Tunneling and undermining; know the difference

(Editor’s note: The answer to this month’s Wound Solutions question is provided by Wound Care editorial advisory board members Kathi Thimsen Whitaker, RN, CETN, MSN, president of Sierra Clinical & Research Associates in Carson City, NV, and Liza G. Ovington, PhD, president of Ovington & Associates in Fort Lauderdale, FL.) 

Question: What is the best way to manage a tunneling wound? 

Answer: Managing a tunneling wound requires first determining the extent of tunneling or undermining. Undermining is less extensive, while tunneling penetrates more deeply into tissue. Probe the perimeter of the wound gently to determine the extent of penetration. 

Determine whether or not the wound is infected and what the causative organism is. Redness, swelling, drainage, warmth at the wound site, and complaints of pain are all signs that an infection may be present. A culture is needed to find out if the wound is infected and what the underlying cause is. 

The federal Agency for Health Care Policy and Research (AHCPR) recommends taking a small sample of tissue, but there is some controversy over this method. It is invasive and expensive, and submits the patient to stress. Another method, a swab culture, involves collecting a sample of the fluid in and around the wound using a sterile cotton-tipped applicator. This is quicker and cheaper, but some say it’s not as accurate. Others contend there is evidence showing a correlation between the results of swab cultures and tissue biopsies. 

Once the underlying infectious organism has been identified, it can be targeted with the appropriate antibiotic. The use of wide-spectrum antibiotics is discouraged because of the emergence of drug-resistant strains of infectious organisms. 

The wound should be irrigated with saline at a safe pressure, which ranges from 4 psi to 15 psi, according to the AHCPR. Pressures lower than 4 psi won’t clean the wound adequately. At pressures greater than 15 psi, you run the risk of actually driving bacteria into the tissue rather than washing them off. 

Pack the wound loosely. You can choose from a number of products, such as plain 1/4-inch gauze, alginates (which come in rope form), or 1/4-inch gauze impregnated with hydrogel. The absorbency of the material will depend on how much fluid the wound exudes. Make sure to fill the entire cavity, or "dead space," which will aid wound healing without risking premature closure. 

The following case report may help illustrate the treatment of a tunneling wound: 

The patient, K.M., is an 85-year-old man with a history of stroke, Parkinson’s disease, swallowing difficulties, malnutrition, and multiple pressure ulcers. An initial assessment revealed that the coccyx wound was non-stageable because of the presence of necrotic tissue. Topical treatment was initiated to remove the necrosis. After three weeks of applying a debriding enzyme, a full-thickness wound was revealed. 

A wound assessment demonstrated the following: 

• A 6.2 cm x 4.3 cm wound with full-thickness or Stage 4 wound involvement. 

• Wound depth of 3.1 cm at the center. 

• Tunneling/undermining recorded: 12 o’clock position — 2.1 cm; 1 o’clock — 2.1 cm; 2 o’clock — 1.2 cm; 3 o’clock — 2.4 cm; 4 o’clock — 2.7 cm; 5 o’clock — 3.1 cm; 6 o’clock — 2.1 cm; 7 o’clock — 2.2 cm; 8 o’clock — 1.9 cm; 9 o’clock — 2.0 cm; 10 o’clock — 1.1 cm; 11 o’clock — 2.0 cm. 

• Note: Undermining is defined as 1.0 to 1.4 cm, tunneling as greater than 1.4 cm. 

Here is the wound care plan that was used for treatment: 

1. Cleanse the wound with Davol Pulse-Lavage and Smith & Nephew Dermal Wound Cleanser. 

2. Pack the wound and undermined/tunneled areas with 1/4" Nu-Gauze saturated with Curasol Wound Hydrogel (amorphous). 

3. Apply moisture barrier to periwound skin. 

4. Cover with a 5 x 9 Surgi-Pad. 

5. Change dressing daily or prn if soiled. 

The packing technique should result in a loosely filled wound cavity and other areas of involvement. Use narrow gauze strips to facilitate tunnel filling to prevent premature closure or tunnel collapse, which may show up as false wound closure and increase the potential for abscess formation or wound recurrence. Tight packing may lead to wound ischemia caused by intrawound pressure.

[Editor’s note: Send questions you would like answered in future issues to: Wound Care, P.O. Box 740056, Atlanta, GA 30374. Or you can fax them to Managing Editor Glen Harris at (404) 261-3964, or e-mail us at glen_harris@medec.com.]