Numerous approaches are used to avoid transfusion of allogeneic blood. Primary methods include, but are not limited to, erythropoietin and iron supplementation, pre-operative autologous donation, acute normovolaemic haemodilution, haemoglobin-based blood substitutes and infusible oxygen-carrying fluids, and the use of cell salvage systems. Of the accepted strategies mentioned above, cell salvage offers the medical community a safe, resource-saving, and relatively inexpensive method to avoid allogeneic red cell transfusion.
Intra-operative cell salvage is the process whereby shed surgical field blood is collected, filtered, and washed to produce red blood cells for transfusion to the patient. There are many types of cell processors. Cell processors are red cell washing devices that collect anticoagulated shed or recovered blood, wash and separate the red blood cells (RBCs) by centrifugation, and reinfuse the RBCs. RBC washing devices can help remove by-products in salvaged blood such as activated cytokines, anaphylatoxins, and other waste substances that may have been collected in the reservoir suctioned from the surgical field. However, they also remove viable platelets, clotting factors, and other [plasma proteins] essential to whole blood and homeostasis. The various RBC-savers also yield RBC concentrates with different characteristics and quality.
Background: Providing safe blood for transfusion remains a challenge despite advances in preventing transmission of hepatitis B, hepatitis C, AIDS/HIV, West Nile virus(WNV), and transfusion-transmitted bacterial infection. Human errors such as misidentifying patients and drawing blood samples from the wrong person present much more of a risk than transmissible diseases. Additional risks include transfusion related acute lung injury (TRALI), a potentially life-threatening condition with symptoms such as dyspnea, fever, and hypotension occurring within hours of transfusion, and also transfusion-associated immunomodulation, which may suppress the immune response and cause adverse effects such a small increase in the risk of postoperative infection. Other risks such as variant Creutzfeldt-Jakob disease (vCJD), an invariably fatal disease, remain worrisome. Blood centres worldwide have instituted criteria to reject donors who may have been exposed to vCJD. Screening for transmissible diseases and deferral policies for vCJD designed to improve safety have contributed to shrinking the donor pool. Blood shortages exist in the United States and worldwide. In many industrialized countries 5% or less of the eligible population are blood donors.
Red blood cells processed by cell salvage and stored at room temperature can be safely transfused up to 6 hours following collection. As a result, the global medical community has increasingly moved from allogenic blood (blood collected from another person) towards autologous infusion, in which patients receive their own blood. Another impetus for autologous transfusion is the position of Jehovah's Witnesses on blood transfusions. For religious reasons, Jehovah's Witnesses will not accept any allogeneic transfusions from a volunteer's blood donation, but may accept the use of autologous blood salvaged during surgery to restore their blood volume and homeostasis during the course of an operation, although not autologous blood donated beforehand.
During the surgical procedure, wall suction is not utilized to clear the operative field; the cell salvage suction pressure can be regulated if the field needs to be cleared quickly. Heparinised normal saline or citrate anticoagulant is added as the shed blood is collected. Filtering and washing remove contaminants such as cell fragments, fat globules, bone chips, and potassium leaked from haemolysis (Haemolysis is a condition that occurs when haemoglobin is released from red blood cells when the cell membranes are damaged.). The final washing steps utilize only normal saline to produce red blood cells (no functional platelets or clotting factors) suspended in saline for transfusion to the patient.
The technology of cell salvage has evolved since its initial implementation in the 1970's. In the early days, cell salvage was limited to simply filtering by gravity. Subsequently, washing techniques involved "bowl technology", centrifugation within a constrained bowl, with a full bowl mandatory for effective, efficient washing. The most advanced technology utilizes "coil technology", with the shed blood directed into a continuous washing chamber, allowing for continuous processing.
This technology avoids wasting partially filled bowls of shed blood and allows for a readily available product to be transfused to the patient. The computerised process of the cell salvage equipment facilitates the role of the perfusionist in balancing the suction pressure, the washing chamber fill rate, and the wash cycle flow rate to the priority of the patient's physiological need for red blood cell transfusion.
As with all health care technology, the relative advantages and limitations of intra-operative cell salvage must be weighed up in the clinical setting. Intra-operative cell salvage is most effective in major surgical blood loss (1000 ml or greater) procedures and especially effective for patients with adequate pre-operative haemoglobin.
Contamination of the surgical site, ongoing infectious processes, use of topical antibiotics or anticoagulants, potential presence of amniotic fluid or cancer cells in the surgical field is controversial when considering intra-operative cell salvage. If 1 to 1 ½ times the patient's blood volume is shed, close monitoring for signs of coagulopathy (a disease or condition affecting the blood's ability to coagulate) becomes essential. Financial aspects to bear in mind include the cell salvage device itself, the disposables required for each patient, the availability of skilled operators (perfusionists), and the frequency of surgical cases where cell salvage is applicable.
