Ultrasound control of local anaesthetic location after TAP block performed using landmark-based technique: a cohort study

Objective

TAP is a regional anaesthetic technique where local anaesthesic (LA) is injected between the internal oblique and the transversus abdominis muscles in order to block intercostal nerves. The technique originally described, is based on the identification of the lumbar triangle of Petit as the area where to insert the needle before the LA injection. We performed a study to determine, using ultrasonography, the actual location of the LA when TAP block was performed using landmark-based technique.

Study design

Prospective and observational study.

Methods

Fifty-two patients scheduled for ileostomy closure surgery under general anaesthesia received a TAP block (20 mL 0.75% ropivacaine) based on standard anatomical landmarks technique. Ultrasonography was used immediately after the block to determine the LA placement. Failed blocks were considered when the patient required intravenous morphine in the immediate postoperative period for pain localised at the operative site.

Results

LA solution was injected in the right place in 14 cases out of 52. Only one of these patient received morphine in the postoperative period. In the remaining 38 blocks, the LA was administered in adjacent anatomical structures and 25 failed. Two injections in the peritoneum were observed.

Conclusion

The localization of LA after the TAP block being performed by landmark-based techniques is highly variable. In the majority of patients, the LA was injected in adjacent anatomical structures with unpredictable block results. This may promote the use of ultrasound-guided technique to perform the TAP block.