Portal de Periódicos da CAPES

Iodinated Organic Compounds as Contrast Media for Radiographic Diagnoses

1946; Radiological Society of North America; Volume: 47; Issue: 1 Linguagem: Inglês

10.1148/47.1.47

1527-1315

William H. Strain, J. D. French, Glenn E. Jones,

Airway Management and Intubation Techniques

After myelography with oil-type contrast media, some of the opaque substance may be left in the spinal canal at the end of the examination. When Pantopaque was developed for myelography, it was reported that such residues were absorbed in a relatively short time (6). Clinical experience, however, has shown that there is great variability in the rate of absorption in man (4, 11), and it seemed desirable to study both pathways and mechanisms by which the medium is eliminated. In dogs this work has lead to the discovery that the cribriform plate is permeable to Pantopaque, and that this pathway may be an important avenue for the escape of the medium from the subarachnoid space in lower orders. Experimental demonstration of the permeability of the cribriform plate to Pantopaque is easily carried out in dogs by running the medium into the cranial cavities of an anesthetized animal in a prone position with its head down. Oil-type media of lower viscosity than Pantopaque pass through the plate even more readily, but more viscous media, such as lipiodol, do not seem to penetrate; emulsions of oil-type media also do not permeate the plate. After passing through the cribriform plate, Pantopaque follows along the tissues of the nasal cavities to the lymphatics of the head and finally collects in the lymph nodes of the head and neck. A series of roentgenograms showing the progressive extension of the medium is reproduced in Figure 1 (A–F). From these films it is apparent that extension also occurs along the cranial nerves to some extent. Demonstration of the passage of Pantopaque through the cribriform plate is conveniently carried, out with dogs under continuous Nembutal anesthesia. In a typical experiment, an animal weighing 20 kg. was placed in a prone position with its head down and its body elevated at an angle of about 15° to the horizontal. A cisternal puncture was made, 8 c.c, of spinal fluid aspirated, and 5 c.c. of Pantopaque introduced into the subarachnoid space. Dnder continuous anesthesia the dog was maintained with its head down for a period of six hours. Lateral and ventrodorsal roentgenograms taken at intervals showed that the medium passed rapidly through the cribriform plate after about two hours, although the rate may be a function of the degree of inclination of the animal. Complete visualization of the tissues of the nasal cavities and of the lymphatics of the head was obtained after five or six hours. The dog survived the experiment well and did not show any deleterious effects over an observation period of several months. Similar experiments with lipiodol and with a 50 per cent aqueous emulsion of Pantopaque gave negative results. Ethyl iodophenylvalerate (3) and iodobenzene, media much less viscous than Pantopaque, in many ways gave superior visualization but were so toxic that they could not be employed for survival experiments.