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Translation of sonoelastography from Thiel cadaver to patients for peripheral nerve blocks*

Translation of sonoelastography from Thiel cadaver to patients for peripheral nerve blocks*

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Authors

  • S. Munirama
  • A. R. Satapathy
  • A. Schwab
  • R. Eisma
  • G. A. Corner
  • S. Cochran
  • R. Soames
  • G. A. McLeod

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Info

Original languageEnglish
Pages721-728
Number of pages8
JournalAnaesthesia
Journal publication dateJul 2012
Journal number7
Volume67
DOIs
StatePublished

Abstract

Ultrasound guidance is now common in regional anaesthesia practice, but remains limited by poor visibility of the needle tip and poor quantification of local anaesthetic spread. Sonoelastography based on tissue compression is a technique depicting tissue strain. Hitherto used largely for tumour diagnosis, we used it in both Thiel embalmed cadavers and two patients receiving interscalene and femoral blocks to observe changes in tissue strain during local anaesthetic injection. The primary aim of our study was to measure the area under the curve (weighted for time) of the strain pattern in Thiel perineural tissue when using a range of volumes of embalming fluid (0.25, 0.5, 1, 2.5, 5 and 7.5 ml) for interscalene and femoral blocks using sonoelastography. Our secondary aims were to evaluate static images of anatomy and videos of needle insertion and perineural injection using combined B-Mode ultrasound and sonoelastography. Independent raters assessed the anatomy and spread using a 7-point Likert scale, ranked from extremely poor to extremely good. We performed 83 blocks in cadavers. Concordance between both raters was good, with weighted Kappa (95% CI) 0.66 (0.610.71). The characteristics of spread were similar with both interscalene and femoral block; spread increased with injectate volume up to 1 ml. Analysis of variance showed differences in spread between injection volumes (p = 0.009), but not between regional blocks (p = 0.05). Post-hoc analysis showed greater spread with 1 and 2.5 ml volumes compared with 0.25 ml. In patients, visibility of strain during injection was better with sonoelastography than with B-Mode ultrasound and showed a dose response from 1 to 5 ml volumes of local anaesthetic. Colour strain recognition using sonoelastography offers the ability to differentiate between nerve and surrounding tissue during local anaesthetic injection by improving visibility of spread (p = 0.04).

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