Anaesthesia
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Anaerobic threshold (AT), determined by cardiopulmonary exercise testing (CPET), is a well-documented measure of pre-operative fitness, although its reliability in patient populations is uncertain. Our aim was to assess the reliability of AT measurement in patients with abdominal aortic aneurysms. Eighteen patients were recruited. ⋯ There was no significant or clinically substantial change in mean AT across the tests (p = 0.68). The typical within-patient error expressed as a percentage coefficient of variation was 10% (95% CI, 8-13%), with an ICC of 0.74 (95% CI, 0.55-0.89). We consider the reliability of the AT to be acceptable, supporting its clinical validity and utility as an objective marker of pre-operative fitness in this population.
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Clinical Trial
Effects of sevoflurane on QT parameters in children with congenital sensorineural hearing loss.
Sevoflurane prolongs the QT interval (QTI). Patients with congenital sensorineural hearing loss (SNHL) often have a prolonged QTI. This study was to investigate the effects of sevoflurane on the QTI in SNHL and control children. ⋯ In both groups, QTc and QTVI increased during anaesthesia, but Tp-e did not change. There were no differences in QTc, QTVI, Tp-e, low- and high-frequency power between the two groups. In both groups, sevoflurane lengthened the QTc and QTVI intervals but not Tp-e.
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We retrospectively reviewed 60 normal magnetic resonance imaging scans to assess the anatomical shape of the thecal sac at the L3/4 and L4/5 vertebral interspaces. In all cases the thecal sac was oval at L3/4 but in 26 (43%; 95% CI 31-55%) the thecal sac changed from oval at the L3/4 interspace to triangular at L4/5 (with the apex of the triangle presenting to the posterior epidural space). We propose that this anatomical variant would make it more difficult to obtain cerebrospinal fluid at the lower level, as a slightly lateral approach could lead to identification of the epidural space but failure to puncture the thecal sac. This may offer an explanation for a 'dry tap' when a lower interspace is chosen.
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Interscalene brachial plexus block: assessment of the needle angle needed to enter the spinal canal.
Attempts were made to place 8-cm 22G needles into the spinal canals of four preserved cadavers using the skin entry point most commonly associated with the lateral interscalene brachial plexus block or Winnie approach (that is, at the level of the cricoid cartilage). Eleven successful attempts were confirmed by computed tomography. ⋯ The only needle entry into the spinal canal with a needle angle of > 50 degrees to the transverse plane (< 40 degrees to the sagittal plane) entered the intervertebral foramen at a depth of 7.7 cm from the skin. We conclude that the use of markedly caudad angulations of needles no longer than 5.0 cm may minimise the chances of spinal canal entry and spinal cord damage.