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Abstract
Background and objectives The transversus abdominis plane (TAP) block is the most widely used abdominal field block in colorectal surgery with a postoperative enhanced recovery pathway. We aimed to determine whether the laparoscopic-assisted and ultrasound-guided TAP (US-TAP) blocks provide superior pain relief compared with placebo. We separately investigated whether the laparoscopic-assisted technique was non-inferior to the ultrasound-guided technique in providing pain relief, with a non-inferiority margin of 10 mg morphine dose equivalents.
Methods 340 patients undergoing elective minimally invasive colon surgery were randomly allocated to one of three groups: (1) US-TAP block, (2) laparoscopic-assisted TAP (L-TAP) block, or (3) placebo. Superiority and non-inferiority were tested for the primary outcome: 24-hour postoperative morphine equivalent consumption. Secondary outcomes, including patient-reported quality of recovery, were included in the superiority analysis.
Results 127 patients were included in each block group and 86 in the placebo group. The US-TAP block was no different from placebo at −1.4 mg morphine (97.5% CI −6.8 to 4.0 mg; p=0.55). The L-TAP block was superior to placebo at −5.9 mg morphine (97.5% CI −11.3 to −0.5 mg; p=0.01) and non-inferior to the US-TAP block at −4.5 mg morphine (98.75% CI −10.0 to 1.1 mg).
Conclusion The L-TAP block was superior to placebo and non-inferior to the US-TAP block. However, neither met our predetermined estimate of the minimal clinically important difference of 10 mg morphine.
Trial registration number NCT04311099.
- Pain Management
- Ultrasonography
- Nerve Block
- Pain, Postoperative
- Anesthesia, Local
Data availability statement
Data are available upon reasonable request. After deidentification, individual participant data that underlie the results reported in this article, the statistical analysis plan, and analytic codes will be available 9 months following the article’s publication to researchers who provide a methodologically sound proposal. Proposals should be directed to claus.anders.bertelsen@regionh.dk. Data requestors must sign a data access agreement to gain access.
This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, an indication of whether changes were made, and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/.
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WHAT IS ALREADY KNOWN ON THIS TOPIC
Though widely used, the clinical relevance of any beneficial effect of the transversus abdominis plane (TAP) block is still debated.
WHAT THIS STUDY ADDS
To our knowledge, no previous trial of this size has been conducted assessing the effect of the TAP block versus placebo, nor the laparoscopic-assisted TAP block versus the ultrasound-guided TAP block, in minimally invasive surgery.
HOW THIS STUDY MIGHT AFFECT RESEARCH, PRACTICE OR POLICY
Since the TAP block did not provide a clinically meaningful benefit compared with placebo, these authors believe the TAP block should not be a standard procedure in minimally invasive colon surgery.
Introduction
Enhanced recovery protocols are considered the gold standard of care after elective colorectal surgery. Enhanced recovery protocols improve recovery with reduced morbidity and shorten the length of stay.1 Efficient and reliable pain management is an essential and integral part of the enhanced recovery protocols, which aim at reducing postoperative opioid medication and thus decreasing opioid-related adverse effects. Epidural analgesia has been largely abandoned for regional analgesia after minimally invasive colorectal resections were introduced.2 The transversus abdominis plane (TAP) block is the most commonly used abdominal field block after colorectal surgery and other abdominal surgery procedures.3
TAP blocks can be applied using different techniques, such as ultrasound-guided4 TAP (US-TAP) block and laparoscopic-assisted5 TAP (L-TAP) block. Though widely used, the clinical relevance of any beneficial effect of the TAP block is still debated.3 Large multicenter randomized trials are warranted to determine whether TAP block is clinically relevant in minimally invasive colon surgery.
We designed a multicenter randomized clinical trial to determine the following: first, US-TAP and L-TAP block techniques were compared separately to placebo to determine superiority. Second, non-inferiority of L-TAP to US-TAP block was examined. Superiority needed to be established as a premise for any relevance in establishing non-inferiority of L-TAP to US-TAP block. The non-inferiority design was included because the L-TAP block has several established benefits compared with the US-TAP block.5 6 We aimed to determine whether TAP block provides superior pain relief, measured by 24-hour morphine consumption, compared with placebo and whether L-TAP block is non-inferior to the US-TAP block in patients undergoing minimally invasive colon surgery under general anesthesia.
