Apparatus for reducing fat content of blood

Apparatus for reducing the fat content of blood and in particular to an apparatus for reducing the fat content of pericardial suction blood has a conduit for blood, an absorbing filter located in the conduit and an associated temperature control device for adjusting the temperature of blood before it flows through the filter.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an apparatus for reducing the fat content of blood and in particular to an apparatus for reducing the fat content of pericardial suction blood.

2. Description of background Art

Extra corporeal circuits are regularly used during surgery and in particular for open heart surgery and are controlled by a Perfusionist. Venous blood bypasses the heart in one such circuit and is reintroduced into an artery in a patient's body after it has been oxygenated. Pericardial blood is also removed from the surgical site and is combined with the venous blood, oxygenated and subsequently reintroduced into the patient's body. One of the remaining problems associated with cardiac surgery is post-operative neurological dysfunction. Cardiopulmonary bypass (CPB) operations have been linked with micro embolisms in the small arteries of the brain, known as SCADS. The embolic material found in the arteries is believed to contain liquid fat from the pericardial suction blood which is reintroduced into the patients body after collection.

A number of solutions have been proposed to overcome this problem. One such solution is to wash the pericardial suction blood, however this technique is relatively expensive and time consuming. Another solution is filtration, a technique that can be inefficient due to the difficulties associated with filtration of fat in liquid phase. A third solution is to avoid re-transfusion of the pericardial suction blood. This solution adds known problems associated with an increased use of allogeneic blood, such as immunological modulation.

SUMMARY OF THE INVENTION

It is an object of the present invention to overcome the problems associated with the above outlined solutions associated with removal of fat from pericardial blood by providing an efficient and relatively inexpensive technique for fat removal.

Accordingly, there is provided an apparatus for reducing fat in blood comprising a conduit for blood, an absorbing material of a filter located in the conduit and an associated temperature control means for adjusting the temperature of the blood before it makes contact with the absorber.

Preferably, the absorber comprises a porous structure, a mesh structure, or a fibrous mass structure of lipophilic material of variable depth that increases the contact surface area to blood, herein referred to as filter. The term filter may also comprise a thin structure of surface coating when so is described.

Ideally, the absorbing filter is in contact with blood, not necessarily meaning blood passing thorough the filter from one side to the other.

As the solid or high viscosity fat makes contact with, or passes through, the absorbing filter it adheres to the filter thereby reducing the fat content of the blood.

In another aspect of the invention, the temperature control means maintains the blood at a suitable temperature for transfusion back into the patient's body. At the maintained temperature, or slightly heated, the separation of fat from the blood medium may also be facilitated as the viscosity of fat is maintained or lowered.

Preferably, the temperature control means is provided by a heat exchanger in contact with the conduit.

Ideally, the absorber is manufactured from cellulose or polyester fiber but can also be based on derivatives of polyamides, polyolefins, or polyvinyl fluoride, although not being limited to any of these materials.

In another aspect of the invention, there is provided an apparatus for reducing fat in blood comprising a chamber having an inlet and an outlet wherein the chamber is arranged with a first compartment for receiving blood via the inlet and a second compartment in fluid communication with the first compartment via a channel which connects the base of the first compartments with the base of the second compartment, the second compartment defining the outlet, the compartments being dimensioned and spatially arranged relative to one another whereby in use blood flowing into the second compartment from the first compartment reaches the same vertical height as blood in the first compartment preventing the last portion of the blood in the first compartment flows out of the first compartment. Advantageously, the last portion of blood which has collected adjacent the top surface of the blood in the first chamber has a high concentration of fat which always remains in the first compartment.

Preferably, the channels are releasably sealable by sealing means.

Ideally, a blood pipe passes through the inlet, the chamber and the outlet and the portion of the blood pipe within the chamber defines perforations.

Preferably, a separate filter is located within at least one compartment.

Preferably, the heat exchanger is mounted on the chamber.

Ideally, the heat exchanger is provided by a heat exchange chamber having and inlet and an outlet.

In another embodiment, the heat exchanger is provided by a piezoelectric element.

Preferably, the apparatus can be supported on a holder.

Ideally, the holder is constructed from a light coloured material.

