Chemical apparatus and process disinfecting – deodorizing – preser – Blood treating device for transfusible blood – Oxygenator
Reexamination Certificate
1993-06-01
2003-01-14
Sykes, Angela D. (Department: 3762)
Chemical apparatus and process disinfecting, deodorizing, preser
Blood treating device for transfusible blood
Oxygenator
C422S044000, C604S004010, C604S006140, C128SDIG003, C261SDIG002
Reexamination Certificate
active
06506340
ABSTRACT:
FIELD OF THE INVENTION
This invention is in the field of medical devices, specifically defoaming components for extracorporeal blood processing devices such as oxygenators and cardiotomy reservoirs.
BACKGROUND OF THE INVENTION
Blood processing apparatus including oxygenators, cardiotomy reservoirs and defoamers, blood filters, autotransfusion devices, drip chambers, and other devices through which blood is moved, e.g., by pumping, often require agitation such that air is mixed with blood, causing foaming. This foam must be removed before the blood is put into the patient's circulatory system.
Many surfactants are used as industrial antifoaming agents including selected block copolymer polyol surfactants, polyether block copolymers, polyoxyethylene sorbitan esters and silicone-based surfactants. These surfactants are generally used as defoamers by mixing them into the liquid to be defoamed.
TWEEN 80™ (ICI Specialty Chemicals, see ICI product literature) is a well-known industrial and biological surfactant which is a polyoxyethylene sorbitan ester. TWEEN 80™ has been used as a debubbling agent in blood-containing medical devices.
Block copolymer polyol surfactants composed of ethylene oxide and propylene oxide are used as defoamers and antifoamers in a wide variety of applications such as industrial processing, latex paints, cleaning, water treatment and fermentation. Currently two groups of polyol surfactants are commercially available. These are PLURONIC™, PLURONIC-R™, TETRONIC™, TETRONIC-R™ and PLUROFAC™ surfactants (BASF product literature 1989). Polyols with various structures and molecular lengths can be synthesized by altering the reaction sequences and degree of polymerization with or without adding ethylenediamine coupling agent. Block copolymers composed of ethylene oxide are hydrophilic while those composed of propylene oxide are hydrophobic. These polyol surfactants have not been known to be applied as defoamers/antifoamers in blood-contacting medical devices especially for use in extracorporeal circulation.
ANTIFOAM A™, Dow Corning Corporation, Midland, Mich. (Dow Corning Product Literature, 1985), a polydimethylsiloxane surfactant, has been used as an antifoaming agent for blood processing devices. Dow Coming also manufactures a similar polydimethylsiloxane defoaming agent sold under the trademark SIMETHICONE™ which may be used in blood processing devices. ANTIFOAM A™ is coated on blood-contact surfaces of such devices to prevent foaming. Device surfaces are usually coated by dipping them in a solution of ANTIFOAM A™ in a halogenated hydrocarbon. Generally, defoaming units of blood processing devices provide a very large surface area which is covered by the defoaming agent. The surface area is usually composed of a synthetic material such as polyurethane foam, polypropylene mesh, polyvinylchloride strips or stainless steel wool. Other surfactants containing silicone which are water-soluble are also known to the art including those of GE Silicone Division, Waterford, N.Y. such as SM-70.
Silicone-containing surfactants used in blood processing devices, specifically, ANTIFOAM A™, have recently been implicated in the formation of emboli in patients who died after cardiopulmonary bypass surgery. (J. M. Orenstein, et al. (1982), “Microemboli Observed in Deaths Following Cardiopulmonary Bypass Surgery,” Human Pathology 13:1082-1090.) ANTIFOAM A™, as a hydrophobic surfactant, has the further disadvantage of retarding liquids in the defoaming unit of oxygenating instruments, thus unnecessarily impeding blood flow through the unit.
