Oxygen delivery and consumption and P50 in patients with acute myocardial infarction

We investigated the relationship between oxygen delivery (DO2), oxygen consumption (VO2), and influence of oxyhemoglobin dissociation (P50) on VO2 in 40 patients with complicated myocardial infarction. A decrease in VO2 and an increase in P50 were observed as DO2 decreased due to pump failure. In a given range of DO2, VO2 was related to P50 in survivors (r values .472 to .647, p less than .01). Each millimeter of mercury increase in P50 was associated with a 5.2 to 6.5 ml/min X m2 increase in VO2 when DO2 was less than 450 ml/min X m2. No similar correlation was found for nonsurvivors. Lactate was higher in nonsurvivors despite the fact that DO2 and VO2 were similar in the two groups. The lack of compensatory increases in P50 may be pathologic in nonsurvivors. However, the value of VO2 as an indicator of tissue oxygenation or survival in patients with acute myocardial infarction is questionable.