To the Editor:
We thank Drs Bader and Ranier for their interest in our case report. They raise 2 main questions—whether it is appropriate to maintain a normal fibrinogen concentration during major vascular surgery rather than waiting until surgical hemostasis has been obtained, and whether ethics committee approval and patient consent were obtained for frequent ROTEM measurements and the use of fibrinogen concentrate.
It has been our routine practice for over a decade to undertake frequent ROTEM measurements during thoracoabdominal aortic aneurysm surgery, and in recent years our aim has been to maintain a normal plasma fibrinogen concentration during surgery. The FIBTEM MCF range of 9-25 mm referred to by Drs Bader and Ranier is the normal range for this parameter. In practice, our aim of maintaining a normal fibrinogen concentration (≥1.5 g/L) meant that we aimed for a FIBTEM MCF ≥9 mm.
We perform type IV thoracoabdominal aortic aneurysm surgery
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without the use of a bypass circuit or full heparinization. A single dose of heparin (5,000 U) is given before aortic clamping. Hypothermia (minimum temperature 32-33°C) is used during the period of ischemia of the liver, bowel, and kidneys. It is our experience that not treating coagulation abnormalities, such as hypofibrinogenemia or severe thrombocytopenia, until the end of the surgery is associated with severe microvascular bleeding during surgery and increased blood loss. Severe diffuse bleeding in this situation can make it difficult to determine if there is adequate surgical hemostasis. Therefore, we aim to correct these coagulation abnormalities during surgery. A similar approach has been adopted by other units undertaking this type of surgery.2
Drs Bader and Ranier suggested that the infusion of fibrinogen concentrate is not helpful. We disagree with this interpretation for 3 reasons: FIBTEM MCF >9 mm was achieved successfully (as shown in Fig 2 of our case report), satisfactory hemostasis was achieved clinically, and it was not necessary to give fresh frozen plasma (FFP). They also described our administration of fibrinogen concentrate as pre-emptive. Again we disagree because fibrinogen concentrate was administered only in response to pathologic FIBTEM MCF values.
Cell salvage with centrifugation and washing indeed removes most of the fibrinogen, other coagulation factors, and platelets from shed blood to produce concentrated red cells. However, not using cell salvage results in the same loss of fibrinogen, other coagulation factors, and platelets plus the additional loss of red blood cells.
Fibrinogen concentrate has a marketing authorization (license) for the treatment of hypofibrinogenemia. In some European Union countries, where the marketing authorization is for the treatment of congenital and acquired fibrinogen deficiencies, fibrinogen concentrate has been used widely in bleeding surgical patients for many years and is regarded as the standard of care for the treatment of patients with acquired fibrinogen deficiency. In other countries, including the UK, the marketing authorization currently is only for the treatment of congenital fibrinogen deficiency. However, fibrinogen concentrate is used in the UK for the treatment of some bleeding patients with acquired hypofibrinogenemia because of concerns about the safety of cryoprecipitate and FFP. The use of fibrinogen concentrate to treat acquired hypofibrinogenemia is included in current guidelines from the British Committee for Standards in Haematology
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and the Association of Anaesthetists of Great Britain and Ireland.4
The patients described in the case report were not involved in a research study; therefore, ethics approval was not sought. The management of the patients was identical to our previous routine management of patients having repair of type IV thoracoabdominal aortic aneurysm apart from our use of fibrinogen concentrate rather than FFP to treat hypofibrinogenemia. Our use of fibrinogen concentrate was in accordance with the General Medical Council's guidance on prescribing medicines for use outside the terms of their licence,
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and this guidance does not suggest that written consent is required. However, the patients provided written consent to the publication of the case report.Drs Bader and Ranier also referred to the cost of fibrinogen concentrate. The cost of fibrinogen concentrate in some countries, including the UK, is lower than the range they stated, and the true costs of using allogeneic blood products often are underestimated.
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However, a comparison of the costs of different strategies of managing impaired hemostasis during surgery was beyond the scope of our case report.References
- Contemporary results for open repair of suprarenal and type IV thoracoabdominal aortic aneurysms.Br J Surg. 2010; 97: 45-49
- Complex abdominal aortic pathologies: Operative and midterm results after pararenal aortic aneurysm and type IV thoracoabdominal aneurysm repair.Vascular. 2009; 17: 121-128
- Guidelines for the diagnosis and management of disseminated intravascular coagulation.Br J Haematol. 2009; 145: 24-33
- Blood transfusion and the anaesthetist: Management of massive haemorrhage.J Anesth. 2010; 65: 1153-1161
- Good practice in prescribing medicines—Guidance for doctors.(Accessed: March 22, 2012)
- Estimating the cost of blood: Past, present, and future directions.Best Pract Res Clin Anaesthesiol. 2007; 21: 271-289
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Published online: July 03, 2012
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© 2012 Elsevier Inc. Published by Elsevier Inc. All rights reserved.
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- Is It Necessary to Maintain Fibrinogen During Hypothermia and Major Bleeding in Vascular Surgery?Journal of Cardiothoracic and Vascular AnesthesiaVol. 26Issue 5
- PreviewIn the case reports by Morrison et al,1 3 patients undergoing open thoracoabdominal aneurysm repairs received a continuous infusion of purified human plasma–derived fibrinogen concentrates (CSL Behring, Marburg, Germany) under the guidance of the FIBTEM assay on ROTEM (TEM International, Munich, Germany). There are some concerns about these cases.
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