Blood Simulant for Instructional Use in Autologous Blood Salvaging Machines at Perfusion Schools and Institutions

Robyn Berent, B.S.

Midwestern University – Cardiovascular Science Program        

19555 N. 59^th Avenue  

Glendale, AZ 85308

Introduction

Training personnel to use an autologous blood salvaging machine currently requires the use of blood products to visualize the mechanisms of the machine.  Typically, human or bovine whole blood is utilized.  However, the use of bovine or human blood raises concerns over pathogen exposure and cost per unit of blood.  The price range for 500mL of bovine whole blood with an anticoagulant is $60 – $150, and one liter of bovine whole blood can cost $100 – $250 (1, 2).  Whole blood must also be stored in a temperature-controlled refrigerator, and generally expires within 35 days. (3, 4).  Another concern is the risk of exposure to pathogens or prions in the blood, and the transmission of these pathogens to medical personnel (5).  The goal was to create a blood simulant that could be utilized in the training and competency evaluations of personnel in the use of all autologous blood salvaging machines (6).

A blood simulant would have the advantages of being non-pathogenic, having a long shelf life without storage restrictions, and a minimal cost to the institution.  The only disadvantage of using a blood simulant would be that the operator would be unable to measure post-processing values, such as hematocrit and plasma-free hemoglobin, to determine if the process was done correctly.  However, for perfusion and autotransfusion students, the use of a simulant would allow them to repeatedly practice using an autologous blood salvaging machine without the risk of pathogenic infection.  Additionally, a blood simulant would be easy to dispose of once processing was complete, unlike the use of real blood which requires specific handling of biohazardous waste.

An autologous blood salvaging machine functions by centrifugal force on the blood.  As the centrifugal bowl spins within the machine, the heavier red blood cells are pushed outwards while the lighter elements (serum, white blood cells) flow inwards toward the bowl’s center (7).  As blood is pumped into the centrifugal bowl, the lighter components are pumped out of the bowl into the waste bag until the bowl is filled with red blood cells (7).  Saline is then pumped into the bowl to wash the red blood cells, and then pumped out into the waste bag (7).  After the wash cycle, the remaining red blood cells are pumped out into a collection bag (7).  The desired simulant would behave the same as blood when subjected to centrifugal force in the autologous blood salvaging machine.

The blood simulant was tested on the two autologous blood salvaging machines available in our laboratory, the COBE™ Brat 2 and the Haemonetics™ Cell Saver 4.  The Brat 2™ uses a Baylor centrifugal bowl to process blood (1500 to 5600 RPMs), while the Cell Saver 4™ utilizes a Latham centrifugal bowl (3000 to 6000 RPMs) (8, 9).  The hypothesis was that the blood simulant would work equally well in either the Cell Saver 4™ or the Brat 2™, and produce results visually similar to that of human or bovine blood.

Description

Due to the high costs of obtaining blood to illustrate the functions of an autologous blood salvaging machine, there is a need to create a simulant to use in these machines in an educational setting.  The simulant would have to behave like blood under centrifugal forces and the various cycles of the blood salvaging machines.  Taking cost under consideration, the components of the simulant came to be oil and water to represent the serum and red blood cells, respectively.  Since oil and water do not mix, it was hypothesized that the oil would be forced out of the processing bowl while leaving the water behind.  Because water has a greater specific gravity (=1) compared to mineral oil (=0.85-0.9) (10), the hypothesis was that the oil (“serum”) would be forced out of the centrifugal bowl during the filling phase of the blood salvaging machine.  The remaining water (“red blood cells”) would then remain in the bowl, and would be washed with a saline simulant.  After the washing phase, the water would then be pumped up into a collection bag.

After a few attempts, the final mixture consisted of water, mineral oil and several dyes to achieve the look of human arterial blood (see Table 1). Additionally, a small amount of isopropyl alcohol was added as an antimicrobial agent. The water, isopropyl alcohol, food coloring and red paint were mixed into one container, while mixing the mineral oil with the yellow paint in a separate container.  After combining the two mixtures into a blood bag, the final mixture had the appearance of human blood. A saline “simulant” consisting of mineral oil (see Table 2) was also created in order to ensure that the color of the “red blood cell layer” would not be diluted.

