Regional anesthesia of the hand: ultrasound-guided vs tumescent anesthesia

Resident Clinical Pearl (RCP) – February 2018

Sean Hurley Emergency Medicine PGY1 (FRCPC), Dalhousie University, Halifax, Nova Scotia

Reviewed by Dr. David Lewis

Table 1 and 2 from Amini et al., 2016 ¹

Three major nerves, median, ulnar, and radial, provide sensory innervation of the hand (Figure 1). Each nerve needs to be blocked in a simple straightforward approach, which was shown to to be quick, safe and effective. After a 1-hour training session, residents, fellows, and staff emergency physicians had 100% success rate with no rescue anesthesia on 11 hand pathology patients presenting to the ED. The blocks were performed in a median time of 9 minutes with no complications ².

Figure 1. Cutaenous innervation of the hand. https://www.nysora.com/wrist-block

Figure 2. Indications for different nerve blocks of the hand http://highlandultrasound.com/forearm-blocks/

Radial Nerve: Palpate the radial artery in the volar aspect of distal forearm then place the US probe over the artery in a transverse orientation. Move the probe proximally until you clearly identify the radial nerve (Figure 3), which is located at the radial aspect of the radial artery. Insert your needle using an in-line approach (Figure 4). Inject 5-10cc of 1% lidocaine with epinephrine until you can clearly see the nerve bathed in lidocaine.

Pearl: The radial nerve is often difficult to visualize in the forearm. The radial nerve is more easily visualized above the elbow along the spiral groove of the humerus. Place the probe in a transverse orientation along the lateral aspect of the humerus between the brachioradialis and brachialis muscles. This block is more proximal and will require longer time to peak anesthesia.

Ulnar nerve: Use the exact same 2-step approach but on the ulnar side of the forearm. The ulnar nerve is located at the ulnar aspect of the ulnar artery (Figure 3).

Median nerve: The median nerve lies between the palmaris longus and the flexor carpi radialis. Position the probe in the transverse plane over this location. Insert your needle from either side using an in-plane or out-of-plane approach

Pearl: the median nerve and the many tendons of the distal forearm can be difficult to distinguish. You can identify the nerve by tilting the probe, which causes the tendons to disappear, as the US waves are no longer reflected back to probe, while the median nerve fibers still reflect waves back to the probe. Alternatively, you can slide the probe proximally where the tendons transition to muscle fibers, allowing the median nerve to be easily distinguishable.

Pearl: The palmar cutaneous branch of the median nerve that supplies the thenar eminence branches off before the carpal tunnel. Make sure you move the probe proximally before blocking the nerve so you don’t miss this important sensory branch.

Pearl: The more local anesthetic, the better! Some resources recommend 3-5cc of 1% lidocaine per nerve. Why not use 10cc or more for each nerve? You will still be safely under 7mg/kg limit.

Figure 3. Ultrasound identification of the ulnar nerve (left), median nerve (middle), and radial nerve (right). (Figure from Liebemann et al, 2006) ².

Figure 4. Ultrasound guided ulnar nerve block using an in-plane technique (Figure from Sohoni et al., 2016) ³.

Please see link to excellent descriptions and videos of ulnar, radial, and median US-guided nerve blocks in the ED. www.highlandultrasound.com/forearm-blocks/

Method 2: Tumescent anesthesia

Tumescent means “Swollen”. In relation to local anaesthesia, Dr. Lalonde provides the following definition in his textbook Wide-Awake Hand Surgery: “Injecting a large enough volume of local anesthetic that you can see it plump up the skin and feel its slightly firm consistency with your finger through the skin” ⁴. The tumescent anesthesia approach has been described in depth for a variety of hand surgeries ^4-6.

Using a 10cc syringe, aim for the space directly between the median and ulnar nerve (figure 5 and Video 1).  As you puncture the skin, Inject 3-5cc in the subcutaneous space. This is critical to block superficial nerves in this region, including the palmar cutaneous branch of the median nerve. Then, move your needle >3-4mm deeper through the superficial fascia in the forearm compartment where the median and ulnar nerves reside. Inject the remainder of your 10cc syringe into this space. With a single poke, the ulnar and median nerve distributions should be completely anesthetized.

Now, all that remain are the superficial branches of radial nerves and the posterior interosseus nerve. The superficial branches of radial nerve lie over the anatomical snuffbox. Insert your needle within 1cm of your previously anesthetized skin and blow local anesthesia into the subcutaneous space as you slowly move your needle towards the radial aspect of the wrist until you have a tumescent area of local anesthesia over the snuffbox. For the PIN, which is primarily a motor branch of radial nerve but has some sensory contribution, palpate the distal radial ulnar joint  of the dorsal aspect of the wrist. The PIN runs along the interosseous membrane so the needle needs to pass through the deep fascia of the forearm. Inject another 5cc of lidocaine in this location.

Figure 5. Tumescent anesthesia of the median and ulnar nerve ⁵.

Video 1. Tumescent anesthesia of the hand (courtesy of S. Hurley).

Which approach is better?

No studies have directly compared the two approaches discussed in this article. A recent Cochrane review article reviewed compared US-guided vs. anatomical landmark technique vs. trans-arterial vs. peripheral nerve stimulation for lower and upper limb blocks by trained anaesthetists. They found US-guided had greater success rates, less conversions to general anesthetic, lower rates of parathesias and vascular puncture ⁷.

A recent small randomized control trial compared US-guided nerve blocks of the forearm to anatomical landmark-based technique and found 14 of 18 ultrasound-guided forearm blocks were successful, as opposed to 10 of 18 for the anatomical technique ³.

Pearl: The tumescent anesthesia technique blocks both smaller and larger nerves of the hand and will likely achieve faster anesthesia compared to nerve blocks of the ulnar, median, and radial nerve.  Expect up to an hour for the large nerve blocks to take full effect.

Conclusions

Both methods, US-Guided nerve blocks and tumescent anesthesia are safe, effective, and relatively easy options to achieve complete anesthesia of the hand. For both techniques, remember basic principles for minimizing pain during injection of local anaesthesia to optimize patient comfort and satisfaction ^4-6.

References

1. Amini R, Kartchner JZ, Nagdev A, Adhikari S. 2016. Ultrasound‐Guided nerve blocks in emergency medicine practice. Journal of Ultrasound in Medicine 35: 731-736.
2. Liebmann O, Price D, Mills C, et al. 2006. Feasibility of forearm ultrasonography-guided nerve blocks of the radial, ulnar, and median nerves for hand procedures in the emergency department. Ann Emerg Med 48: 558-562.
3. Sohoni A, Nagdev A, Takhar S, Stone M. 2016. Forearm ultrasound-guided nerve blocks vs landmark-based wrist blocks for hand anesthesia in healthy volunteers. Am J Emerg Med 34: 730-734.
4. Lalonde D. 2016. Wide awake hand surgery, CRC Press, Taylor & Francis Group. Boca Raton, FL.
5. Lalonde DH. 2010. “Hole-in-one” local anesthesia for wide-awake carpal tunnel surgery. Plast Reconstr Surg 126: 1642-1644.
6. Farhangkhoee H, Lalonde J, Lalonde DH. 2012. Teaching medical students and residents how to inject local anesthesia almost painlessly. Can J Plast Surg 20: 169-172.
7. Lewis SR, Price A, Walker KJ, McGrattan K, Smith AF. 2015. Ultrasound guidance for upper and lower limb blocks. The Cochrane Library.

This post was copyedited by Kavish Chandra @kavishpchandra