Tissue oxygen saturation is positively correlated with oxygen delivery and cardiac output in a canine hemorrhagic shock and resuscitation model

OBJECTIVE To determine if tissue oxygen saturation (StO(2)) correlates with oxygen delivery (DO2) and/or cardiac output (CO) in a canine hemorrhagic shock model. ANIMALS 8 healthy purpose-bred dogs. METHODS Dogs were anesthetized, and hemorrhagic shock was induced by withdrawing up to 60% of total blood volume, targeting a mean arterial pressure (MAP) of 40 mm Hg. The withdrawn blood was returned to the patient in 2 equal aliquots. Data was collected at 4 time points: 10 minutes after MAP was stabilized under anesthesia (time point [TP]-1), 10 minutes after up to 60% of blood volume was removed to target a MAP of 40 mm Hg (TP2), 10 minutes after the return of 50% of shed blood (TP3), and 10 minutes after the return of the remaining 50% of shed blood (TP4). Total blood volume withdrawn, StO(2), CO, heart rate, and MAP were recorded, and DO2 was calculated at each TP. RESULTS Mean StO(2) significantly decreased between TP1 (77.8% [+/- 9.54]) and TP2 (44.8% [+/- 19.5]; P < .001 vs TP1). Mean StO(2) increased to 63.1% (+/- 9.85) at TP3, but remained significantly lower compared to TP1 (P = .002). There was no difference between mean StO(2) at TP4 (82.5% [+/- 12.6]) versus TP1 (P = .466). StO(2) has a strong, positive correlation to both CO (r = 0.80; P < .001) and DO2 (r = 0.75; P < .001). CLINICAL RELEVANCE A decrease in StO(2) may be used in conjunction with physical examination findings and diagnostic parameters to support a diagnosis of shock. The return of shed blood was correlated with increases in StO(2), DO2, and CO, suggesting that StO(2) may be used as a marker of adequate resuscitation.