Methods
Study design
A multicenter, patient, clinician, and investigator-blinded, controlled, three-arm randomized, superiority and non-inferiority clinical trial comparing superiority of US-TAP and L-TAP block versus placebo and non-inferiority of L-TAP to US-TAP block in minimally invasive colon surgery.7 The trial is reported according to the Consolidated Standards of Reporting Trials statement.8 Recruitment was undertaken in five Danish colorectal centers. The trial was registered with ClinicalTrials.gov (NCT04311099) on March 17, 2020, with the first patient enrolment on January 18, 2021.
Study population and randomization
Enrolment was undertaken in the outpatient clinic by a colorectal surgeon familiar with the trial protocol. Patients older than 18 years undergoing elective minimally invasive surgery for colon cancer or adenoma with curative intent and without a planned ostomy were considered for the study. Oral and written informed consent were collected from 360 patients, with final inclusion on February 9, 2024. Exclusion criteria were known allergy to local anesthetics (LA), liver failure Child-Pugh Score Class C, body weight <40 kg, concurrent conditions associated with pain or a weekly intake of WHO step II, III, or adjuvant step I analgesics, predictably non-compliant due to language barrier or psychiatric disease, known inflammatory bowel disease, history of open abdominal surgery with a midline or upper abdominal incision of more than 8 cm, incisional hernia, resection of abdominal wall musculature, or pregnancy. Patients with a history of minimally invasive surgery were not excluded.
Patients were randomly assigned to one of three groups: (1) active US-TAP and placebo L-TAP block; (2) placebo US-TAP and active L-TAP block; or (3) placebo US-TAP and placebo L-TAP block in a 3:3:2 ratio using random blocks of 8, 16, and 24. The Capital Region Pharmacy conducted blinding and packaging in sequentially numbered and indistinguishable containers. Patients were excluded from the modified intention-to-treat analysis if a protocol violation occurred, resulting in no valid data on the primary outcome being registered (figure 1). Further, patients were excluded from per-protocol analysis if converted from minimally invasive to open surgery, if a situation arose in which surgery could not be completed, or if rescue TAP block or epidural analgesia was performed. No further protocol violations occurred regarding the primary outcome.
Exclusion, randomization, and eligibility for analysis. L-TAP, laparoscopic-assisted TAP; TAP, transversus abdominis plane; US-TAP, ultrasound-guided TAP.
Interventions
As a pragmatic study, surgery was performed following the participating hospitals’ guidelines and under the discretion of the attending surgeon. No local infiltration analgesia was administered at the trocar sites per the study protocol. All patients received infiltration analgesia around the extraction site with a fixed dose of 40 mL of ropivacaine (1 mg/mL) at the end of surgery. Total intravenous anesthesia (TIVA) was the preferred method for general anesthesia, but alterations according to hospital guidelines or at the anesthesiologist’s discretion were accepted. Intraoperative administration of glucocorticoids, antiemetics, and opioids was also accepted according to hospital guidelines. The intraoperative analgesic protocol consisted of remifentanil with a fentanyl bolus given towards the end of surgery at the anesthesiologist’s discretion. The fentanyl dose administered was registered as a secondary outcome. Due to block randomization and clinician blinding, a variation in anesthetic protocol between sites was permissible and was not anticipated to influence outcomes. There were no changes in perioperative or anesthetic care during the study period, and the COVID-19 pandemic did not affect the treatment of the chosen research population.
Before surgery, the site investigator collected a randomized package containing the trial medication. Following intubation and just before surgical draping, the anesthesiologist applied the US-TAP block according to the protocol. All participating anesthesiologists were trained in the US-TAP block application. The surgeon applied the L-TAP block after the pneumoperitoneum was established and the first port was placed. All participating surgeons were trained in the L-TAP block application.
All blocks were applied using ropivacaine (2 mg/mL) or isotonic saline (placebo). One injection of 20 mL of ropivacaine (2 mg/mL) or placebo was applied on each side for the US-TAP block. Two injections amounting to 20 mL of ropivacaine (2 mg/mL) or placebo were applied on each side for the L-TAP block. All patients received both a US-TAP and an L-TAP block bilaterally to maintain blinding.
