Combination of venoarterial PCO2 difference with arteriovenous O2 content difference to detect anaerobic metabolism in patients

Intensive Care Med. 2002 Mar;28(3):272-7. doi: 10.1007/s00134-002-1215-8. Epub 2002 Feb 8.


Objective: Under conditions of tissue hypoxia total CO2 production (VCO2) should be less reduced than O2 consumption (VO2) since an anaerobic CO2 production should occur. Thus the VCO(2)/VO(2) ratio, and hence the venoarterial CO2 tension difference/arteriovenous O2 content difference ratio (DeltaPCO2/C(a-v)O2), should increase. We tested the value of the DeltaPCO2/C(a-v)O2 ratio in detecting the presence of global anaerobic metabolism as defined by an increase in arterial lactate level above 2 mmol/l (Lac+).

Design and setting: Retrospective study over a 17-month period in medical intensive care unit of a university hospital.

Patients: We obtained 148 sets of measurements in 89 critically ill patients monitored by a pulmonary artery catheter.

Results: The DeltaPCO2/C(a-v)O2 ratio was higher in those with increased ( n=73) than in the normolactatemic group (2.0+/-0.9 vs. 1.1+/-0.6, p<0.0001). Among all the O2- and CO2-derived parameters the DeltaPCO2/C(a-v)O2 ratio had the highest correlation with the arterial lactate level ( r=0.57). Moreover, for a threshold value of 1.4 the DeltaPCO2/C(a-v)O2 ratio predicted significantly better than the other parameters (receiver operating characteristic curves) the presence of hyperlactatemia (positive and negative predictive values of 86% and 80%, respectively). The overall survival estimate at 1 month was greater when the DeltaPCO2/C(a-v)O2 ratio was less than 1.4 on the first set of measurements (38+/-10% vs. 20+/-8%, p<0.01).

Conclusion: The DeltaPCO2/C(a-v)O2 ratio seems a reliable marker of global anaerobic metabolism. Its calculation would be helpful for a better interpretation of pulmonary artery catheter data.

MeSH terms

  • Bacteria, Anaerobic / metabolism*
  • Bacterial Infections / blood
  • Bacterial Infections / metabolism*
  • Biomarkers
  • Blood Gas Analysis
  • Carbon Dioxide / blood
  • Carbon Dioxide / metabolism*
  • Catheterization, Swan-Ganz
  • Critical Care
  • Female
  • Hemodynamics*
  • Humans
  • Lactates / blood*
  • Male
  • Middle Aged
  • Oxygen Consumption
  • ROC Curve
  • Retrospective Studies


  • Biomarkers
  • Lactates
  • Carbon Dioxide