Assessing Opacification and Flow Rates of Contrast Media in Neonate and Pediatric Cardiac Catheterization Charles Prickett, III, M.S., and John Leslie Johnson, M.D., F.A.C.A. LOS

ANGELES,

CALIFORNIA

A bstract The accuracy and advantages of determining the flow rates of opaque media in catheters used in the infant and pediatric age group is essential in obtaining proper opacification with minimum toxicity to the patient. Flow rates expressed as cubic centimeters per second and grams of iodine per second were determined by using representative standard pediatric catheters in various sizes and lengths. Three representative opaque medias were used to determine these findings. Although present-day injector pumps are frequently calibrated in delivery rates, they cannot be applied directly to the cardiac catheters usually used with infants and small children. Introduction In the last 20 years there has been a rapid development in angiocardiographic studies of infants and children. In angiocardiography and selective cineangiography it is important that the contrast medium to be injected rapidly. Many factors govern the rate of flow of contrast medium through a catheter, including the internal diameter, length, and type of catheter material; pressure of injection; iodine content; density and viscosity of the contrast media; osmolarity, sodium content, and specific toxicity of the contrast material; and the general condition of the patient, such as the state of hydration and hematocrit

level. Laws and Fox’ examined the factors controlling the rate of injection of contrast media in angiocardiography. They used the large size No. 7 to No. 10

French catheters and found that by far the most important factors in achieving rapid flow were the type and size of cardiac catheter. Their studies showed that for a given external diameter of catheter and injection pressure, the National Institute of Health modified Lehman catheters gave a consistently higher flow rate than the Cournand type catheter. Fischer and his associates’ evaluated several factors influencing injection rates in angiography. They found that the most rational approach to angioa

From the Cardio-Vascular

Diagnostic Laboratory, Huntington Memorial Hospital

and Medical

Center, Pasadena, California; White Memorial Hospital and Medical Center, Los Angeles, California; and University of Southern California Medical School, Los Angeles, California.

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catheter flow rates requires that the values be expressed as grams of iodine per second, upon which radiopacity depends. They found that neither Poiseuille’s nor Blasius’ law satisfactory in predicting the flow of highly concentrated contrast media through small diameter catheters. They suggested that the angiographer should determine from actual testing what performance is to be expected from individual catheters and certain media. However the data of Cooley and BeentjeS3 suggested that in most practical cases Blasius’ law rather than Poiseuille’s law should be applied to establish the expected flow rates of contrast substances injected through catheters. These formulae are described in detail elsewhere. 3,4 But often Poiseuille’s and Blasius’ laws cannot be applied since flow through small-bore catheters used in pediatic angiocardiography is more likely to be turbulent rather than laminar, because of the viscosity of the contrast agents used and the lack of uniformity of the internal diameter along the catheter and, in some instances, because of interrupted injection of contrast media. The present study was undertaken to supply practical clinical information on the grams of iodine and the volume of commonly used contrast media injected per second through properly used representative pediatric angiographic catheters.

graphic

Materials and Methods Contrast Media. The media tested were low viscosity Hypaque 50% and medium viscosity Hypaque 75% (Winthrop Laboratories, 90 Park Avenue, New York, NY 10016), and Renografin 76% (E. R. Squibb & Sons, Box 4000, Princeton, NJ 08540). Fifty percent Hypaque contains only sodium diatrizoate with an iodine content of 300 mg/ml and a density of 1.303 g/cc at 37°C. Seventy-five percent Hypaque contains sodium diatrizoate and methylglucamine diatrizoate in 1:2 ratio, with an iodine content of 385 mg/ml and a density of 1.318 gs/cc at 37°C. Seventy-six percent Renografin contains sodium diatrizoate, 10%, and methylglucamine diatrizoate, 66%, with an iodine content of 370 mg/ml and a density of 1.321 g/cc at 37°C. Measurement Techniques. The injection of contrast material was done by a Turner Syringe Pump (not presently on the market) set at 400, 600, 800, and 1000 pounds per square inch (PSI). The recording element of the injector was connected to a DC amplifier of an Electronics for Medicine DR-8 recorder (Electronics for Medicine, 30 Virginia Road, White Plains, NY 10603). Recorder paper was run at a speed of 50 ml/sec with time-line markings at 0.1I second. Three popular catheter types were tested: The National Institutes of Health (NIH) Catheter (U.S. Catheter Company, Box 566, Billerica, MA 01821), the Cordis Left Ventricular Pigtail (Cordis Corporation, 10727 White Oak Avenue, Suite 113, Granada Hills, CA 91344), and the Brockenbrough catheters. We selected a wide range of lengths and diameters of the catheters in each of these

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819 groups. The catheters were flushed with saline following a maximum of three injections. All determinations were made at body temperature (37°C) with the catheter tip placed in a flask containing varying amounts of the opaque media being tested. The material was warmed and used again for further injections. Flow rates were then plotted in cubic centimeters per second for each pressure setting, and the average flow rate expressed was as the slope (cubic centimeters per second). The grams of iodine injected per second were then computed and both sets of values were listed in clinically usable tables. Flow rates were used to compare types of catheters, lengths and diameters of catheters, and the kind of contrast media. ’

