Large volume dye spread in transversus abdominis plane block via three injection sites: a cadaveric study

Background: Transversus abdominis plane (TAP) block is a recently described regional anaesthesia technique that provides analgesia for the abdominal wall. Three access points for injection have been described: via the lumbar triangle of Petit (LTOP), via the midaxillary line and via the subcostal region (SC). This study aimed to investigate the spread of dye following injection via all 3 sites with a large volume injectate. Materials and Methods: 24 hemiabdomens were injected with 40 mL 25% black food dye: 8 via the LTOP) 4 via the MAL, 4 via the SC. Dissection was performed to reveal the extent of nerve involvement and dye spread. Results: Variation in the size and shape of the LTOP was found between cadavers. Mean areas of dye spread (range of nerve involvement) in the remaining 16 hemiabdomens for LTOP, MAL and SC were 77.9 cm2 (T10-ilioinguinal), 50.3 cm2 (T10-ilioinguinal) and 91.3 cm2 (T7-ilioinguinal) respectively. Communications were seen between nerves within the TAP in one dissection. Dye staining was seen to involve nerves outside the TAP. Conclusion: Subcostal injection gives more superior dye spread, with a greater area and awider range of nerve involvement. This should perhaps be the preferred injection site, and could have broader indications

Three different approaches to Transversus abdominis plane

Aim The transversus abdominis plane (TAP) block is a new techniquefor providing analgesia to the anterior abdominal wall. There is ongoing debate regarding access point for TAP block. The aim of this cadaveric study was to compare the spread of 40 mL of dye using three different approaches to TAP: subcostal , via the mid-axillary and via the lumbar triangle of Petit (LTOP). Methods Injection of black dye into the TAP was performed for each hemi-abdominal wall of 13 embalmed human cadavers by using 3 different access points: subcostal (9 hemi-abdomens), mid-axillary (9) and LTOP (8). This was followed by dissection to determine the extent of dye spread and nerve involvement in the dye injection. The shapes of the dye were traced onto clear plastic, which was then photographed. These digital photographs were loaded into the mathematical software programme Matlab, and the outline of the dye spread was digitised using a piecewise cubic spline, enabling the shapes to be plotted on a graph and the areas to be calculated. Results The area of the dye spread for subcostal, mid-axillary and LTOP was 85.1 (T7-L1), 58.9 (T10-L1) and 77.9cm2 (T10-L1), respectively. There was statistically significant difference between area of dye spread between subcostal and mid-axillary approach (p<0.01). Conclusion This dye injection study in a cadaver model indicates that subcostal approach is associated with a larger area of spread of dye than the mid-axillary approach. Dye injected through subcostal, mid-axillary and LTOP approaches demonstrated different nerve involvement