The result of our randomized controlled trial showed that cumulative tramadol consumption was lower in TAP compared to II/IH group during the total 48 hours follow up period. Pain scores were similar between TAP & II/IH groups until 24 hours both at rest and on purposeful movement. However, at 36 & 48 hour intervals pain score was lower in TAP group with a statistically significant result. A differences in time to first analgesic request, proportion of pruritus, nausea vomiting and sedation score were not statistical significant.
Post-operative tramadol consumption was found to be comparable at 12 (p = 0.931) & 48 (p = 0.402) hour intervals. However, at 24 & 36 hour intervals median tramadol consumption was lower in TAP group compared to II/IH groups with p = 0.021 & p = 0.005 respectively. On top of this cumulative 48 hour median tramadol consumption was lower in TAP group with p = 0.018. Though there are limited research on a landmark techniques, our finding is in line with L. Vamsee Kiran, et al, where interval and cumulative 24 hour tramadol consumption were lower in TAP group compared to II/IH group after an ultrasound guided block in patients who underwent cesarean section under spinal anesthesia (p = 0.00) [15]. Similarly, C. Aveline et al, in their ultra-sounded guided block comparison between TAP & II/IH nerve block for inguinal day case surgery found that postoperative morphine requirements were lower during the first 24 h in the TAP block group (p = 0.03) [16]. A nearly similar result was found by Bessmertnyj AE et al from Russia in their prospective randomized study where they concluded that both TAP & II/IH were comparable in terms of postoperative opioid consumption after caesarean delivery for the first 24 hours [17].
In contrast to our finding, retrospective analysis of TAP Vs. II/IH block for post cesarean delivery pain after spinal – epidural by Yulu Jin et al, found that cumulative morphine consumption were comparable between groups until 12 hour (all p > 0.05). Yet, at 24 & 48 hour II/IH group consumed less morphine than their counter parts with p < 0.05 and P < 0.001 respectively. Study design (non-randomized, retrospective), the use of intrathecal morphine & blocks done with ultrasound guided technique could have contributed for the difference seen to our finding [18]. Similarly a cohort by Seid et al, in a study done in Gondar, Ethiopia found that 24 hour total tramadol consumption was lower in II/IH group compared to TAP group (P = 0.009) [19]. Difference in study design and different people performing the blocks in their cohort could explain this discrepancy. In addition the use of diclofenac as part of multimodal analgesia in our case for control of visceral pain could have contributed for this difference.
Our study also demonstrated that TAP block had a superior analgesic benefit beyond 24 hour as evidenced by interval and cumulative tramadol consumption was lower. TAP is accustomed to provide prolonged (48 hour) analgesia in other placebo controlled studies too [20–22]. The reasons for the prolonged duration of analgesic effect after TAP blockade may relate to the fact that the TAP is relatively poorly vascularized area, and therefore drug clearance may be slowed [31]. A study by Abdellah et al, found that posterior TAP block, have prolonged effect than a lateral TAP in terms of lower post-operative morphine consumption and pain score until 48 hours post-operative (p < 0.05) [23].
Regarding time to first analgesic request there is no statistically significant difference between between TAP and II/IH groups with median time of 1200.0 (95% CI, 861.9 to 1538.1) & 1285.0 (95% CI, 1245.31 to 1324.69) minutes respectively (χ2 (1) = 0.467, p = .494). Similarly Yulu Jin et al [18] didn’t find statistically different result in terms of time to first analgesic request between groups. In contrast to our finding Seid et al and Bessmertnyj AE et al, found that time to first analgesic request were longer in II/IH group compared to TAP group for post cesarean delivery patients with P < 0.05. [17, 19]. The difference in study design in the former & technique of block (Ultrasound guided) in the later could have contributed for this difference. Compared to the above mentioned researches our RCT showed that the time to first analgesic request time was longer for both groups. The use of diclofenac on TID basis as part of multimodal analgesia for visceral pain control might have contributed for this.
In our study median pain score (NRS) at rest & on purposeful movement were similar between groups at 0, 4, 8, 12 and 24 hours post operatively. However, at 36 & 48 hour intervals was pain scores were lower in TAP compared to II/IH group both at rest & on purposeful movement (p < 0.0005). Seid et al, Anatoli Stav, et al & Sofiene Ben Marzouk et al found no difference in NRS score between groups both at rest and on movement during their 24 hour follow up for post cesarean section pain (P > 0.05)[19, 24, 25]. Our result is also supported by a study comparing TAP with IINB + wound infiltration for post-operative analgesia after inguinal surgery in adults, did not found significant difference in pain score between groups (P > 0.05) [26]. In contrary to our finding two studies comparing intrathecal morphine to TAP and II/IH for post cesarean section, did not find differences in pain score at 36 & 48 hour interval [27, 28]. Similarly our result is in contradiction with a study done by Faiz SHR et al, on patients undergoing open inguinal surgery where patients who received IINB block who expressed less pain at rest (4, 8, and 12 hours) & on movement 48 hours after the nerve block [29]. Different population and method of block (blind Vs ultrasound) may have contributed for the discrepancy.
The proportion of patients who had either nausea vomiting, pruritus or sedation were similar between groups in our study (P > 0.05). On top of this there were no request of ant-emetic medication in any case. In the same way C. Avelin et al also did not find any differences in terms of PONV and ondansetron consumption (5.9% vs 9.3%, p = 0.69) between TAP and II/IH after day case open inguinal surgery [30]. In contrast to our result, Ghassan E et al, found that Nausea scores were higher in patients who too intrathecal morphine group than were those in the TAP group (P = 0.02) [24]. The use of a short acting opioid (fentanyl) for intrathecal use in our patients might not have the aforementioned side effects as compared to morphine which is more potent and long acting. Additionally, our strict protocol of dexamethasone administration might have contributed to the fact that less patients are experiencing in both groups and had not requested anti-emetic during the 48 hour follow up. Our action was supported by Anatoli Stav et al, who concluded that the use of prophylaxis for PONV was effective in their RCT [28].
In summary both ilioinguinal-iliohypogastric and transverses abdominis nerve block were equally effective in decreasing post-operative pain after cesarean section, total tramadol consumption within 24 hr. TAP block has achieved longer analgesic duration compared to Ilioinguinal-iliohypogastric nerve block.
Lack of adequate literatures and the use of landmark techniques for the abdominal nerve block is among the limitation of the study