossover study. Hot, cold, pinprick and light touch sensations, compound motor action potentials (CMAP), sensory nerve action potentials (SNAP) and skin temperature were recorded at 2-min intervals. Hot, cold, pinprick, light touch sensations, SNAP and CMAP were significantly inhibited, and skin temperature was significantly increased after administration of both agents. ⋯ Bupivacaine and mepivacaine inhibited SNAP and CMAP with a similar time delay to steady-state. Bupivacaine produced steady-state inhibition of hot and cold sensations significantly later than mepivacaine; nevertheless, the sequence that sensory modalities failed, with few exceptions, and the extent of anaesthesia at 40 min were similar for both agents. Our technique provides a novel, multi-modal method of comparing local anaesthetics and related agents over time.
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Randomized Controlled Trial Comparative Study Clinical Trial
Spinal anaesthesia for paediatric day-case surgery: a double-blind, randomized, parallel group, prospective comparison of isobaric and hyperbaric bupivacaine.
We have compared bupivacaine 5 mg ml-1, either isobaric in saline 0.9% or hyperbaric in 8% glucose, for spinal anaesthesia in 100 children, aged 2-115 months, in a double-blind, randomized, parallel group, prospective study. Children were premedicated with diazepam 0.5 mg kg-1 orally. Seventy-two children were sedated before, and 25 children after, lumbar puncture, with either propofol or thiopental (thiopentone). ⋯ Etilefrin was administered to one child to treat hypotension and atropine to one child to treat bradycardia. The study gave an impression of a delayed onset time of spinal block, as most of the nine children who required either fentanyl or a sedative for a mild reaction to skin incision had complete block when transferred to the recovery room after operation. Five children developed a mild, position-dependent headache.
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We have studied the incidence of gastro-oesophageal reflux associated with the laryngeal mask airway (LMA) in 82 paralysed patients undergoing ventilation for elective orthopaedic surgery. Anaesthesia was managed by skilled LMA users. A pH-sensitive probe was passed nasally into the oesophagus before induction and recordings made during five phases of anaesthesia. ⋯ There were no reflux events (pH < 4.0) during any phase of anaesthesia. We conclude that the incidence of gastro-oesophageal reflux is low in paralysed patients undergoing ventilation for elective orthopaedic surgery when antagonism of neuromuscular block is avoided. The validity of these findings for unskilled LMA users is unknown.
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Several cases have been reported in which symptoms suggestive of transient radicular irritation occurred after the use of lidocaine (lignocaine) for spinal anaesthesia. We report three patients in whom we observed similar symptoms after uneventful spinal anaesthesia using isobaric 2% mepivacaine.