Cell salvage and leucocyte depletion filters

Abstract

We read with interest the recent editorial ‘cell salvage induced hypotension and London buses’ concerning hypotension associated with the use of the leucocyte depletion filters [1]. At the Royal Cornwall Hospital Trust, we routinely collect blood for cell salvage at the time of caesarean section. We are currently recruiting to a study involving re-infusion of cell-salvaged-blood and following up women post re-infusion. At the time of caesarean section, the collected blood is washed and processed if there is enough in the collection bowl, or if there are clinical signs of blood loss. We consent women for a re-infusion of the cell-saved blood. All women who have their blood returned are monitored during the re-infusion and are followed up at three and six months postoperatively. At follow-up, a blood sample is taken to test for antibody formation. We have re-infused cell-saved blood to 70 patients. All these patients have received the re-infusion through a leucodepletion filter (Pall LeukoGuard® RS Filter; Pall Europe, Portsmouth, UK), and in all cases only one suction device was used. We have not observed any haemodynamic changes attributable to these re-infusions. However, we have not pressurised the bag or syringed the contents through the filter. We are aware that users have pressurised blood through the LeukoGuard RS filter without complication, although the manufacturer’s product instructions state: ‘use of this filter with a pressure cuff should comply with the recommendations of cell salvage equipment manufacturers’ instructions for use’. We have already demonstrated alpha-fetoprotein is significantly reduced post wash following cell-salvage, to levels well within the normal range for the general population, before passing through the filter. Heparin is also eliminated and whilst the washing process does not eliminate the presence of fetal squames, their significance in the circulation remains unknown [2]. Whilst the decision to re-infuse salvaged blood from a particular patient or patient group is a clinical one, the LeukoGuard RS filter has not been validated by the manufacturer for its ability to remove fetal squames from salvaged blood during re-infusion. Consequently, one cannot rely on the filter’s ability to remove these contaminants during re-infusion of salvaged blood and the filter is not currently endorsed for use for this purpose. The product instructions state that the filter is only validated and indicated for the removal of leucocytes, fat particles and microaggregates from intra-operative salvaged-blood intended for re-infusion. We found the LeukoGuard RS filter significantly reduced the presence of fetal squames with only two out of 34 cases testing positive after filtration [2]. Transfusion-induced hypotension is a recognised phenomenon and has been reported both with and without the use of bedside leucocyte removal filters. Although some publications have suggested that this is an event secondary to the use of leucocyte removal filters [3], a 9-year study of adverse transfusion reactions found an overall incidence of anaphylactic or anaphylactoid reactions of 1.3% (21 of 1613) and of these, nine had associated hypotension [4]. None of these reactions involved the use of bedside leucocyte removal filters. We recognise the limited flow achievable through a filter is a limitation when re-infusing cell-saved blood during hypovolaemic resuscitation. In such cases, we estimate and provide minimal volume resuscitation and transfusion of peri-operative allogenic blood, and subsequently commence slower re-infusion of cell-saved blood. In patients who decline allogenic blood, such as Jehovah’s Witnesses, we would consider removing the filter from the re-infusion. No external funding and no competing interests declared. Previously posted at the Anaesthesia Correspondence website: http://www.anaesthesiacorrespondence.com.