High mixed venous oxygen saturation levels do not exclude fluid responsiveness in critically ill septic patients

INTRODUCTION: The aim of this study was to determine whether the degree of fluid responsiveness in critically ill septic patients is related to baseline mixed venous oxygen saturation (SvO(2)) levels. We also sought to define whether fluid responsiveness would be less likely in the presence of a high SvO(2 )(>70%). METHODS: This observational study was conducted in a 32-bed university hospital medicosurgical ICU. The hemodynamic response to a fluid challenge was evaluated in 65 critically ill patients with severe sepsis. Patients were divided into two groups (responders and nonresponders) according to their cardiac index (CI) response to the challenge (>10% or <10%). RESULTS: Of the 65 patients, 34 (52%) were fluid responders. Baseline SvO(2), CI, heart rate (HR) and mean arterial pressure (MAP) were not statistically different between groups. The responders had lower pulmonary artery occlusion pressure (PAOP) and central venous pressure (CVP) at baseline than the nonresponders. After the fluid challenge, there were no differences between the two groups in MAP, CVP, PAOP or HR. There was no correlation between changes in CI or stroke volume index and baseline SvO(2). Receiver operating characteristic analysis showed that SvO(2 )was not a predictor of fluid responsiveness. CONCLUSIONS: The response of septic patients to a fluid challenge is independent of baseline SvO(2). The presence of a high SvO(2 )does not necessarily exclude the need for further fluid administration.