The Effect of the Hemobag® Ultrafiltration System on Blood Conservation and Coagulation After Cardiopulmonary Bypass



Status:Completed
Conditions:Hematology
Therapuetic Areas:Hematology
Healthy:No
Age Range:18 - Any
Updated:6/7/2018
Start Date:September 2011
End Date:December 2014

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This proposal is designed to mitigate hemodilution (blood diluted with an electrolyte
solution) and loss of plasma proteins responsible for normal blood clotting as well as
platelets at the completion of cardiopulmonary bypass (CPB). The Hemobag® system is a device
qualified by the US Food and Drug Administration (FDA). Many cardiac centers, such as
Englewood Hospital and Medical Center in Englewood NJ are using the Hemobag® system for
Jehovah's witnesses and other patients who go to that center for bloodless cardiac surgery
(cardiac surgery performed without the use of blood or blood products). The system is
designed to filter excessive water from blood left in the heart lung machine (cardiopulmonary
bypass) after it is separated from the patient during the performance of cardiac surgery.
Consequently the likelihood of excessive post-operative bleeding and transfusion with
allogeneic blood (blood bank blood from donors) is decreased.

Background:

Cardiopulmonary bypass (CPB) consists of an extracorporeal (outside of the body) circuit
which allows the circulation and oxygenation of blood during cardiac surgery. The circuit
includes an oxygenator, a reservoir and tubing, all of which needs to be primed with a
balanced electrolyte solution. Prior to initiating CPB, the venous and arterial ends of the
CPB circuit are appropriately attached to the patient. The volume of the circuit is usually
1.5 liters which is equivalent to 30-38% of a typical patient's total blood volume that is
generally between 4 and 5 liters.

When CPB is initiated, the patient's blood is mixed and diluted by the CPB priming fluid.
Consequently, when the operation is completed and the CPB is discontinued, the content of the
CPB circuit consists of the patient's diluted whole blood. The standard practice is to return
as much of this hemodiluted CPB contents as the patient will accommodate and process the rest
of the contents of the circuit with a cell washer and return packed red blood cells to the
patient.

When the cell washer is used, plasma proteins, clotting factors and platelets are not
returned to the patient. An alternate approach would be to use an ultrafiltration device to
remove this non-cellular water and preserve proteins,

clotting factors and platelets as well as red blood cells that can then be returned to the
patient. This alternate approach is the basic principle of the Hemobag®, an ultrafiltration
technology and method.

Ultrafiltration is a well documented technique usually used in-line (interposed in the
circuit) during CPB. The Hemobag® is a collection reservoir used to facilitate
ultrafiltration of the CPB circuit after the patient has been disconnected from CPB). It
represents a novel and safe modification of the modified ultrafiltration system (MUF). MUF is
a technique commonly used in cardiac surgery for many years, especially with smaller
hemodiluted patients, and mainly in the pediatric population.

The focus of the Hemobag® system is on whole blood volume recovery as opposed to red cell
volume recovery only, and helping to satisfy the requirements of the patient after CPB has
been discontinued: hemostasis, reversal of dilutional effects, and returning back to
homeostasis, which is the normal physiologic and metabolic status of the patient.

The investigators hypothesize that the Hemobag® method of returning residual CPB blood is
superior to the current practice of cell washing and concentration. This hypothesis is based
on previous studies that have shown that the ultrafiltrated whole blood product is superior
to the cell-washed RBC product. The main purpose of this study is to discover the differences
in outcome measures when, at the end of CPB, the residual diluted pump blood is processed by
either cell washing or by the Hemobag® method. The null hypothesis states that there would be
no difference in post-operative patient outcomes when residual pump blood is processed by
either a cell washing method or the Hemobag® protocol.

Pilot Study:

The investigators did an Maine Medical Center (MMC) Institutional Review Board (IRB)-approved
pilot study in March 2011 which consisted of ten (10) cases in order to confirm the
significant treatment effect shown in other studies and to familiarize the team with the
Hemobag® system. Outcome metrics included chest catheter drainage in the first 24 hours
post-operative, allogeneic blood component requirements (red blood cells (RBC's), platelets,
plasma), platelet counts, evidence of acute kidney injury by the Acute Kidney Injury Network
(AKIN) definition, mortality, stroke, and requirements for inotropic support on the second
post-operative day. The results of the pilot study showed a promising trend with regard to
less chest catheter drainage and higher platelet counts.

Materials and Methods and Analysis:

The investigators propose to do a randomized, controlled trial comparing the two methods as
described above: The standard method of returning the residual pump volume to the patient as
washed, centrifuged cells (control group) and the Hemobag® method of returning residual CPB
blood (study group).

Outcome metrics will be the same as they were for the pilot study:

(1) Chest catheter drainage in the first 24 hours post-operative; (2) Allogeneic blood
component requirements (RBC's, platelets, plasma); (3) Pre and post operative platelet
counts; (4) Evidence of acute kidney injury by AKIN definition; (5) Mortality; (6) Stroke;
(7) Requirements for inotropic support on the 2nd post-operative day.

The investigators propose to enroll 100 patients, 50 in the control group and 50 in the study
group. The study will be limited to adults (18 years and older) who have heart surgery (valve
and /or coronary) using CPB who do not have anemia or coagulation disorders preoperatively.

An interim analysis will be performed by an independent, unblended analyst to determine
efficacy and safety half way through the study (50 patients). Terminating the study early
would be a consideration if one group were clearly superior to the other or if there were
safety issues. In the event that there are no concerns regarding superiority or safety, the
study would continue until the entire sample size has been studied. The results of the
interim analysis will be submitted to the IRB.

Conclusion:

There are a number of intra-operative blood management strategies in cardiac surgery and the
salvage of post-CPB whole blood using ultrafiltration from the CPB circuit is emerging as one
of the most significant contributors to reducing allogeneic blood component use in
cardiovascular surgery. The investigators hypothesize that the Hemobag® method of returning
residual CPB blood is superior to the current practice of cell washing and concentration and
more expeditious than modified ultrafiltration (MUF).

Inclusion Criteria:

All adult cardiac surgery patients (age 18 or older) Cardiopulmonary bypass

Exclusion Criteria:

Patients under age 18 Off pump surgery
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