Anaesthesia
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Randomized Controlled Trial Comparative Study
A randomised controlled trial of perineural vs intravenous dexamethasone for foot surgery.
We used 20 ml ropivacaine 0.75% for ankle blocks before foot surgery in 90 participants who we allocated in equal numbers to: perineural dexamethasone 8 mg and intravenous saline 0.9%; perineural saline 0.9% and intravenous dexamethasone 8 mg; or perineural and intravenous saline 0.9%. Dexamethasone increased the median (IQR [range]) time for the return of some sensation or movement, from 14.6 (10.8-18.8 [5.5-38.0]) h with saline to 24.1 (19.3-29.3 [5.0-44.0]) h when given perineurally, p = 0.00098, and to 20.9 (18.3-27.8 [8.8-31.3]) h when given intravenously, p = 0.0067. ⋯ Dexamethasone did not affect the rates of block success, postoperative pain scores, analgesic use, or nausea and vomiting. The route of dexamethasone administration did not alter its effects.
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One advantage of effect-site target-controlled infusion is the administration of a larger initial dose of propofol to speed up the induction of anaesthesia. This dose is determined by the combination of the pharmacokinetic model parameters, the target setting and the blood-effect time-constant, ke0. ⋯ With an effect site target of 4 μg.ml(-1) , in a 35-year-old, 170-cm tall, 70-kg male subject, the ke0 values delivering a dose of 1.75 mg.kg(-1) with the Marsh, Schnider and Eleveld models were 0.59 min(-1) , 0.20 min(-1) and 0.26 min(-1) , respectively. These ke0 values have the attractive feature that, when used to simulate the administration schemes used in two previous studies, predicted effect site concentrations at loss of consciousness were close to those required for maintenance of anaesthesia.