Pain Profiles: ‘TAP IN’ – Transverse Abdominus Plane (TAP) Blocks

Author: David Cisewski, MD (@PainProfiles – EM Resident Physician, Icahn School of Medicine at Mount Sinai) // Edited by: Stephen Alerhand, MD (@SAlerhand); Manpreet Singh, MD (@MPrizzleER); Alex Koyfman, MD (@EMHighAK); and Brit Long, MD (@long_brit)

Welcome back to the Pain Profiles series from David Cisewski! This week we look at a promising nerve block: the Transverse Abdominus Plane (TAP) Block.

The Case:

A 32 year-old-male, with no known past medical history presents to the emergency department after he ‘fell down some stairs’. When asked for specific details, he refuses to discuss further, citing “rule #1 and #2”.  The patient appears mildly intoxicated but otherwise alert and oriented; intermittent tangential thought and perceived auditory hallucinations are noted by multiple staff members.   On physical exam, a clean, linear 12 cm superficial subcutaneous laceration is noted extending parallel to the midline on the right side of the abdomen. The wound is not actively bleeding and does not penetrate the underlying dermis.  Despite 975 mg acetaminophen and 15 mg IV ketorolac, the patient notes continued 9/10 pain.   A discussion is had with the patient to provide localized anesthesia using a ‘TAP Block’ which the patient agrees to.  Analgesia is achieved, the wound is sutured, and the patient is safely discharged with wound care instructions and close return precautions.

What is the TAP Block?

“TAP” is shorthand for transversus abdominis plane. The TAP sits atop the transversus abdominis muscle along the anterolateral abdominal wall, deep to the internal oblique muscle and superficial to the underlying peritoneum of the abdominal wall (image 1).  The application of regional anesthesia along this transversus abdominal plane (ie, TAP Block) is an effective way of providing localized regional anesthesia along the abdominal wall. Though historically used among anesthetists in the preoperative abdominal surgery setting (think, inguinal hernia repair) [1], TAP Blocks have also found success among patients with abdominal pathology in the emergency setting [2].  The TAP Block supplies anesthetic denervation to the T7 to L1 sensory distribution– intercostal (T7-11), ilioinguinal (L1), and iliohypogastric nerves (T12/L1) which supply sensation to the skin, muscles, and parietal peritoneum along the anterolateral abdominal wall (image 1) [3].

Image 1 – Sensory distribution and anatomy of the anterior abdominal wall – the sensory distribution of the anterior abdominal is supplied by thoracolumbar innervation (T6-L1) (left).  The nerves are situated along the transversus abdominis plane (TAP) separating the internal oblique (IO) muscle and the transversus abdominis (TA) muscle (right).

What is a TAP Block used for?

In 2012 Herring, et al described the utilization of the TAP block in the ‘Ultrasound-guided abdominal wall nerve blocks in the ED’ (Herring, 2012).  In this landmark paper, the authors described the success of the TAP block for emergency department abdominal wall pathologies such as abscesses, hematomas, surgical wounds, and inguinal hernia [1].  Worth noting, this is a lateralizing block.  That is to say, patients with wounds or abscesses that cross the midline would need bilateral TAP blocks in order to provide effective analgesia.

What supplies do I need for the block?

As with all nerve blocks there is a list of core essentials. Dr. Arun Nagdev came out with a fantastic article in ACEPNow last year (How to Implement Ultrasound-Guided Nerve Blocks in Your ED) in which he mentioned the burden of supply collection as one of the major limitations for physicians in performing nerve blocks in a busy ED.  He recommended “Block Bags” as a way to alleviate this barrier.  An example ‘block bag’ can be seen in image 2 (disclaimer – 100% of the credit for this ‘block bag’ shown here goes to Dr. Nagdev, though a major oversight in Dr. Nagdev’s setup was to not include coffee – aka, rocket fuel – for which I am a strong advocate for provider consumption prior to ALL nerve blocks!).

Image 2 – Nerve Block Set up. Each bag should include a skin marker, subcutaneous insulin injector for superficial anesthetic skin wheal, IV extension, 2 x 12 cc syringes, gauze, sponge, 18G draw needle, anesthetic of choice (bupivacaine, lidocaine).

Okay great, I’m in…. how do I block the TAP?

Variations of the ultrasound-guided TAP Block technique have been described in previous anesthesiology literature using a high-resolution linear probe [4, 5].  Note – Before any block, be sure to do an adequate safety check, neurovascular assessment, and obtain patient consent. Ideally the patient should be on a monitor and you should be well-aware of where to find lipid emulsion in the event of systemic toxicity.    A simplified step-wise approach to the TAP Block is as follows:

1) Situate patient in supine position, lying flat on the stretcher (image 3).

2) Expose the abdomen and sterilize overlying skin.

3) Use a skin marker, identify the inferior (iliac crest) and superior (inferior costal margin) landmarks.

Image 3Patient positioning and landmark identification. With patient in the supine position, use a sterile marker to label the inferior costal margin and the iliac crest which define the superior and inferior border of the TAP block location.