To avoid problems of blood interaction with the blood-contact surfaces which may cause trauma to the blood, the use of defoaming agents has been described in combination with heparin in blood processing devices. (L-C. Hsu, et al., “Thrombo-resistant Coating for Defoaming Applications,” PCT Publication WO 92/21387.) Defoaming agents are described as comprised of both active compounds and carriers, occasionally including a spreading agent. Typical active compounds listed include fatty acid amides, higher molecular weight polyglycols, fatty acid esters, fatty acid ester amides, polyalkene glycols, organophosphates, metallic soaps of fatty acids, silicone oils, hydrophobic silica, organic polymers, saturated and unsaturated fatty acids, and higher alcohols. Typical carriers include paraffinic, naphthenic, aromatic, chlorinated, or oxygenated organic solvents. ANTIFOAM A™ dissolved in a mixture of FREON (DuPont Co.) and methylene chloride in combination with heparin is a preferred antifoaming composition in this patent application for avoiding problems of blood interaction with blood-contact surfaces.
Nogawa, et al. U.S. Pat. No. 5,162,102 describes the use of nonionic surface-active agents which are polyethers consisting of block copolymers of propylene oxide and ethylene oxide (i.e., PLURONIC™ and TETRONIC™ surfactants), to coat blood-contacting surfaces of medical devices for debubbling purposes. In that patent a debubbling agent is used to coat the hydrophobic blood-contact surfaces so that air can be removed from the system during a priming operation prior to blood circulation, leaving few bubbles adhered to the surfaces, as the patent teaches that during blood circulation, such bubbles gradually enter the blood, causing blood foaming. The surfactant may be used by coating on the inside of the housing. Then when the priming liquid is passed into the system, the surfactant dissolves and is distributed over the entirety of the blood-contact surfaces, and renders them more hydrophilic. In the preferred embodiment disclosed in this patent, a “debubbler” or defoaming unit to remove bubbles from blood is described. This defoaming unit (such as a urethane, cellulose, or nylon foam), works to remove bubbles from blood by allowing bubbles to grow by virtue of its hydrophobic nature. Thus, this patent teaches away from the use of a surfactant durably deposited onto the blood-contact surfaces, particularly onto defoamer surfaces, as such would interfere with the function of the defoamer described in said patent. The PLURONIC F68 debubbling composition disclosed in U.S. Pat. No. 5,162,102 is not suitable as a defoaming composition as defined herein. As set forth in the BASF product literature (1989), page 13, F68 is a water-soluble surfactant that produces foam and should only be used in applications where foam production is desirable.
A number of water soluble PLURONIC™ or TETRONIC™ surfactants have been found to produce fair to excellent results when used in combination with buffers and osmolality fillers as debubbling agents for sheath streams in biomedical analytical systems. These are PLURONIC P85™, P84, P105, P87 and TETRONIC 908™. European Patent Publication 0 214 614 published Mar. 18, 1987, for “Non-Lytic Sheath Composition.” The water solubility of these surfactants at operating temperatures would preclude their use in defoaming applications where durable retention on a hydrophobic surface is desired.
The nonbiotoxic nature of polyol surfactants was known about thirty years ago. Generally the polyols have low acute oral and dermal toxicity and low potential for causing irritation or sensitization. The typical oral LD50™ is greater than 10 grams per kilogram and dermal LD50™ is greater than five grams per kilogram. In medical applications, the PLURONIC F68™ polyol has been extensively studied. Adding F68 to blood to minimize fat globulemia during cardiopulmonary bypass surgery was corroborated on clinical patients. (E. S. Wright et al. (1963), Fat Globulemia in Extracorporeal Circulation,“Surgery 53:500-504; and Y. Miyauchi et al. (1966),“Adjunctive Use of a Surface-Active Agent in Extracorporeal Circulation,” Supplement I to Circulation, 33 & 34, I-71-1-77.) Concentrations less than five percent F68 were shown to protect erythrocytes against osmotic hemolysis. (C. Roze (1966), “Osmotic Behavior of Erythrocytes in Solutions of a Non-ionic Detergent: Pluronic F-68,” C.R. Acad. Sci. 263:1615-1618.) The use of F68 as a blood plasma expander in hea
Haynes Robert E
Tsai Chi-Chun
Bianco Patricia
Cobe Cardiovascular, Inc.
Popovich & Wiles, P.A.
Sykes Angela D.
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