• Louis Catalano, MD
• Jerry D. Vloka, MD

I.	INTRODUCTION
II.	REGIONAL ANESTHESIA ANATOMY
III.	EQUIPMENT
IV.	TECHNIQUE Block of Volar & Dorsal Digital Nerves at the Base of the Finger Transthecal Digital Block
V.	BLOCK DYNAMICS & PERIOPERATIVE MANAGEMENT General Guidelines
VI.	CHOICE OF LOCAL ANESTHETIC
VII.	COMPLICATIONS & HOW TO AVOID THEM

INTRODUCTION

Strauss¹ provided the first description of the digital block in 1889 for the condition of an ingrown toenail, using 20% cocaine at the base and under the nail. In 1905, Braun reported the synergistic advantage of adding epinephrine to local anesthetics.^2,3 However, the use of epinephrine in digital block anesthesia has been avoided due to the theoretical risk of ischemia and possible gangrene. More recently, however, Wilhelmi and colleagues⁴ demonstrated the safety and efficacy of epinephrine-containing local anesthetic for digital block, which made its use only more controversial. Digital block is one of the most common nerve block techniques, frequently used in the emergency department and primary care settings for various procedures such as lacerations of the finger or toe, nail removal, nail bed repair, paronychia drainage, removal of foreign bodies, and any other painful procedures on digits.

In 1990, approximately a century after the first publication of traditional digital block, Chiu⁵ described a technique of digital block that produced complete finger anesthesia with a single injection into the flexor tendon sheath at the level of the distal palmar crease. In anatomic studies he showed that after injection of methylene blue into the flexor tendon sheath there was “complete staining of the entire flexor tendon sheath and centrifugal diffusion of the blue dye circumscribing the entire circumference of the proximal phalanx” (see section on Transthecal Digital Block). The advantages of this technique are ( 1 ) rapid onset of action, (2) only a small volume of anesthetic solution required, (3) only a single injection required, and (4) absence of risk of direct trauma to the neurovascular bundles.⁶–⁸ Although Chevaleraud and coworkers⁹ did not accomplish anesthesia of the dorsum of the finger in all cases, some authors consider the transthecal method to be as effective as a traditional digital nerve block.¹⁰ Others have found that it results in anesthesia comparable to the newer singleinjection subcutaneous digital blocks,¹¹ both in experimental and clinical situations.¹²՝¹³ Transthecal anesthesia appears to be safe and effective without a risk of any long-term damage to the tendon sheath.

A digital block is the technique of blocking the nerves of the digits to achieve anesthesia of the finger(s). This technique is simple to perform and essentially devoid of systemic complications. It is a commonly used and effective method of anesthesia for a wide variety of minor surgical procedures on the digits. As such, this block should be in the armamentarium of every anesthesiologist. Several different techniques of digital block and their modifications are available; in this chapter, we chose to describe the one that is most commonly used in our institution.

REGIONAL ANESTHESIA ANATOMY

The common digital nerves are branches of the median and ulnar nerves, which divide in the distal palm into the volar aspect, tip, and nail bed area (Figure 30-1). The main digital nerves, accompanied by digital vessels, run on the ventrolateral aspect of the finger immediately lateral to the flexor tendon sheath (Figure 30-2). Small dorsal digital nerves run on the dorsolateral aspect of the finger and supply innervation to the back of the fingers as far as the proximal joint.