US-TAP block
US-TAP block was performed bilaterally using the posterior approach,3 4 targeting the TAP approximately 1 cm anterior to fascia layers tapering into the thoracolumbar fascia (online supplemental figure 1).
Supplemental material
L-TAP block
L-TAP block was performed using a dual subcostal approach. Both a medial and a lateral injection (dual-TAP block), previously described as the medial and lateral intercostal TAP blocks,9 or upper and lower subcostal TAP blocks,10 were carried out (online supplemental figure 2). No direct visual confirmation of fascial separation is possible for this technique.6 11
Supplemental material
Postoperative care
Postoperative pain management consisted of a basic regimen of oral paracetamol (1000 mg) every 6 hours. Non-steroidal anti-inflammatory drugs were not used as standard care. Supplementary intravenous and oral opioids were administered patient-controlled and pro-necessitate using either morphine (intravenous 5 mg; oral 10 mg) or oxycodone (intravenous 5 mg; oral 5 mg). In case of morphine-resistant breakthrough pain, a repeated (rescue) TAP block with ropivacaine or epidural analgesia would be offered to supplement the multimodal pain management regimen at the discretion of the attending anesthesiologist. For a rescue block to be conducted, at least 12 hours would have to pass from the trial block application, and the rescue block would then be conducted with a local anesthetic dose according to patient weight.
Outcomes and measures
The primary outcome was total morphine dose equivalents (online supplemental table 1) (intravenously in mg) administered in the first 24 hours, counting from arrival at the postanesthesia care unit (PACU). Secondary outcomes are shown in box 1. Superiority and non-inferiority were examined for the primary outcome. Superiority was examined for secondary outcomes.
Supplemental material
Outcom e measurements in the OPMICS trial
Primary outcome
Total morphine dose equivalents7 (intravenously in mg) administered during the first 24 hours from admission to the PACU.
Secondary outcomes
Total morphine dose equivalents7 (intravenously in mg) administered in the operating theater 30 min prior to extubating.
Total morphine dose equivalents7 (intravenously in mg) administered in the PACU.
LOS (min) in the PACU.
NRS pain scores (0–10, no pain–worst possible pain) during rest between 08:00 and 10:00 on POD1.
NRS pain scores (0–10, no pain–worst possible pain) during activity between 08:00 and 10:00 on POD1.
Number of patients (n) in need of supplementary antiemetic medication during the first 24 hours after admission to the PACU.
Incidence of postoperative nausea (0=no nausea, 1=mild, 2=moderate, 3=severe) until the morning of POD1.
Incidence of postoperative vomiting (0=no vomiting, 1=once, 2=two–three, 3=>three) until the morning of POD1.
Mobilization (1=without assistance, 2=need a little assistance, 3=need a lot of help, 4=cannot be mobilized) morning POD1.
Need of a rescue transversus abdominis plane block or epidural analgesia (n).
Quality of recovery (QoR-15 questionnaire,29 score=0–150) between 08:00 and 10:00 on POD1.
LOS/time to discharge from hospital (days).
30-day postoperative complications according to the Clavien-Dindo classification30 (n and severity, 1–5).
30-day hospital readmission rate (n).
LOS, length of stay; NRS, Numeric Rating Scale; PACU, postanesthesia care unit; POD1, postoperative day 1.
All data were registered in a REDCap database12 and managed according to the General Data Protection Regulation of the European Union and Danish legislation. The Regional Data Protection Agency approved the trial database on October 1, 2020.
Sample size
For the superiority analyses of US-TAP and L-TAP block versus placebo, alpha was set to 0.025 as multiple analyses were performed. Based on previous studies,6 13 the mean opioid use during the first 24 hours after surgery in the TAP block groups was estimated to be 20 mg and 30 mg in the placebo group, that is, a difference of 10 mg. The SD was estimated to be 20 mg. With a power of 80%, each group had to include 77 patients eligible for analysis. For the non-inferiority analysis comparing L-TAP with US-TAP block, a non-inferiority limit of 10 mg opioid use was employed, and an alpha of 0.0125 and a power of 90% were chosen due to the non-inferiority design. Each TAP block group had to include 105 patients eligible for analysis. We estimated that 10%–20% of patients would be converted to open surgery, have an unplanned ostomy, be lost to follow-up, or drop out. Thus, we planned to include 90 patients in the placebo group and 135 in the US- and L-TAP block groups, respectively.
