Perfusion Policies 101: Vacuum Assisted Venous Return

VAVR (Vacuum assisted venous return)

Vacuum-assisted venous return (VAVR) offers some alternatives to conventional cardiopulmonary bypass (CPB) techniques.  It uses negative pressure to assist or augment venous return over traditional siphon drainage technique.  This technique utilizes a wall suction source to generate a vacuum and enhance venous drainage during open heart surgery.  Using VAVR allows smaller venous cannulae usage, smaller venous line size, and reduced prime.  It can be used on hard-shell venous reservoirs, as well as soft venous bags enclosed in a rigid, sealed, non-disposable housing.

VAVR WITH  A HARD-SHELL VENOUS RESERVOIR

Initial setup before going on bypass:

1. Assemble CPB circuit as per standard procedure. Test and install the positive pressure relief valve onto a vacuum-assist-capable hard-shell venous reservoir.  Place occluding plugs on all unused ports.
2. Properly occlude all roller pump heads. If using a centrifugal arterial head, make sure a one-way valve is placed between the centrifugal head and the oxygenator io prevent air from being pulled across the oxygenator fiber in the event of centrifugal pump stoppage.
3. Attach the “To Vacuum” connector of Bentley Vacuum Controller to a reliable hospital-grade (NFPA-U.S.) vacuum source.
4. Attach a calibrated means of monitoring negative pressures to the venous line and/or cardiotomy reservoir.
5. Verify that the “Conversion Module” vacuum line is connected to the moisture trap.
6. Attach the Conversion Module vacuum line to the To Reservoir connector of the Bentley Vacuum Controller, and the moisture trap to the vent port of the appropriate venous reservoir.
7. Clamp the venous reservoir drain line between the arterial pump head and the venous reservoir.
8. Clamp the venous line just distal to its connection to the venous reservoir pressure monitoring site.
9. Verify that all other ports and lines to the venous reservoir are closed to the atmosphere.
10. Verify that all roller pumps are off.
11. Clamp the To Reservoir vacuum line just below the Bentley Vacuum Controller.
12. Increase vacuum level to beyond -90mmHg to test the Safety Vacuum Interrupter.
13. Remove the clamp from just below the To Reservoir line and place it on the vacuum vent line of the Conversion Module.
14. Observe the venous drain line pressure and verify tht it is at least 60 mgHg to confirm (neg. pressure, needs to be here) system vacuum integrity.
15. Remove all unnecessary line clamps.
16. Clamp the To Reservoir vacuum line just below the Bentley Vacuum Controller.
17. Reduce vacuum level to -45mmHg.
18. Unclamp the To Reservoir vacuum line.

Initiating Bypass

1. Clamp arterial and venous lines.
2. Connect the extracorporeal circuit to the patient’s cannulae. Note: The venous return line need not be primed (follow current protocol).
3. To initiate bypass, verify that the arterial line is air free and unobstructed. Unclamp line and slowly initiate arterial flow.
4. Place clamp on the vacuum vent line of the Conversion Module, then unclamp the venous return line.
5. Adjust vacuum to achieve an appropriate and consistent rate of venous return and arterial flow.
6. Open arterial filter purge prtt when appropriate.
7. Verify that no air is trapped in the venous return line. (If air remains in the venous line, transiently increase the vacuum applied to the reservoir.  Once the air is removed, readjust the vacuum to an appropriate level.)
8. The roller pumps driving the vent and suckers may be started when required.
9. To achieve the desired venous return flow rate, adjust the vacuum using the Bentley Vacuum controller suction regulator knob.

