In 1884 Carl Koller published his work on local anesthesia with cocaine for eye surgery.
Within a year over 60 reports on the use of local anesthesia with cocaine were published in the US and Canada.1 Many surgeries were now to be performed with local infiltration.
Almost 140 years after we must debate if wound infiltration is good enough. Where did we go wrong?
The transversus abominis plane (TAP) block was first described as landmark based block by Rafi in 2001.2 An ultrasound guided (USG) approach was described by Hebbard in 2007.3 In ASRA second assessment on ultrasound guided regional anesthesia4 evidence-based recommendation for USG TAP blocks was given a Grade of Recommendation A, with a la-IIb level of evidence. There are studies providing information that landmark based truncal blocks may achieve around 70% of success, while ultrasound view allows a correct injection in the fascial plane, allowing a larger success. TAP block has thus evolved to a better understanding of its anatomy and performance using ultrasound guided techniques.
When we look at studies comparing TAP blocks to wound infiltration, have we been fair to the latter? A freshly evolved technique compared to a rusty version of the first local anesthesia infiltrations?
Kingsnorth in appealing to Local Anesthesia (LA) as the gold standard technique for Inguinal hernia repair, is very clear to recognize that ‘The LA technique has a learning curve that requires specific training’.5 On one side we have enthusiastic regional anesthetist doing state of the art TAP blocks, and on the other side do we have the same enthusiastic surgeon doing wound infiltration, recognizing the correct place and technique for wound infiltration?
Wound infiltration technique should consider not only the skin but the meticulous injection of all planes under direct vision. Even skin infiltration may not be as simple. An injection to shallow in the dermis may be too painful in an awake patient and deep subcutaneous may have a slower response. Just deep to the dermis in the superficial subcutaneous zone should be preferred.6
For surgery involving the abdominal wall, muscle layer seems to be more important to block than the superficial layers. The muscle layer may be infiltrated between the peritoneum and muscle or below the muscle fascia after it has been closed. Wound catheter placed between de peritoneum and the muscle have lower pain scores.7 Volume of infiltration is important too. In a publication of over 100.000 inguinal hernia repair using local anesthesia, the author reports the use of 150ml of total infiltration 80-100ml injected as a subcutaneous regional infiltration and 20 ml underneath the external oblique fascia and a similar amount around the internal ring.8
Despite this disadvantage, I will present a short review of current guidelines and latest evidence on the use of wound infiltration where it may be compared to TAP blocks. I will focus on 4 clinical settings: Midline laparotomy, Laparoscopic colorectal surgery, Inguinal hernia, and Cesarean section.
Midline laparotomy In a systematic review and network meta-analysis, epidural, abdominal wall blocks (AWB) (this included TAP or rectus sheath block with and with continuous injection), wound infiltration with and with continuous injection and control patients were compared.9 Primary outcome was pain at 24 hours: with a minimal significant difference of 1, epidural analgesia was clinically superior to control and single-shot AWB; epidural was statistically but not clinically superior to continuous wound infiltration (WI); and no statistical or clinical difference was found between control and single- shot AWB. For morphine consumption at 24 hours with a minimum clinical difference of 10 mg, epidural and continuous AWB were clinically superior to control; epidural was clinically superior to continuous WI, single-shot AWB, single-shot WI; and continuous AWB was clinically superior to single-shot AWB. According to this study, single injection TAP block or single injection wound infiltration are of little benefit, and a continuous technique should be selected, probably an epidural, if not, either continuous AWB or continuous wound infiltration.
Laparoscopic Colorectal Surgery
ERAS Society’s 2018 recommendation guidelines for perioperative care in colorectal elective surgery gives a strong recommendation for TAP blocks in minimal invasive surgery with moderate evidence.10 A randomized trial comparing wound infiltration plus TAP block or no TAP, found that adding TAP block did not augment wound infiltration analgesia.11 A nonrandomized direct comparison between TAP and wound infiltration was published in 2015.12 There was no difference in pain scores, between both groups but less opioid consumption at 24 and 48 hours for TAP. However, this was not associated with less opioid side effects. A more recent randomized trial comparing TAP and WI found no difference at all, suggesting WI should be preferred because of less technical difficulties.13
For some, this should be a surgery done with LA.5 But perhaps because of inadequate teaching of local infiltration, patients’ expectations or other, surgery is done in many places with general anesthesia or spinal. Landmark-based peripheral blocks have shown to benefit postoperative analgesia when surgery is done under spinal anesthesia14 as wound infiltration before incision or at closure provide better analgesia than no intervention.15
Iliohypogastric-Ilioinguinal (which I accept as a surrogate to a TAP for this surgery) was found to provide better analgesia in a pediatric population.16 In another study comparing USG TAP, caudal block, and wound infiltration,17 caudal and wound infiltration, TAP resulted in an effective longer lasting analgesia, and wound infiltration was found to be a poor alternative. 3 other trials show mix results: no difference, Tap better and WI better. Please take note poor description on local infiltration in all these studies and perhaps low volume on injection. Prospect recommendations for open inguinal hernia repair includes, on top of multimodal pharmacological analgesia, local infiltration analgesia and or a regional analgesia technique (Ilioinguinal or TAP).18
Cesarean Section For this topic, I shall only point out a recent systematic review and meta-analysis of randomized trial. Riemma et al19 found 5 trials meeting inclusion criteria. TAP block technique was homogenous throughout studies, Wound infiltration had a larger variation in technique volume and in 2 cases included wound catheters. Results show no difference in cumulative opioid consumption, no difference in pooled pain scores, no difference in adverse effects, no difference in patient satisfaction either. ESRA-Prospect recommendations state as the regional analgesia technique of choice for cesarean section the use of intrathecal morphine. However, in the event that intrathecal morphine cannot be used, wound infiliteration with local anesthetics(single-shot) or continuous wound infusion and/or regional analgesia techniques such as TAP blocks, quadratus lumborum blocks and erector spinae plane blocks) are recommended (Grade A) for their effect in reducing pain scores and opioid requirements.20
In summary, evidence suggests that single shot TAP blocks and Wound infiltration provide similar benefits in the more common surgeries. Although WI being seemingly more simple and technically easier to do, I recommend caution. USG TAP are most often performed by anesthesiologist who have trained in the technique, use state of the art ultrasound guidance and take time for proper injection in the correct site, while wound infiltration nowadays may lack of all this conditions: not being taught thoroughly, no injection site precision, no evidence on volume to be injected. But despite these fact, WI still manages to the job fairly well.