4) Place a linear probe transversely midway along the midaxillary line between the costal margin and the iliac crest with the probe hand resting on the stretcher and the injector hand firm against the patients iliac crest to optimize stabilization (image 4). [Butterfly Pro-tip:  With the advent of portable ultrasounds like the Butterfly, the ease of performing bedside ED blocks has increased substantially.  However, two hands are required for the block leaving you one hand short.  Instead of requesting your patient hold your phone while you stick a needle in them, invest in a GorrillaPod or similar cellphone mounting device that can be attached to an IV pole or bed rail (image 4)].

Image 4TAP Block Injection. Place linear probe (or 3-in-1 Butterfly probe as shown here) transverse along the midaxillary line.  Approach the TAP with the needle point in-plane and the dominant hand resting on the patient’s iliac crest for stabilization (left).  Orient the ultrasound screen in-plane with yourself and the ultrasound probe and your injecting hand to maximize ergonomic efficiency (right).

5) While orienting the probe transverse along the midaxillary line, identify intra-abdominal landmarks (from superficial to deep): subcutaneous tissue/adipose => external oblique (EO) => internal oblique (IO) => transverse abdominis (TA) above the peritoneum.Your target is the hyperechoic fascial plane between the IO and TA (ie, TAP) (see image 5A) [Tip: the best ergonomic approach is to orient the probe, the hand administering the injection, and the ultrasound viewing screen to be along the same line of sight to maintain optimal safety and efficacy).

Image 5Layers involved in TAP Block localization. From superficial to deep: subcutaneous/adipose, external oblique (EO), internal oblique (IO), transversus abdominis plane, transversus abdominis, and the underlying peritoneum.  The directionality of needle for the in-plane approach with visualization of hypoechoic wheal at the injection site (right) (images captured with Butterfly Ultrasound).

6) Using a 3.5 inch 22G spinal needle (or the longest needle you have), approach the TAP in-plane (parallel to long axis of linear probe) for full needle visualization throughout the block, following the directed needle tip so as to avoid bowel perforation (image 5 – left).

7) Following negative aspiration, inject small 3cc aliquots of anesthetic to visualize the spreading of the fascial plane (image 5 – right; actual nerves will not be identified with ultrasound but exist along the plane). Always know where your needle tip is – if you do not see an anechoic ballooning of the injected anesthesia stop immediately and locate needle tip to ensure you are not injecting intravascularly.

8) Once plane is confirmed, continue anesthetic injection and visualize the spread of the fascial plane as a full 20-30cc anesthetic is injected (so as not to reinvent the wheel, see this great video on the TAP Block by Jacob Avila at 5MinSono).

Ultimately the anesthetic will spread along the facial plane, bathing the surrounding nerves that innervate the anterior abdominal wall.  Learning point – a plane block is different than a peripheral nerve block. Plane blocks require higher volumes of anesthetic to spread across the entire plane whereas peripheral nerve blocks (eg, radial or ulnar nerve block) can be accomplished with much small volumes.  Note, the success of the TAP block is dependent on the user’s ability to identify this fascial plane between the IO and TA.  [Expert tip from Jake Avila of 5MinoSono: if the planes are challenging to distinguish, ‘start low, go high’ – i.e., visualize the bowel, move up to the peritoneum, and then to the TAP].

Which anesthetic should I be using for TAP blocks?

This is user preference and a number of alternatives are available.  The goal of a TAP Block is long-acting pain relief, which can be accomplished with bupivacaine or ropivacaine.  Higher volumes of more dilute anesthetic (0.5% vs 0.75% bupivacaine) allow for more efficient spread across the fascial plane (NYSORA, 2018).

What are the risks/adverse effects?

You’re sticking a needle into the stomach…. The risk of bowel perforation, bowel wall hematoma, or liver laceration are possible [6].   And as with all nerve blocks, there is always the risk of infection, hematoma formation, bleed, nerve injury, and lidocaine-associated systemic toxicity (LAST) which can be minimized with proper (sterile) technique and ultrasound guidance[7].  A lesser described adverse effect, though equally important, is failure to obtain analgesic effect (due to missed target) which can delay ED stay and pain management up to an hour while waiting for anesthetic effect.

Any new research on the TAP block?

Mahmoud, et al (including several members of the original ED TAP Block team at Highland Hospital) want you to know that TAP Blocks may not be for just superficial abdominal injuries any more [8].  A recently released case report based on their experience explains that acute appendicitis may be the next target (I’ve been name-dropping this as the ‘Appie TAP’in the hopes it catches on).

What did this study look at (patients and intervention)?

This was a small case series based using a multidisciplinary protocol established at Highland Hospital between the general surgery department and the ED that includes the TAP block in the pre-surgical analgesic protocol for appendicitis.   Three separate patient case reports were described with the use of an Ultrasound-Guided TAP Block (20 to 30 cc long acting anesthetic) for patients suffering from visceral pain secondary to a radiologically-confirmed appendicitis.

What were the outcomes?

