Intravenous carbon dioxide as an echocardiographic contrast agent

Intravenous carbon dioxide (CO₂) was employed to cause echocardiographic contrast in 40 patients. One to 3 cc of medically pure CO₂ were agitated with 5 to 8 cc of 5% dextrose in water and rapidly injected into an upper extremity vein. Contrast was obtained in all patients. In 33 patients contrast density from 5% dextrose was compared with that from 5% dextrose‐CO₂ injections. Six of these patients had no contrast on the initial 5% dextrose injection and definite contrast with the subsequent injection containing CO₂. Of the 33, 12 patients had initial contrast with 5% dextrose injections and greater contrast density when CO₂ was added; 15 showed no definite difference; and none had less contrast with intravenous CO₂‐5% dextrose than with 5% dextrose alone. Intravenous CO₂‐5% dextrose is a useful method of increasing contrast in those patients who fail to demonstrate echocardiographic contrast when routine techniques are employed. It is also safe, provided precautions emphasized in this paper are observed.