Efficacy of ultrasound-guided transversus abdominis plane block in breast reconstruction surgery with abdominal myocutaneous flap

Ana Luísa Afonso, Luís Pereira, Joana Correia, Mónica Ferreira, Nuno Lareiro, Joana Filipa Paulo, Germano Cardoso, Luís Botelho Antunes, Rui Valente Resident in Anaesthesiology, Instituto de Oncologia do Porto, Francisco Gentil, EPE, Porto Portugal, Assitant of Anaesthesiology, Centro Hospitalar do S. João, EPE, Porto Portugal, Resident in Anaesthesiology, Centro Hospitalar Baixo-Vouga, EPE, Aveiro, Portugal, Graduate Assitant in Anaesthesiology, Instituto de Oncologia do Porto, Francisco Gentil, EPE, Porto Portugal, Epidemiologist, Department of Clinical Epidemiology, Instituto de Oncologia do Porto, Francisco Gentil, EPE, Porto Portugal.

Introduction TAPB was first introduced as a landmarkguided technique. 1,2 This approach was associated with low success rates. Nowadays, the gold standard is US-guided approach, with injection of local anaesthetic between transversus abdominis and internal oblique muscles. 3 This technique is associated with fewer complications. 4 An important component of the pain experienced by patients after autologous breast reconstruction with TRAM flap is from the abdominal wall incision. Multimodal analgesia scheme including the performance of TAPB could reduce pain, systemic opioid consumption and their adverse effects. Published literature about TAPB efficacy in this type of surgery is limited. [8][9][10] Postoperative pain control can be challenging in the oncological patient. In this group of patients, pain is a complex pathologic process. Mediators liberated by cancer cells sensitize nociceptors, altering endogenous anti nociceptive mechanisms and inducing peripheral and central sensitization. 11 The goal of this study was to evaluate the efficacy of US-guided TAPB as part of a multimodal analgesia protocol for breast reconstructive surgery with TRAM and mastectomy (partial or total) followed by TRAM reconstruction.

Methods
This was an observational retrospective study conducted from April 2015 to June 2017 after obtaining our Institutional Ethics Committee's approval.
The study was conducted in the Anaesthesiology Department of an Oncological Institute with extensive experience in breast reconstructive surgery. In 2014, a TAPB protocol was approved (described below) and since then, this locoregional technique has been adopted in this type of surgery.
The inclusion criteria were patients older than 18 years old scheduled for unilateral breast reconstruction surgery with TRAM flap (surgery 1) or to mastectomy (partial or total) followed by TRAM reconstruction (surgery 2). Anaesthetic protocol included general balanced anaesthesia (GBA) or general anaesthesia combined with US guided bilateral TAPB (GBA+TAPB). Only the cases in which TAPB was performed according to our anaesthesiology department's protocol and systemic analgesia followed by an institutional protocol for major somatic surgery were studied.
The exclusion criteria included patients suffering from substance abuse (addiction syndrome); body mass index (BMI) equal to or greater than 40 kg/m 2 and patients subjected to other surgeries besides surgery 1 or surgery 2 within the same operative time.
Intraoperative and postoperative electronic records of the included patients were analysed.
In all included cases the monitoring standards of American Society of Anaesthesiologists (ASA) were adopted. Patients were submitted to GBA with oro-tracheal intubation. Intravenous fentanyl was administered at anaesthetic induction (1-2 µg/kg) and during maintenance (bolus of 0.5-1 µg/kg). Before surgical incision, patients received parecoxib (40 mg) i.v. and 15 minutes before the conclusions of surgery i.v. paracetamol (1000 mg) was administered.
In the included cases of the GBA+TAPB group, TAPB was performed by the assigned anaesthetist after anaesthetic induction, before surgical incision. The technique and the administered volume and concentration of local anaesthetic followed the protocol of our anaesthesiology department, as described below: -Aseptic technique; -US-guided technique (Toshiba Nemio XG iStyle Ultrasound Scanner ® ), in-plane approach; Linear 8 MHz frequency probe; 85 mm, 21G needle (Vygon, Echoplex ® ); -At the midaxillary line, halfway between costal margin and iliac crest, transversus abdominis, internal and external oblique muscles were identified; -After aspiration, 10 ml of ropivacaine 0.375% was administered on each side of abdominal wall, between transversus abdominis and internal oblique muscles. Ultrasound dispersion of local anaesthetic was observed; -Maximum administered ropivacaine dosage was 3 mg/kg. Postoperative systemic analgesia protocol included i.v. parecoxib (40 mg) 12hrly, i.v. paracetamol (1000 mg) each 6hrly and supplemental i.v. morphine (2mg boluses until a maximum of 6mg in 1 hour).
Total number of bolus (2-5 mg) and total amount of consumed morphine during PACU stay, and total number of administered morphine boluses (2mg) during the first 4 postoperative hours after discharge from PACU and between 4 and 24 postoperative hours were registered.
Records of pain assessment at rest and on movement were checked at admission and at discharge from PACU and at the 4 th and 24 th postoperative hours. The following 5-point verbal rating scale was used: "no pain", "slight pain", "moderate pain", "severe pain", "excruciating pain".
Analgesia time, defined as the time, in minutes, since the conclusion of surgery until the moment of the first analgesic request, was registered as well as the worst pain assessed at this point. "No pain" classification was attributed to cases that no rescue analgesia was administered during the study's duration.
Primary endpoints were opioid consumption during intraoperative period and in PACU stay, and analgesia time. Secondary outcomes included opioid consumption after discharge from PACU, pain assessment, total modified Aldrete score and incidence of nausea and vomiting.

