Acute appendicitis is a frequent abnormality in the paediatric population and is treated in most cases by an appendicectomy through an incision in the right lateral abdominal wall at McBurney's point. Transversus abdominis plane (TAP) block without ultrasound guidance has been shown to be effective for postoperative analgesia in paediatric patients because it reduces postoperative morphine doses by nearly half during the first 48 h.1 We would like to share our experience with use of ultrasound guidance when performing TAP blocks as compared with our previous usual experience without TAP blocks for open appendicectomies in children.
The medical records from the Paediatric Anaesthesiology Service for 20 children who underwent open appendectomy using McBurney's laparotomy technique and who also received a TAP block for postoperative analgesia were retrospectively studied after obtaining institutional ethical approval. Demographic data analysed included age, weight, sex and type of appendicitis. Postoperative pain was measured hourly. In patients over 6 years old, a visual analogue scale (VAS) (where 0 was no pain and 10 was the worst pain imaginable) was used, whereas in children under 6 years old or who were uncooperative with the VAS survey, the 11 point (0–10) Spanish observational scale ‘LLANTO’ was employed.2 All patients received general anaesthesia induction with propofol (2–3 mg kg−1). Conditions for endotracheal intubation were obtained after intravenous (i.v.) administration of muscle relaxant (atracurium 0.5 mg kg−1) and an opiate (fentanyl 2 μg kg−1). Anaesthesia was maintained with sevoflurane at 1 Minimum Alveolar Concentration (MAC) adjusted to patient age in oxygen/air at 30/70 concentration. Patients were given a TAP block with a single dose of 0.5 ml kg−1 of levobupivacaine 0.5%. The technique used had been previously reported3 using a linear probe (25 mm Broadband Linear Array 6–13 MHz) and is shown in Fig. 1a. We included those patients whose ultrasound images revealed an oval spread of the local anaesthetic between the two layers as shown in Fig. 1b.
After anaesthetic recovery, a nurse either in the Post-Anaesthtetic Care Unit (PACU) or the postsurgical ward administered rescue medication consisting of paracetamol (15 mg kg−1 i.v.) in case of pain scores at least 3/10 or if requested by the patient. Initial pain scores after the patients were fully awake after anaesthesia recovery, the length of time before receiving the first analgesic treatment after surgery (measured in hours) or the need for rescue analgesia with opiates were recorded too. One case in which lidocaine instead of levobupivacaine 0.5% was used and three additional patients in whom ultrasound images showed that injections were inside the internal oblique muscle were excluded because they required an intraoperative increase in fentanyl doses. Another patient who received paracetamol due to fever was also excluded.
The study included 20 patients with a mean age of (9.4 ± 2.6 years), mean weight (34.4 ± 10.1 kg), and sex (10 females/10 males) or type of appendicitis (eight gangrenous/12 phlegmonous) distributions. Initial pain scores in the PACU measured through VAS or LLANTO scales were lower than 3 points in all the cases and the mean duration of postoperative regional analgesia (hours from the end of surgery until the patients had pain scores less than 3/10 or required paracetamol) was 8.4 h (interquartile range values 7–9 h). None of the patients required rescue analgesia with opiates due to insufficient analgesia after paracetamol administration.
TAP block is a recently described anaesthetic technique that can produce postoperative analgesia through local anaesthetic instillation between the transverse abdominal muscle and internal oblique abdominal muscle in the vicinity of Petit's triangle.4 It has been suggested for use in paediatric patients,3 specifically for open appendicectomies,1 but not in the less painful approach of laparoscopic appendicectomy in children.5
The aim of this study was to check if the addition of TAP block under ultrasound guidance could improve the quality of immediate postoperative analgesia after this frequent type of paediatric surgery. In our study, i.v. analgesic agents were only administered when the patients started to present mild pain (score of ≥3, pain on both scales ranged from 0 to 10) or even before when this was requested by the patients. Thus, this study was able to observe the duration of the analgesic effects of the 0.5% levobupivacaine. Although there was an important variability in analgesic duration, the analgesic effect lasted a mean of 8 h after the end of surgery.
Again, the design of this study revealed that none of the patients needed rescue analgesia with opiates due to effective postoperative regional analgesia over the abdominal wall. This fact is remarkable because the fentanyl dose employed (2 μg kg−1) is sufficient for blocking haemodynamic responses associated with endotracheal intubation, but not to block the postoperative pain associated with the skin incision.6 Moreover, the use of the hypnotic agent, sevoflurane, was maintained at concentrations equivalent to 1 MAC, a lower concentration than the 1.45 MAC that has been described to block the adrenergic response associated with skin incision in children.7 In this sense, it is important to note that all the patients showed very low pain scores in the first hours after surgery demonstrating a sustained postoperative analgesia.
In summary, in our experience ultrasound guidance allowed us to try this block approach; the direct visual guidance avoids fear of major complications, as well as a more effective placement of the TAP blocks in children, improving our usual previous postoperative analgesia management.
The authors would like to thank Ms Carol F. Warren for her language assistance. The authors declare that they have not received any financial support nor do they have any conflicts of interest.
1. Carney J, Finnerty O, Rauf J, et al. Ipsilateral transversus abdominis plane block provides effective analgesia after appendectomy in children: a randomized controlled trial. Anesth Analg
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