ABSTRACT
CO2 is a safe contrast agent for inferior vena cavography if the current CO2 delivery
methods (the hand-held syringe and the plastic bag system) are used correctly. CO2 can
provide accurate measurement of vena caval diameter and anatomy necessary for filter
placement and caval interventions. Therefore, CO2 is the preferable contrast medium
because intravascular administration of the gas does not cause allergic reaction or renal
failure. In order to optimize the use of CO2, a thorough understanding of the physical prop-
erties of CO2 and proper techniques for its use are required. Without air contamination
during CO2 injection, vital signs should remain stable during and after CO2 injection in
quantities of up to 60 cc. Because of the low viscosity of CO2, the gas can be injected using
an end-hole catheter, eliminating the need for the use of a pigtail catheter used for contrast
vena cavography. CO2 should be used with caution in patients with severe pulmonary
hypertension because intracaval injection of the gas causes a transient increase in pulmonary
arterial pressure. The presence of intracardiac shunt is a relative contraindication to the use
of CO2 for vena cavography. When multiple injections are required, the injections should
be separated by two to three minutes to allow complete absorption of the gas injected.
