Benefits

Clinical Context

Modern reconstructive surgery often involves the reattachment, transfer, or transplant of body tissues. For example, if a finger is traumatically separated from the hand, reconstructive surgery techniques are used to reattach the finger and the blood supply (arteries, veins) that supply the finger. Other examples are breast reconstructions following cancer surgery, and bone grafts to rebuild a jaw after injury or cancer. There have even been recent cases involving transplants of entire hands.

The replanted, transferred, or transplanted tissue is referred to as a “flap,” and is often a multilayered structure of varied geometry and size, containing some combination of skin, muscle, bone, fascia, or adipose tissue. The use of microsurgical techniques is growing to encompass large tissue regions, and is critically important to restoring function, rehabilitative potential, and quality of life.

To ensure positive outcomes, however, postoperative care of patients undergoing microsurgical procedures must be refined to ensure viability of replanted, transferred, or transplanted tissue.

Complications of Venous Congestion

A common postoperative complication of reconstructive microsurgery is blood clot formation within the venous outflow, which can create a condition known as venous congestion. With venous congestion, the tissue flap becomes congested with blood, flow ceases, and if uncorrected, tissue dies and the flap is lost.

In cases of venous congestion, surgical repair of the venous reconstruction is always indicated when feasible. Unfortuntately, this is not always successful, particularly in cases of posttraumatic injury. Removing the excess blood from the tissue via an alternative method is then essential to prevent tissue death, and to allow time for the ingrowth of new venous outflow from the surrounding normal tissues.

The Problem of Medicinal Leeches

Currently, the only available treatment for venous congestion is the use of live, medicinal leeches (Hirudo medicinalis), a treatment used for the entire 40-year history of modern microsurgery. Medicinal leeches are placed upon the tissue flap to facilitate removal of excess blood until microvenous circulation can be effectively re-established, approximately 4-10 days after surgery.

However, blood emission from a single leech wound is limited and multiple leeches must be employed over the course of days. This causes significant damage to the tissue and requires substantial levels of blood transfusion. In one recent paper, 215 leeches were needed on average over the course of 6.6 days to encourage tissue decongestion. Other methods of decongestion must be developed for unsalvageable tissue flaps.

The use of medicinal leeches has substantial limitations, including negative patient and family perception, unreliability of leech attachment (i.e., the leeches may not attach to, or may migrate from the impaired tissue and may feed on healthy adjacent skin), excessive cost due to constant staff monitoring, and the possibility of infection.

Overall, medicinal leeches are usually unable to salvage the tissues being treated, particularly large regions of tissue. As microsurgery progresses to include transplantation and replantation of increasing sizes of tissue and entire limbs, it is clear that alternative methods for tissue decongestion must be developed.

Advantages of the AutoFlow Technology

When compared to leech therapy, AutoFlow offers significant advantages to the treatment of venous congestion, including improved outcomes and tissue survival for both small and large tissue flaps. In addition, AutoFlow provides the following advantages:

• Modulation of device actions based on the amount of blood volume removed
• Autotransfusion of removed blood
• Greatly improved biosafety for health care workers, in that AutoFlow provides adequate biohazard containment of removed blood
• Decreased risk of infection for patients undergoing decongestion therapy
• Greatly reduced nursing time and staff burden

Societal Value

With a mechanical device that more effectively treats venous congestion, the psychologically traumatic and typically ineffective use of live leeches can be discontinued in modern medicine.

Development of this type of device can be viewed as particularly compassionate when one considers the stress placed on patients and their families undergoing difficult surgeries for life-threatening conditions, only to experience a complication that compromises their reconstruction. Placing live leeches on patients only compounds an extremely difficult clinical situation. Although patients are generally willing to do just about anything to save their replanted tissue, it is not difficult to imagine the distress experienced by patients at having to rely on a leech to solve their medical problems.

Effective salvage of free tissue transfers, replantations, or transplants will mean a patient’s function in daily life, general appearance, and quality of life can be rehabilitated to an acceptable level. For head and neck surgery patients, survival of replanted tissue leads to adequate swallowing and speech rehabilitation following trauma or cancer surgery. In plastic and orthopedic surgery, the successful salvage of an amputated limb or finger clearly enhances physical, occupational, and vocational rehabilitative potential.

As the field of reconstructive surgery moves forward in replanting larger and larger regions of tissue, including entire limbs, it will become necessary to use more effective methods for tissue decongestion. Therefore, development of an effective automated device for the purpose of promoting tissue survival following microsurgery has clear and profound societal benefits.