TAP Block for Gynaecological Laparotomies - a Comparison of Ultrasound-guided Block and Blind Technique

Overview

Transversus abdominis plane (TAP) block is an application of local anaesthetic solution into the plane between internal oblique and transversus abdominis muscles at the triangle of Petit located superiorly to the iliac crests bilaterally. Anterior divisions of segmental spinal nerves, which provide innervation to the abdominal wall, run inside this compartment. TAP block been shown to provide good postoperative pain relief following surgical laparotomies, gynaecological laparotomies, appendicectomies, inguinal hernia repairs and open prostatectomies. The goal of this study is to compare the effect of blind and ultrasound-guided TAP block on postoperative pain relief and morphine consumption following to gynaecological laparotomies. Null research hypothesis for the study is that there is no difference between the performance (as defined by morphine consumption and patient satisfaction/ pain scores) of the TAP block procedure via 'blind' or ultrasound guided techniques for gynaecological laparotomies.

Transversus abdominis plane (TAP) block is an application of local anaesthetic solution into the plane between internal oblique and transversus abdominis muscles at the triangle of Petit located superiorly to the iliac crests bilaterally. Anterior divisions of segmental spinal nerves, which provide innervation to the abdominal wall, run inside this compartment. The TAP block has been shown to provide good postoperative pain relief following surgical laparotomies, gynaecological laparotomies, appendicectomies, inguinal hernia repairs and open prostatectomies. It also reduces the post operative morphine consumption seen after such procedures. This allows a more comfortable recovery with reduced incidence of nausea and vomiting, as well as potentially earlier mobilisation and discharge. Currently the technique employed is that first described by Mc Donnell. This involves a blind 'two pop' technique signifying the needle passing through the two muscle layers. On detection of these two pops the local anaesthetic is injected into this plane between the muscle layers. It is the anaesthetising of the nerves in this muscle plane that aides post operative pain relief for as much as 24 hours. TAP nerve blocks have become common practice due to the very low reported complication rate occurring while using the 'blind technique'. Such complications are minor in themselves. It is our hope that these complications will be further reduced with the use of an ultrasound guided technique. The use of an ultrasound machine would allow the direct visualisation of the needles progress through the tissues and muscle layers. It would confirm the correct position during infiltration of local anaesthetic and prevent inadvertent puncturing of organs or entry to the abdominal space. Studies have shown that in other commonly used nerve blocks, the introduction of an ultrasound guided technique has improved the efficacy of the nerve block itself. We hope to show a similar trend when using an ultrasound guided technique in the insertion of a TAP block. Trials are underway comparing different dosage and volume regimes, but to our knowledge no other trial is comparing the use of an ultrasound machine to the conventional 'blind' technique in order to assess pain relief and morphine consumption post operatively. Only recently have ultrasound machines become commonplace in anaesthetic departments, and we feel this research will show their valuable contribution to patient comfort in this subgroup of patients undergoing abdominal gynaecological procedures. We wish to assess whether we can achieve better patient satisfaction, less morphine consumption and ultimately shorter hospital stay with an ultrasound technique compared to a blind technique.