Intra-operative Cell Salvage

Intraoperative Cell Salvage (ICS) is a technique used to recover and re-infuse red blood cells during and after surgery, to reduce transfusion requirements of the patient. It removes non-cellular matter by centrifugation commonly or a counter-current system. It receives blood from:

  • Suction – use large-bore suction tip (>4mm; e.g. Yankauer), avoid surface skimming and set vacuum pressure to lowest required.
  • Washing swabs – can be up to 30% – 50% of total blood loss.

Indications

  • Anticipated loss > 1L or 20% volume
    • Advantageous in off-pump (OPCAB), complex cardiac
    • CABG/isolated valve – not better than vigorous blood conservation programme (?)
  • Low Hb, high risk for bleeding
  • Multiple Ab or rare blood type
  • Objections to receiving donor blood

When NOT to use cell salvage

It is mainly the presence of contaminants that limits the use of cell salvage. This is a relative contraindication as the technology for cell salvage improves. Contaminants include:

  • Infection / gross bacterial contamination
  • Malignant cells
  • Substances not licenced for intravenous use are present in surgical field and could be aspirated into ICS, e.g. topical clotting agents, iodine, non-iv antibiotics. In this case, irrigate with saline to remove offending agent and then resume ICS.

Advantages

  • Reducing allogeneic txreq by 40% (Cochrane review)
  • Reduce risks of using other strategies to counter blood loss (antifibrinolytics, lysine analogues, coag factor concentrates, allogeneic tx)
  • No pre-op prep required of patient
  • Initial set-up of only collection phase until enough blood collected.
  • Lipid microemboli from pericardial aspirate may not be effectively removed by arterial line/filters. Use of ICS before returning it to CPB circuit may lead to short-term improvement in cognitive function.

Disadvantages

  • Coagulopathy  after cardiac surgery – as platelets and plasma proteins are lost during salvage.
  • Salvaged blood syndrome – coag activation with increased cap permeability can cause lung and renal injury.
  • Free Hb from haemolysis can cause renal damage
  • Report adverse events to SHOT/SABRE – Serious Hazards of Transfusion (shotUK.org). E.g. incidents in 2013 include hypotension during use of leucodepletion filter (LDF) during re-infusion, possibly related to elevated IL-6.
  • Post-operative drain blood is of variable quality (dilute, haemolysed, defibrinated, high cytokines) – wash before transfusion

Special circumstances

  • ?use with collagen haemostats
    • McClure 1987 – microfibrillar collagen able to pass through 40-micron filter and promoting platelet aggregation. Dose-dependent
    • Orr 1994 –  Collagen removed by 20-micron filter + LDF, and did not promote aggregation.
    • Currently – CVUHB – 40micron for reducing fat embolism in orthopaedics
  • ?use with sickle cell/thalassaemia
    • Only level 4/5 evidence (case studies/expert opinion) available.
    • SCD: increased proportion of sickled cells after processing, so ICS not advised
    • B-thal: no untoward effect in case report, so assess on individual basis.
  • ?CO from electrocautery
    • Possibility CO from electrocautery displacing O2 from Hb.
    • Slucky 1996 – not clinically relevant

Mechanism

  1. Aspiration & Anticoagulation (A&A) of blood – blood is sucked and mixed with heparin/citrate, passed through filter to remove large particulate matter (clots, etc)
  2. Separation of RBC – by centrifugation
  3. Washing of RBC – mixing with normal saline to achieve 45-65% Hct; can be triggered by optical sensors of Hct. Larger volumes for wash if high contamination risk.
  4. Re-infusion of RBC – transfuse within 8 hours from end of processing (AAB guidelines – 4h for intraop, 6h for postop collected blood). Re-infuse with standard kit (120-200 micron filter). If malignancy, can use leucocyte depletion filter (20-40 microns)

Types of Cell Salvage Centrifuge

  1. Fixed volume bowl – Processes blood in batches of ‘fixed volume’
    • Anticoag blood pushed into bowl
    • Spinning bowl (6000 rpm) separates RBC from supernatant
    • Supernatant drained through outlet port into waste bag
    • When a certain level of RBC detected, triggers saline wash to be pumped into bowl, creating another non-RBC supernatant layer, which is pumped out into waste bag.
  2. Variable volume – permits ‘variable volume’ of RBCs to be processed
    • Elastic silicone diaphragm changes size/shape to achieve fixed Hct.
    • Processes 100ml at a time
    • Concentrates low volume (<15ml) blood losses before washing
    • Used for constant, slow blood loss in long procedures
  3. Continuous rotary – continuously removing supernatant and washing RBC
    • All stages of ICS takes place concurrently
    • Needs only small volume to process but decision to process made on an individual patient basis.