FREQUENCY OF MORTALITY AND MYOCARDIAL-INFARCTION DURING MAXIMIZING OXYGEN DELIVERY - A PROSPECTIVE, RANDOMIZED TRIAL

Objectives: To determine the frequency of myocardial infarction and mo rtality during treatment that increased oxygen delivery (Do(2)) to gre ater than or equal to 600 mL/min/m(2). To define the characteristics o f patients achieving a high Do(2) without inotropes in order to guide future studies. Design: A prospective, randomized, controlled trial. S etting: Two surgical intensive care units at The Queen's Medical Cente r in the University of Hawaii Surgical Residency Program. Patients: Ei ghty-nine surgical patients (greater than or equal to 18 yrs of age), who were admitted to a surgical intensive care unit and who required p ulmonary artery catheter monitoring, were selected for the study. Diag noses included sepsis, septic shock, adult respiratory distress syndro me, or hypovolemic shock. Patients facing imminent death were excluded from the study. Interventions: The treatment group received fluid bol uses, blood products, and inotropes, as needed, to achieve a Do(2) of greater than or equal to 600 mL/min/m(2) in the first 24 hrs. Using th e same interventions, we treated the control group to reach a Do(2) of 450 to 550 mL/min/m(2). Measurements and Main Results: Hemodynamic me asurements were obtained every 4 hrs until the pulmonary artery cathet er was removed. Do(2) and oxygen consumption were calculated by standa rd formulas. Serial creatine kinase myocardial fraction and electrocar diograms were documented for the first 48 hrs after study entry and fo r any new onset of arrhythmia or increasing hemodynamic instability. T he patients who generated a high Do(2) (greater than or equal to 600 m L/min/m(2)) with only preload treatment were reflective of patients wi th better cardiac reserve and low mortality rates. These patients, fro m both treatment and control groups, were excluded in the final analys is. The treatment group who received inotropes to achieve the high Do( 2) had a 14% mortality rate. Those patients who failed to achieve the high Do(2) had a 67% mortality rate, and the control group who achieve d a normal Do(2) 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. L ogistic regression analysis showed that age of greater than or equal t o 50 yrs could be used to classify patients as not self-generating, wi th an 83% chance of being correct. Conclusions: The group that require d catecholamines to achieve a Do(2) of greater than or equal to 600 mL /min/m(2) had a lower mortality rate, with no increase in the frequenc y of myocardial infarction. Future prospective, controlled trials exam ining select groups of patients (age 150 yrs) may demonstrate a differ ence between control and treatment groups by eliminating the majority of patients who generate the high Do(2) with only preload augmentation .