Do right atrium to mixed venous oxygen saturation gradients mirror heart oxygen uptake?

Objective

To analyze behavior of venous oxygen saturation (SvO₂) measured in the coronary sinus and to correlate it with central to mixed venous SvO₂ gradients.

Methods

Sixteen large white pigs, weight 35 kg, in general anesthesia (isofluorane, fentanyl, pancuronium), fully monitored (electrocardiography, etCO₂, invasive pressure, pulmonary artery catheter, portal vein Doppler ultrasound flow, small bowel tonometry), were studied. Fifteen pigs were submitted to fecal peritonitis sepsis (1 g/kg feces plus 150 ml warm saline) after fluoroscopy-guided coronary sinus catheterization and the last one was the sham. Laboratory data (blood samples collected from the coronary sinus, right atrium, pulmonary artery) and hemodynamic data were registered hourly. After the experiments, pigs were sacrificed with a sedative overdose and KCl 19.1% injection.

Results

Central to mixed venous SvO₂ curve distances vary along time (hours) (Figure 1) more in septic pigs than in the sham (Figure 2). Measurements of SvO₂ from the coronary sinus reach extremely low values (Figure 3).

Figure 1

Central venous to pulmonary artery SvO ₂ gradients.

Figure 2

Time series plot of SVCO ₂ ; SVMO ₂ – sham.

Figure 3

Time series plot of median SSC.

Conclusion

Absolute SvO₂ gradient variations along time, in sepsis, may be the consequence of coronary sinus contribution, considering the extremely low values observed. Further studies should explore whether these gradient variations may be an indicator of myocardial oxygenation status.