Frequency of mortality and myocardial infarction during maximizing oxygen delivery

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Abstract
To determine the frequency of myocardial infarction and mortality during treatment that increased oxygen delivery (DO2) to > or = 600 mL/min/m2. To define the characteristics of patients achieving a high DO2 without inotropes in order to guide future studies. A prospective, randomized, controlled trial. Two surgical intensive care units at The Queen's Medical Center in the University of Hawaii Surgical Residency Program. Eighty-nine surgical patients (> or = 18 yrs of age), who were admitted to a surgical intensive care unit and who required pulmonary artery catheter monitoring, were selected for the study. Diagnoses included sepsis, septic shock, adult respiratory distress syndrome, or hypovolemic shock. Patients facing imminent death were excluded from the study. The treatment group received fluid boluses, blood products, and inotropes, as needed, to achieve a DO2 of > or = 600 mL/min/m2 in the first 24 hrs. Using the same interventions, we treated the control group to reach a DO2 of 450 to 550 mL/min/m2. Hemodynamic measurements were obtained every 4 hrs until the pulmonary artery catheter was removed. DO2 and oxygen consumption were calculated by standard formulas. Serial creatine kinase myocardial fraction and electrocardiograms were documented for the first 48 hrs after study entry and for any new onset of arrhythmia or increasing hemodynamic instability. The patients who generated a high DO2 (> or = 600 mL/min/m2) with only preload treatment were reflective of patients with better cardiac reserve and low mortality rates. These patients, from both treatment and control groups, were excluded in the final analysis. The treatment group who received inotropes to achieve the high DO2 had a 14% mortality rate. Those patients who failed to achieve the high DO2 had a 67% mortality rate, and the control group who achieved a normal DO2 had a 62% mortality rate (p = .005). The frequency of myocardial infarction after study entry was 5.6% (five of 89 patients). This rate was not higher among the groups who received inotropes. Logistic regression analysis showed that age of > or = 50 yrs could be used to classify patients as not self-generating, with an 83% chance of being correct. The group that required catecholamines to achieve a DO2 of > or = 600 mL/min/m2 had a lower mortality rate, with no increase in the frequency of myocardial infarction. Future prospective, controlled trials examining select groups of patients (age > or = 50 yrs) may demonstrate a difference between control and treatment groups by eliminating the majority of patients who generate the high DO2 with only preload augmentation.