Statistical analysis
All analyses were performed using R statistical software, V.4.2.3.14 All available data were used, and no imputations were performed. Continuous data are presented as median and IQR, and categorical data as frequencies and proportions.
Alpha was set at 0.025 (two-sided) to determine statistical significance for the primary and secondary outcomes regarding superiority of L-TAP and US-TAP block versus placebo. For the analysis of non-inferiority of L-TAP versus US-TAP block regarding the primary outcome, a two-sided 98.75% CI was used corresponding to an alpha of 0.0125. Continuous outcomes were analyzed using linear regression, binary outcomes using logistic regression, and outcomes with multiple categories using Fisher’s exact test. Statistical model assumptions were assessed by residual diagnostics. Superiority was assessed for primary and secondary outcomes, non-inferiority of L-TAP versus US-TAP block was assessed for the primary outcome, and all were assessed using a modified intention-to-treat and per-protocol analysis. Post-hoc sensitivity analyses of the primary outcomes were performed using inverse probability of treatment weighting (IPTW) to obtain an unbiased estimation of treatment effects based on propensity scores. The following covariates were used for the model: age, sex, weight, body mass index, American Society of Anesthesiologists score, Hospital Anxiety and Depression Scale15 score, Pain Catastrophizing Scale16 score, tobacco, alcohol, procedure, secondary colon resection, other organs resected, injury to other organs, length of surgery, conversion to open surgery, stoma creation, and TIVA.
Results
Study population
360 patients consented to participate in the trial between January 2021 and February 2024 across five Danish colorectal centers. 20 patients were excluded postrandomization, 8 patients were excluded after one center had to be closed due to excessive protocol violations, and 12 patients were excluded due to protocol violations, resulting in no primary outcome available for analysis. The modified intention-to-treat analysis included 127 patients assigned to L-TAP block, 127 patients assigned to US-TAP block, and 86 patients assigned to placebo (figure 1).
Patient characteristics
Table 1 summarizes the characteristics of patients included in the modified intention-to-treat analyses, and online supplemental table 2 those of the patients included in the per-protocol analyses. Though conducted in a blinded, randomized setting, the patient characteristics differed between groups, notably between sex and perioperative organ lesions. For this reason, post-hoc sensitivity analyses using IPTW were performed for the primary outcomes.
Clinical characteristics of the study groups
24-hour total morphine dose equivalents administered
Modified intention-to-treat
The median 24-hour total morphine dose equivalents were 19.2 mg (IQR, 6.8–33.8 mg) in the US-TAP block group, 15.8 mg (IQR, 8.3–25.2 mg) in the L-TAP block group, and 22.0 mg (IQR, 13.3–33.3 mg) in the placebo group.
US-TAP block and placebo were not statistically different, with an absolute difference of −1.4 mg morphine equivalents (97.5% CI −6.8 to 4.0 mg; p=0.55). L-TAP block was superior to placebo with an absolute difference of −5.9 mg morphine equivalents (97.5% CI −11.3 to −0.5 mg; p=0.01). L-TAP block was non-inferior to US-TAP block at the 10 mg morphine non-inferiority margin with −4.5 mg morphine equivalents (98.75% CI −10.0 to 1.1 mg).
Per-protocol
The median 24-hour total morphine dose equivalents were 18.0 mg (IQR, 6.7–29.4 mg) in the US-TAP block group, 15.7 mg (IQR, 7.2– 25.0 mg) in the L-TAP block group, and 22.5 mg (IQR, 13.3–33.5 mg) in the placebo group.
US-TAP block and placebo were not statistically different, with an absolute difference of −4.1 mg morphine equivalents (97.5% CI −9.7 to 1.5 mg; p=0.10). L-TAP block was superior to placebo with an absolute difference of −6.5 mg morphine equivalents (97.5% CI −11.9 to −0.5 mg; p<0.01). L-TAP block was non-inferior to US-TAP block at the 10 mg morphine non-inferiority margin with −2.4 mg morphine equivalents (98,75% CI −8.0 to 3.3 mg).