Preferably, the holder includes an illuminating background which makes the layer of fat easier to see.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings and initially toFIG. 1, there is shown a chamber2for separating fat from blood. The chamber2has an inlet5and an outlet6. The chamber2has a substantially rectangular shape and a pipe4extends along one edge7of the chamber2. The chamber2has a slot8on the edge7exposing a portion9of the pipe4. The remaining portion18of the pipe4between the inlet5and the outlet6is enclosed within the chamber2and has perforations201. The pipe4may be located anywhere within the chamber2with opening8exposing a portion of the pipe4. A sealing clamp10is mounted on the exposed portion9of the pipe4. The chamber2is divided into two compartments11and12by a welded seam14. The compartments11and12are in communication via a first channel15due to an interruption in the seam14and a second channel, in this embodiment provided by the portion9of the pipe4bridging the slot8. A de-foamer16and an air escape valve17are located along the uppermost edge19of the chamber2when the chamber2is in an in use position. A volume scale20for each of the compartments11and12is incorporated into the plastic material of the chamber2. A second sealing clamp22is mounted on a portion23of the pipe4outside the chamber2after the outlet6. The chamber2and pipe4described in this embodiment are produced from a pliable transparent plastic material, although they are not limited to this particular material. A chamber2manufactured from a rigid material is also within the scope of the invention.

In use, pericardial suction blood from a surgery site is pumped to the inlet5of the pipe4and continues down through the pipe4until it reaches the clamp10. As blood abuts against the blocked pipe4, barometric pressure forces blood and air from the wound out through perforations201in the portion18of the pipe4. Blood collects in compartment11and the fat contained therein flows to the top of the blood under a normal process of separation. If the blood fills the compartment11, it can flow over into compartment12via channel15. The de-foamer16is activated in the event of foaming of blood in its vicinity. Seam14and an additional seam31promote the flow of blood towards the clamp10and the outlet6respectively when the chamber2is held in an in use position. When the perfusionist is satisfied that a substantial portion of the fat has collected in a layer on top of the blood in compartment11, the clamp10is opened and under normal barometric pressure, the blood flows from compartment11into compartment12. The geometry of compartments11and12and their spatial orientation relative to one another is designed so that a final volume of blood containing the layer of fat which has collected on top of the blood in compartment11remains in compartment11after the transfer of the blood to compartment12. This design feature of the chamber2reduces the need for careful visual monitoring of the transfer of blood from compartment11to compartment12by a perfusionist, improving the functionality of the chamber2. When substantially all of the blood from compartment11has transferred to compartment12, the clamp10is reapplied to the exposed portion9of the pipe4. It is not necessary, but it is possible, to stop the pump at any stage of the process. The compartment11refills with inflowing blood from the surgery site. The separated fat layer remains adjacent the surface of the blood. Fat contained in the blood flowing into the compartment11again begins to float towards the surface of the blood stored in the compartment11. The fat contained in the blood stored in compartment12also floats towards the top surface. There is no turbulence from incoming blood to disturb the process of separation in compartment12so further separation of fat and blood occurs efficiently. The second clamp22is opened after a predetermined time and blood flows from the compartment12into a venous reservoir (not shown) or directly back to the body of a patient. The perfusionist prevents the last portion of the blood which contains the layer of fat from leaving compartment12through the outlet6. The scale20on the chamber2is used for this purpose in conjunction with visual monitoring by the perfusionist.

This construction of chamber2provides the operator with a variety of uses for the chamber2when the chamber is manufactured from a pliable plastic material. On delivery, the chamber2is rolled around the pipe4. If an operator wishes to avail of the function of fat separation, the chamber2is uncoiled from the pipe4and mounted on a holder (not shown). Alternatively, the chamber2can be manufactured having a short pipe4which is connected, or cut in, to an existing pipe used for standard and commercially available machinery of heart lung technology. These pipe-to-pipe connectors are of standard design and commercially available. The inlet pipe5and outlet pipe6may have branched connectors for in and out coming pipes. The chamber2includes a recess (not shown) in or about edge19for receiving a spike for releasably securing the chamber2on the holder. Alternatively, the chamber2can be used as a standard blood pipe4with the chamber2remaining wrapped around the pipe4during use. The air valve17is in a closed position on delivery and must be opened if the fat separation function is needed. If a large volume of blood is being removed from the surgery site, it is possible to use the chamber2in an open system, allowing blood to flow through the system continuously provided the inlet5and outlet6are in direct communication.

Referring toFIG. 2, there is shown a chamber2substantially as described inFIG. 1. Reference numerals used to designate features of the chamber2ofFIG. 1are used to designate identical features of the chamber2inFIGS. 2 to 6, which illustrate similar embodiments of the chamber2. InFIG. 2, an additional compartment41is shown having an integral filter42welded or glued to the plastic material of the compartment41. A second recess43exposes an additional portion44of the pipe4and a third clamp45is mounted on this portion44. The chamber2works in the same way as the chamber2ofFIG. 1but including the additional step of blood in compartment12flowing into compartment41and contacting the absorbing material of the filter42prior to the blood flowing back to the venous reservoir or back into the patient's body. The filter42absorbs fat from the blood which has reached a partially solid state or fat which has an increased viscosity due to (1) cooling as a result of the blood being stored in the chamber2during the separation process and/or (2) cooling by a heat exchanger (not shown). This chamber2is also suitable for allowing through flow of blood by removing all the clamps10,22,45, if high volume bleeding occurs at the surgery site.

