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Anaesthesia - Digital nerve block

Indications

Digital pain (from injury or procedure)

Contraindications (absolute in bold)

Vascular compromise

Infection at the site of injection

Allergy to local anaesthetic agents

Alternatives

Local infiltration of local anaesthetic

Other regional nerve blocks

Informed consent

Verbal consent

Less complex non-emergency procedure with low risk of complications

Potential complications

Failure

Vasovagal reaction on insertion (syncope)

Allergic reaction

Pain at injection site

Haematoma (particularly if anticoagulated)

Nerve damage

Infection introduced by infiltration

Procedural hygiene

Standard precautions

Aseptic non-touch technique

PPE: non-sterile gloves

Area

Any clinical space

Staff

Procedural clinician

Equipment

5ml syringe and drawing up needle

23g needle for the adult injection

25g needle for paediatric injection

Positioning

Supine or sitting

Limb supported on a flat surface at working height for proceduralist

Injections made through the dorsal surface of the finger just distal to the MCP

Medication

2-5ml lignocaine 1-2% without adrenaline (duration 40 minutes)

2-5ml bupivacaine 0.25% (duration several hours)

1% means 10mg per ml (i.e. a 100% solution is 1000mg in 1ml)

For lignocaine 1%, the 3mg/kg maximum dose is approximately 20ml for a 70kg adult

For bupivacaine 0.25%, the 2mg/kg maximum dose is approximately 50ml for a 70kg adult

Sequence (dorsal approach)

Insert the needle on the dorsal aspect of the finger proximal to the finger web and distal to knuckle

Inject 0.5-1ml subdermally (blocking dorsal digital nerve)

Advance the needle along the bone until the palmer skin tents

Inject 0.5-1ml subdermally (blocking volar digital nerve)

Repeat on the opposite side of the finger

Massage the area for 30 seconds to enhance diffusion of anaesthetic

Wait five minutes for block to become effective

Test sharp sensation prior starting the surgical procedure

Post-procedure care

Inform patient the area may remain numb for up to six hours (bupivacaine)

Document the procedure and any immediate complications

Tips

Higher concentrations can reduce injection volume and discomfort

Cardiac monitoring is recommended for multiple infiltrations of anaesthetic (greater risk of toxicity)

Always confirm the dose of local anaesthetic is within safe limits

Discussion

Digital nerves can be blocked anywhere along their course including sites on the finger, in the webspace and between the metacarpals of the hand.

We have suggested the dorsal approach due to the advantage of thinner, less pain-sensitive skin than encountered on the volar approach. Our generally preferred site is just proximal to the finger webs, due to consistent nerve location and greater soft tissue to accommodate local anaesthetic. More proximal injections between the metacarpals may be required for some injuries.

Peer review

This guideline has been reviewed and approved by the following expert groups:

Emergency Care Institute

Please direct feedback for this procedure to ACI-ECIs@health.nsw.gov.au.

References

Australian and New Zealand College of Anaesthetists. Guidelines for the management of major regional analgesia. PS03. Melbourne, Vic: ANZCA; 2014. Available from: http://www.anzca.edu.au/documents/ps03-2014-guidelines-for-the-management-of-major-r.pdf

NSW Agency for Clinical Innovation. Local and regional anaesthesia. Sydney: ACI; 2019 Sep 2. Available from: https://aci.health.nsw.gov.au/networks/eci/clinical/clinical-resources/procedures/local

Roberts JR, Custalow CB, Thomsen TW. Roberts and Hedges' clinical procedures in emergency medicine and acute care. 7th ed. Philadelphia, PA: Elsevier; 2019.

Dunn RJ, Borland M, O'Brien D (eds.). The emergency medicine manual. Online ed. Tennyson, SA: Venom Publishing; 2019.

Australian medicine handbook online. Adelaide (SA): Australian Medicines Handbook; 2000. Bupivacaine. Australian Medicines Handbook. (updated 2020 Jan). Available from: https://amhonline.amh.net.au

Australian medicine handbook online. Adelaide (SA): Australian Medicines Handbook; 2000. Lidocaine (anaesthesia). Australian Medicines Handbook. (updated 2020 Jan). Available from: https://amhonline.amh.net.au

Baldor R, Mathes BM. Digital nerve block. In: UpToDate. Waltham (MA): UpToDate. 2020 Apr 10. Retrieved July 2019. Available from: https://www.uptodate.com/contents/digital-nerve-block

Knoop K, Trott A, Syverud S. Comparison of digital versus metacarpal blocks for repair of finger injuries. Ann Emerg Med. 1994;23(6):1296‐1300. doi:10.1016/s0196-0644(94)70355-8

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