A digital nerve block anesthetizes a finger.
(See also Local anesthesia for laceration treatment.)
Indications for Digital Nerve Block
Laceration or other surgically treated lesion of a finger*
Ring removal
A digital nerve block has advantages over local anesthetic infiltration; it typically causes less pain, provides better anesthesia, and does not distort wound edges, which is important because there is little extra space in the fingers.
* This includes fracture, dislocation, fingernail removal, infection.
Contraindications to Digital Nerve Block
Absolute contraindications
History of allergy to the anesthetic agent
Absence of anatomic landmarks needed to guide needle insertion (eg, due to trauma)
Relative contraindications
Infection in the path of needle insertion: Use procedural sedation or a different means of anesthesia.
Coagulopathy*: When feasible, correct prior to procedure, or use a different means of analgesia.
* Anticoagulant medications (eg, for atrial fibrillation) increase the risk of bleeding with nerve blocks, but this must be balanced against the increased risk of thrombosis (eg, stroke) if anticoagulation is reversed. Discuss any contemplated reversal with the clinician managing the patient's anticoagulation and then with the patient.
Complications of Digital Nerve Block
Adverse reaction to the anesthetic (eg, allergic reaction to the anesthetic [rare] or to methylparaben [a preservative]) (see Local anesthesia for laceration treatment)
Hematoma
Neuritis
Spread of infection, by passing the needle through an infected area
Most complications result from inaccurate needle placement.
Equipment for Digital Nerve Block
Gloves (sterile gloves are not required)
Personal protective equipment as indicated (eg, face mask, safety glasses or face shield, cap and gown)
Syringe (eg, 3 mL) and needle (eg, 25 or 27 gauge) for anesthetic injection
* Local anesthetics are discussed in Local anesthesia for laceration treatment.
Additional Considerations for Digital Nerve Block
Document any preexisting nerve deficit in the medical record before doing a nerve block.
Stop the nerve block procedure if you are unsure where the needle is or if the patient is uncooperative. Consider procedural sedation for patients who are unable to cooperate.
Relevant Anatomy for Digital Nerve Block
Each finger is innervated by 4 nerves: bilateral dorsal and palmar digital.
The palmar digital nerves originate from the medial and ulnar nerves.
The dorsal digital nerves originate from the cutaneous branches of the ulnar and radial nerves that wrap around to innervate the dorsum of the hand.
Digital nerve blocks are traditionally placed in the web space adjacent to the metacarpal head, with 1 needle insertion on each side of the finger.
The middle 3 fingers can be anesthetized by blocking only the palmar digital nerves of those fingers.
The thumb and fifth digit are anesthetized by blocking both their palmar and dorsal digital nerves.
Positioning for Digital Nerve Block
Position the patient with the arm supported. The hand is supinated for volar injections and pronated and flat for dorsal injections (eg, ring block).
Step-by-Step Description of Digital Nerve Block
Check sensation of the finger (palmar and dorsal surfaces).
Wear gloves and use appropriate personal protective equipment.
Cleanse the site with antiseptic solution.
Bilateral dorsal injections (traditional ring block)
Place the hand and wrist prone (palm down).
On one side of the finger, insert the needle perpendicularly into the dorsal web space, adjacent to the medial aspect of the metacarpal head. Slowly inject about 1 mL of anesthetic to block the dorsal digital nerve. Then continue to advance the needle downward into the palmar space, while slowly injecting another 1.5 mL of anesthetic to block the palmar digital nerve. Take care not to penetrate the palmar aspect of the finger.
To complete the digital block, duplicate the needle insertion and injection on the other side of the finger.
Single volar injection
Place the hand and wrist supine (palm facing up).
Identify the digital-palmar crease (where the finger joins the palm). If necessary, have the patient flex the finger against resistance to make the crease more prominent.
Insert the needle vertically at the midpoint of the crease and advance the tip subcutaneously.
Aspirate to exclude intravascular placement, and then slowly inject about 3 mL of anesthetic.
Massage the injection area to spread the anesthesia.
If paresthesia occurs during needle insertion, withdraw the needle 1 to 2 mm before injecting.
Allow about 5 to 10 minutes for the anesthetic to take effect.
(For more details on digital anesthesia, see reference [1].)
Aftercare for Digital Nerve Block
Ensure hemostasis at the injection site.
Instruct patient regarding anticipated time to anesthesia resolution.
Warnings and Common Errors for Digital Nerve Block
To minimize the risk of needle breakage, do not bend the needle, insert it to its full depth (ie, to the hub), or attempt to change direction of the needle while it is inserted.
To help prevent nerve injury or intraneural injection, instruct patients to report paresthesias or pain during the procedure.
To help prevent intravascular injections, aspirate before injecting.
Tricks and Tips for Digital Nerve Block
References
1. Cannon B, Chan L, Rowlinson JS, et al: Digital anaesthesia: One injection or two? Emerg Med J 27:533-536, 2010. doi:10.1136/emj.2009.072850
