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Regional Anesthesia For Abdominal Surgery

By Stephen M. Anderson, M.D.

Regional anesthesia plays an important role in patient recovery. Opioid-sparing techniques show benefits including decreased length of stay (LOS), improved postoperative pulmonary function and decreased overall morbidity and mortality. This article will discuss indications for regional anesthesia for abdominal surgery, the techniques by which they are used, and the risks and benefits of each, as well as thoracic epidural analgesia (TEA), transversus abdominis plane (TAP) blocks and rectus sheath blocks.

Comparison of sensory block achieved by rectus sheath block (large black circle over abdominal midline), bilateral standard TAP block (grey semi-circle over lower abdomen), and unilateral oblique subcostal TAP block (which can vary but approximately covers the area shaded in grey in the upper abdominal quadrant)7

Thoracic Epidural Analgesia (TEA)
Open abdominal surgery is associated with significant pain that typically requires a substantial opioid regimen to control. The benefits of TEA have long been recognized, such as improved pulmonary function with decreased incidence of postoperative respiratory depression and pneumonia, increased coronary perfusion and decreased incidence of postoperative ileus. In addition to organ system-specific benefits, TEA is associated with improved pain scores, decreased opioid requirements, shortened LOS and improved mortality.1

Risks and limitations are also associated with TEA. Organ-specific risks include vasodilation and hypotension, paresthesias with placement, post dural puncture headache (PDPH), subarachnoid placement, limitations associated with anticoagulation regimens and coagulopathy, and epidural abscess and/or hematoma formation. In addition, adequate nurse education, cost of placement and management teams and time constraints must be taken into account.1 When there are significant limitations or for patients for whom TEA would be contraindicated, multimodal analgesia regimens have also been shown to have benefits.2,3

Transversus Abdominis Plane (TAP) blocks
As mentioned earlier, abdominal surgery is often associated with significant pain, and most of this pain originates from the anterior abdominal wall. Traditionally, this pain has been relieved with an opioid regimen or a combination of multimodal analgesia, which may or may not have included neuraxial analgesia. While effective at treating pain, opioids have significant side effects including nausea, sedation, urinary retention and inhibition of gastrointestinal function.4

Even thoracic epidurals, which have long been considered the gold standard of regional analgesia for abdominal surgery, are not without limitations and complications. Coagulopathy, infection at the insertion site, prior spine surgery or trauma, hypovolemia, sepsis, hemodynamic instability and patient refusal are just a few of the contraindications.5 Limitations of epidurals are also significant and include hypotension, splanchnic hypoperfusion, patient immobility and cost.4

A good multimodal analgesia regimen that adequately controls pain and minimizes the side effects of opioids is essential to an ERAS protocol for abdominal surgery. TAP blocks have been shown to decrease pain scores, decrease opioid requirements and shorten hospital length of stay in patients following laparoscopic abdominal surgery.4 However, compared to trocar site infiltration by the surgeon, TAP blocks showed no analgesic or opioid-sparing benefits.5

Limitations of TAP blocks include cost of equipment (specifically ultrasound), training of block nursing staff, accidental peritoneal puncture, accidental intravascular injection causing local anesthetic toxicity and preoperative time limitations.

Target for Local Anesthetic Infiltration during a rectus sheath block (RAM = Rectus Abdominis Muscle)

The introduction of ultrasound has greatly improved the anesthesia provider’s ability to provide regional anesthesia in general and TAP blocks specifically. The direct visualization of vessels, muscles and other structures has not only aided in the placement of local anesthesia in the correct fascial plane, but it has allowed us to minimize the complication rate of intravascular injection and peritoneal puncture.

The ultrasound probe is placed in a transverse fashion between the lower costal margin and iliac crest on the lateral abdominal wall at the midaxillary line. The abdominal muscle layers are then identified from shallow to deepest: external oblique (EO), internal oblique (IO) and transversus abdominis (TA). Deep to those are the peritoneum and bowel contents.

The needle is inserted in plane, and local anesthetic is deposited in the plane between the IO and TA. With this posterior approach, it is reasonable to expect analgesia between T10 and L1.6

If a higher level of analgesia is desired, the posterior TAP may need to be supplemented with a subcostal TAP to achieve a level up to T7. In this approach, the ultrasound probe is placed just beneath the costal margin. The needle is introduced into the fascial layer separating the rectus abdominis and the transversus abdominis.6

Rectus Sheath Block
The aim of this technique is to block the terminal branches of the T7-12 nerves, which run in the plane between the internal oblique and transversus abdominis muscles to penetrate the posterior wall of the rectus abdominis muscle (RAM) and end in an anterior cutaneous branch supplying the skin of the umbilical area. Like TAP blocks, rectus sheath blocks relieve somatic pain of the anterior abdomen and not the visceral structures. This block is more clinically useful for umbilical hernia repairs and more midline surgeries.

Like TAP blocks, care must be taken to avoid accidental peritoneal puncture. In addition, with epigastric arteries running in the midline, ultrasound with or without Doppler is recommended to avoid vascular puncture and intravascular local anesthetic injection. Local anesthetic toxicity is also a concern since this block may be combined with TAP blocks, which are high-volume blocks.

The patient is placed in the supine position, and the transducer placed in the transverse position immediately lateral to the umbilicus. Color Doppler can be used to identify the epigastric arteries. The oval shaped RAM is identified, and the needle is inserted in-plane in a medial to lateral orientation through the anterior rectus sheath. The needle is further advanced through the body of the muscle until the tip rests in the posterior rectus sheath. In an adult patient, 10 mL of local anesthetic (e.g., 0.5 percent ropivacaine) per side is usually sufficient for successful blockade.8 Since this paired muscle is separated in the midline by the linea alba, the block will need to be repeated on the other side to achieve bilateral analgesia.


References
1. Gan, TJ; et al. Enhanced Recovery for Major Abdominal Surgery. First Edition. Professional Communications, Inc. 2016. 165-168.
2. Ahmed, Aliya; Latif, Naveed; Khan, Robyna. Posteroperatiev analgesia for abdominal surgery and it’s effeectiveness in a tertiary care hospital. J Anaesthesiol Clin Pharmacol. 2013 Oct-Dec; 29(4): 472–477.
3. Rigg, John; et al. Epidural anaesthesia and analgesia and outcome of major surgery: a randomised trial. The Lancet. Volume 359: 9314. 1276–1282. April 2002 4. Ris, F; Findlay, JM; Hompes, R; Warwick; Cunningham, C; Jones, O; Crabtree,N; Lindsey, I. Addition of transversus abdominis plane block to patient controlled analgesia for laparoscopic high anterior resection improves analgesia, reduces opiod requirement and expedites recover of bowel function. Ann R Coll Surg Engl. 2014; 96: 579-585
5. Chawla, J; Schraga, E. Epidural Nerve Block. Medscape; 2015
6. Mukhtar, K. Transversus Abdominis Plane (TAP) Block. The Journal of NYSORA. 2009. 12: 28-33.
7. Webster, Katrina. Ultrasound guided rectus sheath block – analgesia for abdominal surgery. Update in Anesthesia. 2010. 12-16
8. Truncal and Cutaneous Blocks. The New York School of Regional Anesthesia. 2013. http://www.nysora.com/techniques/ultrasound-guided-techniques/3253- truncal-and-cutaneous-blocks.html

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