The primary outcome of the modified intention-to-treat and per-protocol analyses are presented in figure 2, and the sensitivity analyses with IPTW in online supplemental figure 3.
Supplemental material
![[rapm-2024-105712supp002.jpg]](https://rapm.bmj.com/content/rapm/early/2024/11/13/rapm-2024-105712/DC1/embed/inline-supplementary-material-1.jpg?download=true){kind=link}
![[rapm-2024-105712supp003.jpg]](https://rapm.bmj.com/content/rapm/early/2024/11/13/rapm-2024-105712/DC2/embed/inline-supplementary-material-2.jpg?download=true){kind=link}
![[rapm-2024-105712supp004.jpg]](https://rapm.bmj.com/content/rapm/early/2024/11/13/rapm-2024-105712/DC4/embed/inline-supplementary-material-4.jpg?download=true){kind=link}
24-hour morphine dose equivalents (mg) for the modified intention-to-treat and per-protocol analyses. Continuous outcomes were analyzed by linear regression and presented as the absolute difference with 97.5% CI for superiority and 98.75% CI for non-inferiority. L-TAP, laparoscopic-assisted transversus abdominis plane; US-TAP, ultrasound-guided transversus abdominis plane.
Secondary outcomes
Total morphine dose equivalents administered in the PACU were statistically significant for L-TAP block versus placebo –5.2 mg (97.5% CI –9.4 to –0.9 mg; p<0.01) and demonstrated that most morphine during the first 24 hours was administered in the PACU.
There was no significant difference in intraoperative morphine dose equivalents or other secondary outcomes (tables 2 and 3, and online supplemental tables 3, 4). The QoR-15 questionnaire is a validated patient-reported outcome and demonstrated no difference in the quality of recovery between groups.
Secondary outcome measures of US-TAP versus placebo
Secondary outcome measures of L-TAP versus placebo
Some patients required rescue interventions of supplementary TAP block or epidural analgesia due to insufficient pain control, with 5 (5.8%) in the placebo group, 8 (6.3%) in the L-TAP block group, and 14 (11.0%) in the US-TAP block group. However, no significant difference was found between groups.
Discussion
This randomized clinical multicenter trial demonstrated superiority of L-TAP block to placebo and non-inferiority of L-TAP to US-TAP block concerning 24-hour postoperative morphine consumption. Neither L-TAP nor US-TAP block met the pretrial estimate of the minimal clinically important difference (MCID) of 10 mg morphine equivalents. US-TAP block was clinically equivalent to placebo. Importantly, patient quality of recovery as a validated patient-reported outcome showed no difference between groups.
As a multicenter trial conducted in an enhanced recovery setting, the generalizability is high. In all Danish hospitals, enhanced recovery protocols, considered the gold standard of perioperative care, had been an integrated part of the clinical setting for over a decade before the study period. Thus, other contributing factors of the enhanced recovery pathways should not confound the results of this trial. To resemble an actual clinical setting, this pragmatic trial provides evidence of the actual clinical effect of the TAP block.
Our modified intention-to-treat analysis reached the predetermined sample size to address the issue of superiority. The per-protocol population fell short by one patient in the placebo group and five in the US-TAP block group. Superiority tests should be based on the intention-to-treat analysis, with the consensus that non-inferiority tests should be based on the per-protocol analysis. Notably, the CI between the L-TAP and US-TAP block in the non-inferiority analysis was well within the predefined non-inferiority margin. Despite the shortfall in sample size, the power seems not to be a significant concern in interpreting the study. A type II error of clinical relevance, that is, US-TAP block being statistically superior to placebo in the per-protocol analysis of the intended sample size, seems unlikely.
Despite TAP blocks being widely used, the optimal approach regarding a clinically relevant effect is still debated.3 Several TAP block approaches have been described: subcostal,9 10 lateral,9 10 and posterior TAP blocks,4 including dual-TAP blocks.9 17 Multiple injections provide more extensive coverage to optimize any clinical effect,9 17 The literature on dermatomal coverage of different approaches and projecting coverage as a measure of effect suggests using the subcostal and posterior approaches instead of the lateral.3 The posterior is considered to cover a broader range of dermatomes due to the proximity to the paravertebral space,18 thus being commonly used in Denmark. Unfortunately, the retroperitoneal posterior injection point is impossible to reach with laparoscopic guidance. L-TAP block can be administered within 1–2 min,5 6 9 11 thus we intended to test the optimal single injection ultrasound-guided technique and a simple, less time-consuming laparoscopic approach. We chose the posterior US-TAP block and the dual-injection subcostal L-TAP block.
