Anaesthesia
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We measured total and free plasma concentrations of ropivacaine following high-volume, high-dose local infiltration analgesia in 28 patients aged 65 years or over undergoing unilateral total knee arthroplasty. Patients received infiltration of ropivacaine 400 mg followed by infusion at 20 mg.h(-1) through an intra-articular catheter. Total and free plasma levels of ropivacaine were measured at specified time intervals during a 24-h period after tourniquet release. ⋯ Six samples had total plasma ropivacaine levels greater the toxic threshold of 2.2 μg.ml(-1). No samples reached the toxic threshold for free venous ropivacaine concentration. We conclude that the use of high-dose ropivacaine infiltration and catheter infusion for total knee arthroplasty in an elderly population does not result in free plasma ropivacaine levels previously associated with toxicity but that raised total plasma levels may be observed.
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In a previous paper, one of the authors (JBC) used a chi-squared method to analyse the means (SD) of baseline variables, such as height or weight, from randomised controlled trials by Fujii et al., concluding that the probabilities that the reported distributions arose by chance were infinitesimally small. Subsequent testing of that chi-squared method, using simulation, suggested that the method was incorrect. This paper corrects the chi-squared method and tests its performance and the performance of Monte Carlo simulations and ANOVA to analyse the probability of random sampling. ⋯ The number of Fujii randomised controlled trials with unlikely distributions was less with Monte Carlo simulation than with the 2012 chi-squared method: 102 vs 117 trials with p < 0.05; 60 vs 86 for p < 0.01; 30 vs 56 for p < 0.001; and 12 vs 24 for p < 0.00001, respectively. The Monte Carlo analysis nevertheless confirmed the original conclusion that the distribution of the data presented by Fujii et al. was extremely unlikely to have arisen from observed data. The Monte Carlo analysis may be an appropriate screening tool to check for non-random (i.e. unreliable) data in randomised controlled trials submitted to journals.
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Comparative Study
Comparison of the identification and ease of use of two alarm sound sets by critical and acute care nurses with little or no music training: a laboratory study.
The melodic alarm sound set for medical electrical equipment that was recommended in the International Electrotechnical Commission's IEC 60601-1-8 standard has proven difficult for clinicians to learn and remember, especially clinicians with little prior formal music training. An alarm sound set proposed by Patterson and Edworthy in 1986 might improve performance for such participants. In this study, 31 critical and acute care nurses with less than one year of formal music training identified alarm sounds while they calculated drug dosages. ⋯ The mean (SD) percentage of alarms correctly identified by nurses was 51.3 (25.6)% for the IEC alarm set and 72.1 (18.8)% for the Patterson-Edworthy alarms (p = 0.016). Nurses using the Patterson-Edworthy alarm sound set reported that it was easier to distinguish between alarm sounds than did nurses using the IEC alarm sound set (p = 0.015). Principles used to construct the Patterson-Edworthy alarm sounds should be adopted for future alarm sound sets.
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We have developed a peripheral nerve catheter, attached to a needle, which works like an adjustable suture. We used in-plane ultrasound guidance to place 45 catheters close to the femoral, saphenous, sciatic and distal tibial nerves in cadaver legs. ⋯ In 10 cases, we confirmed catheter position by magnetic resonance imaging. We judged 43/45 initial placements successful and 42/43 secondary placements successful by ultrasound, confirmed in 10/10 cases by magnetic resonance imaging.