Continuous subcostal oblique transversus abdominis plane block provides more effective analgesia than single-shot block after gynaecological laparotomy

Editor, The transversus abdominis plane (TAP) block provides good analgesia in patients after abdominal surgery.1 However, the duration of the single-shot TAP block postoperatively varies across studies.1–3 The duration of analgesia can be prolonged by adding a continuous local anaesthetic infusion.4–6 We conducted a prospective, randomised, controlled, observer-blinded trial to compare the efficacy of continuous TAP block and single-shot TAP block in patients undergoing elective open gynaecological cancer laparotomy. The study was performed after obtaining ethical approval (Ethical Committee number 12088-3) from the Institutional Review Board (Clinical Research at Osaka University Hospital, Chairperson Prof Y. Yamamoto) on 13 September 2012 and written informed consent from the participants, and was registered with the University Hospital Medical Information Network (UMIN000008949). Patients aged 20 to 80 years were enrolled in the study and randomly assigned to the continuous or the single-shot TAP group. All patients received a standardised general anaesthetic regimen with multimodal analgesia. Intravenous (i.v.) flurbiprofen (50 mg) was given at the time of wound closure. Fentanyl i.v. (10 μg h-1) was administered postoperatively and the dosage was increased to 30 μg h-1 according to the intensity of continuous pain at rest. Rescue analgesia for breakthrough pain was provided with a fentanyl bolus (30 μg) or, in the case of nausea, 50 mg of i.v. flurbiprofen. Metoclopramide i.v. (10 mg) was given for persistent nausea or vomiting. Patients with treatment-resistant nausea received lower doses of fentanyl on request. All patients were asked to ambulate with the assistance of the attending nurse 12 h postoperatively. If they were unable to stand or walk, the attempt was re-scheduled by consulting the ward doctor. All patients received bilateral ultrasound-guided TAP injections after wound closure. Blocks were performed with 'subcostal oblique TAP block with hydrodissection'1,4 modified according to the surgical incision. The block commenced near the costal margin passing towards the iliac crest, and a hydrodissection pocket was made crossing the anterior cutaneous branches of the multiple thoracoabdominal nerves. The pocket length was adjusted to provide analgesia to the entire incision. During hydrodissection, patients received 20 ml of levobupivacaine 0.25% or 40 ml of levobupivacaine 0.125% on each side (total dosage, 100 mg levobupivacaine; total volume, 40 or 80 ml, according to the length of the pocket). For patients in the continuous TAP group, a catheter (Perifix; B-Braun Medical, Bethlehem, Pennsylvania, USA) was passed through the needle after the initial injection. Catheter placement was confirmed by the injection of air bubbles through the catheter and the subsequent detection of the high echoic area on an ultrasound image. Two separate catheters were placed bilaterally in the caudal direction with the tip near the iliac crest, and the entry site was covered by gauze for blinding. In addition, 0.1% levobupivacaine (6 ml h-1 per side for a total dosage of 12 ml h-1) was provided for 24 h through the catheter. For patients in the single TAP group, a sham catheter was taped near the initial injection site and bandaged for blinding. Surgical incision length was recorded as either 'below' or 'above' the umbilicus according to the cranial end of the incision. We compared pain intensity using a visual analogue scale (VAS) at rest and on movement, cumulative fentanyl and flurbiprofen consumption, incidence of postoperative nausea and vomiting (PONV) and time to ambulation. Patients were interviewed at 6, 15 and 24 h postoperatively by observers blinded to group allocation. VAS scores were assessed using two-way analysis of variance (ANOVA) with repeated measures. A posthoc test using Tukey's honestly significant difference test was performed when there was significance. Other continuous variables were assessed using Student's t-test. Categorical variables were assessed using a χ2 test. Of the 90 patients eligible for the study, 80 were randomised, thus there were 40 patients in each group. Finally, 38 and 37 patients were analysed in the single-shot and continuous TAP block groups, respectively. Reasons for exclusion were reoperation, massive bleeding, allergies and patient refusal to follow-up. The two groups did not differ in age, body weight, height or duration of surgery. Sixteen and 10 patients in the continuous and single TAP groups, respectively, had incisions extending above the umbilicus (P = 0.12). We had no complications due to the TAP block procedures. The outcomes are summarised in Table 1. VAS on movement did not differ between the two groups at different time points except for the values obtained after 24 h, being lower in the continuous TAP group (P = 0.004).Table 1: Outcomes in patients receiving single or continuous transversus abdominis plane blockAmbulation is one of the most painful activities after abdominal surgery. In our study, the lower VAS scores on movement observed 24 h postoperatively in the continuous TAP group may be attributed to the prolonged analgesia provided by the continuous TAP block, as fentanyl consumption did not differ between the two groups. As the positioning and length of the hydrodissection pocket could be easily modified according to the surgical wound, the subcostal oblique TAP block was ideal for catheter insertion. There are several limitations to this study. First, the adjustment of fentanyl infusion rate and combined use of flurbiprofen might eliminate the differences in VAS scores at rest and make comparisons of individual analgesic consumption difficult. Because this approach could not prevent PONV in all cases, opioid dose reduction and other analgesics were needed in such situations. Second, the surgical procedure and extent of incision were often modified and determined by the spread of disease and findings during surgery. Third, conventional methods for evaluation of sensory block, such as the cold test or pinprick test, could not be performed because of the dressing film and gauze for blinding. Hence, we tried to test sensory block by palpation. Continuous TAP block seems to provide better postoperative analgesia. However, objective methods of assessing the sensory block are preferable and may provide more accurate results. In conclusion, under the present experimental design, continuous TAP block performed for gynaecological laparotomy provided better analgesia in terms of pain intensity on movement and perhaps ambulation 24 h postoperatively than the single-shot TAP block. Acknowledgements relating to this article Assistance with the letter: We are grateful to all the study participants, nurses, anaesthesiologists, gynaecologists and other staff who made the study possible. Financial support and sponsorship: none. Conflicts of interest: none.