Why is 3/16" the "Chosen one" for cardioplegia lines. Why not 5/32"

Jorge L. Molina, PA-C CCP FPP

Why is 3/16" the "Chosen one" for cardioplegia lines. Why not 5/32"

Every since Gary Cornelius educated me that there other size tubing availability that can be used clinically, I was intrigued. I always like to be educated/corrected/intrigued which is the reason the side by side/separate CR/VR was designed (Nikaidoh) and now CRs and VRs do not share the same guts anymore. Gary has since retired and was Big Dog's (M Debakey) Chief Perfuisionist for many years at Fondren Brown/Methodist.

I went back to Dallas and tested tubing sizes (1/16, 3/32, 1/8, 5/32, 3/16, 1/4, 5/16, 3/8, 7/16, 1/2, 9/16, 5/8). Most folks do not really want to change much. Well, Gary G. opened my eyes back in 82 to new areas of perfusion. It was fun.

5/32" tubing is a good one for the 3/16" reducer adapter on the FX/RX 05 because it fits over it very nicely. It also has a 100 mmHg pressure drop at 760 ml/min over the 1/8" tubing (requires a connector adapter) which has a 100 mmHg pressure drop of at 460 ml/min. 5/32" tubing exiting the cardiotomy reservoir on the Fresenius tubing.

Usually we do not flow over 500 ml/minute on cardioplegia in adults so why not use 5/32" tubing (Terumo has it on stock sterile; ask Terry Walsh). 3/16" hits a 100 mmHG presssure drop at about 1600 ml/minute and is probably never used at those flows for cardioplegia. Gorno still uses 1/8" tubing for adult size pediatric patients and it still works as long as you know the flow studies on your sizes/products/cannulas.

Out of courtesy, to Gary Cornelius as well, told me about 5/16" tubing. Gorno and I tested it and it hits 100 mmHg pressure drop at 5500 ml/minute. There are still some programs that still use it. Two thoughts but most would say it's overkill. That's ok but at least thinking is good.

* 5/16" x 3/8" up to 80 kilos?
* 5/16 x 7/16" (yep it does exist) up to 100 kilos?
* 5/16" for venous lines with flows up to 2.3 liters/minute without vaccum?
* Don't forget Aaron Hill's publication on 5/8" tubing.
* Don't forget for inquiring minds 9/16" (this I have never used)

Just some information for sharing with our colleagues. My writing is scrambled as is the way I think so forgive my typos etc.... Thinking is always Great & Good!

Stay Safe.

Jorge Molina, PA-C, CCP, FPP


45211 Helm St., Plymouth, MI 48170

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