CELL SALVAGE

Cell Salvage

  Introduction -

• Commonly known as a "cell saver", the cell salvage machine suctions, washes, and filters blood so it can be given back to the patient. Cell salvage first proposed in 1818 and first mentioned in the literature in 1885
• Advantage is patient receives own blood instead of donor blood, so there is no risk of contracting outside diseases.
• The cell saver is also a viable alternative for patients with religious objections to receiving blood transfusions(Jehova’s witness)
• These systems aspirate blood ( simultaneously adding some heparinised saline or citrate) with a controlled vacuum and the RBCs are then automatically washed with saline and separated by centrifugation.
• Washed RBCs are returned to CPB or given intravenously.

    Advantages-

1. Removes undesirable materials like microaggregates, fat,gross air,tissue debris,potassium,hormones,bioactivators.
2. Increases haematocrit
3. Removes potassium so useful in hyperkalemia
4. Decreases SIRS
5. reduces blood transfusion rate.
6. Fat microembolic load is decreased by as much as 85%

Disadvantages-

1. May actually cause activation of WBCs and release of cytokines
2. Delay in processing and blood availability (turn around time)
3. Loss of plasma proteins especially albumin
4. Loss of coagulation factors
5. Loss of platelets
6. Expensive
7. Vigilance required during operation
8. Bacterial contamination can occur

Types –

CATS : Continuous Auto Transfusion System

DATS : Discontinuous Auto Transfusion System

Both equally effective in function

Interleukin 6, TNF alpha, myeloperoxidase (MPO) and reductase decreased 95% by both but interleukin 2 decreased by 85%

DATS caused greater leukocyte and platelet activation but causes superior removal as well – 50 to 90%

CATS only 35-50% removal, more fat removal.

Components of a autotransfusion device-

Centrifuge

Centrifugal bowl

Aspiration set

Anticoagulant

Wash fluid

Waste bag

Reinfusion bag

Cardiotomy reservoir

Technique –

• Wash the scavenged blood, usually with normal saline (.9% sodium chloride), and return solution of red blood cells suspended in normal saline with a hematocrit of 50–70%.
• The Fresenius Continuous AutoTransfusion System (CATS®) device (Fresenius HemoCare Inc., Bad Homburg Germany) is the cell salvage apparatus that uses a continuous technique allowing scavenged blood to be collected, washed, concentrated, and returned in an uninterrupted process.
• It allows the conservation of red blood cells whilst reducing the retransfusion of fat micro-emboli, activated coagulation and inflammatory markers.
• When the blood is aspirated from the pericardium, heparin is delivered at an appropriate rate to the tip of the suction cannula to minimize activation of coagulation.
• The salvaged blood is then stored in a reservoir containing additional heparinised saline prior to processing.
• During processing the red cells are retained in the bowl whilst the plasma, platelets, heparin, free haemoglobin, and inflammatory mediators are discarded with the wash solution.
• This process may be discontinuous or continuous, and the resulting red cells are finally resuspended at a haematocrit of 50-70% in normal saline, and reinfused.
• The quality of finished product is affected by absolute aspiration pressure,fill speed of the bowl,wash rate,quantity of the wash volume .

Safety features on autotransfusion machines –

• Air sensing capabilities
• Level detectors
• Air and foam detectors
• Hand cranking
• Two bag reinfusion systems
• Waste bag overfill automatic shutoff

   Contraindications to cell salvage -

• Contaminated wound sites and septic procedures
• Aspiration during caeserean section
• Concurrent use when microfibular collagen agents are used.

  Problems with cell salvage -

• The issue of air-fluid interfaces remains, although the avoidance of "skimming" and the presence of heparin at the tip of the suction apparatus reduces the activation of the clotting and inflammatory cascades.
• Large volumes of blood are processed through a cell saver, it will deplete that volume of blood of platelets and clotting factors.
• The process of cell salvage results in the activation of white blood cells leading to the release of inflammatory mediators (IL-6, C5a, C3a, terminal complement complexes). However unlike cardiotomy suction blood, the centrifugation and washing processes reduce the concentration of white blood cells by 30 – 80% and inflammatory mediators by 90 – 95% as they are discarded in the wash solution.

