This current study exhibited that TAPB and CEB for bilateral IHR have similar early efficient analgesia in children. However; caudal epidural block patients experienced higher FLACC scores at the postoperative 6th and 24th hours, and the need for additional analgesics was higher and the length of hospital stay was longer than in comparison to transversus abdominis plane block patients. One should note, chronic pain was not observed in any of our patients who are older than 4-years.
Opioids remain as an important part of perioperative pain management. However; especially for pediatric population, important side effects like respiratory depression and/or constipation lead clinicians to use non-opioid methods. CEB is safely applied as the gold standard postoperative analgesia method in lower abdominal surgeries in children . TAPB block, which has now become safer with the introduction of USG into anesthesia practice, has been investigated in several studies as an alternative method to CEB [10, 12, 13]. These blocks can be preferred according to clinician's experience, the clinical and the anatomical characteristics of the patient or the surgical method. In open IHR, pain originates from somatic nerve fibers . Therefore we think TAPB will provide effective analgesia in this procedure.
To our knowledge; this is the first study comparing the US-guided TAPB and US-guided CEB for perioperative pain management in pediatric bilateral open IHR surgery. Two randomized clinical trials including only pediatric unilateral IHR surgeries showed that CEB and TAPB were indistinguishable from each other in terms of analgesic efficacy within the postoperative first six hours. In fact, it has been shown that TAPB block provides more effective analgesia in the following postoperative hours without significant side effects [12, 13]. Contrary to these data, a retrospective study revealed that the first analgesic requirement was earlier in TAPB block compared to CEB.  None of these three studies indicated the surgery type (open or minimal invasive) for IHR which may affect the overall outcomes. Perhaps, chosen surgical technique might have change the results obtained. The results of our study are consistent with the results of these two RCT.
The main component of pain in open IHR is somatic alone . In line with this, TAPB provided superior analgesia than CEB for the late postoperative period according to our results. Spesific surgeries involving visceral nerves cause higher postoperative pain density. Bryskin et al. showed that the efficacy of TAPB on visceral pain was less than CEB, but the total opioid consumption from the 6th hour postoperatively was lower with TAPB than with CEB.  The use of higher amounts of oxybutynin to prevent bladder spasm in patiens with TAPB group can be explained by this. There is also a randomized controlled trial showing that TAPB and CEB have similar pain scores in the first 6 hours postoperatively, but that TAPB is superior after the 6th hour in bladder and colon surgeries that cause predominant visceral pain . Similar to our result, all studies show that TAPB cumulatively reduces the total need for additional analgesics in the first 24 hours postoperatively.
Currently data regarding block complications are quite sparse, perhaps more randomized clinical trials with larger sample size are necessary to distinguish safest technique. In line with the literature; the complication rates were found quite low and similar in both TABP and CEB groups [12, 13]. In an inclusive study with a number of more than 100000 pediatric patients, it was shown that there is a 6-fold increased risk of complications in central blocks than peripheral blocks . Therefore, more clinical studies are needed to determine the superiority of one block over another in terms of procedural complications.
Length of stay is rather important parameter of regional blocks since it reflects postoperative recovery. In our study, length of stay at hospital in TAPB group was found to be approximately 4 hours shorter. Since no procedural complications were observed, we believe shorter stay was related to adequate pain management for the late postoperative period. Of note, peripheral blocks in bilateral surgeries necessitates to apply two separate blocks which causes a relatively longer anesthesia duration and TAPB group anesthesia duration was longer in our study as expected.
Parental satisfaction has been one of the quality indicators of health services . Alsadek et al. showed that the parents were definitely more satisfied thanks to a more successful analgesia regimens in children . The satisfaction scores of all families were elevated and close in our investigation, also.
The chronic pain incidence after IHR is claimed to be approximately 10% in adults and 5.1% in children in the literature . Effective acute postoperative pain management in pediatric surgery may decrease the incidence of chronic pain . So that, multimodal and preemptive analgesia regimens including regional analgesia may prevent the development of chronic postoperative pain. Although higher postoperative pain scores are considered as a risk factor for postoperative chronic pain in adults, data are inconclusive and sparse in pediatric surgery . There are several studies specifically investigating the incidence of chronic pain after IHR of TAPB and neuraxial block in adults, but the results of these studies are also conflicting [19, 20, 21, 22]. To our knowledge, there are no studies presenting chronic pain data in pediatric surgery. We have assessed chronic pain two months after the surgery with Bieri Faces pain scale . None of the 21 children experienced chronic pain, accordingly. However, the absence of a control group that did not receive regional analgesia stands as a limitation for our study, Therefore, further prospective, randomized and controlled studies with larger participation are required to show whether these two blocks have a protective effect on chronic pain in children.
There are also some other limitations for this current study. First, the number of our patients was rather low to assess complication ratios. Second, children under 4-years are not compatible for chronic pain assessment, since the revised Bieri faces pain scale cannot be used for this age period. It could not be observed whether these blocks had an effect on the incidence of chronic pain in this age group.