The two approaches neither target nor cover the same anatomic dermatomes.4 11 The subcostal dual US-TAP block would likely produce the same outcome as the subcostal dual L-TAP block,19 though dermatomal coverage has not been validated as an estimate of pain management in TAP blocks.
The difference in outcome could reflect that the subcostal approach is superior to the posterior approach in minimally invasive colon surgery. Interestingly, the necessity for exact LA deposition in the TAP fascial plane could be unfounded, as the L-TAP block has a high likelihood of intramuscular injection.11 20 The L-TAP block, with its established benefits, was first described in 2011.5 Unlike the US-TAP block, the L-TAP block is a blind technique. Confirmation of LA deposition in the TAP is impossible with the L-TAP block, as it is applied without ultrasound guidance.6 11
A fixed dose of 40 mL of ropivacaine (2 mg/mL) was used for TAP block application, with an additional 40 mg of ropivacaine for local wound infiltration, equal to the maximum tolerated dose for a 40 kg individual (120 mg=3 mg/kg), to avoid the risk of LA systemic toxicity and to keep the blinding process simple in a large multicenter trial. Multiple studies have examined different LA concentrations using a fixed volume and found minimal differences between low and high concentrations of ropivacaine on postoperative pain scores and analgesic consumption.3 21 The use of local infiltration analgesia around the incision used for bowel extraction could obscure some of the impact of the TAP block. However, local infiltration analgesia is standard practice in minimally invasive surgery, and if this renders the analgesic effect of the TAP block clinically irrelevant, then the conclusion remains the same.
There were multiple considerations regarding the timing of the TAP block application. Based on the existing literature, there is no consensus regarding the optimal timing in relation to the surgical procedure. However, a recent meta-analysis looking at the efficacy of TAP blocks in colorectal surgery showed a tendency towards preoperative administration being the optimal time to fully benefit from the analgesic effect.22 Performing the L-TAP block at the start of the surgical procedure was considered prudent to avoid the trocar sites and bowel extraction incision influencing the spread of the LA. The US-TAP block was administered preoperatively to achieve the smallest possible time gap between the two procedures. The duration of the sensory effect of ropivacaine is reported to be approximately 10 hours.4 With an expected median surgical time of 3 hours, sufficient postoperative analgesic effect should be obtained with the study design. However, pain scores were not assessed until postoperative day 1 (POD1), when the block would have likely worn off. In multimodal analgesia, pain may be well controlled on POD1 due to medications alone. This was a compromise chosen for practicality.
The significant difference in 24-hour morphine equivalent consumption after L-TAP block was 5.9 mg less than after placebo. This did not meet our pretrial estimate of the MCID of 10 mg morphine equivalents, which is the consensus.23 However, a recent post hoc analysis of three randomized controlled trials (RCTs) showed that the MCID in 0–24 hour postoperative intravenous morphine consumption after orthopedic surgery is 5 mg.24 They found a difference of 6 mg between no versus mild events (nausea, vomiting, sedation, and dizziness), 5 mg between mild versus moderate events, and 0 mg between moderate and severe events. Considering that patients undergoing abdominal surgery are more prone to nausea and vomiting, an MCID of 5 mg might be considered too low, and our pretrial estimate seems more clinically relevant.
To our knowledge, four RCTs have compared L-TAP with US-TAP block in colorectal surgery, with only one including a placebo group. Non-inferiority was confirmed in three trials.13 25 26 In the fourth trial, superiority was demonstrated of L-TAP to US-TAP block and placebo, and similar to the present trial, superiority of US-TAP block to placebo was not found.6
Several meta-analyses have assessed the TAP block procedure in colorectal and minimally invasive surgery. One compared L-TAP with US-TAP block, local infiltration analgesia, and placebo and showed significant but clinically negligible differences of 1–3 mg in the 24-hour morphine consumption between groups.27 Another meta-analysis investigating TAP block in laparoscopic colorectal surgery showed similar results.28 Both meta-analyses were based on studies with small populations, and the effect seems too small to meet the MCID.
