The relationship between oxygen delivery and oxygen consumption during fluid resuscitation of burn-related shock

Although burn-related shock resuscitation based on invasive hemodynamic monitoring has been reported at an increased rate, little is known about appropriate hemodynamic end points. Shock resuscitation based on oxygen transport criteria has been widely used for patients with trauma and patients who undergo surgery, and supranormal values of oxygen delivery (DO2) have been reported in association with an improved survival rate. This improved survival rate has been attributed to a shifting of the critical threshold of DO2 to higher values in these patients. In patients with thermal injuries, the effects of the manipulation of hemodynamics to optimize oxygen transport have not been proven. It is still unclear whether these patients exhibit delivery-dependent oxygen consumption (VO2) during the shock phase. The goal of this study was to evaluate the existence of oxygen supply dependency and to determine critical levels of DO2 in patients with burns. In a prospective study that included 16 patients with serious thermal injuries, we studied the effects of volume loading on DO2 and VO2. A transpulmonary double dilution technique was used for hemodynamic monitoring, and resuscitation end points included a normalization of preload and cardiac output parameters within 24 hours of the thermal injury. Fluid loading with crystalloids and colloids, according to our resuscitation protocol, was used to augment cardiac output and DO2. Of the 16 patients with a mean of 46% total body surface area burned (range, 22%-80%), 8 patients survived and 8 patients died. With the use of progressive fluid loading, cardiac index was restored within 24 hours of admission in all of the patients. Successful resuscitation was associated with increased levels of DO2 and VO2 and with declining serum lactate levels. VO2 appeared to be dependent on DO2 during the resuscitation period (r = 0.596), and the correlation was significantly stronger in the patients who survived (r = 0.744) than in the patients who died (r = 0.368; P < .05). A critical threshold of oxygen supply could not be identified. We concluded that increasing DO2 by fluid resuscitation increases VO2 during hypovolemic shock after a severe burn injury.