Division of plastic surgery, Department of Surgery, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan, Republic of China

Received 24 January 2011; revised 5 February 2011; accepted 8 February 2011

Abstract

Background: A modified subcutaneous single-injection approach to achieve digital block using a tumescent technique is described.

Method: A convenient sample of patients requiring digital anesthesia for minor surgical procedures on the fingers or thumb in the emergency and plastic departments were enrolled into the study. Digital nerve block was performed by injecting 1% lidocaine into the volar subcutaneous space at the proximal digit to create a firm, turgid feel to the tissue, the so-called tumescent state. The volume of anesthetic was based on the size of the digit. All nerve blocks were performed by 1 surgeon. Successful digital anesthesia was defined as complete loss of pinprick sensation on both the dorsal and volar aspects of the digit and the ability to complete the anticipated minor surgical procedure without pain. All patients were followed for 1 month to assess for adverse events.

Result: Between August 2009 and January 2011, 123 patients (123 digits) requiring digital anesthesia were enrolled into the study. Thirty-nine (32%) were volar lesions, and 84 (68%) were dorsal lesions. The tumescent technique single-injection digital block was successful in all digits. No adverse events were reported.

Conclusion: The tumescent technique in digits to achieve a single-injection digital nerve block is an easy, safe and effective method for digital anesthesia. These data confirm the applicability of the tumescent technique in digits for patients with finger and Thumb injuries or tumors that require minor surgical procedures.

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Introduction

Finger injuries are common presentations at emergency departments and often require minor surgical management. A digital anesthetic is frequently used to facilitate the completion of most of these procedures. This type of regional anesthetic is commonly prescribed by emergency physicians for fingertip injuries, laceration repair, dislocation reduction, foreign body

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E-mail address: [email protected] (S.-G. Chen).

removal, and wound debridement or by hand surgeons for tumor excision. Conventional digital nerve block techniques require multiple injections of anesthetics for each [1] (Fig. 1). A ring block or bilateral digital nerve block in the tightly confined space at the base of the phalanges is hazardous.

A transthecal digital nerve block performed via a single injection into the flexor tendon sheath (Fig. 2) was first described in 1990 [2]. In 1997, Whetzel et al [3] modified the transthecal approach to improve anesthesia and simplified it by providing more readily identifiable landmarks (Fig. 3). Harbison [4] has described an

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Fig. 1 A 25-gauge needle is inserted into the dorsum of the base of the digit, and then the same maneuver is performed on the opposite side of the digit. Next, additional local anesthetic is injected subcutaneously over the dorsum of the base of the digit from the site of the first injection to the site of the second injection.

alternative single-injection technique that uses a subcuta- neous location and is purported to be easier to administer (Fig. 4), yet offers similar advantages to Chiu’s techniques. He noted that “the only disadvantage is that the dorsal digital nerves are not always anesthetized.”

We modified the subcutaneous single-injection digital block by giving a larger volume of local anesthetic until the digit reached a tumescent state (Fig. 5). This method has similar advantages to Harbison’s technique, and the dorsal digital nerves are always anesthetized.

Fig. 2 A 25-gauge needle is inserted into the volar skin through the subcutaneous tissue and down to the flexor tendon sheath. The anesthetic is injected into the potential space between the flexor tendon sheath and the flexor tendon.

Fig. 3 A 25-gauge needle is inserted perpendicular to the skin surface and advanced until bone resistance is felt. Low pressure is applied to the syringe plunger, and the needle is slowly withdrawn. Anesthetic does not flow until the bone and tendon proper are cleared. As the withdrawing needle enters the tendon sheath, an easy flow of lidocaine can be detected. The lidocaine is infiltrated into the flexor tendon sheath.

Fig. 4 A 25-gauge needle is inserted perpendicular to the skin surface, and anesthetic is injected into the subcutaneous tissue superficial to the flexor tendon sheath.

Patients and Methods

This is a prospective, descriptive study of the efficacy of a modified subcutaneous single-injection digital block. The patients were all adults examined in the emergency department or the plastics outpatient department with dorsal or volar finger injuries or tumors distal to the metacarpal crease that required procedures with local anesthesia. Procedures included laceration repair, nail bed repair, incision of paronychia, foreign body removal, dislocation reduction, nail removal, tendon repair, and tumor excisions.

