Anaesthesia
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Observational Study
Lumbar neuraxial anatomical changes throughout pregnancy: a longitudinal study using serial ultrasound scans.
This observational study was designed to investigate the anatomical changes of the lumbar spine over the course of pregnancy using serial ultrasound scans. We performed paramedian scans on 58 women at the L2-3, L3-4 and L4-5 levels; these were done at four periods of 11+0-13+6, 19+0-23+0, 28+0-32+0 and 38+0-40+0 weeks gestation. At each intervertebral level, the length of the interlaminar space, length of the visible intervertebral posterior dura and depth of the posterior dura mater from the skin were measured. ⋯ The other spinal measurements were not affected by gestation. These findings indicate that the L2-3 level is the most appropriate puncture site for epidural anaesthesia in pregnant women. Our results ought to be embraced as a departure point towards developing neuraxial insertion techniques guided or aided by ultrasound.
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Randomized Controlled Trial
The minimum effective concentration (MEC90 ) of ropivacaine for ultrasound-guided supraclavicular brachial plexus block.
The aim of this study was to determine the minimum effective concentration of ropivacaine for ultrasound-guided supraclavicular brachial plexus block. Fifty-one patients undergoing arm surgery received double-injection ultrasound-guided supraclavicular block using ropivacaine 40 ml. The concentration of ropivacaine administered to each patient started at 0.225% and then depended on the response of the previous one, based on a biased coin design up-and-down sequential method. ⋯ In the case of a successful block, the next patient was randomised to the same concentration or a concentration 0.025% w/v less. Success was defined as complete sensory blockade of the brachial plexus 30 min after the block together with pain-free surgery. The minimum effective ropivacaine concentration in 90% of subjects was 0.257% w/v (95% CI 0.241-0.280%).