Hemodynamic and oxygen transport responses in survivors and nonsurvivors of high-risk surgery

Abstract

Objectives: To describe temporal hemodynamic and oxygen transport patterns in a large series of high-risk surgical patients in order to document physiologic patterns, to develop therapeutic goals for a wide range of surgical conditions, and to propose a mechanistic model for acute postoperative circulatory failure.

Design: Prospective, longitudinal study. Patients identified as high risk were studied prospectively. The data were analyzed immediately after they were acquired, again on formal rounds twice daily, and at a formal data review after completion of monitoring.

Setting: A university-run county hospital.

Patients: The patient series consisted of 708 consecutively monitored high-risk surgical patients.

Interventions: Hemodynamic and oxygen transport values and their responses to surgical trauma are known to vary widely with age and prior medical conditions; they may be used to predict outcome with a high degree of accuracy. Temporal hemodynamic and oxygen transport patterns in a large series of high-risk surgical operations were treated by one group, using a well-developed protocol.

Measurements and main results: Hemodynamic and oxygen transport monitored variables were analyzed before, during, and at frequent intervals after surgical operations. We stratified the temporal patterns of survivors and nonsurvivors in each of the following groups: a) patients without evidence of cardiovascular disease whose preoperative baseline cardiac index values were normal; and b) patients with high or low preoperative baseline cardiac index values due to the presence of preoperatively identified medical conditions that affect the circulatory status. In addition, we stratified patients in various age ranges who were without known cardiovascular diseases. The present study analyzed over 20,000 data sets with up to 32 variables in each data set or > 500,000 values. The major findings were intraoperatively reduced circulatory functions, principally cardiac index values, oxygen delivery (DO2), and oxygen consumption (VO2). These reductions in circulatory functions intraoperatively were followed, in the early postoperative period, by increases in these variables. The postoperative increases in cardiac index, DO2, and VO2 values were greater in survivors than in nonsurvivors; these findings were more apparent when the postoperative patterns of each strata were related to their own preoperative control values.

Conclusions: The data indicate that there are increased metabolic requirements after surgical trauma and that the changes in cardiac index and DO2 represent compensatory increases in circulatory functions stimulated by increased metabolic needs. However, these metabolic needs change with age, gender, severity of illness, type of operation, associated medical conditions, duration of shock, complications, organ failure, and outcome.