Evaluation of the FloTrac uncalibrated continuous cardiac output system for perioperative hemodynamic monitoring after subarachnoid hemorrhage

Early hemodynamic assessment is of particular importance for adequate cerebral circulation in patients with aneurysmal subarachnoid hemorrhage (SAH), but is often precluded by the invasiveness and complexity of the established cardiac output determination techniques. We examined the utility of an uncalibrated arterial pressure-based cardiac output monitor (FloTrac) for intraoperative and postoperative hemodynamic management after SAH. In 16 SAH patients undergoing surgical clipping, arterial pulse contour cardiac index, and stroke volume variation (SVV) were analyzed via the radial FloTrac system. The hemodynamic values after induction of anesthesia until 12 hours after surgery were compared with reference transpulmonary thermodilution cardiac index (TPCI), calibrated pulse contour CI, and global end-diastolic volume index determined by the PiCCO system and central venous pressure. Arterial pulse contour cardiac index underestimated CI as overall bias±SD of 0.57±0.44 L/min/m and 0.54±0.46 L/min/m compared with TPCI and calibrated pulse contour CI, resulting in a percentage error of 24.8% and 26.6%, respectively. Subgroup analysis revealed a percentage error of 29.3% for values obtained intraoperatively and 20.4% for values measured under spontaneously breathing after tracheal extubation. Better prediction of cardiac responsiveness to defined volume loading for increasing stroke volume index >10% was observed for SVV under mechanical ventilation with greater area under the receiver operating characteristics curve than that for global end-diastolic volume index or central venous pressure. These data suggest that the FloTrac underestimates the reference CI, and is not as reliable as transpulmonary thermodilution for perioperative hemodynamic monitoring after SAH. SVV is considered to be an acceptable preload indicator under mechanical ventilation.