© The Board of Management and Trustees of the British Journal of Anaesthesia 2004
CORRESPONDENCE |
Blood loss during repair of craniosynostosis
Editor—I write regarding two papers published some time ago, as an issue for clarification or correction. Both papers come from the same group in Paris and both use the same method for estimation of blood loss, detailed in the text and appendix of the two papers, respectively.1 2 This method was based on and attributed to the method used by Kearney and colleagues.3I believe there is an error in the method used by the Paris group in the calculation of estimated red cell deficit (ERCD). They state that ERCD=estimated red cell volume (ERCV)xpacked cell volume (PCV) in Meyer and colleagues' paper,1 and ERCD=ERCVxdifference in haematocrit in Dahmani and colleagues' paper.2 But, ERCD should be calculated as estimated blood volume (EBV; not red cell volume)xdifference in haematocrit. This method has been used in a number of other studies that have taken ERCD=EBVxdifference in haematocrit.4
Birmingham, UK
Editor—We thank Dr Carver for his interest in our contribution. In reply to his comments we would like to point out that in our studies we used a method derived from the method of Kearney and colleagues.3 In this study, blood loss was calculated on the basis of estimated red cell mass (ERCM), with ERCM=estimated blood volume (EBV)xhaematocrit/100, and ERCMdeficit=ERCMpretransfusion+ERCMtransfused–ERCMpost-transfusion. In our two studies,1 2 blood loss was calculated on the basis of estimated red cell deficit (ERCD)=estimated red cell volume (ERCV)xdifference in haematocrit (or variation in PCV), with ERCV=EBVxhaematocritpretransfusion, and total blood volume loss as ERCD+ERCVtransfused.1 2
Therefore, we agree with Dr Carver that there is a difference between the method of Kearney3 and our method.1 2 With our formula we have taken into account the volume of blood transfused during and after surgery: ERCMtransfused=EBVx0.75, where 0.75 represents the mean haematocrit in packed red cells. From our point of view, this method allows more precise estimation of ERCD. With this mode of calculation we found some negative values indicating overcompensation of blood loss (Table 1). We think that estimating blood loss without taking into account the red cell volume transfused is not appropriate in this kind of haemorrhagic surgery. Dr Carver suggests using another method of calculation of ERCD, with ERCD=EBVxdifference in haematocrit, in accordance with other studies.4 However, using this formula (ERCD=EBVxdifference in haematocrit) does not significantly modify the results or their interpretation. To illustrate this point we have performed the statistical analysis again with both the new,4 and the old formulae,1 2 for ERCD, using the data from the study by Dahmani and colleagues (Table 1).2 As can be seen from this table, there is no significant difference between the results obtained with the two methods of calculation of ERCD. In conclusion, therefore, we think that both methods of calculation of blood loss are useable, but that our method allows more precise estimation of total blood loss.
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Paris, France
References
1 Meyer P, Renier D, Arnaud E, et al. Blood loss during repair of craniosynostosis. Br J Anaesth 1993; 71: 854–7
2 Dahmani S, Orliaguet GA, Meyer PG, Blanot S, Renier D, Carli PA. Perioperative blood salvage during surgical correction of craniosynostosis in infants. Br J Anaesth 2000; 85: 550–5
3 Kearney RA, Rosales JK, Howes WJ. Craniosynostosis: an assessment of blood loss and transfusion practices. Can J Anaesth 1989; 36: 473–7[Web of Science][Medline]
4 Walters JH, Lee JS, Klein E, O'Hara J, Zippe C, Potter PS. Preoperative autologous donation versus cell salvage in the avoidance of allogeneic transfusion in patients undergoing radical retropubic prostatectomy. Anesth Analg 2004; 98: 537–42
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