Intra- and postoperative pain associated with abdominal surgery has been treated with various methods depending on the type of surgery, its extent and individual sensitivity of a patient. A considerable component of pain following abdominal procedures is derived from the incision of abdominal wall. The blockade of the sensory nerves supplying the anterior abdominal wall was attempted in the past; yet due to the lack of clearly defined anatomic landmarks and some procedure-related doubts, such attempts have been abandoned for some time.

The technique described by McDonnell and co-workers [1] appears to be simple and effective for the management of pain after abdominal surgeries. The technique is based on the blockade of the sensory nerves supplying the skin, muscles and partially the peritoneum of the anterior abdominal wall. This blockade combined with general anaesthesia is the method substantially reducing pain sensations following abdominal surgery.

This form of anaesthesia alone is not sufficient to carry out the surgery but as an additional method, it is a valuable measure to relieve intra- and postoperative pain.

The most common indications for transversus abdominis plane (TAP) block include additional anaesthesia for surgeries of the lower abdomen, in particular inguinal hernia, Caesarean section, laparoscopic procedures, cholecystectomy, or partial enterectomy, in which epidural anaesthesia cannot be used. The TAP block is a quite novel method and not all its assets and drawbacks are known; therefore, the indications for the block are likely to be modified with time. The absolute contraindications include: lack of patient`s consent, allergy to local anaesthetics, or block site infection. The relative contraindications are coagulopathy, therapy with anticoagulants and sepsis.

The abdominal wall consists of three muscle layers: the external oblique, internal oblique and transversus abdominis with the fascias. The central part contains the rectus abdominis muscle with its associated fascia.

The skin, muscles and some part of the peritoneum of the anterior abdominal wall are supplied by six inferior thoracic nerves (Th7-Th12) and the first lumbar nerve (L1). The anterior descending branches of these nerves leave through the intervertebral foramina, run above the transverse process, pierce the muscles of the lateral abdominal wall and run in the neuro-fascial plane between the internal oblique and transverse abdominal muscles. The sensory fibres of nerves in the mid-axillary line send first the lateral skin branch and further pierce the rectus abdominis muscle where they send the anterior branch and supply the skin up to the midline [2] (Fig. 1).

Based on anatomical studies, the optimal place for the block was determined, called the triangle of Petit. This triangle is bounded posteriorly by the latissimus dorsi muscle, anteriorly by the external oblique abdominal muscle, with the iliac crest forming its base [3] (Fig. 2).

The triangle sides are landmarks easy to identify in patients in recumbent position: first, we should find the iliac crest and advance until the boundary of the latissimus dorsi muscle is felt. The triangle of Petit is located anteriorly to the muscle (Fig. 3). After identification of this point, the needle is introduced cephalad from the iliac crest above the triangle of Petit (Fig. 4). Having pierced the skin, the needle is advanced until first resistance is felt; after overcoming it with a characteristic “click”, the needle is in the space between the external and internal oblique fascias and is advanced overcoming another resistance with a characteristic “click” and entering the target place, i.e. between the internal oblique and transverse abdominal muscles.

To perform the block, the following are needed: 40 mL of a local anaesthetic (20 mL for unilateral anaesthesia), two 20 mL syringes, one 5 mL syringe, sterile gloves, surgical mask and gauze swabs, disinfectant, a 22 G short bevel needle, 2-2.5 cm long. In cases of ultrasound-guided blocks, the ultrasound apparatus with the linear probe 8.5-12 MHz and additional equipment is needed as well as a 22 G short bevel needle, 10-15 cm long. The anaesthesia is induced using 0.375% or 0.25% bupivacaine, 0.75% or 0.5% ropivacaine and 0.375% levobupivacaine. Each anaesthetized side is injected with 20 mL (max. 1 mg kg-1 each) aspirating after successive 5 mL of the drug.

The classical technique of anaesthesia based on two “clicks” is simple and does not require sophisticated equipment [2]. However, since its first descriptions, several modifications have been introduced, including the ultrasound-guided option. The  visualization of anatomic structures in real time may prevent improper placement of the needle outside the muscles (behind the peritoneum) or the puncture of the organs situated there. Moreover, the local anaesthetic spread within the tissues may be supervised. The use of ultrasonography is associated with substantially increased costs and requires trainings, particularly in utrasonographic anatomy of the anaesthetized  region.

