Measurements of oxygen saturation of brain, liver and heart areas in the supine and sitting position using near infrared spectrophotometry.

Background And Aims: Regional oxygen saturation (rSO) monitoring of the brain by near-infrared spectroscopy (NIRS) has been mainly used during carotid endarterectomy. The present study was conducted in volunteers and investigates the rSO values of the brain, heart and liver tissue as assessed by NIRS in the supine and the sitting position.

Methods: After obtaining written informed consent from forty-nine healthy volunteers, rSO values were recorded in the heart and liver areas in the supine and the sitting position, while simultaneously the rSO values of the brain.

Results: The rSO brain values in the supine and the sitting position were 69 ± 6.0 and 66 ± 6.1 respectively (p = 0.0001). The rSO values in the supine and the sitting position were 76 ± 10.5 and 79 ± 6.7 for the heart (p > 0.05) and 85 ± 6.8 and 82 ± 7.2 for the liver, (p = 0.007). Heart rSO values were higher than the brain rSO values in both the supine (76 ± 10.4 versus 69 ± 6.6; p = 0.0001) and the sitting position (79 ± 6.7 versus 66 ± 6.1; p = 0.0001). The liver rSO values were also higher than the brain rSO2 values in the supine (85 ± 6.8 versus 69 ± 6.0; p = 0.0001) and in the sitting position (82 ± 7.2 versus 66 ± 5.7; p = 0.0001). Arterial blood pressure and arterial oxygen saturation (SpO) did not differ between the two positions but the heart rate was higher in the sitting position (p = 0.030).

Conclusions: We conclude that brain and liver (but not heart) rSO values are higher in the supine than sitting position. Additionally, NIRS may be used to assess oxygenation of the heart and liver.