Surgery – Diagnostic testing – Liquid collection
Reexamination Certificate
2001-12-12
2003-08-19
Hindenburg, Max F. (Department: 3736)
Surgery
Diagnostic testing
Liquid collection
C604S019000
Reexamination Certificate
active
06607495
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to an apparatus and method thereof for withdrawing fluids, and more particularly to an apparatus and method capable of percutaneous or direct removal of blood and other body fluids.
BACKGROUND OF THE INVENTION
Reconstructive and plastic surgery often involves the transfer of tissue to deep defects, where skin grafts would not be beneficial. During such transfer, the harvested tissue is without blood flow. If the blood flow is not restored quickly, due to microvascular complications, part or all of the tissue may become necrotic and the skin flap will fail. One such complication, venous congestion, involves inadequate venous drainage with a patent arterial inflow, and is due to tissue edema, venous thrombosis, leukocyte aggregation, or the fact that in some cases, microvascular reconnections of the venules are not surgically possible.
By way of background, skin flaps are a common feature utilized by plastic surgeons to reconstruct defects and to cover deep wounds in which a skin graft or replacement is not feasible because a patent vascular bed is absent. A skin flap is a multi-layered tissue that includes dermis, epidermis, subcutaneous tissue, fasciocutaneous, myocutaneous, osseocutaneous, and sometimes muscle tissue, sensory tissue, and possibly underlying adipose tissue, which is based on its own microvascular network. There are many thousands of cases each year that require the use of skin flaps to some degree during a medical procedure whereby these procedures can cost thousands of dollars. Reconnection of arteries to establish adequate arterial flow is vital for the ultimate success of these microsurgical procedures.
Nonetheless, skin flaps with proper arterial flow can still have compromised venous outflow, known as venous congestion, for a variety of reasons. Venous insufficiency has adverse effects, and leads to a majority of the failures in replantation surgeries. Venous congestion is a clinical problem in which extensive effort has been spent in attempts to alleviate or prevent its onset.
As a result, fluid transport techniques such as medicinal leeches are used as a treatment option in these cases to promote nutritive blood flow. The medicinal leech is currently used to initiate blood flow and reduce tissue swelling in skin grafts or replanted digits, and to promote nutritive blood flow. The medicinal leech attaches to its host utilizing three semicircular jaws containing approximately sixty (60) pairs of cutting teeth to create a “Y” shaped incision 1 to 2mm in diameter. Once attached, the bioactive saliva is secreted between each pair of teeth, and the nervous system stimulates the pharynx to pump peristaltically, creating a negative pressure, which aids in driving blood flow into the leech. Leeches will feed until stretch receptors are stimulated by distention in the body. It has been reported that feeding on large mammals, if allowed to proceed undisturbed, will last from 20 to 60 minutes, in which time the leech will ingest 5 to 15 ml, which is up to ten times the initial body weight. Once detached, the bite wound will continue to bleed, which is thought to be an important portion of the therapy. The wound will “ooze” up to 50 ml more in the 24 to 48 hours after feeding. In order for this secondary part of the treatment to be effective, the wound must be continuously cleared of thromboses that form on the patient's skin surface.
The use of leeches establishes a zero or negative pressure outlet for several vessels in the congested area. With the outlet, flow can resume at a basal level, supplying minimal necessary nutrients to the flap. If the flap can survive long enough due to this artificial flow, vessel reconnections can form, leading to survival of the flap.
As stated previously, one of the major factors in a successful tissue transplantation or replantation is the reestablishment of blood flow. The most common cause of flap failure is venous insufficiency, which can be treated with the use of medicinal leeches. However, the use of leeches carries the risk of infection and offers poor flow control. Potential problems for the patient that can arise with the use of the medicinal leech range from psychological problems, such as fear and disgust, to pharmacological problems in nature. Once a patient is comfortable with the procedure, there are other potential problems that can arise. Leeches rely on bacterium for the digestion of the ingested blood, due to the lack of proteolytic enzymes within the gut. One such bacteria is Aeromonas hydrophilia, a gram-negative rod, which has led to seprcaemia, pneumonia and gastroenteritis in humans. These bacteria may be ejected into the patient and cause infection. Infection rates of up to 20 percent have been linked to A-hydrophilia from leeches. Some patients experience anaphylaxis and allergic responses to the bioactive saliva of leeches, while others exhibited excessive scarring from the bite wound site. Continued leech use and persistent bleeding from the wound can result in a significant loss in blood volume. Hemoglobin levels can drop by 1 to 2 gm percent over a five day treatment due to the amount of blood lost, thus requiring a blood transfusion. Finally, if the leech is not monitored, it may wander to a more perfused region of the body to initiate feeding, rendering the treatment useless. Leeches are a widely used clinical tool today as evidenced by Biopharm Ltd. marketing 50,000 leeches per year, while Leeches USA Ltd. typically supplies 20,000 leeches per year. Due to these potential shortcomings of medicinal leeches, alternative methods to leech treatments would be very important to the future of microsurgery.
An alternative approach to medicinal leeches is a mechanical leech disclosed by Smoot in an article entitled “Mechanical Leech Therapy to Relieve Venous Congestion.” It appears that the Smoot device is arranged with an elongated suction chamber with an inflow port for heparinzed saline and an outflow port for continuous suction. In operating mode, the Smoot-device is placed over a biopsy wound measuring 4 mm in diameter and suction is adjusted to achieve a negative pressure.
While the Smoot device appears to overcome some of the psychological and pharmacological failings of traditional medicinal leeching, as it attempts to replace a natural leech, it nevertheless has its own shortcomings. In this regard one shortcoming of the Smoot device is that it is not self-contained. Another major shortcoming relative to the present invention is that the suction pressure of the Smoot device is extremely large (i.e., −80 mmHg), and can not be varied cyclically. Cyclic variations are useful to maintain good flow and prevent blood clotting and/or clogging of channels. Such a large negative pressure, as required by the Smoot device, could collapse blood vessels and compact tissue, leading to clogging of transport channels. Another shortcoming of the Smoot device is that the outlet size of the biopsy wound is much greater than the required insertion of the present invention and could even be considered a wound that is detrmental to the patient A further shortcoming of the Smoot device is that the flow of heparinized saline leads to the susceptibility of spillage. An additional shortcoming of the Smoot device is that the device itself is not contained within a self-powered unit. The Smoot device is also unlikely to work on a clinically venous congested flap. A final shortcoming of the Smoot device is that a punch biopsy is required in the flesh of the subject prior to the “leech” being used, and consequently an increased risk of contamination. Clinicians have previously used skin excisional wounds(large area wounds) to treat seriously coagulated skin flaps. So the Smoot device essentially adjusts suction to a large area wound and would not be effective for venous congested flaps.
There is therefore a need in the art for an effective mechanical leech apparatus for percutaneous or direct removal of blood and other body fluids which does not suffer th
Cottler Patrick S.
Skalak Thomas C.
Decker Robert J.
Foreman Jonathan
Hindenburg Max F.
University of Virginia Patent Foundation
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