The patient should be placed in the supine position. The site of needle insertion is on the upper surface of the abdomen next to the external border. The needle after piercing the skin should be ultrasonographically visible. The needle is introduced into the tissues parallel to the position of the head up to the space between the internal oblique and transverse abdominal muscles (Fig. 5). After aspiration, 1-2 mL of the anaesthetic is injected, which results in ultrasonographically visible separation of the space between those two muscles (Fig. 6) and the remaining anaesthetic dose can be administered (20 mL for each side).

Depending on the injection site, transverse abdominal block is divided into three types of various ranges of anaesthesia. The posterior  access (the classical injection site) –  the range of anaesthesia is the lateral and anterior abdominal part up to the level of the umbilicus (Fig. 7), subcostal access – the range of anaesthesia is the lateral and anterior abdominal part from the umbilicus to the Th7 level (Fig. 8), and subcostal oblique access – the  biggest range involving both regions mentioned above (Fig. 9) [4, 5].

The differences in the extent of anaesthesia between the classical and ultrasonography-guided method result from the completely different skin injection sites and needle courses.

The TAP block complications reported are infection, haematoma, nerve injuries, symptoms of toxic action of the local anaesthetic (related to its administration into the vessel or too high dose), puncture of the peritoneal cavity, intestine perforation, puncture of the liver [1]. Moreover, there is a risk of patient`s injury (fall) if he/she is ambulated too early and the range of block involved the nerves supplying the buttock, lateral thigh or the region supplied by the femoral nerve.

The available literature reports evidence that the method is beneficial for patients after abdominal surgery. Thanks to this method, the overall demands for morphine were reduced and intervals between successive doses were prolonged. The postoperative pain severity was substantially lower within the first 24 h after surgery compared to procedures without the block. Furthermore, the incidence of nausea and vomiting was lower [7]. Similar benefits after TAP block were observed in patients undergoing Caesarean sections [6].

It is worth stressing that the method in question may be used in patients with contraindications for epidural anaesthesia. Obviously, the TAP block cannot replace epidural anaesthesia yet some drawbacks of the latter, e.g. the risk of decreased arterial pressure, may contribute to increasingly wide recognition of this new method.

The use of ultrasonography during TAP blocks may contribute to the reduction of potential risks related to it. Access to penetrated tissues in real time facilitates the identification of the site where the local anaesthetic should be administered and provides higher efficacy of complete abdominal block.

The TAP block should soon win acclaim of anaesthesiologists and patients undergoing abdominal surgeries.

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REFERENCES

1.   McDonnell JG, O’Donnell BD, Tuite D, Farrell T, Power C: The regional abdominal field infiltration (R.A.F.I.) technique: Computerised tomographic and anatomical identification of aapproach to the transversus abdominis neuro-vascular fascial plane. Anesthesiology 2004; 101: 899.

2.   McDonnell JG, O’Donnell BD, Curley J, Carney J, Benton A, Costello J, Maharaj CH, Laffey JG: The analgesic efficacy of transversus abdominis plane block after abdominal surgery. Anesth Analg 2007; 104: 193-197.

3.   McDonnell JG, O’Donnell BD, Farrell T, Gough N, Tuite D, Power C, Laffey JG:

4.   Transversus abdominis plane block: aand radiological evaluation. Reg Anesth Pain Med 2007; 32: 399-404. Hebbard P: Subcostal transversus abdominis plane block under ultrasound guidance, Anesth Analg 2008; 106: 674-675.

5.   Hebbard P: Ultrasound-guided transvesus abdominis plane (TAP) block. Anaesth Int Care 2007; 35: 616-617.

6.   Farooq M, Carey M: Aof liver trauma with ablunt regional anesthesia needle while performing transversus abdominis plane block, Reg Anesth Pain Med 2008; 33: 274-275.

7.   McDonnell JG, O’Donnell B, Curley G, Heffernan A, Power C, Laffey JG: The analgesic efficacy of transversus abdominis plane block after abdominal surgery: arandomized controlled trial. Anesth Analg 2007; 104: 193-197.

8.   McDonnell JG, Curley G, Carney J, Benton A, Costello J, Maharaj CH, Laffey JG: The analgesic efficacy of transversus abdominis plane block after cesarean delivery: acontrolled trial. Anesth Analg 2008; 106: 186-191.

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Address:

*Leszek Urbańczak
Oddział Anestezjologii i Intensywnej Terapii
Szpitala Wojewódzkiego w Zielonej Górze
ul. Zyty 26, 65-046 Zielona Góra
tel.: 0-68 329 63 49

Received: 24.04.2009
Accepted: 07.07.2009