Warnings

1. Obstruction of the vent/vacuum port could result in pressurization aof the reservoir and, potentially, gaseous bubbles passing to the patient and/or damage to the device.
2. Do not allow the venous reservoir to become overpressurized, as this could obstruct the venous drainage, force air retrograde into the patient, or cause air to enter the blood path of the oxygenator.
3. Do not allow the vapor trap to become completely filled during use. This may allow fluid to enter the vacuum controller or may prevent the reservoir from being vented to atmosphere when no vacuum is applied.
4. The cap must be removed from the vent/vacuum port to prevent inadvertent pressurization of the reservoir. The vent/vacuum port must remain open at all times during the operation of the reservoir or be attached to a regulated vacuum source not to exceed -90 mmHg in procedures that utilize VAVR.
5. Ensure that the cap on any unused port is airtight before initiating VAVR.
6. Do not let anesthetic agents, such as isoflurane, come into direct contact with this device. These agents may jeopardize its structural integrity.
7. Utilization of VAVR can lead to negative pressures in the oxygenator and the potential for air to be pulled across the oxygenator membrane into the blood pathway.
   The sample system, the arterial purge line, a hemoconcentrator,  a non-occlusive roller pump, a centrifugal pump, or any other connection between the patient’s arterial line and the reservoir may provide a conduit for the vacuum to be applied to the arterial side of the oxygenator.
8. Do not infuse fluids or drugs to the arterial side of the sample system.

Concluding Bypass:

At the conclusion of bypass, reducing vacuum level will reduce the rate of venous return.  When arterial flow is reduced to an acceptable level, disengage vacuum by removing the clamp from the vacuum vent line and wean the patient from CPB as per standard procedure.

VACUUM-ASSISTED VENOUS RETURN WITH A VENOUS BAG

Augmented venous return allows the perfusionist to use a venous line having a smaller inner diameter, thereby reducing prime volume, and allows the surgeon to use a smaller venous cannulae, resulting in easier insertion, better surgical view, and a smaller surgical incision.  Currently, augmented venous return is achieved either by applying vacuum directly to a hard-shell venous reservoir (vacuum-augmented venous drainage  – VAVD).  The former does not allow use of a closed-bag reservoir, whereas the latter requires an additional pump.  Therefore, users who prefer the safety of venous bags 9VBs) and would like to augment venous return without using a venous pump are unable to do so or must compromise.

Vacuum can be applied to a soft-shell venous reservoir by enclosing it within a rigid housing.  Once the bag is sealed within the rigid structure, vacuum applied to the space surrounding the bag is transmitted across the flexible wall of the bag to the blood.  It is as if the vacuum is applied directly to the blood, but without contacting it.  Thus, whatever negative pressure is in the house in (P housing), this is also the blood pressure in the bag (P blood), P housing- P blood.  A vacuum regulator controls the degree of vacuum of P housing, similar to a hard-shell reservoir.   The system allows the user to make the “atmospheric” pressure around the bag negative, and the negative pressure in the bag provides vacuum-assisted drainage.

WARNINGS AND PRECAUTIONS

• Read all instructions for use before setup.
• Only trained, qualified medical professionals familiar with its operation should use the VB
• CAUTION: Federal ( U.S.A.) law restricts this device to sale by or on the order of a physician.
• The VB is intended for single use only. Do not resterilize.
• Use aseptic techniques during setup and connection procedures.
• It is the responsibility of the surgical team to ascertain the suitability of the VB relative to the pumps, circuit components, and pumping conditions used.
• Tubing should be attached in such a manner as to prevent kinks or restrictions that may alter blood flow.
• The use of safety/warning devices for detecting and eliminating gaseous bubbles in the extracorporeal circuit, as well as a level sensor, an arterial filter, and a prebypass filter are recommended.
• Ensure that the bottom of the VB is positioned above the highest point in the membrane compartment of the membrane oxygenator. This helps ensure that the blood side pressure remains greater than the gas side pressure.
• Ensure that the tube connecting the cardiotomy to the VB inlet loops below the bottom of the VB holder. This minimizes the chance of air siphoned into the venous line via that tube when the cardiotomy is empty.
• Ensure that the support for the inlet tube int eh back of the holder lines up with the venous line ( see holder’s instructions for use.)
• Adequate heparinization must be maintained before and during bypass.

SETUP

1. Remove the VB from its package. The VB is sterile if its package is not opened or damaged.
2. Place the VB in its holder. The VB can be placed with the outlet on the left or right sice, as desired, Because the VB is loaded into its holder from the top, the front plate need not be removed between cases.  Instead, the front plate can be maintained at the desired position from case to case.
3. Remove the aerator cap from the upward facing port of the Y connector of the VB and connect the venous line to that port.
4. Remove the aerator cap form downward facing port of the Y connector of the VB and connect the cardiotomy outlet line to that port.

