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Wiley Online Library : Anaesthesia
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Ultrasound-guided approach to nerves (direct vs. tangential) and the incidence of intraneural injection: a cadaveric study

10. February 2017 - 7:10
Summary

This study evaluated the incidence of nerve puncture and intraneural injection based on the needle approach to the nerve (direct vs. tangential). Two expert operators in regional anaesthesia performed in-plane ultrasound-guided nerve blocks (n = 158) at different levels of the brachial plexus in cadavers, aiming either directly for the nerve (n = 77) or tangentially inferior to the nerve (n = 81). After reaching the outer limit of the nerve, the needle was intentionally advanced approximately 1 mm in both approaches, and 0.2–0.5 ml of saline was injected. Each operator classified (in real time) the needle tip and injectate as intraneural or not. Video clips showing the final position of the needle and the injection were evaluated in the same manner by seven independent expert observers who were blinded to the aims of this study. In addition, 20 injections were performed with ink for histological evaluation. Intraneural injections of saline were observed by the operator in 58% (45/77) of cases using the direct approach and 12% (10/81) of cases using the tangential approach (p < 0.001). The independent observers agreed with the operator in a substantial number of cases (Cohen's kappa index 0.65). Histological studies showed intraneural spread in 83% (5/6) of cases using the direct approach and in 14% (2/14) of cases using the tangential approach (p = 0.007). No intrafascicular injections were observed. There was good agreement between the operators’ assessment and subsequent histological evaluation (Cohen's kappa = 0.89). Simulation of an unintentional/accidental advancement of the needle ‘beyond the edge’ of the nerve suggests significantly increased risk of epineural perforation and intraneural injection when a direct approach to the nerve is used, compared with a tangential approach.

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Effects of acute controlled changes in end-tidal carbon dioxide on the diameter of the optic nerve sheath: a transorbital ultrasonographic study in healthy volunteers

8. February 2017 - 13:30
Summary

Transorbital ultrasonographic measurement of the diameter of the optic nerve sheath is a non-invasive, bed-side examination for detecting raised intracranial pressure. However, the ability of the optic nerve sheath diameter to predict acute changes in intracranial pressures remains unknown. The aim of this study was to examine the dynamic changes of the optic nerve sheath diameter in response to mild fluctuations in cerebral blood volume induced by changes in end-tidal carbon dioxide. We studied 11 healthy volunteers. End-tidal carbon dioxide was controlled by a model-based prospective end-tidal targeting system (RespirAct™). The volunteers' end-tidal carbon dioxide was targeted and maintained for 10 min each at normocapnia (baseline); hypercapnia (6.5 kPa); normocapnia (baseline 1); hypocapnia (3.9 kPa) and on return to normocapnia (baseline 2). A single investigator repeatedly measured the optic nerve sheath diameter for 10 min at each level of carbon dioxide. With hypercapnia, there was a significant increase in optic nerve sheath diameter, with a mean (SD) increase from baseline 4.2 (0.7) mm to 4.8 (0.8) mm; p < 0.001. On return to normocapnia, the optic nerve sheath diameter rapidly reverted back to baseline values. This study confirms dynamic changes in the optic nerve sheath diameter with corresponding changes in carbon dioxide, and their reversibly with normocapnia.

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Standards for hip fracture anaesthesia

8. February 2017 - 9:00
Categories: From Anaesthesia

Issue Information – Editorial Board

8. February 2017 - 9:00
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Sugammadex and laryngospasm

8. February 2017 - 9:00
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Correction

8. February 2017 - 9:00
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Cricoid pressure: release – or adjust?

8. February 2017 - 9:00
Categories: From Anaesthesia

Phrenic nerve block for thoracic surgery

8. February 2017 - 9:00
Categories: From Anaesthesia

Metabolic oxygen requirements

8. February 2017 - 9:00
Categories: From Anaesthesia