What is the role of local anesthesia in the performance of digital nerve blocks?

Updated: May 16, 2018
  • Author: Dmitry Volfson, DO; Chief Editor: Meda Raghavendra (Raghu), MD  more...
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Answer

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.

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.


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