Warning: Avoid siphoning air from an empty cardiotomy to the VB via the venous line by looping the tubing between the cardiotomy and the VB below the bottom of the VB holder.

5. Remove the aerator cap from outlet connector and connect the inlet tubing of the arterial pump to it.
6. Remove the leur fitting off the top leur of the stopcock and connect it via a purge line with a one-way valve, to the inlet of a suction pump. Rotate the stopcock handle to form fluid communication between the VB and the suction pump.

PRIMING

NOTE: For easier debubbling, add noncrystalloid solutions only after priming and debubbling are complete.

1. Ensure that all tubing connections are secure, all leur fittings are tightly closed, and all stopcocks are closed before priming.
2. Prime the venous reservoir before priming the pump and oxygenator system.
3. Clamp the cardiotomy outlet tube.
4. Fill the cardiotomy reservoir with enough priming solution to prime the entire extracorporeal circuit.
5. Clamp the venous blood inlet to the VB.
6. Remove the clamp from the cardiotomy blood outlet tube and allow the priming solution to fill the VB.

CAUTION: Ensure that the suction pump is rotating in the correct direction and the stopcock on the purge line is open.

7. Turn on the suction pump connected to the purge line of the VB and remove all bubbles in the VB.
8. To prime a centrifugal pump, lower the pump head below the VB and propel the prim up the outlet tube of the VB and into and beyond the pump head by compressing the front wall of the VB. Once the head is filled, clamp its outlet, place it back into its drive, turn the pump on, and unclamp outlet tubing.
9. During bypass, thoroughly mixing of drugs added to the venous blood is ensured when adding them through the leur port on the venous inlet connector.

ADDITIONAL INSTRUCTIONS WHEN USING VACUUM-ASSISTED VENOUS DRAINAGE

Warnings

1. Be sure to read the instructions for use of the VAc-Box.
2. Obstruction of the vacuum port could result in pressurization of the reservoir and, potentially, bubbles passing to the patient.
3. Do not allow the venous reservoir to become pressurized, which may obstruct the venous drainage.
4. The vacuum port of the Vac-Box must remain open at all times or be attached to a regulated vacuum.
5. Do not apply a vacuum greater than -60 to the vacuum port.
6. Do not apply vacuum to the Vac-Box without having a forward flow. Without flow, the negative pressure may reach the blood side of the oxygenator and pull air across the membrane into the blood pathway.  Use a one-way valve at the outlet of the arterial pump to minimize that possibility.
7. Prevent anesthetic agents, such as isoflurane, from contacting the VB or Vac-Box. These agents may jeopardize the structural integrity of the VB or Vac-Box.
8. Use only cardiotomy reservoirs that incorporate a pressure relief valve and a vacuum relief valve.

PRECAUTIONS

1. Operating in the VAVD mode can lead to negative pressures in the oxygenator and to the potential for air to be pulled across the oxygenator membrane into the blood pathway. The sample system, the arterial purge line, a hemoconcentrator, a nonocclusive roller pump, a centrifugal pump, or any other connection between the patient arterial line and the reservoir may provide a conduit for the vacuum to be applied to the arterial side of the oxygenator.  Be sure that one-way valves are incorporated where necessary to prevent retrograde flow.
2. Do not connect patient vent lines to the filtered prtts of the cardiotomy reservoir unless some means of preventing retrograde flow toward the patient is located between the patient and the cardiotomy reservoir.
3. Ensure that the bottom of the venous reservoir is positioned above the highest point inside the membrane compartment of the oxygenator. This will reduce the possibility of pulling gas from the gas side into the blood side of the membrane oxygenator.
4. Be sure to monitor the pressure at the inlet to the venous bag. Set the alarm to no higher than -60 mmHg.
5. Use only a reliable wall suction and calibrated vacuum regulator specified for VAVD. Be sure to follow the instruction for use associated with that regulator (e.g., use of vapor trap).

CAUTION: Never apply vacuum to only the cardiotomy or only the Vac-Box.

6. Use caution when infusing drugs or any other fluid during VAVD. The vacuum can increase the rate of infusion into the reservoir significantly higher than clinically desirable.