Referring now toFIG. 3andFIG. 4, there is shown a chamber2as described inFIG. 2above.FIG. 4shows a filter42welded or glued to an internal surface51of the chamber2. The de-foamer16is shown adjacent the top edge52of the chamber2. Referring now toFIGS. 5 and 6, a second embodiment of filter61is shown which is free to move in the compartment12and without blood passing through the filter61. Alternatively, the filter61can be fixed to either or both internal surfaces62of the chamber2. It is also within the scope of the invention to envisage an additional absorbing filter located freely or fixed in the compartment11. In use, the blood contacts the filter61, which is typically but not exclusively manufactured from cellulose or polyester fiber and fat particles adhere to the filter61. This filter61further increases the separation of fat and blood already occurring due to flotation of fat to the surface of the stored blood.

FIGS. 7 and 8show a third embodiment of chamber2having specially formed attachments71integrated into a side74of the chamber2for inlet pipe72and outlet pipe73. A similar attachment71is used for the air escape valve17. This construction removes the need for a pipe4extending within the chamber2. A clamp75is mounted directly onto the chamber2on or about channel13in order to prevent blood from flowing between compartments11and12. It will of course be appreciated that filters of the type described in relation toFIGS. 2 to 6may be incorporated into the chamber2of this embodiment.FIGS. 9 and 10show the chamber2ofFIG. 1incorporating a heat exchanger80. In particular,FIG. 10shows a heat exchanger80having a heat exchange chamber81fixed onto one side, of the chamber2. The heat exchange chamber81has an inlet82and an outlet83and provides a pathway for a flow, preferably although not exclusively a reverse-flow (relative to the direction of flow of blood), cooling or heating medium which can be pumped through the heat exchange chamber81. In use, the cooling medium lowers the temperature of the blood towards approximately 5°-10° C. At lowered temperatures, fat in the liquid form contained in the blood solidifies or has a higher viscosity, and is much easier to remove from the blood by contact with absorbing filters42,61as described above. Alternatively, the blood temperature is maintained at 37° C. or increased towards approximately 40° C. in order to lower the viscosity of fat in liquid form which facilitates its separation from the blood medium. In this configuration, the medium passing through the heat exchange chamber81has a temperature to prevent cooling and may heat the blood above the 37° C. body temperature.FIGS. 11 and 12show a different construction of heat exchanger90which is provided by a coil92fixed to one side of the chamber2. The coil92has an inlet93and an outlet94which, in combination with the coil92, provide a pathway for the temperature-controlling medium.

FIG. 13andFIG. 14show an alternative construction of heat exchanger100provided by a piezoelectric element101mounted on one side of the chamber2. In this embodiment, the piezoelectric element101has a number of recesses102on one face103. The recesses102extend from and are spaced angularly around a central point104which defines an opening into a bore105. Alternatively, the bore105may be located anywhere along any of the recesses102. The bore105extends through the piezoelectric element101and is connected to a vacuum pump (not shown). Alternatively, the bore105may extend and connect to the vacuum pump from other locations of the piezoelectric element101. The piezoelectric element101is placed in contact with the chamber2and the vacuum pump generates a vacuum resulting in the chamber2and piezoelectric element101adhering to one another. The piezoelectric element101induces cooling of the blood flowing through the chamber2via an electrical circuit. A piezoelectric element101can be provided on both sides of the chamber2.

FIGS. 15 and 16show another configuration of heat exchanger110provided by a double-sided coil111. The double-sided coil111is connected via a port112allowing the cooling/heating medium to flow through the coil111on both sides of the chamber2. The cooling/heating medium flows in through inlet114and up along one side of the coil111. The medium passes through port112and flows down along the opposite side of the chamber2and out through outlet115. It is also possible to provide two separate coils111, one on each side of the chamber2.FIGS. 17 and 18illustrate another embodiment of heat exchanger130. In this embodiment a heat exchange chamber131having an inlet132and an outlet133is located within the chamber2. In use, the medium flows into the heat exchange chamber131through inlet132and is pumped up through the heat exchange chamber131contra to the flow of blood or in the same direction.

