194 Discussion and Reply

particularly in the clinical setting of rheumatic mitral disease with chronic atrial fibrilla- tion. This embolic episode which occurred in our 80th study using the polyurethane catheter (Cordis) prompted us to switch to one constructed of polyethylene (Cook) because of reports of lesser thrombogenic possibility.

An additional related problem which came to our attention on a few occasions with our early experience with the polyurethane pigtail catheter was the detection of clot during attempts to withdraw arterial blood from the catheter situated in the abdominal aorta while measuring the cardiac output by the green dye technique. The presence of clot was noted because of inadequate rates of withdrawal which necessitated change of catheter.

Since changing over t o polyethylene, we have not witnessed a single recognizable incidence of clot formation in over 700 consecutive studies. Moreover, we have continued to utilize the pigtail catheter for arterial blood sampling during cardiac output determina- tion with total satisfaction with the technique.

Our mode of catheter insertion and the use of continuous pressurized heparinized flush is similar to that reported except that it has been our practice to add 8,000 units of beef lung heparin to 1,000 ml of 5% dextrose solution. In addition, prior to the insertion of all percutaneous catheters, including the pigtail, undiluted heparin concentrate I.000 p/ml is instilled into the catheter after a test flush. We also employ 2" x 2" gauze sponges impregnated with concentrated heparin solution for wiping the Teflon spring guide wire prior to catheter insertion.

James U . Cardelia. M.D. James L. Hughes, M.D.

Camden. New Jersey

AUTHOR'S REPLY

We are very grateful to Drs. Mullins, Drake, Murray, and Cardelia for their interest and comments regarding our experience with the pigtail catheters. In addition to the initial aspiration and repeated hand flushing of the arterial catheter as mentioned in our paper, we have learned to routinely aspirate and hand flush the catheter at frequent (2-5 min) intervals throughout the procedure. We are also careful not to let the guide wire advance beyond the origin of the left subclavian artery. The duration of guide wire stay in the circulation is kept as short as possible (seldom more than 45 sec). In this regard, we fully agree with the comments made by Drs. Mullins and Drake. Immediately prior to their use. all catheters are test flushed with heparinized dextrose in water solution (0.5%) and their external surfaces wetted with i t . The guide wires are also kept in heparinized dextrose in water solution before their use. Though we try to make the duration of catheter stay in the circulation as short as possible, it was unusually long in the three reported cases for various reasons as previously described.

Until December 1971, we employed the classic Judkins' technique for coronary arteriography. Our initial experience with the pigtail catheters caused us to discard this approach and subsequently led to the adoption of our present method of hand and pressure-drip flushing. Theoretically, this should prevent the entry of blood into the distal end of the catheter and thus protect against local clotting. While continuous flush may be successful when employed with single end-hold catheters such as coronary catheters, it obviously is inadequate when used alone with pigtail catheters.

Ahmad Rashid, M.D.