Equipment
The equipment necessary for performing a digital nerve block includes:
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Sterile gloves, drapes, and gauze pads
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Povidone-iodine (Betadine) solution
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Syringe, 5-10 mL, with an 18-gauge needle for drawing up the anesthetic and a 25- to 30-gauge needle for injection
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Local anesthetic of choice
Anesthesia
Local anesthetic agents have the basic structure of an aromatic and a hydrophilic, separated in the middle by an amino-ester or an amino-amide. This forms the basis of classification of local anesthetics into 2 groups: the ester-type agents (eg, procaine) and the amide-type agents (eg, lidocaine). [3]
The choice of agent is based on the desired duration of analgesia and the patient’s allergy profile. Lidocaine is the most commonly used anesthetic. If longer anesthesia is required, another amide anesthetic, such as bupivacaine, can be used. If the patient is known to be allergic to lidocaine, an ester-type anesthetic, such as procaine, can be substituted. Table 1 summarizes the properties of commonly used agents. For more information, see Local Anesthetic Agents, Infiltrative Administration.
Table 1. Commonly Used Local Anesthetics and Their Properties [4] (Open Table in a new window)
Agent |
Maximum Adult Dose (mg)/Procedure* |
Onset (min) |
Duration |
Lidocaine |
300 |
2-5 |
1-2 h |
Procaine |
500 |
2-5 |
15-45 min |
Bupivacaine |
175 |
2-5 |
4-8 h |
*Administer by small incremental doses. |
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Local anesthetics are to be used without epinephrine in the digits to avoid vasoconstriction of adjacent arteries, which may lead to ischemia or infarction of local tissues. Despite studies that have shown epinephrine to be safe in these circumstances, [5] epinephrine is traditionally avoided in the digits. A study by Sonohata et al showed that a single injection (such as in the transthecal block) of 3 mL anesthetic with epinephrine was effective in achieving adequate analgesia. Also, the time to achieving analgesia was shorter and the effects were longer. Ischemic injury was not reported. [6]
The block should be performed cautiously in areas where nerve function is compromised. Small volumes of anesthetic should be used to minimize local swelling, especially in cases in which compartment syndrome is being considered.
Topical vapocoolant spray during minor procedures can be used to reduce needle penetration pain associated with digital nerve block and pain associated with local anesthetic infiltration. [7]
Monitoring & Follow-up
Numerous potential complications and local anesthetic toxicities have been described in the literature, including the following: [8]
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Pain at injection site
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Infection at injection site, especially with transthecal block
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Wound infection: Local anesthetics have been shown to possess antimicrobial properties. Although studies have shown that use of local anesthetics does not alter incidence of wound infection, their use may produce false-negative wound cultures. [9]
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Local injuries: Injuries to nerves and tendons can result in long-term complications such as neuropathies and tendonitis.
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Inadvertent intravascular injection: This increases the risk of cardiotoxicity and neurotoxicity. [8]
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Allergic reactions
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Vasovagal syncope
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Palmar digital nerves.
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Dorsal digital nerves.
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Needle position for web-space block.
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Needle position for transthecal block.
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Modified transthecal block.
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Medial injection for 3-sided digital block.
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Medial to lateral injection for 3-sided digital block.
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Lateral injection for 3-sided digital block.
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Wing block technique.
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Web-space block technique.
Tables
Agent |
Maximum Adult Dose (mg)/Procedure* |
Onset (min) |
Duration |
Lidocaine |
300 |
2-5 |
1-2 h |
Procaine |
500 |
2-5 |
15-45 min |
Bupivacaine |
175 |
2-5 |
4-8 h |
*Administer by small incremental doses. |
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