Correlation of oxygen delivery with central venous oxygen saturation, mean arterial pressure and heart rate in piglets

Background: Accurate assessment and monitoring of the cardiocirculatory function is essential during major pediatric and pediatric cardiac surgery. Invasive monitoring of cardiac output and oxygen delivery (DO₂) is expensive and sometimes associated with adverse events. Measurement of central venous oxygen saturation (ScvO₂) is less invasive and may reflect the DO₂. Therefore, we investigated the correlation of ScvO₂ with cardiac index (CI) and DO₂ and in comparison the more common monitored parameters heart rate (HR) and mean arterial pressure (MAP) with DO₂ in an animal experimental setting.

Methods: In five fasted, anesthetized and mechanically ventilated piglets CI (transpulmonary thermodilution), venous and arterial blood gases, HR and MAP was measured during normal conditions, volume loading, inotropic support, and exsanguination.

Results: In the five piglets 168 measurements could be performed. In a wide hemodynamic range (CI 22–335 ml·kg⁻¹min⁻¹) we found significant correlations of ScvO₂ with DO₂ (r² = 0.91, P < 0.0001) and CI (r² = 0.88, P < 0.0001) and also between DO₂ and MAP (r = 0.86, P < 0.0001) and HR (r = 0.19, P < 0.05).

Conclusions: ScvO₂ is a better parameter for indirect estimation of DO₂ than MAP and heart rate. Measurement of ScvO₂ is simple and does not necessitate additional invasive techniques. In the clinical setting ScvO₂ should be used in combination with other standard vital parameters, i.e. MAP, central venous pressure, lactate, base excess, and urine output.