A 5-mL syringe with a 25-gauge needle was filled with 4 mL of 1% lidocaine at Room temperature. The patient’s finger was cleaned with povidone-iodine solution while in the supine position. The anesthetic was injected subcutaneously into the volar aspect of the proximal digit (Fig. 6A) to achieve tumescence of not only the volar aspect but also the dorsal aspect (Fig. 6B). A volume sufficient to moderately distend the skin on the volar and dorsal aspects of the proximal digit was injected, typically 3 to 3.5 mL, depending on the size of the finger. Successful digital anesthesia was defined as loss of sensation on both the dorsal and volar aspects of the digit and the ability to complete the proposed procedure without pain. Effectiveness of the digital block was determined 5 minutes after injection.

Result

One hundred twenty-three patients (123 digits) requiring digital anesthesia were enrolled into the study between August 2009 and January 2011. Thirty-nine (32%) digits had volar lesions, and 84 (68%) digits had dorsal lesions. The indications for digital anesthesia are shown in Table 1.

The tumescent technique in digits for a subcutaneous single-injection digital block was successful in all digits, including 113 fingers and 10 thumbs.

All patients were followed at a 48-hour visit and then by telephone at 1 month. The tumescence of the digit disappeared within 30 minutes, and no adverse events were reported.

Discussion

Traditional digital block involves injecting lidocaine on each side of the base of the digit or an additional dorsal injection and has the potential hazard of causing neurovas- cular bundle injuries [5-7]. The single-injection transthecal digital block described by Chiu [2] uses the flexor tendon sheath for anesthetic infusion. It has the advantages of requiring a single injection for anesthesia of the entire digit and of posing no risk of direct mechanical trauma to the neurovascular bundles. To make the transthecal block easier to perform and teach, Whetzel et al [3] modified

Fig. 5 A 25-gauge needle is inserted perpendicular to the skin surface and anesthetic is injected into the subcutaneous tissue until the whole proximal digit becomes tumescent and the dorsal branch is also infiltrated.

Chiu’s technique by inserting the needle until bone resistance was felt, then withdrawing the needle until it entered the tendon sheath. Harbison described an alterna-

Fig. 6 A, 25-gauge needle is inserted perpendicular to the volar skin surface of the proximal digit and anesthetic is injected into the subcutaneous tissue to achieve tumescent status. B, Note that the dorsal aspect of the digit also becomes tumescent. The patient has a hemangioma over the proximal interphalangeal crease.

tive single-injection technique that was subcutaneous and purported to be easier to administer than the transthecal digital block, yet offered similar advantages to Chiu’s technique. The only disadvantage was that the dorsal digital nerves were not always anesthetized.

In our study, we modified Harbison’s technique by injecting anesthetic until not only the volar aspect but also the dorsal aspect of the digit became tumescent. The tumescent technique was described by Klein [8], who injected a larger volume of diluted solution made up of epinephrine, ringer lactate, and lidocaine into the fat underneath the skin to make it swell and firm up. We modified both Harrison’s and Klein’s methods by injecting lidocaine into the subcutaneous space of the proximal digit at a single site to achieve swelling on both the volar and dorsal aspects of the digit. This has the advantage of a simple, single injection similar to Harrison’s technique, and the dorsal digital nerve is always anesthetized.

Two milliliters of lidocaine was effective in Harrison’s technique, whereas in our study, the average amount of anesthetic was 3.5 mL. The tumescence of the proximal digit disappeared within 30 minutes, and none of our patients had any adverse effects. Although the subcutaneous infiltration block can potentially damage the neurovascular bundle directly or indirectly because of the elevated compartment

Table 1 Indication and number of fingers

pressure in the digit [2], this complication is very rare and was not seen in any of our patients.

In conclusion, the tumescent technique in digits for a subcutaneous single-injection digital block is a simple, safe, and highly effective anesthetic technique for patients with finger injuries and tumors, providing an attractive alternative to the conventional digital block, transthecal, and subcuta- neous single-injection techniques that have previously been considered standard.

References

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5. Abadir A. Anesthesia for hand surgery. Orthop Clin North Am 1970;1:205.
6. Sandzen SC. Treating fracture and injuries. Am Fam Physician 1974;9: 74-97.
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