Safety and accuracy of bedside carbon dioxide cavography for insertion of inferior vena cava filters in the intensive care unit

BACKGROUND: Bedside insertion of inferior vena caval filters (IVCFs) avoids risks associated with transporting these critically ill patients to the op erating room or to the radiology suite. But because IVCF insertion requires preinsertion caval imaging, the risk of contrast-induced renal failure rem ains a concern. Carbon dioxide (CO2) as a contrast agent does not cause ren al failure, but its accuracy in determining vena caval diameter (a critical factor in filter selection) and its safety in the critical care population are unknown. This study is designed to assess the safety of using CO2 as a contrast agent in this patient population and to evaluate its accuracy in determining the diameter of the inferior vena cava when used at the bedside . STUDY DESIGN: A prospective study comparing CO2 with iodinated contrast (IC ) material was performed in critically ill patients undergoing vena cavogra phy before bedside IVCF placement. CO2 cavagrams were performed with one or more hand injections of 60 mL of CO2; a single injection of 40 mL of IC ma terial was used. Digital subtraction techniques were used for all of the st udies. Blood pressure, pulse rate, and arterial oxygen saturation, end-tida l CO2, and intracranial pressure (when available) were recorded before, dur ing, and after contrast injection. Statistical analysis was performed using the paired t-test, with p < 0.05 being considered significant. Data are ex pressed as mean +/- SD. RESULTS: Twenty-three patients were studied. Mean transverse inferior vena cava (IVC) diameters measured 20.4 +/- 0.7 mm (IC) and 20.0 +/- 0.7 mm (CO2 ); p = 0.003. The difference in the measurements was 0.4 +/- 0.1 mm, with t he largest difference being 1.7 mm. In the remaining 10 patients, CO2 diffe red from IC in determining IVC diameter by only 0.4 mm, a statistically sig nificant (p < 0.05) but clinically insignificant difference. No adverse eff ects on blood pressure, pulse, arterial oxygen saturation, end-tidal CO2, o r intracranial pressure were noted with the use of CO2. CONCLUSIONS: Carbon dioxide as a contrast agent is safe and provides accura te determination of vena caval diameter and anatomy. Carbon dioxide should be considered the contrast agent of choice in critically ill patients. (J A m Coll Surg 2001;132:168-171. (C) 2001 by the American College of Surgeons) .