Fresenius C.A.T.S (Continuous AutoTransfusion System)
This procedure is used frequently in cardiothoracic, vascular and spinal surgery, in which blood transfusions and the use of blood products have traditionally been high.
Cell savers , or autologous blood salvage systems, have been in use in operating rooms for almost 30 years. Some lend themselves more easily than others to being set up in a more-or-less closed circuit.
"Cell savers" - What equipment is involved and how does it work?
The basic function is as follows: At the “business end,” where the surgeon is making incisions, a technician will suction the blood out of the surgical field using a special type of suction tube, somewhat like the implement the dentist’s assistant uses to suck the fluid out of the patient's mouth when the dentist is drilling. Instead of the aspirated blood simply being flushed down a sink, however, it passes through tubing and is collected in a reservoir. At the same time as the suction occurs, an anticoagulant is introduced into the line. When enough blood has been collected in the reservoir it is sent to the cell salvage machine, resembling in no small way a washing machine/spin drier. The blood is filtered, then spun in a centrifuge, causing the RBCs to separate from the plasma and stick to the sides of the centrifuge bowl. The plasma goes into a waste bag, and a wash fluid (0.9% normal saline) is introduced into the machine to remove platelets and debris. The washed RBCs are then pumped up to a transfusion bag from where they are returned to the patient through an IV in the usual way. (Figure 1 )
The procedure step by step.
Figure 1 - Click here to play Haemonetics animation.
Step 1: Suction
As the surgeon makes his incisions, blood oozes from the dissected tissues and begins to pool in that part of the body cavity that contains the surgical field. The blood is sucked away via a dual lumen tube which mixes the blood immediately with an anticoagulant. Both are then sucked into a reservoir connected to a vacuum pump. The anticoagulant is either heparin or citrate.
Step 2: Collection and filtration
The blood and anticoagulant collects in the reservoir and is filtered to remove large clots and debris.
Step 3: Preparation
Blood and anticoagulant are drawn from the reservoir into a centrifuge to be processed.
Step 4: Separation
A sterile isotonic saline solution is pumped into the centrifuge bowl. The force supplied by the centrifuge holds the more dense red blood cells against the outer wall of the bowl. The less dense white blood cells, platelets, plasma, clotting factors and anticoagulant move toward the centre of the bowl where they spill over into a waste bag.
Step 5: Waste disposal
Waste products, including white blood cells, platelets, plasma, anticoagulant, fat, clotting factors, and free plasma haemoglobin are collected in a bag and are disposed of in harmony with procedures for clinical waste.
Step 6: Red cell salvage
Packed red blood cells are separated from waste products and collected in a separate bag. The quality of the collected red cells depends upon the volume of wash solution used, the degree of concentration achieved, the quality of the blood prior to washing, the type of surgery, and the presence of various substances that remain in the red cell pack.
Step 7: Re-infusion
Red blood cells can then be sent to a transfusion bag. If a patient requests that the circuit be continuous, the blood can be re-infused immediately. Otherwise, it can be taken to recovery ward to be re-infused later. There is, however, a limit of 6 hours during which re-infusion can take place.
During an operation, blood that is lost on swabs and sponges can be collected and given back to the patient. These swabs and sponges are carefully weighed to calculate the amount of blood contained in them before placing into a bowl of anticoagulant. The blood from the bowl is then taken to the reservoir and processed in the same way as blood collected from the surgical field. (Step 3). This ensures that all available blood is salvaged. Considerable volumes of blood can be collected on swabs and sponges.
Major spinal surgery
Major spinal surgery successfully completed using cell salvage. BBC News 9th November 2006
Other blood salvage procedures
Several other processes have been developed to assist in salvaging the patient's own whole blood in the perioperative setting. These include:
- Acute Normovolemic Hemodilution
- Direct Transfusion
- Ultrafiltration of Whole Blood
- Postoperative blood salvage
Direct transfusion is a blood salvaging method associated with cardiopulmonary bypass (CPB) circuits or other extracorporeal circuits (ECC) that are used in surgeries, such as coronary artery bypass grafts (CABG ), valve replacement, or surgical repair of the great vessels. Following bypass surgery the ECC circuit contains a significant volume of diluted whole blood that can be harvested into transfer bags and re-infused into the patient. Residual CPB blood is fairly dilute ([Hb] = 6–9 g/dL; 60–90 g/L) compared to normal values (12–18 g/dL; 120–180 g/L) and can also contain potentially harmful contaminants, such as activated cytokines, anaphylatoxins, and other waste substances that have been linked to organ edema and organ dysfunction, both of which require a diuretic to reverse.
Ultrafiltration of Whole Blood
Hemofiltration or ultrafiltration devices filter the patient's anticoagulated whole blood. The filter process removes unwanted excess non-cellular plasma water, low molecular weight solutes, platelet inhibitors, and some particulate matter including activated cytokines, anaphylatoxins, and other waste substances through hemoconcentration; thus making concentrated whole blood available for reinfusion. Hemofilter devices return the patient's whole blood with all the blood elements and fractions including platelets, clotting factors, and plasma proteins with a substantial Hb level.
These devices do not totally remove the potentially harmful contaminants that can be washed away by most RBC-savers. However, the contaminants that are potentially reduced by using RBC-savers, as shown by data from in vitro laboratory tests, are transient and reversible in vivo with hemostatic profiles returning to baselines within hours. The key is that coagulation and homostasis are immediately improved with the return of concentrated autologous whole blood.
Presently, the only whole blood ultrafiltration device in clinical use is the Hemobag, which can serve as an example of how ultrafiltration works.
Procedure (step by step)
Step 1 (After surgery)
- The ultrafiltration device (the Hemobag® ,*hereafter, the "device) is filled at the surgical field via the extracorporeal*circuits arterial line connected to the device. The circuit's*blood volume is then chased forward with crystalloid displacement.
- The device is applied to the closed TS3 Tubing Set's "Recovery Loop circuit" for hemoconcentration via a spare roller pump not in use and concentrated down to an autologous whole blood product with harmful wastes and excess water removed but all cellular components saved from being discarded.
- With the lines clamped and capped, the device is now ready for labeling and end-product infusion.
See a video of the ultrafiltration device in action.
Postoperative blood salvage/reinfusion.
While cell salvage machines can be utilized to provide postoperative blood reinfusion, there are other systems dedicated to return whole blood to the patient. These include:
Over the years numerous studies have been done to compare these methods of blood salvage in terms of safety, patient outcomes, and cost effectiveness, often with equivocal or contradictory results .
- (2004), "Rightly value your gift of life. ", Watchtower , pp. 14-16
- (2004), "Questions From Readers: Do Jehovah’s Witnesses accept any minor fractions of blood? ", Watchtower , pp. 29-31
- (2000) Questions From Readers: In the light of Bible commands about the proper use of blood, how do Jehovah’s Witnesses view medical procedures using one’s own blood?
- Patients That Refuse Blood Transfusions - FAQs
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