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Central venous to arterial carbon dioxide gap as an indicator of oxygen debt in isovolemic anemia


Anemia can cause an imbalance in oxygen delivery (DO2) and consumption (VO2), which may be difficult to detect. Recently the venous to arterial carbon dioxide difference has been shown to be increased (>5 mmHg) in certain critically ill conditions [1, 2]. No study has yet investigated its significance in severe normovolemic anemia. Therefore, the aim of this study was to investigate the course of the central venous to arterial carbon dioxide gap (dcvCO2) in isovolemic anemia.


An experimental animal study on anesthetized Vietnamese mini-pigs. After splenectomy, mini-pigs (n = 13, weight range: 18 to 30 kg) were bled in five stages (~10% of estimated blood volume/5 minutes, T0 to T5) and blood loss was replaced by the same volume of colloid, after which hemodynamic measurements and blood gas analysis were performed.


The fall of hemoglobin was significant from the first bleeding, from T0 to T5: median = 125 (interquartile range = 113 to 134) to 49 (43 to 55) g/l, P < 0.05, respectively. Despite a significant increase in cardiac index by T1 (T0 = 2.6 (2.3 to 2.8) vs. T1 = 3.3 (2.7 to 3.6) l/minute/m2, P < 0.05), which remained so for the rest of the experiment, the O2 extraction (VO2/DO2) increased significantly only from T3 (T0 = 29 (18 to 33) vs. T3 = 35 (21 to 40)%, P < 0.05). Anemia was accompanied by a significant increase in dcvCO2 from T0 = 5 (3 to 9) to T5 = 6 (6 to 11) mmHg, P < 0.05. There was a strong significant correlation between VO2/DO2 and dcvCO2: r = 0.65, r2 = 0.43, P < 0.001. Furthermore, dcvCO2 with a cut-off value >5 mmHg had a sensitivity of 69% and specificity of 82% to show a VO2/DO2 > 30%, and receiver operating characteristics showed an area under the curve of 0.787 ± 0.054 (CI: 0.682 to 0.892), P < 0.001, for the same VO2/DO2 threshold.


To our best knowledge, this is the first study to show that dcvCO2 could be used to detect oxygen debt in isovolemic anemia.


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Kocsi, S., Demeter, G., Erces, D. et al. Central venous to arterial carbon dioxide gap as an indicator of oxygen debt in isovolemic anemia. Crit Care 15 (Suppl 1), P426 (2011).

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  • Anemia
  • Blood Loss
  • Receiver Operating Characteristic
  • Operating Characteristic
  • Interquartile Range