History of the Development and Evolution of Local Anesthesia Since the Coca Leaf Calatayud J, González A. Anesthesiology 2003;98:1503–8.
Abdominal field block: a new approach via the lumbar triangle. Rafi AN. Anaesthesia 2001;56(10):1024e6.
Ultrasound-guided transversus abdominis plane (TAP) block P. Hebbard, Y. Fujiwara, Y. Shibata, et al. Anaesth Intens Care, 2007;35(4):616-617.
The Second American Society of Regional Anesthesia and Pain Medicine Evidence-Based Medicine Assessment of Ultrasound-Guided Regional Anesthesia. Executive Summary. Neal J, Brull J, Horn JL et al. Reg Anesth Pain Med 2016;41:181–194.
Local Anesthetic Hernia Repair: Gold Standard for One and All. Kingsnorth A. World J Surg 2009;33:142–144.
Updates on Wound Infiltration Use for Postoperative Pain Management: A Narrative Review. Stamenkovic DM, Bezmarevic M, et al. J. Clin. Med. 2021;10:4659.
Preperitoneal or Subcutaneous Wound Catheters as Alternative for Epidural Analgesia in Abdominal Surgery A Systematic Review and Meta-analysis. Mungroop TH, Bond MJ, et al. Ann Surg 2019;269:252–260.
Inguinal hernia repair using local anaesthesia. Glassow F. Annals of the Royal College of Surgeons of England 1984;66:382.
Comparison of analgesic modalities for patients undergoing midline laparotomy: a systematic review and network meta- analysis. Howle R, Ng S. Can J Anesth 2022;69:140–176.
Guidelines for Perioperative Care in Elective Colorectal Surgery: Enhanced Recovery After Surgery (ERAS) Society Recommendations: 2018. Gustafsson UO, Scott MJ et al. World J Surg 2019;43:659–695.
Analgesic efficacy of pre-emptive local wound infiltration plus laparoscopic-assisted transversus abdominis plane block versus wound infiltration in patients undergoing laparoscopic colorectal resection: results from a randomized, multicenter, single-blind, non-inferiority trial. Pedrazzani C, Park SY et al. Surgical Endoscopy 2021;35:3329–3338.
Effect of local wound infiltration and transversus abdominis plane block on morphine use after laparoscopic colectomy: a nonrandomized, single-blind prospective study. Park JS, Choi G et al. Journal of Surgical Research 2015;195:61e66.
Transversus Abdominis Plane Block Versus Local Wound Infiltration for Postoperative Pain After Laparoscopic Colorectal Cancer Resection: a Randomized, Double–Blinded Study. Ren L, Qin P, et al. Journal of Gastrointestinal Surgery 2022;26:425–432.
Preoperative percutaneous ilioinguinal and iliohypogastric nerve block with 0.5% bupivacaine for post-herniorrhaphy pain management in adults. Bugedo GJ, Cárcamo CR, et al. Reg Anesth 1990 May-Jun;15(3):130-3.
Effects of levobupivacaine infiltration on postoperative analgesia and stress response in children following inguinal hernia repair. Cinar SO. Kum U, et al. European Journal of Anaesthesiology 2009;26:430–434.
Comparison of Ultrasoundguided Ilioinguinal Iliohypogastric Nerve Block with Wound Infiltration during Pediatric Herniotomy Surgeries. Karim W, Bathla S et al. Anesth Essays Res. 2020 Apr-Jun;14(2): 243–247.
Is Ultrasound-Guided Transversus Abdominis Plane Block Superior to a Caudal Epidural or Wound Infiltration for Intraoperative and Postoperative Analgesia in Children Undergoing Unilateral Infraumbilical Surgery? A Double-blind Randomized Trial. Rautela MS, Sahni A. J Indian Assoc Pediatr Surg. 2022 May-Jun;27(3):323–328.
Pain management after open inguinal hernia repair: an updated systematic review and procedure-specific postoperative pain management (PROSPECT/ESRA) recommendations. Coppens S, Gidts J. Acta Anaesthesiologica Belgica 2020;71:45-56.
Transversus abdominis plane block versus wound infiltration for post-cesarean section analgesia: A systematic review and meta-analysis of randomized controlled trials. Riemma G, Schiattarella A et al. Int J Gynecol Obstet. 2021;153:383–392.
PROSPECT guideline for elective caesarean section: an update. Roofthooft E, Joshi GP et al. Anaesthesia 2023 Apr 27. doi: 10.1111/anae.16034. Online ahead of print.
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