FIG. 19illustrates an apparatus1having a heat exchanger161having an inlet162and an outlet163providing a flow path for a medium into, through and out of the heat exchanger161. Within the heat exchanger161is a separation chamber164having a blood inlet pipe165and a blood outlet pipe166. The separation chamber164also includes an air escape valve167and has an absorbing filter168housed within the chamber164. The blood outlet pipe166flows to a venous reservoir169, the venous reservoir169being a part of commercially available heart and lung machines used for cardiac surgery. Alternatively, the blood with reduced fat may also be allowed to drain directly into the body of the patient (not shown). In use, pericardial blood is pumped by a standard pump153from surgery site151to the separation chamber164via the blood inlet pipe165. It will of course be appreciated that blood could be aspirated by the standard pump153or a vacuum source (not shown) through the separation chamber164for which mode of action the air escape valve167is omitted. A portion152of the blood inlet pipe165is contained within the heat exchanger161and blood flowing through this portion152is subject to cooling prior to entering the chamber164by the cooling medium flowing through the heat exchanger161. The cooled blood has a temperature towards approximately 5°-10° C. as it enters the chamber164. At this temperature the fat contained within the blood has solidified, or reached a level of high viscosity, and is absorbed by the filter168, which preferably but not exclusively is formed from cellulose or polyester fiber. The fat-reduced blood returns to the venous reservoir169. In this embodiment, blood can flow continuously from the surgery site151through the apparatus without the need for clamps or other flow restrictors. The chamber164is produced from a pliable transparent plastic material, although they are not limited to this particular material. A chamber164manufactured from a rigid material is also within the scope of the invention. The heat exchanger161could have features similar to that described in any of the previousFIGS. 9 to 18.

FIG. 20shows an apparatus1having a pump173mounted on a pipe174between the surgery site172and a heat exchanger175. The heat exchanger175is mounted on a portion of the pipe174leading into chamber2. The chamber2in this embodiment is similar in construction and function to the chamber2described inFIG. 1. A commercially available filter179for through flow of blood such as (PALL LeukoGuard RS®, PALL Medical, Portsmouth, England) is provided on a section of the pipe174leading away from the chamber2. The pipe174is then connected to a venous reservoir176or is connected directly back to the body of the patient177. In use, blood is pumped from the surgery site172by a standard pump173to the heat exchanger175via the pipe174. The heat exchanger175is used to reduce the temperature of the blood towards approximately 5°-10° C. The chamber2includes a number of absorbing filters (not shown) which are preferably, but not exclusively manufactured from cellulose or polyester fiber. Fat in the pericardial suction blood solidifies or reaches a level of high viscosity at reduced temperatures and is absorbed by the filters. In addition, the blood and fat can be separated further in the chamber2as described in the in use description ofFIG. 1. The commercial filter179removes any fat remaining in the blood after it passes through the chamber2. The blood is then alternatively redirected to the venous reservoir176or back to the patient's body177.

Referring toFIG. 21there is shown a chamber181comprising compartments184and185as separate units connected by pipes182and183. It will of course be appreciated that a heat exchanger as previously discussed could also be applied to the apparatus1of this embodiment. The pipe174from the surgery site172branches into two separate pipes202,203which enter a chamber184and185respectively. A clamp187blocks the pipe203entering chamber185. Outlet pipes188,189extend from the base of the compartments184and185respectively and these pipes merge together to form a single pipe190. A second clamp191blocks the pipe188emerging from compartment184and a third clamp192blocks the pipe190. In use, blood flows unimpeded into compartment184until it reaches clamp191. The fat in the blood collecting in compartment184starts to float towards the surface of the blood. When the compartment184has a predetermined amount of blood contained therein, lamp191is opened and the blood flows through the outlet pipe188and up into the compartment185. The fat which has collected adjacent the surface of the blood remains in the compartment184. The clamp191is closed when the desired amount of blood has flown into the compartment185. This blood is allowed to settle again in the compartment185in order to allow additional fat to float to the surface of the blood. After a predetermined period, clamp192is released and all the blood except the blood containing the separated fat is allowed to flow out of the compartment185. This blood flows through filter179removing still further fat. It will of course be appreciated that filters can be located in both or either of the compartments184and185. In an alternative mode of operation, the two compartments184and185can be used separately. In use, blood flows unimpeded into compartment184until it reaches clamp191. When the compartment184has a predetermined amount of blood contained therein, clamp187is opened and moved to instead occlude inlet pipe202. Additional blood now enters the opened inlet tube203and container185. The fat in the blood collected in compartment184starts to float towards the surface of the blood without interference from turbulence of incoming blood. After a predetermined time the lower fraction of blood in container184is emptied by first occluding the outlet pipe189, by moving the clamp192to its new location189, and opening the outlet pipe188by removing clamp191. The top fraction of blood in container184, holding a concentrated amount of fat, is prevented from reaching the patient by re-occluding outlet pipe188using clamp191. The same procedure is carried out with compartment185after filling with further incoming blood being re-directed to again fill compartment184.

