Mild hypothermia alters the oxygen consumption/delivery relationship by decreasing the slope of the supply-dependent line

Objective: To evaluate the effect of mild hypothermia on the relationship between systemic oxygen consumption and oxygen delivery. Design: Prospective animal study. Setting: University research laboratory. Subjects: Anesthetiezd and ventilated rabbits. Interventions: Rabbits were subjected to stepwise cardiac tamponade to reduce oxygen delivery while body temperature was maintained at 34°C (group H, n = 8) or 39°C (group N, n = 8). Measurements and Main Results: The oxygen consumption/oxygen delivery relationship was analyzed by the dual-line method. The slope of the supply-dependent line was significantly decreased in group H (y = 0.57x + 1.3) compared with that in group N (y = 0.72x + 1.7), indicating that the ability of tissues to extract oxygen was impaired during hypothermia. Consequently, the proportion of the supply-independent area over the entire range of oxygen delivery was decreased in response to hypothermia. Conclusion: The potential for tissue hypoxia is likely to be increased during hypothermia when the circulation becomes unstable during hypothermia when the circulation becomes unstable and oxygen delivery decreases.