Anaesthesia
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Case Reports Randomized Controlled Trial
Incidence of clinically symptomatic pneumothorax in ultrasound-guided infraclavicular and supraclavicular brachial plexus block.
The use of periclavicular brachial plexus block as regional anaesthesia for surgical procedures on the upper extremity is common. However, the proximity of the pleura results in a risk of pneumothorax. Without ultrasound monitoring, the pneumothorax risk has been reported to be as high as 6.1%. ⋯ Ultrasound guidance does therefore appear to reduce the risk of pneumothorax. Although all of the anaesthesiologists involved in the complications had previously performed fewer than 20 blocks, we are not able to confirm that a block experience ≤ 20 is a significant risk factor. Faulty image-setting, inability to obtain a view of the needle tip and inadequate supervision are likely to be important risk factors.
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We measured the pulsatility indices in the inferior collateral and posterior recurrent ulnar arteries, which supply the ulnar nerve at the elbow, in 38 conscious adults. Compared with a straight 30° abducted arm, elbow flexion to 120° reduced the mean (SD) pulsatility index in the inferior artery and increased the pulsatility index in the posterior artery: from 3.36 (0.86) to 3.04 (0.94), p = 0.001, and from 3.14 (0.81) to 3.64 (1.05), p < 0.0005, respectively. The mean (95% CI) pulsatility index in the inferior artery was unaffected by shoulder abduction to 120°, but it was decreased in the posterior artery in men, from 3.06 (2.76-3.36) to 2.64 (2.34-2.95), but not women, from 3.22 (2.94-3.50) to 3.25 (2.97-3.53), p = 0.01 for men vs women. Researchers should measure arterial pulsatility indices under general anaesthesia and associate them with measures of nerve function.
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Observational Study
A prospective observational study of stroke volume responsiveness to a passive leg raise manoeuvre in healthy non-starved volunteers as assessed by transthoracic echocardiography.
Current guidelines for intra-operative fluid management recommend the use of increments in stroke volume following intravenous fluid bolus administration as a guide to subsequent fluid therapy. To study the physiological premise of this paradigm, we tested the hypothesis that healthy, non-starved volunteers would develop an increment in their stroke volume following a passive leg raise manoeuvre. Subjects were positioned supine and stroke volume was measured by transthoracic echocardiography at baseline, 30 s, 1 min, 3 min and 5 min after passive leg raise manoeuvre to 45°. ⋯ Of the 11 volunteers evaluated, five (45%) had stroke volume increases of greater than 10%. Mean (SD) maximum percentage change in cardiac index was 14.8 (9.7)% (p = 0.004). A wide variation in baseline stroke volume and response to the passive leg raise manoeuvre was seen, suggesting greater heterogeneity in the normal population than current clinical guidelines recognise.
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Current methods to assess the airway before tracheal intubation are variable in their ability to predict a difficult airway accurately. We hypothesised that sublingual ultrasound could provide additional information to predict a difficult airway with greater success than current methods. We recruited 110 patients to perform sublingual ultrasound on themselves following brief instruction. ⋯ Visibility of the hyoid using ultrasound was associated with a laryngoscopic grade of 1-2 (p < 0.0001), and (p < 0.0001) had a positive likelihood ratio of 21.6 and a negative likelihood ratio of 0.28. Each of the other methods had considerably lower positive likelihood ratios and lower sensitivity. Our results suggest that sublingual ultrasound is a potential tool for predicting a difficult airway in addition to conventional methods.