Audit of initial use of the ultrasound-guided transversus abdominis plane block in children

The extent of dermatomal block post transversus abdominis plane block is described in adults as T7-L1; other authors argue extent above T10 is infrequent (supra-iliac 20 ml injection). A paediatric guideline recommends this block for upper and lower abdominal surgery using 0.2 ml/kg. We aimed (through prospective audit) to document the multi-level block achieved with ultrasound-guided transversus abdominis plane block in children having abdominal surgery, during a departmental training period. Data included patient, anaesthetic and surgical details, transversus abdominis plane block characteristics (anterior supra-iliac injections) and dermatomal blockade to ice. Twenty-seven children received 38 blocks performed by 58% consultant and 42% trainee operators (90% novices): 16 unilateral/11 bilateral for umbilical (1), inguinal (13), laparoscopic (8) and laparotomy (5) surgery. Dermatomal assessment for 35 blocks (mean local anaesthetic volume 0.4 ml/kg [SD 0.2]) revealed the median blockade achieved was 3 dermatomes (interquartile range 3 to 4) involving T10 to L1 in 75% of patients. Eight blocks (six patients) also involved T8 and T9, following 0.31 to 0.81 ml/kg. One patient (3% of assessed blocks) had no block to ice at 60 minutes, but required no postoperative analgesia. Ultrasound-guided transversus abdominis plane blocks performed by supra-iliac approach and novice operators produced lower abdominal sensory blockade in children of usually 3 to 4 dermatomes, and should be offered for lower abdominal surgery only, as only 25% had upper abdominal block extension. The optimal local anaesthetic dose/volume, duration of effect and utility for these blocks in relation to peripheral and neuraxial blockade needs clarification.