Liquid purification or separation – Casing divided by membrane into sections having inlet – Each section having inlet
Reexamination Certificate
1999-09-24
2001-03-06
Kim, John (Department: 1723)
Liquid purification or separation
Casing divided by membrane into sections having inlet
Each section having inlet
C210S321600, C210S321790, C210S321880, C210S321890, C210S416100, C210S433100, C210S500230, C422S105000, C422S105000, C436S177000, C436S178000, C604S082000
Reexamination Certificate
active
06197194
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a system for obtaining autologous plasma from a patient during surgery. The invention further relates to a method for preparing fibrin gel and other hemostat or tissue sealant preparations from the autologous plasma.
2. Background Information
Preparations of human coagulation factors including fibrinogen and thrombin, have been used extensively in surgery over the last ten years. These biological fibrin sealants (also known as fibrin glue, fibrin adhesive, or fibrin tissue sealant) promote hemostasis and wound healing by sealing leakage from tissues, sutures, staples, and prostheses and are particularly useful during open heart surgery in heparinized patients. The sealants also have limited use as an adhesive for the bonding of tissues and they reduce the amount of blood required for transfusions by controlling intraoperative bleeding. Their effectiveness is reflected in the extensive range of surgical applications for which they have been used, including cardiovascular surgery, plastic surgery, orthopedics, urology, obstetrics and gynecology, dentistry, maxillofacial and ophthalmic surgery.
Fibrin sealant products can be prepared from pooled human plasma. However, such preparations potentially risk transmission of HIV, hepatitis B and other serologically transmitted illnesses. Also, in some instances these preparations could cause immunologic reactions.
As an alternative, some hospitals are preparing fibrin sealant in-house using the patient's own blood (autologous) or single-donor (homologous) plasma as a source of fibrinogen and Factor XIII. The components are typically prepared by freezing plasma at temperatures below −20
7
C. overnight, slowly thawing the material at 0-4
7
C., centrifuging, and transferring the cryoprecipitate to a syringe or spray container. The procedure usually requires several hours, making the product unavailable for emergency cases. The lengthy manipulations currently required to generate fibrin sealant also introduce the risk of contaminating the product and transmitting viral infections to the technicians involved.
The thrombin, usually purified from bovine plasma, can be obtained commercially and is typically prepared in a separate syringe or spray container. The two solutions are delivered simultaneously or alternately to generate fibrin sealant at the site of the wound.
The hemostatic efficacy of fibrin glue has been well established. Autologous fibrin gel, made from plasma rather than a fibrinogen-containing precipitate, appears to have comparable hemostatic properties to traditional fibrin glue as well as valuable sealant properties. For instance, fibrin gel is useful in sealing air leaks in pulmonary procedures.
In preparing fibrin gel, plasma is typically obtained from autologous blood following centrifugation for about ten minutes to separate blood cells from anticoagulated blood, followed by removal of the plasma. Centrifugation in the operating room, however, may be inconvenient because of the required instrumentation, potential for aerosolization with its concomitant contamination risks, and difficulty in decontaminating instrumentation between procedures. If centrifugation takes place external to the OR, aseptic transport of the plasma fraction to the operative site is required.
Hollow fiber devices permitting separation of plasma from blood without the need for centrifugation have been used for plasma exchange therapy (PET). In PET, the separated plasma is eliminated and the separated blood cells with replacement fluids are returned to the patient.
Recently, hollow fiber filtration technology has been developed to meet the requirements of cell separation from cell cultures—including shear-sensitive mammalian cells—while allowing free passage of soluble proteins. This membrane technology offers an alternative to centrifugation, precipitation and conventional filtration techniques for bioseparations, eg. the processing of fermentation products, and is available for small volume applications. Sterilizable, disposable filtration modules are available from at least one manufacturer.
SUMMARY OF THE INVENTION
The described invention uses compact, small-volume disposable filtration technology to separate plasma from blood. In contrast to PET applications, the separated blood cells trapped by the filter are disposed of along with the filter. The separated plasma is used as a source of autologous material—eliminating the risk of cross-infection of immunological consequences. Preparation of the plasma requires no instrumentation and can be performed quickly and conveniently at the time and location of the surgical or medical procedure for which the material will be used. Specific uses for the autologous plasma obtained in this manner include preparation of fibrin gel and other hemostatic/tissue sealant formulations based on proteins and or clotting factors.
A single use system for obtaining autologous plasma according to the present invention comprises a plasma separator for separating plasma from whole blood. The plasma separator comprises a single use filter unit having a first inlet and a second inlet in fluid communication with each other, an outlet, and a filtration membrane separating the inlets from the outlet. The filtration membrane is selectively permeable to blood plasma. A manually operable, single use first pump comprises a receiving chamber connected to the first inlet. The receiving chamber has a manually moveable wall for altering the volume of its receiving chamber. A manually operable, single use second pump comprises a receiving chamber connected to the second inlet and a manually moveable wall for altering the volume of its receiving chamber. A flow path is defined along the membrane between the first and second pumps. Thereby, whole blood can be repeatedly exchanged between the receiving chambers in the first and second pumps, past the membrane, to cause plasma to flow across the membrane and out of the outlet.
Preferably, the membrane comprises one or more hollow fibers, each of the one or more fibers having a lumen therethrough, and the flow path extends through the lumens of the one or more fibers. Also preferably, the filter unit comprises an elongated housing having a first end and a second end with the one or more hollow fibers extending axially therethrough. Each of the one or more fibers has an outer surface, the housing has an inner surface and an interior space is thus formed between the outer surfaces of the fibers and the inner surface of the housing. Pottings at the first and second ends of the housing secure the fibers therein and separate the lumens from the interior space. The first pump connects to the housing first end and the second pump connects to the housing second end, each with its respective receiving chamber in fluid communication with the lumens of the hollow fibers. The outlet is in fluid communication with the interior space whereby when the blood is pumped through the lumens of the hollow fibers by the first and second pumps, the plasma flows through the membrane into the interior space of the housing and out of the outlet. Preferably, the first and second pumps comprise syringes. A collection syringe preferably connects to the outlet for receiving the plasma.
The system can further comprise an applicator for preparing and applying fibrin gel in a medical procedure. The applicator comprises a first injector containing a thrombin solution, a second injector containing the plasma, the plasma containing an amount of fibrinogen, and a manifold in communication with the first and second injectors for applying the thrombin solution and plasma simultaneously to a site on a body. Preferably, the first and second injectors comprise syringes. Also, the syringe forming the second injector is preferably the collection syringe.
The system can be provided in a sealed sterile package containing the plasma separator and the fibrin applicator; and instructions for obtaining whole blood from a patient in the first
Farmer Andrew C.
Kim John
LandOfFree
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