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- Open Access
Near-infrared spectroscopy during stagnant ischemia: a marker of ScvO2–SvO2 mismatch in septic patients with low cardiac output
© BioMed Central Ltd 2008
- Published: 13 March 2008
- Septic Patient
- Superior Vena
- Septic Shock Patient
- Thenar Muscle
- Tissue Oxygen Consumption
Monitoring of oxygen saturation in the superior vena cava (ScvO2) was suggested as a simpler and cheaper assessment of the global DO2:VO2 ratio and was used successfully as a goal in treatment of patients with septic shock and severe sepsis . In patients with low cardiac output (CO) the difference between SvO2 and ScvO2 is more expressed and problematically large confidence limits and poor correlation were found between the two values . The thenar muscle oxygen saturation (StO2) measured with near-infrared spectroscopy (NIRS) during stagnant ischemia (cuff inflation-induced vascular occlusion) decreases slower in septic shock patients . This may be due to slower muscle tissue oxygen consumption in sepsis. This phenomenon possibly contributes to the ScvO2–SvO2 mismatch in patients with low CO by adding more oxygenated venous blood to flow through the superior vena cava. The aim of present study was to determine the relationship between the StO2 deceleration rate and the ScvO2–SvO2 difference in septic patients with low CO.
In septic patients with low CO and no signs of hypovolaemia, catheterization with a pulmonary artery floating catheter was performed. Blood was drawn from the superior vena cava and pulmonary artery at the time of each StO2 measurement in order to determine ScvO2 and SvO2. The thenar muscle StO2 during stagnant ischemia was measured using NIRS (InSpectra™) and the StO2 deceleration rate (StO2%/min) was obtained using the Inspectra Analysis Program V2.0.
Fifty-four patients (47 male, seven female), age 68 ± 13 years, SOFA score 12.2 ± 2.5 points. CI 2.5 ± 0.7 l/min/m2, SvO2 67 ± 10%, ScvO2 77 ± 8%. Lactate 3.5 ± 3.0 mmol/l, CRP 127 ± 78 mg/l. NIRS data: basal StO2 89 ± 8%, deceleration rate -12.6 ± 4.9%/min, StO2 deceleration rate versus ScvO2–SvO2 0.651, P = 0.001(Pearson correlation, P value).
The StO2 deceleration rate during cuffing is inversely proportional to the difference between ScvO2 and SvO2 in septic patients with low CO. When using ScvO2 as a treatment goal, this simple noninvasive NIRS measurement might be useful to discover those patients with normal ScvO2 but probably abnormally low SvO2.
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