R esul ts Tables 1 and 2 list the flow rates of 50% Hypaque, 76% Renografin, and 75% Hypaque through frequently used lengths and diameters of NCI, Cordis, and Brockenbrough catheters at 400, 600, 800, and 1000 pounds per square inch of

injection

pressure. The values are determined with the Turner Syringe Pump, using plastic >. syringes. The tables also list flow rates in grams of iodine per second and volume (ml) per second expressed as the slope of multiple determinations. In the smallbore catheters, grams of iodine per second from 50% Hypaque were equal to and often decidely higher than the rates with the other two agents. For the slightly larger bore catheters, the iodine output for 76% Renografin was often . slightly higher than that of 75% Hypaque at the same catheter length. Fifty percent Hypaque was not tested in large-bore catheters because it is used mainly in infants. However, details for flow rates with 50% Hypaque in larger catheters have been reported by one of us previously.&dquo; Discussion

The influence of catheter caliber and length on flow rate is apparent from these data. The shorter the length and the larger the bore, the greater the flow rates. At the same bore diameter, the shorter the length, the greater the flow rates.

reported the flow of contrast media to be roughly the inversely proportional to length of the catheter and directly proportional to the fourth power of the radius of the catheter.1.3.5-8 To show results in flow rates as cubic centimeters of contrast media per second gives incomplete information. Therefore the present analysis was patterned after the scheme of Fischer and coworkers,2 expressing flow rates as grams of iodine per second, indicating an injection’s true physical capacity to opacify. Expressing flow rates in grams of iodine per second shows the great influence of viscosity in the use of small-bore, pediatric-size angiographic catheters. There are obviously mechanical differences between different models of Other researchers have

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820 Comparison of the

Flow

TABLE 1 Media

of Contrast

Through

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NIH Catheters

821 TABLE 1

Thirty cubic centimeters of

contrast

media

were

(Continued)

injected by

Turner

Syringe Pump, and temperature

set at 37° C.

PSI

=

pounds

per square

inch; NIH = National Institute of Health; F

=

french.

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822 TABLE 2

Comparison of the Flow of Contrast

Media

Through Cordis Left Ventricular Pigtail Catheters

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and

Brockenbrough

823 TABLE 2

(Continued)

pressure injectors,

but the flow rates to be expected with any pressure and catheter can be estimated from the tables. The type of contrast media can then be selected to yield the maximum opacification of the area in question and, most importantly, with the least toxicity. Obviously, toxicity and osmolarity of each medium must be considered when choosing a catheter and injection pressure. Osmolarity can effect hydration and is probably the most important criterion in deciding the amount of material to be used in pediatric cases. It was the purpose of this study, however, to evaluate injection force and catheter limitations. Despite the variation of mechanical features from injector pump to injector pump we believe that the flows in the various catheters at the pressure settings indicated in the tables are accurate enough for the clinician to consult confidently them when deciding which media, catheter, and pressure to use for a given procedure. When applied to small-bore pediatric catheters, the use of Medium-concentrated and moderately viscous contrast media such as 76% Renografin results in no better and, in some catheters in poorer flow rates than less concentrated agents such as 50% Hypaque. The suitability of contrast media for injection through a small-bore catheter cannot be predicted from Poiseuille’s or Blasius’ formula. Data for flow rates must be obtained for specific pressure settings and catheter types form Invetral Laboratory studies. The importance of these data, especially for catheter sizes used in small infants, is that blood vessels leading to the heart are always a limiting factor. It is therefore crucial to know which relative pressure injector settings and catheter size will deliver a desired iodine content. Because of the difficulties of manipula;

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f.

&dquo;

-

824

tion and the toxicity inherent in multiple afforded few attempts at opacification.

injections in infants, the investigator is John Leslie Johnson, M.D., F.A.C.A. Clinical Professor of Pediatrics USC Medical School Los

Angeles, California

References 1. Laws, J. W., Fox, J. G. C.: Factors controlling the rate of injection of contrast media in angiocardiography. Br. J. Radiol., 33: 119-123, 1960. 2. Fischer, H. W., Roller, G., Hubbard, P. G.: An analysis of several factors influencing injection rates in angiography. Radiology, 83: 396404, 1964. 3. Cooley, R. N., Beentjes, L. B.: An inquiry into the physical factors governing the flow of contrast substances through catheters. Am. J. Roentgenol. Radium Ther. Nucl. Med., 89:

308-314,1963. 4. Johnson, J. L., Turner, F.: Evaluation of flow of cardiovascular contrast media through the catheters usually used in pediatric cardiac catheterization and angiocardiographic study. Angiology, 19: 612-624, 1968. rates

5.

R. N., Derrick, J., et al.: Technical considerations of selective arteriography. Radiology, 74: 81-83, 1960.

Agnew, C. H., Cooley,

6. Lehman, J. S., Debbas, J. N.: An evaluation of cardiovascular contrast media. Radiology, 76:

548-563, 1961. 7. Pattinson, J. N.: Sodium metrizoate. Clinical experience with a new contrast medium in angiocardiography. Br. J. Radiol., 35: 824-830, 1962. 8.

Rodriguez-Alvarez, A., Martinez De Rodriguez, G.: Studies in angiocardiography: The problems involved in the rapid, selective, and safe injections of radiopaque materials. Development of a special catheter for selective angiocardiography. Am. Heart J., 53: 841-853, 1957.

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Assessing opacification and flow rates of contrast media in neonate and pediatric cardiac catheterization.

Assessing Opacification and Flow Rates of Contrast Media in Neonate and Pediatric Cardiac Catheterization Charles Prickett, III, M.S., and John Leslie...
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