Combined cardiotomy/venous/pleural drainage autotransfusion unit with filter ...

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COMBINED CARDIOTOMY/VENOUS/PLEURAL
DRAINAGE AUTOTRANSFUSION UNIT WITH
FILTER AND INTEGRAL MANOMETER AND

WATER SEAL 5

FIELD OF THE INVENTION

The field of this invention pertains to surgical apparatus. More particularly, it lies within the field of surgical apparatus for use in open-heart and chest cavity sur- 10 gery. Such surgery can be performed utilizing oxygenators and certain reservoirs, as well as post operative devices for the patient. This invention pertains to such operation and post operative devices.

BACKGROUND OF THE INVENTION

During certain operations such as cardiopulmonary bypass operations, the function of the heart and lungs are interrupted and blood is artificially handled. The patient's body temperature is lowered and the heart 20 itself stops beating. Circulation is maintained by withdrawal of the venous return stream through a venous cannula inserted into the right atrium, passed to a venous reservoir, passed through a blood pump (artificial heart) to a blood oxygenator (artificial lung), arterial 25 blood filter which removes fine air bubbles and any undesirable particles that may be present in the blood before it is returned to the patient through an aortic annula.

Also, during a cardiopulmonary bypass operation, it 30 is essential to suction away the various fluids including, for example, air, debris such as bone chips, blood, saline solution, liquids applied to the heart and the like. This must be accomplished as quickly and efficiently as possible without causing injury to the patient primarily in 35 order to avoid damage to the heart from the fluid pressure but also to aid the surgeon.

Such fluids are termed "cardiotomy blood" which requires filtration prior to reinfusion. This term is distinguished from "shed blood" used to describe the blood 40 accumulation which takes place after surgery and which is characterized by being of much higher quality and requiring less filtration.

Normally, a cardiotomy reservoir is used in conjunction with relatively high vacuum suction in order to 45 remove and collect the cardiotomy blood and other liquids as quickly as possible. This vacuum can be provided through a standard air driven cardiotomy sucker through a roller pump. Use of the roller pump is clearly the method of choice since the suction can be carefully 50 controlled and monitored.

Blood collected within a cardiotomy reservoir can be filtered and defoamed to remove air, debris and clots after which it can be reinfused to the patient. This can take place during or after surgery. 55

In recent years it has been found desirable during surgery to combine the cardiotomy blood with the venous blood in a single reservoir which replaces the separate cardiotomy reservoir and separate venous reservoir formerly used. This created some problems since 60 the flow rate of venous blood is about 3 times greater than the flow of cardiotomy blood. Moreover, the venous blood is clean requiring only minimal defoaming and filtration. When venous blood was subjected to the same filtration as used for cardiotomy blood, it was 65 found detrimental to the blood cells.

In recent years, in order to overcome this problem, separate filter chambers were provided within a single

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chamber to provide for separate filtering of venous blood and cardiotomy blood. Such a device is described in U.S. Pat. No. 4,642,089. This device comprises a hollow housing made of a rigid material having disposed substantially annularly a filter chamber spaced from the exterior walls of the unit. The filter chamber contains two separate chambers, an upper chamber for introduction and filtration of cardiotomy blood through a non-woven depth filter and a defoaming material and a lower chamber including a defoaming filter material but free of the non-woven depth filter.

Cardiotomy blood enters the upper filter chamber from the top of the unit and venous blood enters the lower filter chamber through the bottom of the unit. Blood entering either chamber passes through the filter and/or defoamer and is combined in a space defined by the outer walls and the filter chamber where it can be withdrawn for reinfusion to the patient.

There are several drawbacks associated with the cardiotomy/venous blood unit of U.S. Pat. No. 4,642,089. For example, venous blood, which is normally obtained by gravity flow, enters the unit from the bottom of the unit into the bottom venous chamber, where it passes through the defoaming filter prior to discharge through a bottom discharge port. The disadvantage is that this condition can lead to resistance to entry of venous blood and to discharge in the bottom leading to stasis. When the bottom or venous compartment is partially filled, the incoming venous blood must enter against this resistance. There is an inverted flow director facing downwardly within the venous chamber for direction of blood from the venous inlet toward the filter. However, this flow director is insufficient to avoid stasis. It is not good to have blood standing anywhere in the reservoir due to the formation of clots.

In U.S. Pat. No. 4,642,089, the upper cardiotomy chamber has a baffle spaced from the inlet to the cardiotomy chamber for purposes of directing the cardiotomy blood flow downwardly into the cardiotomy chamber. A flow director in the form of a truncated cone having 4 opposed fins extends the length of the cardiotomy chamber to prevent splashing and to direct the cardiotomy blood flow against the surrounding filter. The filter is comprised of a non-woven depth filter material which filters by excluding a range of size of particles and is thus only partially effective for filtration. Finally, this device does not permit postoperative drainage of shed blood or pleural drainage.

After surgery, it is desirable to provide drainage of shed blood and fluid from the area around the operative site using relatively low suction pressure as compared with the suction used for cardiotomy suction. This is a requirement to avoid injury to body tissues.

Similar low suction pressure requirements exist for pleural drainage whereby fluid, blood and gases including air are removed from the pleural space between the lungs and the rib cage to maintain the lung in the fully expanded condition. The need for pleural drainage can arise as a result of surgery, piercing of the rib cage or from illness.

