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Positive central-mixed venous oxygen saturation gradients: high oxygen saturation in the inferior vena cava confirms high splanchnic oxygen extraction


Central venous oxygen saturation (ScvO2) is increasingly used as a surrogate for mixed venous oxygen saturation (SvO2). On average, there is a positive gradient between ScvO2 and SvO2 that has been explained by the low inferior vena cava saturation (SivcO2). We aimed to clarify the dynamics and associations between different venous saturations in an experimental setting of porcine peritonitis.


Thirty-two anaesthetized pigs (40.3 ± 3.8 kg (mean ± SD)) were randomly assigned (n = 8 per group) to a nonseptic control group or one of three septic groups in which the pigs were observed for 6, 12 or 24 hours. Thereafter, resuscitation was performed for 48 hours. The pulmonary artery, superior vena cava and inferior vena cava (IVC) were catheterized. The catheter for IVC measurements was placed 5 cm below the diaphragm. SvO2, ScvO2 and SivcO2 were measured at 12-hour intervals starting at study baseline. Differences between saturations at different time points were tested with a t test for paired measurements.


One hundred and ninety-two (136 in septic and 56 in control animals) simultaneous measurements of SvO2, ScvO2 and SivcO2 were analysed. Mean SvO2 was 58.7 ± 7.2%, ScvO2 61.5 ± 8.3% and SivcO2 66.7 ± 8.5%. Dynamics of the saturations throughout the study are presented in Figure 1. ScvO2 was numerically higher than SvO2 in 133 (69.3%) of all measurements. In 122 of these 133 measurements (91.7%), SivcO2 exceeded SvO2 as well.

Figure 1

Dynamics of mixed venous, superior and inferior vena cava saturations. §Difference between SvO2 and ScvO2, P < 0.05. *Difference between SvO2 and SivcO2, P < 0.005.


In most of the measurements, both ScvO2 and SivcO2 were higher than SvO2. Our results suggest a high oxygen extraction of splanchnic organs as the reason for positive ScvO2-SvO2 gradients.

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Correspondence to A Reintam Blaser.

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Blaser, A.R., Correa, T., Djafarzadeh, S. et al. Positive central-mixed venous oxygen saturation gradients: high oxygen saturation in the inferior vena cava confirms high splanchnic oxygen extraction. Crit Care 15, P42 (2011).

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  • Peritonitis
  • Inferior Vena Cava
  • Inferior Vena
  • Superior Vena
  • Oxygen Extraction