John Libbey Eurotext

Hématologie

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Effects of erythrocytes transfusion in O 2 transport and consumption and on microcirculation Volume 11, issue 4, Juillet-Août 2005

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Authors
Clinique d’anesthésie et de réanimation, hôpital Huriez, CHRU de Lille, 59037 Lille Cedex
  • Key words: acute anemia, transfusion, O 2 venous saturation, O 2 extraction, O 2 transport
  • Page(s) : 249-57
  • Published in: 2005

The correct oxygen (O 2) transport (TaO 2 = Q  · CaO 2, with Q : cardiac output, and CaO 2, arterial O 2 concentration) that matches body O 2 requirements (VO 2) during acute anemia is that one which allows TaO 2 > TaO 2crit (TaO 2crit : critical TaO 2, value at which any further decrease in TaO 2 is associated with a decrease in VO 2). Transfusion decision in an individual relies on critical CaO 2 (CaO 2crit), and critical hemoglobin concentration ([Hb]crit) since CaO 2 ≈ 1,39  · [Hb]  · SaO 2 (with SaO 2 : arterial O 2 saturation). The way the body can increase Q is as much determining as [Hb] in transfusion decision since CaO 2crit is inversely related to Qcrit (Qcrit : critical value for Q). Mixed O 2 venous saturation (SvO 2) is a value which incorporates key tissue oxygenation determinants. Indeed, SvO 2 = SaO 2 -VO 2  / (Q  · [Hb]  · 1,39). At TaO 2crit, SvO 2 is close to 40 % and O 2 extraction capabilities, ERO 2, are close to 60 % when SaO 2 ≈ 100 %. It is therefore tempting to consider central venous-derived SvO 2, ScvO 2, as an easy-to-obtain surrogate marker of Swan-derived SvO 2 measurement, which can help in transfusion decision and monitoring when [Hb] is decreasing acutely.