SETUP PROCEDURES

1. Ensure that the mounting bracket of the Vac-Box is securely fastened to the pump console and oriented to provide maximum visibility during use.
2. Rotate the volume adjustment levers to retract the back pusher-plate to its open-most position to allow easy insertion of the VB.
3. Lift and rotate the retaining knobs, lo0cated along the left and riht top of the Vac-Box, to allow insertion of the VB.
4. Insert the VB into the Vac-Box by angling the front portion lower than the back to allow the white plate to of the VB to slip under the lip of the front railing of the VAc-Box. Align this white plate within the space provided by the railing of the VAc-Box.  This will assure a proper seal.
5. Rotate the retaining knobs, located along the left and right top of the VAc-Box, 180* until they push against the sides of the white top-plate of the VB.
6. Connect a ¼” Y connector to the outlet of the vacuum regulator and attach a ¼” tubing to one of its open ends.  This tubing, referred to as the vacuum bleed line, should be easily reached.  Clamp this bleed line to apply vacuum and uinclamp it to relieve the vacuum.

CAUTION: The same vacuum must be applied to the cardiotomy reservoir as is applied to the Vac-Box.  Equalizing the vacuum applied to the VB and the CArdiotomy reservoir assures that operation of the cardiotomy relative to the venous bag will be the same as without vacuum.  This is achieved by step 7.

7. Connect a second ¼” Y connector to the open end of the first Y connector. Connect the one open end of the second Y connector to the Vac-Box and the other end to the cardiotomy reservoir via a vapor trap.  The vapor trap should be replaced for each case.  This arrangement provides the same vacuum to the cardiotomy reserfoir as is applied to the Vac-Box.

CAUTION: Use only a cardiotomy with pressure and vacuum relief valves and follow the instructions for use associated with that unit for VAVD mode (e.g. plugging all unused ports).

8,  Be sure that all pumps are off.

9. Clamp the outlet tubing of the venous reservoir.
10. Clamp the inlet tubing to the venous reservoir above the location of the pressure sensor.
11. Verify that all other ports and lines to the cardiotomy reservoir are closed to the atmosphere.
12. Clamp the vacuum bleed line – this directs the vacuum to the VAc-Box and cardiotomy reservoir.
13. Increasethe vacuum via the vacuum regulator beyond – 80 mmHg and observe that the vacuum reading on the vacuum auge does not increase beyond -100 mmHg. If – 100 mm Hg is exceeded, replace the Vac-Box.
14. Remove all unnecessary line clamps.
15. Clamp off the vacuum line exiting the vacuum controller. Use the vacuum regulator to reduce vacuum to -45 mmHg.
16. Unclamp the vacuum bleed line – this removes vacuum from the Vac-Box.

Initiating Bypass

17. Initiate bypass per your protocol.
18. Place clamp on the vacuum bleed line.
19. Adjust the vacuum regulator until venous drainage is as desired.

CAUTION: Do not exceed a vacuum of -60 mmHG.

20. Rotate the volume adjustment levers to adjust the back pusher-plate to adjust the maximum volume the VB accommodates. The filling volume can be adjusted between a minimum of 880ml aqnd a maximum of 1750 ml.

Concluding Bypass

At the conclusion of bypass, reduce vacuum level to reduce venous drainage until arterial flow is reduced to an acceptable level, until vacuum is no longer needed.
Disengge the vacuum by removing the clamp from the vacuum bleed line, and wean the patient from CPB as per standard prodedure.

CLEANING/DISINFECTING THE VAC-BOX

CAUTION: The Vac-Box is made of Lucite (an acrylic) and therefore contact with solutions containing chlorine, ammonia, or solvents must be avoided. (Box 1)

The Vac-Box can be cleaned using mild soap and warm water  It can be disinfected by wiping its surface with 70% isopropyl alcohol.

Routine Maintenance

The Vac-Box should be visually inspected to assure that it is crack free and that the seal along the top opening is intact.

Unit Specifications

Model # Vac-Box15

A rigid housing for use with the VB for VAVD applications.

IFUVB – 0102

US Pat. 6337049, others pending.