Initial trials of the blood simulant were conducted using a microcentrifuge. After successful separation of the “red blood cells” from the “serum” in a microcentrifuge, the Cell Saver 4™ was used initially try out the simulant.  After the initial success with the Cell Saver 4™, the blood simulant was used in the Brat 2™ to replicate the results (see Figure 1).  In both blood salvaging machines, the salvaged “red blood cells” had a consistent color after processing.  Additionally, the supernant in the waste bag had a pink color similar to that of processed, hemolysed blood. 

The initial trial of the blood stimulant in the Haemonetics™ Cell Saver 4 resulted in successful separation of the simulant.  The blood stimulant was centrifuged in a Latham bowl at 5650 RPMs, and the separation of the “red blood cell layer” produced was similar to that of human blood.  The second trial in the COBE™ Brat 2 also produced a successful separation of the simulant, which was centrifuged in a Baylor bowl at 5600 RPMs (see Figure 2).

Discussion

The goal was to create a solution that mimics the action of human blood as it is processed in an autologous blood salvaging machine.  The combination of mineral oil, water, isopropyl alcohol and dyes were used to create a blood simulant that was inexpensive, non-pathogenic, has a long shelf life, and easy to separate. 

The blood simulant was tested in the 2 machines available in the Midwestern University Cardiovascular Science laboratory, the Haemonetics™ Cell Saver 4 and the COBE™ Brat 2.  The blood simulant separated into a “RBC layer” that was transferred into a collection bag, while the “serum layer” and saline simulant were collected into the waste bag.  The contents of the waste bag had the appearance of hemolysed blood, much like the supernant of human or bovine blood.  Overall, the processing of the blood simulant had visually similar results compared to real blood.

The cost for 1 liter of bovine whole blood with an anticoagulant can cost over $100, while the blood simulant costs approximately $4.90 for 1 liter. Additionally, the saline simulant for use with the blood simulant costs approximately $6.32 for 1 liter, while sterile water or saline costs substantially more.  Further cost savings can be achieved by purchasing the simulant components in large quantities. 

Operators of autologous blood recovery systems require training sessions, with additional re-evaluation to assure competency in the operating room (6).  Creation of this simulant provides opportunity to reduce costs, eliminate pathogens, and offers easy storage and disposal while training people.  This blood simulant thus offers a great opportunity for perfusion schools, institutions and companies involved with training personnel on how to operate an autologous blood salvaging machine.

References

1. Hemostat Laboratories, 2004.  Downloaded 06/26/04 from: http://www.hemostat.com/price/products.php
2. Innovative Research Inc, 2004.  Downloaded 6/36/04 from: http://www.innov-research.com/pricing2.htm
3. Puget Sound Blood Center Online, 2004.  Downloaded 6/26/04 from: http://www.psbc.org/medical/transfusion/bcrm/section_e/default.htm
4. Midwest Animal Blood Services, 2004.  Downloaded 07/17/04 from: http://www.midwestabs.com/VetInfo/mabsprbc.pdf
5. Tereskerz P. M., Pearson R. D., Jagger J.  Occupational Exposure to Blood among Medical Students.  N Eng J Med 1996, 335:1150-1153
6. Schrader T., Austin J., Blumhoff S., Riley J., Itsell J., and Moisuk P.  Competency Evaluation for Autologous Blood Recovery System Operators.  JECT 2004.
7. Gravlee G., Davis R., Kurusz M., and Utley J.  Cardiopulmonary Bypass, Principles and Practice.  Second Edition, 2000.  Lippincott Williams & Wilkins, Philadelphia PA.  122-123.
8. COBE Cardiovascular.  Downloaded 09/12/04 from: http://www.cobecv.com/autotransfusion.htm
9. Hemotech Inc.  Downloaded 09/12/04 from: http://www.hemotechinfo.com/product.html