In addition to low suction pressure, it is a second requirement to prevent backflow of air to the patient which could cause an emboli or introduce microorganisms into the shed blood or pleural drainage fluids to the detriment of the patient. This can happen if the vacuum is interrupted such as during transfer of the patient.

In the past such postoperative or pleural drainage has been effected by means of a three bottle system. This system consisted of a collection bottle, a liquid seal for gases to bubble through and prevent backflow into the patient, and vacuum regulation of suction flow. 5

It is desirable for the above reasons to closely monitor negative or vacuum pressures during pleural drainage. Also, if the vacuum is lost for any reason, a water seal prevents air from flowing freely back into the pleural cavity. When the patient coughs, the negative pressure 10 can be excessive which can result in water being sucked out of the manometer into the' water seal or collection chamber.

More recently, the three bottle system has been combined with a flexible and detachable blood bag in a IS device of the type described in U.S. Pat. No. 4,781,707. This device collected shed blood in a detachable blood bag for reinfusion to the patient. This device, however, is not suitable for cardiotomy and venous blood collection during surgery. 20

SUMMARY OF THE INVENTION

An improved unit is provided by this invention having combined cardiotomy and venous reservoir capabilities with filtration and defoaming for autotransfusion of 25 cardiotomy blood and venous blood during surgery and for postoperative wound site pleural drainage of shed blood for continued autotransfusion using the same unit. Vacuum regulation in the form of a manometer combined with a water seal are integral with the unit. 30

The unit is comprised of a rigid, substantially cylindrical housing having a top, bottom and side walls and having an annularly disposed central substantially cylindrical filter spaced from the outer housing walls and extending from the top of the housing to a point spaced 35 from the bottom of the unit.

The cylindrical filter is divided into an upper cardiotomy blood chamber for receipt, defoaming and filtration of cardiotomy blood and a lower venous blood chamber for receipt, defoaming and filtration of venous 40 blood. The area between the housing side walls and the substantially cylindrical filter as well as the area between the housing side walls and an inner wall extension defines a filtered blood reservoir where filtered cardiotomy blood from the cardiotomy blood reservoir 45 chamber and filtered venous blood from the venous blood reservoir chamber are combined.

The filtered blood reservoir has a downward slant on one side for gravity flow of blood to an outlet port for removal of blood for reinfusion. 50

Disposed within the filtered blood reservoir and extending along the length thereof are two long, relatively narrow chambers which extend from top to bottom of the unit and are juxtaposed relative to each other. A first chamber acts as a water seal and the second cham- 55 ber acts as a manometer for postoperative use for pleural drainage and collection of shed blood for reinfusion to the patient. The two chambers are integrally formed within the filtered blood reservoir.

The cardiotomy chamber includes a support grid 60 surrounded on both sides by an open cell sponge filter coated with a defoaming agent. The chamber also includes a pleated filter made up of a 28 micron screen filter which excludes all particles larger than 28 microns in size. The microporous screen filter is sandwiched 65 between and supported by two layers of mesh screen.

The unit of the invention preferably uses a defoaming agent which is an antifoam silicone oil with 4.5% of

silicone dioxide particles of about 4 microns in diameter suspended therein. The defoaming agent is sprayed onto the open cell sponge filter prior to emplacement within the unit. The use of a pleated filter provides a larger surface area for filtration than is provided by the nonwoven depth filters of the prior art devices resulting in more effective filtration.

The venous blood filter includes a polyurethane reticulated sponge filter having 20 pores per inch which is coated with a defoaming agent and which is supported by a grid.

The combination unit of the invention provides good throughput of both cardiotomy and venous blood by providing novel flow directors and good surface contact between blood and filters.

Several upright flow director fins surround the central venous tube inlet to direct suctioned cardiotomy blood and other additives into an inverted truncated conical member which opens into the cardiotomy reservoir chamber.

Venous entry takes place centrally at the top of the unit by means of relatively large diameter tubing to provide free flow without resistance. The venous inlet tube has an integral coiled wire reinforcement embedded therein to prevent kinking of the tubing.

The large diameter venous blood entry tubing passes through the upper cardiotomy reservoir chamber to enter the upper part of the venous reservoir chamber. The presence of the central venous tube within the cardiotomy reservoir provides for volume displacement to minimize splashing and it also serves as a flow director for incoming blood within the cardiotomy reservoir chamber. This condition helps to avoid stasis within the cardiotomy reservoir chamber.

The venous reservoir chamber is provided with an upwardly oriented substantially conical flow director to drain all venous blood toward and through the sponge filter and defoamer where the downward slant of the reservoir directs its flow by gravity to the exit or outlet port.

Another feature of this combination unit of the invention is the provision of a relatively large diameter entry port within the top of the device in communication with the cardiotomy reservoir chamber for postoperative use for pleural drainage and collection of shed blood. The provision of a top entry provides for free flow into the unit.

The invention provides an advantage of functioning as a cardiotomy reservoir and a venous reservoir for filtration and autotransfusion of cardiotomy blood and venous blood during surgery. After surgery, the same unit can be used for pleural drainage and collection of shed blood for autotransfusion to the patient. The integral water seal and manometer avoid the need for a separate manometer which is extrinsic to the unit. The use of the same unit during surgery and for pleural drainage minimizes the possibility of introducing microorganisms into the blood being transfused.

The use of the combination unit of the invention helps to conserve the blood of the patient as well as minimizing the risk of transfusion related infections and serves to return the patient's plasma and electrolytes.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more clearly understood by reference to the description below taken in conjunction with the accompanying drawings wherein: