This study evaluates the safety and effectiveness of carbon dioxide (CO2) as a contrast agent in patients in the intensive care unit undergoing vena cava filter (VCF) insertion. We prospectively evaluated patients in the intensive care unit undergoing bedside VCF insertion using CO2 cavagraphy. Blood pressure, pulse rate, mixed venous oxygen saturation, and intracranial pressure were monitored before, during, and after the CO2 injection. Fifty patients in the intensive care unit (mean age 48.2 +/- 16.5 years) were included in the study. Five patients had decreases in blood pressure, which resolved without intervention. Two patients required iodinated contrast as a result of inadequate CO2 imaging. All patients had successful insertion of VCF. The use of CO2 as a contrast agent is a safe and highly effective alternative for vena cava imaging and can be considered the first-line contrast agent for all critically ill patients requiring VCF placement.