INTRODUCTION

Split thickness skin graft (SSG) is one of many tools in a plastic surgeons’ reconstructive toolbox, frequently harvested under local anesthetic (LA) for small clean defects. Donor site pain can prove the most distressing symptom to the patient perioperatively through multiple passes of a needle during LA infiltration and stimulation of nociceptive fibers during the partial thickness injury caused by the graft harvest.[12]

The use of hyaluronidase has been described in a variety of settings: treating extravasation of chemotherapy agents and its potentiating effect when used with LA in ophthalmic surgery.[3] Hyaluronidases are a family of endoglycosideses breaking down hyaluronic acid, the main component of extracellular matrix linking protein filaments, collagen fibers, and connective tissue cells within the skin.[4]

We describe a technique using hyaluronidase to uniformly anesthetize an SSG donor site with one injection, in one pass, of one needle.

TECHNIQUE

1. Preop application of EMLA cream to the donor site minimizing pain of needle entry.

2. Buffer 9 mL 1% lidocaine with adrenaline 1:200,000 with 1 mL 8.4% sodium bicarbonate. Mix this 10 mL with 1 vial of Hyaluronidase 1500 units powder for injection.

3. The SSG donor site margins are determined.

4. In the middle of the proximal aspect of the donor site, enter perpendicular to the skin and inject the LA mixture subdermally using a long 27G needle creating a mound [Figure 1].

5. Maneuver the needle near parallel to the skin and inject the remaining anesthetic along the width of the donor site [Figures 2 and 3].

6. Using a rolled 4 × 4 swab, apply firm advancing pressure to distribute the mound across the remaining width and length of marked donor site [Figure 4].

7. As the mound advances, the LA mixture distributes uniformly across the donor site within the same plane. Blanching skin secondary to the adrenaline identifies its distribution [Figure 5].

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Figure 1

Injection of local anesthetic by creating a mound

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Figure 2

Injection of local anesthetic along one half of the width of the donor site

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Figure 3

Injection of the remaining local anesthetic along the other half of the width of the donor site

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Figure 4

Apply firm advancing pressure to distribute the local anesthetic using a 4 x 4 swab

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Figure 5

Advance the rolled swab across the full length of the marked area

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DISCUSSION

Harvesting an SSG under LA is known to be painful for patients for a number of reasons:

• Cold LA

• Secondary to the acidic PH of the LA

• Multiple injections to the donor site for anesthetic and hemostatic control

• The blade of the dermatome or knife in incompletely anaesthetized donor sites

• Exposure of nerve endings following graft harvest

• Patient anxiety reducing the threshold for pain tolerance

A randomized controlled trial (RCT) assessing efficacy of LA with hyaluronidase in scalp nerve blocks showed lower pain scores in these patients at 2, 4, 6 and 8h postoperatively. Intraoperatively this cohort had lower heart rates and blood pressure compared to those with LA without hyaluronidase.[5] This was also evident in an RCT assessing pain scores in carpal tunnel decompression.[6]

Studies comparing LA infiltration with hyaluronidase highlight its use results in immediate onset compared to a mean of 1 min 28s in LA without.[7] Furthermore, the area anaesthetized was increased by a mean factor of 2.45 and volunteers reported less discomfort during the infiltration. The rapid diffusion of the infiltrated bolus we illustrate in this technique results in a smooth contour, this, combined with the good biocompatibility of hyluronidase and rare incidence of allergic reaction (<0.1% of the cases) is optimal for uniform SSG harvest under LA.[8] Haemostatic control is provided by the use of LA with adrenaline.

Per ampoule of 1500 units, hyaluronidase costs £13.6 ($17.23).[9] This is comparable to the LA (1% xylocaine with adrenaline 1:200000) of £9.66 ($12.23) per vial[10] and sodium bicarbonate price of £11.41 ($14.45) per vial.[11]

We dilute 1 vial of hyaluronidase with 10 mL of LA mixture; however, the literature describes diluted concentration of 15 units/mL[12] increasing longevity and cost effectiveness.

CONCLUSION

The technique described is a fast and reproducible technique to:

1. Anaesthetize an SSG donor site in a single pass, of a single needle.

2. Distribute the anesthetic uniformly across the donor site, optimizing uniform graft harvest.

3. Maintain haemostatic control of the entire donor area without additional risk or time.