Referring to the drawings and finally toFIG. 22there is shown an apparatus1having a chamber300comprising compartments301and302and with an interconnecting conduit303. The chamber300is substantially as described inFIG. 1with reference to chamber2but with a spatial arrangement of compartment301being above compartment302. An inlet304directs blood via pipe305to collect in compartment301via perforations306identical to what is described for pipe4, compartment11, and perforations201inFIG. 1. The pipe305is here illustrated to have essentially a central location within chamber300but can be located along the edge of chamber300similar to what is described for pipe4of chamber2inFIG. 1. The chamber300has an opening307positioned within the space of compartment301created by an encircling welded seam308exposing a portion309of the pipe305. A first sealing clamp310is mounted on the exposed portion309of the pipe305to block the pipe305in order for blood to collect in compartment301. Air that collects in compartment301together with blood pumped from the patient's wound escapes from compartment301via a valve opening311that is positioned essentially along the top edge of compartment301, similar to what is described for valve17inFIG. 1. In the case of excess of blood in compartment301, due to accidental filling by the perfusionist, blood escapes through the named valve311. The valve311could be connected by a separate pipe to the venous reservoir (not shown). The compartment301is in connection with compartment302via the conduit303. The conduit303comprises a channel312at the bottom of compartment301, an entrapped space313of compartment301created by two welded seams314that connects with the welded seam308, perforation315of pipe305, an extension316of pipe305into compartment302, and perforation317of pipe305. The spatial arrangement of the details312,313,315, and316of conduit303create together a water-lock mechanism320. The water-lock mechanism320is symmetrically arranged on both sides of the pipe305but can also be single-sided in the case the pipe305is located along the edge of the chamber300, similar to what is described inFIG. 1. It is of course appreciated that the arrangement of details within the water-lock mechanism320is not limited to the described design. The conduit303has an opening321, similar to307, exposing a section322of the pipe316. A second sealing clamp325is mounted on the exposed section322of the pipe316to open and close the conduit303. Located at the top of the entrapped space313is a venting port327consisting of a pipe328inside compartment301in connection with the top of chamber300. The pipe328could connect with the valve opening311. It is of course appreciated that the port327and venting pipe328can have a path outside compartment301. The venting port327of conduit303prevents a negative barometric pressure to build up within the water-lock mechanism320to prevent a portion of the blood that has accumulated in compartment301to fill over to compartment302when the sealing clamp325is released. Fat collects at the top surface of blood in compartment301and remains in compartment301together with the top portion of blood that is prevented to flow over into compartment302. The flow rate by which fat-reduced blood fills over from compartment301to compartment302is controlled by the flow resistance of conduit303, in particular but not limited to a narrowing within channel312. A typical drainage time is about 30 seconds but can set to other time duration depending on use of the apparatus1. The compartment302comprises an extension316of pipe305with one or more perforations317, and pipe305emerges at the bottom of compartment302to form an outlet330. A third sealing clamp331is mounted on the pipe305at outlet330of compartment302to control drainage of blood from the chamber300into the venous reservoir (not shown) or back into the patient's body. This chamber300is also suitable for allowing through flow of blood by removing all the clamps310,325,331, if high volume bleeding occurs at the surgery site. It is well appreciated within the scope of the invention that the design of compartment302can be similar to what is described for compartment301comprising a second water-lock mechanism identical to the water-lock320. The second water lock prevents the last portion of blood in compartment302, containing a concentrated amount of fat that has accumulated at the top surface of blood, to reach the patient's body. It is also understood that additional compartments, identical to301and302, can be connected in series to form a multi-compartment fat-separation chamber. It will further be appreciated that a fat-absorbing filter of the type described in relation toFIGS. 2 to 6may be incorporated into the chamber300of this embodiment, that a heat exchanger as previously discussed could also be applied to the apparatus1of this embodiment, and that pipe connections71ofFIGS. 7 and 8could be used within this embodiment. The chamber300and pipe305described in this embodiment are produced from a pliable transparent plastic material, although they are not limited to this particular material. A chamber300manufactured from a rigid material is also within the scope of the invention.

It will of course be appreciated that the clamps described are not limited to manual actuation and could be operated mechanically, electrically, pneumatically or hydraulically.

It will of course be appreciated that the invention is not limited to the detailed description of the specific embodiments, which are given by way of example only, and that various alterations and modifications may be made to the embodiments without departing from the scope of the invention as defined in the appended claims.