Ultrasound-guided peripheral regional anaesthesia: a feasibility study in obese versus normal-weight women

Abstract

The novel technique of comparing histogram grey-scale values to determine the visibility of the peripheral nerve in different patient categories was found feasible. Median nerves are appropriately visible by US in both normal and obese subjects, whereas sciatic nerves are less visible in obese as compared with normal-weight women. Our results serve as the rationale behind difficulties in peripheral regional anaesthesia in obese patients.

The impact of biological sex in peripheral nerve blockade: A prospective pharmacodynamic, pharmacokinetic and morphometric study in volunteers

“…The ultrasonographic appearance of nerves is a crucial factor for the successful performance of regional nerve blocks. In 2014, we developed a method to quantify the ultrasound visibility of peripheral nerves via grey tone analysis [8]. Similar to pharmacokinetic outcomes in the present study, we did not detect significant biological sex dependent differences in the grey tone analysis of the ulnar nerve.…”

“…Prior to nerve blockade, a JPEG image of the nerve and the surrounding tissue was stored for subsequent grey-tone analysis with the Affinity Photo 2.0.4 for MAC image analysis software (Serif Europe Ltd, Nottingham, UK). The median value of grey-tone was evaluated of the ulnar nerve and the surrounding tissue in the 12, 3, 6 and 9 o´clock positions and the difference in grey-scales was calculated according to the formula: Relative visibility of the nerve ¼ Grey scale value nerve=ðSGrey scale values ð12 þ 3 þ 6 þ 9 o0clockÞ=4Þ [8]. In addition, the Vienna Scoring System [9,10] for descriptive evaluation of peripheral nerves (1 = internal structure of the nerve visualized, 2 = the nerve is visualized as a circular or oval-shaped blight halo, the epineurium, 3 = the nerve is visualized as reflection determined by the anatomy of the surrounded tissue, 4 = the anatomical position of the nerve shows no response to the ultrasound beam, or isoechoic behaviour), was used to mark differences of echotexture.…”

Effective local anaesthetic volumes for sciatic nerve blockade: a clinical evaluation of the ED99

“…The inter-individual variability in the number of LA molecules that are required for a successful peripheral nerve block is highlighted in a recent editorial by O 0 Donnell and Sz€ ucs [11]. Another important finding is the independence of the nerve size in relation to morphometric parameters [12,13], which makes recommendation regarding volumes of LA according to body weight and particular nerve blocks clinically useless.…”