Background and Goal of Study: The transversus abdominal plane (TAP) block is performed blindly through the triangle of Petit or under ultrasound guidance. The triangle is variable in term of size, shape and location behind the midaxillary line (1). During the blind technique, depending on the description, the tip of the needle is considered to be located in the TAP after the feeling of one or two successive “pops” (2,3). In this prospective observational study, we confirmed the position of the tip of the needle after the performance of the blind technique at the level of the midaxillary line with an ultrasound examination and test the hypothesis of relations between misplacements of the needle and characteristics of the patients.
Materials and Methods: During a period of six months, patients scheduled for surgery involving incision of the abdominal wall were included in the study. The needle is inserted 2 cm above the iliac crest on the midaxillary line and advanced until the feeling of two successive pops. Then, the tip of the needle and a 2 ml test dose of L-bupivacaine 0.375 mg/mL are visualized under ultrasound examination. If necessary, the needle is repositioned under ultrasound guidance before injection of the TAP with 20 mL of L-bupivacaine 0.375 mg/mL. Statistical comparisons (mean±SD) are performed using paired Student t-test, Wilcoxon Two sample Test, Fisher's exact test (P< 0.05 significant).
Results and Discussion: 75 patients were enrolled in the study and 139 TAP blocks were performed. The needle is located in the TAP in 53.2% of the blocks. Others locations are the plane between internal and external oblique muscles, the internal oblique muscle, the transverse muscle, the preperitoneal and the intra-peritoneal position in respectively 1.4%, 25.1%, 6.5%, 0.7% and 6.5% of the cases. 6.6% of the locations could not be confirmed. There are no risk factors of misplacement of the needle related to the age, weight, BMI, sexe and type of surgery (p>0.05).
Conclusion(s): In order to inject local anaesthetics inside the TAP and avoid intraperitoneal organ puncture and intramuscular injection, the block should be performed under ultrasound guidance, whatever the characteristics of the patients are.
1. Jankovic Z.B. et al.
Anesth Analg 2009;109:981-5
2. Rafi A.N. et al.
Anaesthesia 2001; 56: 1024-6
3. Mc Donnell J.G. et al.
Anesth Analg 2007;104:193-7