In each of the 3 cases, complete pain relief and reduced need for rescue analgesia was described following the TAP Block and continued pain relief until patients were taken to surgery.  No complications or adverse side effects were described in each of the 3 cases.

Authors conclusions on the study:

The ultrasound-guided TAP block could be an effective analgesic method for patients in the emergency department diagnosed with acute appendicitis and an alternative to the classic monomodal approach using opioids.

The Upshot:

First, this is a fantastic example of the emergency and surgery team working together to provide a patient-centered analgesic plan and continued care during the transition from the ED to the inpatient stay. Any chance to collaborate on pain management is a win for the field of medicine.

A word on the pathophysiology. The hypothesized effectiveness of this block is based on the ability to relieve referred pain from the abdominal viscera. The superficial sensory fibers that converge with the visceral afferent sensory fibers enter the spinal cord at the same level and preventing the propagation of intrabdominal pain signaling occurs by blocking the overlying sensory fibers we ‘refer’ to (i.e., referred pain) in these presentations.

A word on safety.  There is the looming, undeniable risk of abdominal perforation with the TAP Block as previously mentioned. Though reduced with ultrasound guidance, we’re talking about a patient with appendicitis who may be writhing on the stretcher and doesn’t have a fluid buffer zone we may see in our patients with ascites receiving paracentesis.  Particularly in thin patients, the margin of error may be anxiety-provoking (especially if you overdosed on your pre-block coffee bolus).  No injuries or adverse effects were reported in this case series.

A word on analgesia.  In each of these cases, complete resolution of pain was obtained following the block. However, it’s worth noting that each of the three patients received pre-block IV hydromorphone (1 or 2 mg), one patient received an additional 1,000 mg IV acetaminophen (1,000 mg) prior to the block, and one of the three patients received an additional 1 mg hydromorphone following the TAP Block for pain relief.  I’m not calling into question the use of hydromorphone in situation – I believe opioids serve a purpose in moderate to severe emergency pain presentations–  but I am having a hard time parsing out what portion of the analgesic relief should be attributed to the block itself.  Additionally, I would be interested in knowing how many times this block was unsuccessful in eliminating appendicitis-induced abdominal pain (unreported in this case series).

A word on TAP block in appendicitis. I admit I have never had appendicitis  or any other intraabdominal surgical pathology so I can’t speak to the level of pain associated with it.  However, I can attest to the TAP block as being a relatively painful procedure in an already sensitive area of the abdomen – I’ve had rib fractures that hurt less than this (note – I make a point to experience the nerve blocks I offer to my patients as I wouldn’t expect a patient to tolerate a procedure I wouldn’t tolerate myself).  As part of the research Friedman, et al conducted on the greater occipital nerve block for migraines, they assessed how many of the patients would want the same treatment again (recall, only about 40% of the patients wanted the great occipital nerve block again in future visits).  I would be curious how many of these patients be willing to be TAP Blocked twice.

Bottomline, I love the idea of the “Appie TAP” and will incorporate it in my own practice going forward as an adjunct analgesic. Congrats to Dr. Mahmoud, et al on these findings – I look forward to more great work like this from the Highland team in the future.

 

TAP Block Summary

  • Uses– abdominal wall pathologies; abscesses, hematomas, surgical wounds, and inguinal hernia; possibly appendicitis
  • Nerves blocked– the T7 – L1 sensory distribution (abdominal wall)
  • External landmarks– midaxillary line between inferior costal margin and iliac crest
  • Internal landmarks– adipose, external oblique (EO), internal oblique (IO), transverse abdominus, transverse abdominus plane, and the underlying peritoneum
  • Complications– abdominal perforation, infection, intravascular injection

Further Reading

References

  1. Rafi, A.N., Abdominal field block: a new approach via the lumbar triangle. Anaesthesia, 2001. 56(10): p. 1024-6.

  2. Herring, A.A., M.B. Stone, and A.D. Nagdev, Ultrasound-guided abdominal wall nerve blocks in the ED. Am J Emerg Med, 2012. 30(5): p. 759-64.

  3. Rozen, W.M., et al., Refining the course of the thoracolumbar nerves: a new understanding of the innervation of the anterior abdominal wall.Clin Anat, 2008. 21(4): p. 325-33.

  4. McDonnell, J.G., et al., The analgesic efficacy of transversus abdominis plane block after abdominal surgery: a prospective randomized controlled trial. Anesth Analg, 2007. 104(1): p. 193-7.

  5. Hebbard, P., et al., Ultrasound-guided transversus abdominis plane (TAP) block. Anaesth Intensive Care, 2007. 35(4): p. 616-7.

  6. Farooq, M. and M. Carey, A case of liver trauma with a blunt regional anesthesia needle while performing transversus abdominis plane block. Reg Anesth Pain Med, 2008. 33(3): p. 274-5.

  7. Jankovic, Z., et al., Transversus abdominis plane block: how safe is it?Anesth Analg, 2008. 107(5): p. 1758-9.

  8. Mahmoud, S., et al., Ultrasound-guided transverse abdominis plane block for ED appendicitis pain control. Am J Emerg Med, 2019.

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