Statistical analysis
Continuous variables were assessed for normality using Shapiro-Wilk test. Summary measures were used to describe continuous and categorical variables. All conducted analyses were stratified by type of surgery (surgery 1 vs surgery 2). P values of < 0.05 were regarded as significant.
Distribution of continuous variables were compared between both groups using nonparametric test Mann-Whitney U. Chi Square or Fisher tests were used when appropriate to verify associations between categorical variables.
The "analgesia time" variable was analysed using Kaplan-Meier curves and the differences between both groups were verified using logrank test. Software SPSS® (Version 24.0, Chicago, IL) was used.

Results
One hundred and seven patients were included: 80 submitted to surgery 1 and 27 submitted to surgery 2. No significant differences were found between GBA and GBA+TAPB groups in age, BMI, ASA classification and anaesthesia duration for both surgeries (Table 1). All studied patients were classified as ASA physical status II. According to intraoperative records, propofol was the intravenous anaesthetic used in all included cases and sevoflurane or desflurane were used as volatile maintenance agents. Antiemetic prophylaxis with i.v. ondansetron (4 mg) or droperidol (1.25 mg) or both was administered 15-30mins before conclusion of surgery. and total amount of supplemental morphine were significantly lower in GBA+TAP group.
No statistically significant differences were found in opioid consumption after discharge from PACU. We found that the number of administered boluses of supplemental morphine was below 2 in most patients in both surgeries ( Table 2). Regarding the opioid consumption, no significant differences were detected in surgery 2.  Figure 1). Upon the first rescue analgesic administration, GBA group referred higher pain intensity with 56.3% of patients referring "moderate pain" / "intense pain" compared to 25% in GBA+TAPB group (p=0.006).   Also in surgery 1, at admission at PACU, 81.3% in GBA+TAPB group and 60.4% in GBA group referred "no pain" at rest (p=0.049). Considering pain on movement, 71.9% in GBA+TAPB group and 35.4% in GBA referred "no pain" (p=0.001). At discharge from PACU, 90.6% in GBA +TAPB group referred "no pain" on movement compared to 58.3% in GBA group (p=0.002). No difference was found at rest ( Figure 2). No significant differences were detected in surgery 2.
At 4 th postoperative hour, in surgery 1, 84.4% in GBA+TAPB group and 54.2% in GBA group referred "no pain" at rest (p=0.005). Considering pain on movement, 28.1% in GBA+TAPB group and 6.3% in GBA group referred "no pain" (p=0.011) (Figure 2). Regarding surgery 2, a significant difference was identified only at rest (p=0.029). In addition, concerning pain on movement, 93.8% of patients in GBA group and 71.9% in GBA+TAPB group referred at least "mild pain" for both surgeries.
At the 24 th postoperative hour, in surgery 1, 90.6% in GBA+TAPB group and 64.6% in GBA group referred "no pain" at rest (p=0.009) (Figure 2). No significant difference was observed in the recovery time (PACU stay) between groups in both surgeries.
At discharge from PACU, considering surgery 1, GBA+TAPB group presented higher total modified Aldrete score. No significant differences were observed in surgery 2 ( Table  3). Table 3: Analysed variables during PACU stay No significant differences were found regarding the length of in-hospital stay between both groups.
No differences were identified in regard to nausea or vomiting incidence. In fact, the main registered medical complication in GBA group, considering both surgeries, was constipation. Regarding surgery 1, constipation incidence was 31.3% in GBA group and 3.1% in GBA + TAPB group. Considering surgery 2, constipation incidence was 22.2% for GBA group and 0% for GBA + TAPB group.