Theatre activity data must be analysed to estimate the number of suitable cases and the pattern of the demand. Intra-operative cell salvage is indicated during "clean" surgery where the anticipated blood loss is >20% of the patient's blood volume, that is one litre for a 70kg man. Cell salvage will not always replace the need for donor blood, particularly with large volume losses, but may make a contribution to the transfusion requirements.
The hospital case mix is important. Some types of elective surgery will guarantee a supply of suitable cases. Examples of these include:
- Open cardiac surgery
- Vascular surgery
- Major orthopaedic surgery
At this stage the difficult issue of cell salvage in tumour surgery must be faced. This remains controversial and there has been no clear lead from national bodies. Medical and theatre staff will need clear guidance on what is acceptable in their Trust and this has clear implications for the caseload.
Having established an estimate of case numbers, the pattern of the demand should be examined. For hospitals with a significant emergency workload 24-hour availability must be the gold standard. At present there are probably only a handful of hospitals in the UK that are able to guarantee this. Even if this standard cannot be met at the outset, it is worth building towards it.
On-line Learning resources for Cell Salvage
It is recommended that anyone involved in cell salvage access the Learn Cell Salvage module and on-line assessment at www.learnbloodtransfusion.org.uk.
Intraoperative Cell Salvage (ICS) Education Workbook
This education workbook has been developed by the UK Cell Salvage Action Group (UKCSAG) to support the theoretical aspects of training for ICS. The workbook includes background information relevant to the use of ICS e.g. basic haematology. It provides the learner with in-depth theory relating to ICS e.g. indications and contraindications, principles of use and the practicalities for each step of the process. At the end of each section there are self directed learning questions intended to develop the learner’s awareness of their own organisation's ICS service. The workbook is linked to the ICS Competency Assessments and can be downloaded as a complete document or as individual sections.
This training framework for intra-operative cell salvage (ICS) operators has been developed on behalf of the NHS Blood and Transplant Appropriate Use of Blood Group and the Clinical Advisory Group in Wales. It has been reviewed by the UK Cell Salvage Action Group. To help address training concerns and the lack of competency assessments for operators in this specialist field, this workbook has been developed in consultation with cell salvage “champions” and other national groups with blood safety and conservation as an essential part of their remit. The competencies are linked to the National Occupational Standards for cell salvage, which are available on the Skills for Health website www.skillsforhealth.org.uk. The competencies have been split into 5 sections to allow assessment to be tailored to the responsibilities of the individual learner. Sections of the competency assessment inappropriate to the level of responsibility of an individual learner should be removed from the workbook by the trainer. Each section is then further divided into “Knowledge and Understanding” and “Performance Criteria”. Learners must complete all indicators for both Knowledge and Understanding and for Performance Criteria within a section in order to be signed off as competent for that section. Knowledge and Understanding need only be completed once, Performance Criteria should be completed for each device the learner will be using in clinical practice.
It is essential that all staff involved in the operation of ICS machines are trained to the level at which they are expected to operate. Training should include both theory and practice. Operators need to develop a broad understanding of the appropriate use of ICS including the contra-indications and implications of administration and reinfusion of salvaged blood. It is recommended that along with practical training in a non-clinical environment learners complete the UK cell salvage e-learning package www.learnbloodtransfusion.org.uk, the ICS Education Workbook (which can be downloaded from the Better Blood Transfusion Toolkit at www.transfusionguidelines.org.uk) and a period of supervised clinical training prior to commencing this workbook.
Hospitals involved in training staff in the use of ICS should adopt the following principles: -
- Identify a key trainer/s (it is suggested that these people should have a recognised teaching and assessing qualification).
- Theory training and assessment of knowledge should be completed prior to undertaking practical training.
- Staff should be allowed dedicated time for practical training which can be delivered by manufacturer and/or “in-house” trainers. (“In-house” training should be carried out by key trainers).
- “In-house” trainers should assess competency (it is suggested that “in-house” trainers have completed this workbook and that they hold a teaching and assessing qualification).
- Certificates of competence should be issued by the Organisation.
- Documented training records should be kept by the Organisation and the learner.
Procedural documents/policies should be available to staff giving clear guidance on: -
- Indications and contraindications
- Who can operate the machines and levels of independent operation
- How to operate the equipment
- Warnings regarding contamination of the surgical field
- Rules on labelling, expiry date and time of salvaged blood
- Reinfusion of salvaged red cells · Recognising and reporting serious adverse event
Audit
It is recommended that Organisations should undertake periodic audit to verify the principles outlined above are being adopted. It is suggested that a designated person is made responsible for this activity.
Sources:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3096856/
http://en.wikipedia.org/wiki/Intraoperative_blood_salvage
https://www.transfusionguidelines.org/transfusion-practice/uk-cell-salvage-action-group/intraoperative-cell-salvage-education
