Friday, March 27, 2009

Maggots and Leeches

As early as 1500 BC, the Egyptians advocated using honey, lint and animal grease for chronic, non-healing wounds. Throughout the ages, healers have tried everything from natural sunlight to sugar and antacids to hasten wound closure.

Back in the 19th century, leeches and maggots were considered invaluable therapies for wound care, but they fell out of favor as new therapies came along. Today, however, these organisms are finding a place in the modern arsenal of interventions for non-healing wounds.

Reducing Venous Congestion
The renewed interest in medicinal leeches, which were FDA-approved as a medical device in 2004, comes from the plastic surgery arena. As physicians developed microsurgical techniques for reattachment or transplantation of fingers, toes and ears, they were stymied by venous congestion at the surgical site that led to swelling and prevented healing.

"As leeches bite and suck blood from an area, they leave behind an anticoagulating chemical that produces bleeding, serves as a local anesthetic and acts as a local vasodilator [with some antibiotic properties]," said Sharon Mendez, RN, CWS, Holy Family Hospital, Spokane, WA, and an executive board member of the BioTherapeutics Education & Research Foundation. "Those actions reduce venous congestion in areas you don't want compressed. Say a patient has had neck surgery and is developing pressure on the jugular vein. You would place leeches where the congestion is occurring, which may be on the more vascular side of the surgical site or on the gravity side."

Mendez employed leech therapy early in her career, only to see the modality fall into disuse. In response to interest from local plastic surgeons, she is developing a protocol to introduce this therapy at her hospital.

"There are a number of specialty surgeons who find leeches extremely effective for patients who have had head and neck procedures, finger reattachments, flaps or grafts," she said. "The leech removes a little bit of the blood that's compressing the site, and then there's oozing of a significant amount of blood over the next 10-12 hours."

Debridement Therapy
Maggot debridement therapy (MDT), which employs sterile maggot larvae, is FDA-approved for chronic, non-healing wounds with necrotic tissue, such as pressure ulcers, diabetic foot ulcers, venous stasis ulcers, post-surgical wounds and trauma wounds.

MDT "is not the first choice for these wounds - most wounds will heal well no matter what you use - but I would consider using maggot therapy for wounds whose anatomy would require extensive and complicated surgery to access," said Ronald A. Sherman, MD, MSc, DTM&H, assistant researcher, University of California, Irvine. "Surgical debridement is "not the best choice in many wounds because these patients are poor surgical risks or have poor blood flow and removal of too much viable tissue could be a big problem."

MDT also is appropriate for non-healing wounds in patients allergic to certain types of wound care products, or for open areas that fail to respond.

"For example, a wound may not respond to topical and/or systemic antibiotics, or to an enzymatic debrider," Sherman said. "Let's say you've been surgically debriding the wound at the bedside week after week, and the necrotic tissue continues to re-accumulate. That might be the time to think about MDT."

Maggot larvae secrete digestive enzymes into the wound bed, and then crawl around the wound to locate nutrients in dissolving tissues. First "the maggots will concentrate on areas of moist tissue because that's where the liquid accumulates, and they drink it up," Sherman explained. "But they can and will debride eschar if there are enough maggots present."

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