Invasive and noninvasive oxygen consumption and hemodynamic monitoring in elderly surgical patients.

A relationship between survival and high cardiac index and oxygen delivery (DO2) has been documented for patients of all ages. Debate continues whether achieving these parameters decreases mortality or whether these parameters merely reflect better physiologic reserve. Younger patients who spontaneously generate high DO2 have low mortality rates and do not present a treatment challenge. The difficulty and controversy concern the use of inotropic agents and blood transfusions in older patients with concurrent myocardial dysfunction who are unable to mount an appropriate DO2 response to increased oxygen demands. Although it is obvious that one DO2 value may not satisfy all patients, there are difficulties in recognizing areas of tissue ischemia, and practioners attempt to keep DO2 > or = 600 mL/min/m2 to ensure tissue perfusion. Logically, assessment of oxygen needs in the elderly should be based on patients' sex, age, muscle mass, premorbid activity level as well as the disease state. Although DO2 augmentation to > or = 600 mL/min/m2 may be appropriate for most critically ill patients, a 450 to 550 mL/min/m2 value may be equivalent to a "high" DO2 in relation to the basal needs for the very old (age > 75 yrs). Keeping oxygen extraction ratios < or = 0.25 during early resuscitation may be used as an additional guide in titrating DO2. Technology which allows identification of ischemic areas may assist in guiding individual treatment rather than utilizing a global DO2, goal.