Relationship between oxygen extraction (OER) and age in septic patients

Introduction

A pathologic dependency between oxygen consumption (VO₂) and oxygen transport (DO₂) is characteristic of septic patients. Septic state appears to be associated with a defect in oxygen extraction (OER = VO₂/DO₂), causes possible cellular hypoxia, mitochondrial dysfunction and development of multiple organ failure. We studied the relationship between the mean OER and age in septic patients in a 12-bed ICU.

Methods

We investigated 53 septic patients (age range 20–93 years), invasively monitored in a descriptive study. DO₂, VO₂ and OR were obtained in each patient in triplicate during the first 24 h of sepsis diagnosis. Cardiac output (CO) was determined during thermodilution. Lactate concentrations were obtained in 46/53 patients (86%) and were elevated in 39%.

Results

We obtained a significant increase of the mean OER (r = 0.30; P = 0.027, two-tailed) in elderly septic patients. We noted also a significant decrease of DO₂ (P < 0.0001) and VO₂ (P = 0.004) in relation with age. No significant modifications were demonstrated with venous saturation of O₂ (SvO₂, P = 0.16), arterial saturation of O₂ (SaO₂; P = 0.7), hemoglobin concentration ([Hb], P = 0.56) and CO (P = 0.2)] in relation with age.

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Conclusion

In this descriptive study, mean OER increases in elderly septic patients. These results are probably explained by the decrease of DO₂ and VO₂ in relation with age.