Hemodynamic Changes Associated with the Intra-Arterial Injection of Contrast Media

Abstract

The use of radiographic contrast agents as indicators for the blood flow determination (10, a) prompted this controlled experimental study. A precise knowledge of the various hemodynamic disturbances is necessary for the evaluation of the limitations of these radiopaque flow indicators. During this study some aspects of the mechanism of toxicity of the contrast media have been elucidated. The results led the author to the development of a new contrast agent—a bis-additive of iothalamate—which seems to be considerably less toxic than any of the currently available water-soluble iodinated radiopaque materials. In addition, two new nonlethal toxicity tests for these media have been developed and are herein presented. Material and Methods The material consists of 79 mongrel dogs weighing between 21 and 28 kg. Twelve animal investigations represent technical failures and will be omitted from this presentation. Thirty-two dogs were studied for the hemodynamic changes occurring in the hind limb after the injection of contrast agents into the femoral artery. Thirty-five animals were investigated for reactions to carotid artery injections. Of this group, 8 dogs underwent a parietotemporal craniotomy with catheterization of a branch of the middle cerebral artery. Thirteen of this same group were studied for the determination of “The Least Convulsive Dose” of various contrast agents. In the remaining 14 animals various branches of the carotid vessels were exposed for pressure monitoring and for injections at different sites, as will be mentioned in detail below. The Statham strain gauge Model P23DE was chosen for the blood pressure measurement because of its high sensitivity and adequate frequency response. The square wave electromagnetic flowmeter manufactured by Avionics was used. To assure accurate flow measurement the animal was grounded at one point only, and the zero flow was calibrated by arterial occlusion before each reading. The two probes used for the internal carotid flow monitoring had lumina measuring 1 and 0.75 mm in diameter, respectively. Exposure of the Femoral Vessels and Their Branches The femoral artery is exposed just distal to the inguinal ligament. The injection catheter is passed in a retrograde direction through one of the superficial branches of this artery. The encroachment of the tip of the catheter on the lumen of the main artery is carefully avoided to prevent any interference with the blood flow. The electromagnetic flowmeter probe is always positioned proximal to the injection point to preclude the passage of the administered material through the field of the probe. A catheter is placed in the femoral vein through one of its branches for blood pressure measurement. The anterior tibial artery is exposed in front of the ankle joint, and its distal segment ligated. A polyethylene tubing is introduced in its proximal segment for pressure recording. In some experiments the digital artery pressure was also measured.