We read with interest the editorial "Cell salvage induced hypotension and London Buses", and the case reports concerning hypotension associated with the use of the leucocyte depletion filters. 

At the Royal Cornwall Hospital Trust, we routinely collect blood for cell salvage at the time of caesarean section. Currently, we are recruiting for an ethically approved study  "Contamination of salvaged maternal Blood by fetal red cells during caesarean section", and have re-infused cell saved blood to 65 patients. All these patients have received the re-infusion through a leucodepletion filter (Pall LeukoGuard ® RS Filter). We have observed no haemodynamic changes during these re-infusions. However, all have been given without pressurising the bag or syringing the contents through the filter. We are aware of users uneventfully using the Leukogard RS filter in conjunction with pressure cuffs although the following precaution is included on the product's instructions for use: "Pressure Cuff:- Use of this filter with a pressure cuff should comply with the recommendations of cell salvage equipment manufacturer's instructions for use."

We have already demonstrated alpha-fetoprotein is significantly reduced post-wash to levels well within the normal range for the general population before passing through the filter. Heparin is eliminated, and whilst the presence of fetal squames is not eliminated by the washing process, their significance in the circulation remains unknown.

Whilst the decision as to whether or not to re-infuse salvaged blood from a particular patient/patient group is a clinical one, the Leukogard filter has not been validated by the manufacturer for its ability to remove fetal squames from salvaged blood during re-infusion. Consequently, it is not possible to make any claims on the filter's ability to remove these contaminants during re-infusion of salvaged blood, and therefore the Leukogard RS filter is not currently endorsed for this purpose. As stated on the product's instructions for use, the filter is only validated and indicated for the removal of leucocytes, fat particles and microaggregates from intra-operative salvaged blood, which is intended for re-infusion. In our study the Leukogard RS filter has been found to reduce significantly the presence of fetal squames, with only 2 of 34 cases testing positive post filtration [1].

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 [2], a nine year study of adverse transfusion reactions found an overall incidence of anaphylactic or anaphylactoid reaction of 1.3% (21 of 1613) and of these 21 patients, nine had associated hypotension [3].  None of these reactions involved the use of bedside leucocyte removal filters.

We recognise that there is some limitation in using the re-infusion of cell saved blood through a filter for the purposes of hypovolaemic resuscitation. In such cases, our experience has enabled us to estimate and use minimal volume resuscitation and transfusion of peri-operative allogenic blood, whilst awaiting the administration of the slower re-infusion .

In patients who decline allogenic blood, such as Jehovah Witnesses, we would consider removing the filter from the re-infusion.

C Ralph

J Faulds

I Sullivan 

Royal Cornwall Hospital, UK 

References

1. Sullivan I,  Faulds J, Ralph C. Contamination of salvaged maternal blood by amniotic fluid and fetal red cells during elective Caesarean section.  British Journal of Anaesthesia 2008: 101; 225-9.
2. Cyr M, Eastlund T, Blais C Jr, Rouleau JL, Adam A. Bradykinin metabolism and hypotensive transfusion reactions. Transfusion 2001; 41: 136-150.
3. Domen RE, Hoeltge GA. Allergic transfusion reactions: An evaluation of 273 consecutive reactions. Arch Pathol Lab Med 2003; 127: 316-320.