There were neither reported complications associated with TAPB administration nor clinical cases of local anaesthetic toxicity. Discussion US-guided TAPB has been showing promising results in abdominal surgery. It has become a well-recognized postoperative analgesia technique. [2][3][4][5] Multimodal analgesia regimens should include techniques that facilitate postoperative pain control, contributing to reduction of incidence of chronic pain. Considering breast reconstructive surgery, a substantial number of patients reported pain-related complaints for longer periods than was expected. 12,13 Our work is one of the first anaesthesiology studies evaluating bilateral TAPB efficacy in breast reconstructive surgery with TRAM flap. Based on our results and on published studies, an important pain component in this surgery derives from incision in the abdominal donor site, explaining why a peripheral block of abdominal wall, like TAPB, is effective in postoperative pain control. 8,9,14 In truth, no benefit was detected in patients submitted to mastectomy followed by TRAM reconstruction. In these cases, pain in the mammary area may be higher after mastectomy than after a simple flap inset, justifying the use of a thoracic wall block. 9,15,16 As verified in other studies, administration of long-acting local anaesthetics that block the sensory nerves to abdominal wall allows a significant reduction of systemic opioid consumption. In previous studies that evaluated TAPB in breast reconstruction with abdominal flap, reduced morphine consumption in the early postoperative period was reported. 8,10 In our study, reduction of intraoperatively administered fentanyl and immediate postoperative consumption of morphine was identified.
Analgesia time was included in the primary outcomes of our study. It is an important variable to consider when analysing an analgesia scheme's efficacy. 5,17 At this point, we concluded that TAPB was associated with an increase in time to first analgesia request.
Moreover, results of pain assessment at PACU and at 4 th postoperative hour support that the positive effect of bilateral TAPB in TRAM surgery is mainly effective during the first postoperative hours. However, we detected that the incidence of mild, moderate and severe pain was greater on movement, especially in the first four post-operative hours, which is in line with the fact that complete relief of pain on movement is not commonly achieved with local or systemic techniques but through neuraxial techniques. 18,19 To our knowledge, there aren't any studies comparing epidural with TAPB in TRAM surgery.
Published plastic surgery studies evaluated a continuous TAPB technique and reported good results. 8,20 A catheter-based technique would allow extended postoperative analgesia decreasing morphine consumption for more than 24 hours.
The reduction in opioid consumption resulted in higher total modified Aldrete score at discharge from PACU. All the patients submitted to TAPB scored 2 in the consciousness component of Aldrete score and most of them held maximum total modified Aldrete scores.
Even though, no significant difference was detected in the incidence of nausea and vomiting during in-hospital stay, we must consider the variability of patients' risk factors and the different number and classes of prophylactically administered antiemetics.
No complications related to TAPB administration were registered. According to literature, we believe that US-guided bilateral TAPB is a safe technique. 5 The limitations of this study are the reduced number of included patients, the retrospective nature of the study and the fact that this is a relatively novel technique in our daily institutional anaesthetic practice.

Conclusion
US-guided bilateral TAPB presents positive effects in opioid consumption, analgesia time and pain scores in unilateral breast reconstruction with TRAM but not in mastectomy (partial or total) followed by TRAM reconstruction.
An interesting aspect to study in the future is the correlation between TAPB performance and incidence of chronic pain in patients subjected to this surgery.

Conflicts of interest: None.
Financial support: None.