Sreelakshmi and Eldridge have raised concerns in their case report regarding the safety of cell salvage and autologous blood transfusion through a leucocyte depletion filter in obstetric practice. In their case, invasive blood pressure monitoring was instituted during the procedure, rather than at the start. We feel that in cases where large volume blood loss is anticipated, an arterial line is invaluable for the rapid detection of haemodynamic instability and frequent blood sampling.
During the case reported by Sreelakshmi and Eldridge the amniotic fluid was aspirated from the surgical field and then discarded. A prospective randomised study compared the efficiency of cell salvage at removing amniotic fluid in two groups. In the first group two suction devices were used and this was compared to the use of one suction device. There was no statistically significant difference between the two groups, which would suggest that the use of only one suction device is safe and should in theory increase the efficiency of red blood cell recovery [1].
We agree that bacterial contamination and amniotic fluid embolus are unlikely causes for the hypotension in these cases. Various studies have investigated the autologous transfusion of microbiologically contaminated salvaged blood and demonstrated no adverse outcomes or increase in postoperative infectious complications [2-5]. To date, there have been no proven cases in the literature of amniotic fluid embolus caused by re-infusion of salvaged blood [6].
When considering the cause of hypotension, one of the relative contraindications to pressurising salvaged blood is the risk of air embolus due to the presence of air in the bag of autologous blood. An air embolus may have accounted for the cardiovascular instability demonstrated by the patient in the case report. Another important consideration is the administration of allogeneic blood products during the management of massive obstetric haemorrhage and coagulopathy. Immediate or delayed adverse reactions to these blood products are more common than reactions to allogeneic or autologous red blood cells and again could have accounted for the hypotension. Were there any other signs of a blood product transfusion reaction or anaphylaxis such as pyrexia, bronchospasm, urticaria or rash? It would appear that there was a temporal relationship between the administration of cell salvaged blood and the episodes of hypotension in both cases which is most likely to be attributable to bradykinin.
Re-transfusion of cell salvaged blood through a LDF is well established and has a long history in surgery for urological malignancy [7]. Cell salvage has shown to be safe in a 5-year retrospective review of adverse events associated with blood transfusion. They examined over 27 000 cases where salvaged, pre-donated autologous or allogeneic blood was transfused, and found the incidence of adverse events with autotransfusion to be 0.027% compared to 0.14% with allogeneic blood transfusion [8]. The Cochrane Collaboration published a meta-analysis in 2006, which found that cell salvage is safe and efficacious at reducing the need for allogeneic blood transfusion [9]. Both case reports have emphasised that there are many causes of hypotension associated with massive obstetric haemorrhage, and the transfusion of autologous and allogeneic blood products. In most cases the cause of hypotension will be multifactorial, but when transfusing salvaged blood through a LDF, bradykinin is an important differential diagnosis. These reports of hypotension associated with cell salvage and a LDF have been important to highlight the potential problem of bradykinin but should not deter our enthusiasm for the use of cell salvage as an important method of blood conservation.
A. Ashworth
N. O’Keeffe
Manchester Royal Infirmary, Manchester, UK.
A. R.Jones
Royal Oldham Infirmary, Oldham, UK
References
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4. Ozmen V, McSwain NE Jr, Nichols RL, Smith J, FlintLM. Autotransfusion of potentially culture-positive blood (CPB) in abdominal trauma: preliminary data from a prospective study. Journal of Trauma 1992; 32: 36-9.
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6. The Association of Anaesthetists of Great Britain and Ireland (AAGBI) Safety Guideline – Blood transfuion and the anaesthetist: Intra-operative cell salvage. http://aagbi.org/publications/guidelines/docs/cell%20_salvage_2009_amended.pdf.2009 (accessed 27/08/09)
7. Nieder AM, Carmack AJK, Sved PD, Kim SS, Manoharan M, Soloway MS. Intra-operative cell salvage during radical prostatectomy is not associated with greater biochemical recurrencerate. Urology 2004; 65:730-734.
8. Domen RE. Adverse reactions associated with autologous blood transfusion:evaluation and incidence at a large academic hospital. Transfusion 1998; 38: 296-300.
9. Carless PA, Henry DA, Moxey AJ, O’Connell D, Brown T, Fergusson DA. Cell salvage for minimizing peri-operative allogeneic blood transfusion. Cochrane Database Systematic Reviews 2006; 4: CD001888.