Comparison between intrathoracic blood volume and cardiac filling pressures in the early phase of hemodynamic instability of patients with sepsis or septic shock

Purpose: The purpose of this study was to analyze three different variables of cardiac preload; central venous pressure (CVP), pulmonary artery occlusion pressure (PAOP), and intrathoracic blood volume index (ITBVI) that served as the best indicator of cardiac function, that is, cardiac index (CI) or stroke index (SI). Materials and Methods: This was a prospective study in 57 critically ill patients with sepsis or septic shock in whom 581 hemodynamic profiles were analyzed. One patient was included a second time after a period of 6 weeks. All patients were sedated and mechanically ventilated. Each patient had a 7.5-Fr five-lumen pulmonary artery catheter (PAC) and a 4-Fr catheter with an integrated thermistor and fiberoptic that was advanced into the descending aorta via a femoral artery sheath. The study was performed in the surgical intensive care unit of a university hospital. Results: Linear regression analysis of the first profile for each case (n = 58) revealed a significant correlation between ITBVI and SI (r = 0.66). For comparison, correlations for PAOP/SI (r = 0.06) and CVP/SI (r = 0.10) were poor. The analysis of all second profiles showed that only the change in ITBVI reflected the change in SI (r = 0.67), whereas PAOP (r = 0.07) and CVP (r = 0.05) failed. Furthermore, a positive change in SI (n = 265) was most often associated with an increase in ITBVI (n = 189, 71.3%), less for PAOP (n = 122, 46.0%) and CVP (n = 137, 51.7%). A reduction in SI (n = 256) was accompanied by a decrease in ITBVI (n = 176, 68.8%), PAOP (n = 119, 46.5%), and CVP (n = 118, 46.1%). An increase in ITBVI (n = 269) was accompanied by an increase in SI in 189 cases (70.3%). In these, PAOF increased only in 91 (48.1%) and CVP in 101 cases (53.4%), respectively. Accordingly, a positive change in PAOP (n = 218) was associated with an increase in SI in 122 cases (56.0%). ITBVI increased in 91 (74.6%) and CVP in 84 (68.9%) of these cases. A decrease in ITBVI (n = 250) was associated with a decrease in SI in 176 cases (70.4%). Decreases in PAOP (n = 89, 50.6%) and CVP (n = 91, 51.7%) did not reflect these changes. However, when PAOP (n = 229) and SI decreased(n = 119, 52.0%), ITBVI decreased in 89 (74.8%) and CVP in 73 cases (61.3%). Conclusions: In comparison with cardiac filling pressures, ITBVI seems to be the more reliable indicator of cardiac preload in patients with sepsis or septic shock. Copyright (C) 1999 by W.B. Saunders Company.