Considering the benefits achieved with the introduction of minimally invasive surgery in reducing postoperative pain and surgical stress, the benefit of the TAP block seems negligible. As a standard practice in minimally invasive colorectal surgery, the US-TAP block does not meet the beneficial standards to be deemed cost-effective. L-TAP block is faster and less demanding, and we have shown a statistically significant reduction in 24-hour postoperative opioid consumption of 5.9 mg morphine equivalents. However, neither US-TAP nor L-TAP block met our pretrial estimate of the MCID. As we similarly found no difference between groups for secondary- and patient-reported outcomes, these authors believe the TAP block should not be a standard procedure in minimally invasive colon surgery.
Our findings may be due to the low degree of postoperative pain in minimally invasive surgery, and future research should look into the TAP block as a rescue analgesic modality. This would increase the signal/noise ratio and provide a better evaluation of the actual analgesic effect of the TAP block.
Conclusion
We found that the L-TAP block was superior to placebo measured by 24-hour postoperative morphine consumption in patients undergoing elective minimally invasive colon surgery. The difference did not reach our predefined estimate of clinical relevance. No difference was found between US-TAP block and placebo. L-TAP block was non-inferior to US-TAP block within a non-inferiority limit of 10 mg morphine.
Data availability statement
Data are available upon reasonable request. After deidentification, individual participant data that underlie the results reported in this article, the statistical analysis plan, and analytic codes will be available 9 months following the article’s publication to researchers who provide a methodologically sound proposal. Proposals should be directed to claus.anders.bertelsen@regionh.dk. Data requestors must sign a data access agreement to gain access.
Ethics statements
Patient consent for publication
Ethics approval
This study involves human participants and the Regional Committee on Health Research Ethics of the Capital Region of Denmark and the Danish Health and Medicines Authority approved the trial under the following references: j.nr. H-20026773 and EudraCT 2020-001054-22. Participants gave informed consent to participate in the study before taking part.
References
Supplementary materials
Supplementary Data
This web only file has been produced by the BMJ Publishing Group from an electronic file supplied by the author(s) and has not been edited for content.
Footnotes
Collaborators The OPMICS Study Group: Jeanette Lydeking, RN (Department of Surgery, Copenhagen University Hospital – North Zealand, Hillerød, Denmark); Christina Kraiberg Rokatis, RN (Department of Surgery, Copenhagen University Hospital – North Zealand, Hillerød, Denmark); Uffe Schou Løve, MD PhD (Department of Surgery, Regional Hospital of Viborg, Viborg, Denmark, Department of Clinical Medicine, Faculty of Health, Aarhus University, Aarhus, Denmark); Susie Lindhardt Larsen, RN (Surgical Research Unit, Gødstrup Hospital, Denmark); Claudia Jaensch, MD (Department of Clinical Medicine, Faculty of Health, Aarhus University, Aarhus, Denmark, Surgical Research Unit, Gødstrup Hospital, Denmark); Anders Husted Madsen, MD PhD (Department of Surgery, Gødstrup Hospital, Denmark, Department of Clinical Medicine, Faculty of Health, Aarhus University, Aarhus, Denmark).
Contributors CBS: conceptualization, methodology, formal analysis, investigation, resources, data curation, writing—original draft, writing—review and editing, visualization, project administration, guarantor; KHWL: conceptualization, methodology, validation, writing—review and editing; JK: methodology, formal analysis, writing—review and editing; RK: investigation, resources, data curation; LB: investigation, resources, data curation; MM: investigation, resources, data curation; PD: investigation, resources, data curation; KBH: investigation, resources, data curation; JEPO: investigation, resources, data curation; CAB: conceptualization, methodology, formal analysis, resources, data curation, writing—review and editing, visualization, project administration.
Funding Helen Rudes Fond: 190,000 DKK; A & J C Tvergaards Fond: 65,000 DKK; Fru Olga Bryde Nielsens Fond: 31,400 DKK; Louis-Hansen Fonden: 520,000 DKK; Regionernes Medicin- og Behandlingspulje: 846,100 DKK.
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.
Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.