 Cardiotomy suction has –

• Increased TNFalpha and IL 6, C3a
• Pronounced systemic inflammatory response
• Coagulopathy
• Microembolic load.
• This leads to increased blood loss, transfusion requirement and organ dysfunction
• Flow within the cardiotomy suction has concurrent suction of air results in highly turbulent flow with high shear stresses at the air-fluid interface causing cellular damage and this activates systemic inflammatory response.
• Cardiotomy suction blood therefore contains an elevated level of free haemoglobin due to mechanical haemolysis.
• High concentrations of free haemoglobin cause platelet dysfunction and direct injury to the renal tubular cells.
• Platelet numbers are also reduced in cardiotomy suction blood through the rheological trauma.
• Blood collected from cardiotomy suction contains high levels of cellular debris and lipid microparticles, which contributes to the microembolic load leading to neurocognitive dysfunction It has been demonstrated that processing of salvaged blood reduces lipid and other microparticles..
• Fat embolisation was known to be associated with cardiotomy suction.Small capillary and arteriolar dilatations (SCADs) in brains and other organs of patients who died following cardiopulmonary bypass, and confirmed that they were fat emboli lodged within the vessels. Cardiotomy suction blood is known to be saturated with fat released from the subcutaneous tissue and sternal marrow on sternotomy.
• Hence, re-transfusion of cardiotomy blood leads to coagulopathy and increased blood loss, increased incidence of postoperative neurocognitive dysfunction and systemic inflammatory response syndrome.

Pericardial shed blood -

• Blood extravasated into the pericardial or pleural cavities differ from intravascular blood or blood within a closed CPB circuit.
• Surgical trauma from opening the chest results in tissue damage and release of tissue factor.
• Exposure of blood to tissue factor causes rapid activation of extrinsic pathway coagulation system with release of thrombin and fibrin.
• Also, tissue plasminogen activator release stimulates fibrinolysis.
• Activation of coagulation cascade also causes activation of other inflammatory cascades and complementary systems and high levels of inflammatory markers such as TNF-alpha, IL-6, IL-8 are present in pericardial shed blood.
• Platelets are activated when extravasation occurs into the pericardial cavity leading to aggregation, degranulation and consumption of platelets and release of further vasoactive substances.
• The pericardial space also contains a mixture of debris from surgical trauma like sternal marrow fat and air microbubbles.

References

• Cardiopulmonary Bypass: Principles and Practice – Glenn P. Gravlee
• The use of cell salvage in routine cardiac surgery is ineffective and not cost-effective and should be reserved for selected cases.Saina Attaran*, Daniel McIlroy, Brian M. Fabri and Mark D. Pullan,Interactive cardiovasc thoracic surgery vol12,issue5,824-26
• The efficacy of an intraoperative cell saver during cardiac surgery: a meta-analysis of randomized trials. Wang G1, Bainbridge D, Martin J, Cheng D. Anesth Analg. 2009 Aug;109(2):320-30.
• Intraoperative cell salvage is associated with reduced postoperative blood loss and transfusion requirements in cardiac surgery: a cohort study. Vonk AB1, Meesters MI, Garnier RP, Romijn JW, van Barneveld LJ, Heymans MW, Jansen EK, Boer C. Transfusion. 2013 Nov;53(11):2782-9.
• Coronary artery surgery: cardiotomy suction or cell salvage? Kelvin Lau, Hetul Shah, Andrea Kelleher and Neil MoatEmail author Journal of Cardiothoracic Surgery20072:46
• Kaplan’s Cardiac Anesthesia-The Echo Era 6^th Edition.

www.cardiacanaesthesia.in

- by Dr Amarja