The PRONTO Procedure: A New Safety Standard For Oxygenator Change Out by Gary Grist RN CCP Emeritus

I first learned of the PRONTO procedure when I heard Robert Groom*, ‎the Director Of Cardiovascular Perfusion, ‎Maine Medical Center in Portland give a talk about it many years ago. PRONTO stands for Parallel Replacement of an Oxygenator that is Not Transferring Oxygen. Up until then, I was only familiar with oxygenator change out using an ‘in series’ method which required the pump to be halted while the perfusionist changed a failing oxygenator.  His PRONTO procedure was the kind of thing that makes a person say “How come nobody thought of this a long time ago?”

Bob had published an article dryly describing the technique in 2002(1). But it was his live presentation that impressed me the most.  He described an incident when an oxygenator failed at the worst possible moment, requiring a series change out. Even though the primary perfusionist had help, the change out took too long and despite successfully resuming bypass the patient had a bad outcome.  The primary perfusionist was so traumatized by this incident both emotionally and physically, including blackouts and fibromyalgia, that she eventually left her perfusion career.**  The incident prompted Bob and the others at Maine Medical Center to come up with a better solution.  So they developed the PRONTO procedure to make oxygenator change out quicker, easier and without the need to interrupt CPB.

The PRONTO procedure requires that, at set-up, a bypass line be installed around the oxygenator, from the inflow line to the outflow line using two wye connectors; much like the bypass line around an arterial filter (if people still do that).  Since it is impossible to anticipate an oxygenator failure, this PRONTO line needs to be a permanent part of the circuit design. The PRONTO line is initially filled with crystalloid during priming and then clamped off at either end to prevent shunting and to keep the crystalloid stagnant in the bypass line. Normally there is no mixing of the fluid in the PRONTO line with the patient’s blood during CPB.  The PRONTO line crystalloid does not add to hemodilution.

In 2011, the Maine group posted a very informal YouTube video of how the procedure worked (2). The procedure was more formalized for use in my program.  We used a 12 inch PRONTO line; size 3/8 inch for adult circuits and ¼ inch for peds circuits. The line was primed and clamped at each end.  The Quadrox adult and peds units were used for the backup oxygenators which were different than the oxygenators we routinely used for cases. (I do not endorse any specific product.  Almost any oxygenator can be used as a backup.)   A Quadrox holder was positioned on the arm rail near the regular oxygenator.  The Quadrox holder is small and compact and can easily be folded out of the way when not in use, but can be unfolded to hold the backup oxygenator in a perfect position just above the PRONTO line. Because change outs are so rare, perfusionists should not have to go hunting for a holder during a critical moment. So there was always a holder on each of the four pumps.  A lockable utility cabinet was kept near each pump.  Drugs, syringes, needles, clamps, tubing cutters, connectors, stopcocks, prep swabs, spare tubing, an oxygen e-tank and the two back up oxygenators were kept in the cabinet. All of this was within arm’s reach of the perfusionist.

The basic procedure is very simple.  Besides personal protective gear, the only supplies needed are one additional clamp, a sterile tube cutter, prep swab and the backup oxygenator. With the pump still running to support the patient, position the backup oxygenator on its holder near the PRONTO line.  This frees up both hands to cut the PRONTO line in a sterile fashion and connect each open end of the PRONTO line to the backup unit’s blood ports. Remove the distal clamp to retrograde fill the fiber bundle of the backup unit to expunge the air; then reclamp.  Remove the proximal clamp to antegrade fill the heat exchanger side of the unit.  The Quadrox has an air purge port that makes filling the unit and expunging the air quite easy. There is a connection for a purge line that can be connected to the cardiotomy reservoir if the perfusionist so chooses.  During this filling process, the perfusionist must add enough volume to the venous reservoir to fill the new unit. Remove the clamps from the backup oxygenator.  Clamp out the old oxygenator. Finally, move the sweep gas line and the water lines. The transfer is made seamlessly, making only one cut, with minimal blood spillage, and without taking the patient off CPB. And it can be performed by a single, properly prepared perfusionist in 90 seconds with far fewer steps than are needed for an ‘in series’ change out.

The Pronto line can provide a simple method of measuring transmembrane pressure provided an optional Luer lock connector is placed in the tubing at set-up. This could provide important information to those programs which do not include access to measure pre and post pressures in their circuit as a means to diagnose a high transmembrane pressure which is often associated with oxygenator failure.

AmSECT has not made the PRONTO line a Safety Devices Standard like the level and bubble detectors. This is an irresponsible oversite.  In my opinion, the PRONTO line equates to the escape hatches on jet airliners.  They are rarely used, but when they are they save lives. Some would say that the added cost of the materials and methods are not justified based on frequency of use. To that, I would say the cost is justified because it makes CPB “safer.” Fire extinguishers are rarely used in hospitals. Building and maintenance costs would be cheaper without them.  But the hospital would be much less safe. Every time a patient is placed on CPB without a PRONTO line, it is the same as allowing them to ride in a jet with no escape hatches or stay in a hospital with no fire extinguishers. Patients are not aware of the risk that is reduced by a well-practiced PRONTO procedure. So they cannot make an informed decision that their circuit should contain a PRONTO line. Therefore, perfusionists need to be patient advocates to make CPB safer.

Maybe I am preaching to the choir.  I have been retired for three years and, perhaps during that time, most perfusion programs have adopted the PRONTO procedure. But I doubt it!  I realize that series change outs must be taught to students so they can work in programs that do not use the PRONTO procedure.  For example, one 2015 YouTube video teaches students that upon deciding on the need to change the oxygenator, the student should ‘send a nurse or somebody to the pump room to get a long list of specific supplies’ (paraphrased)(3).  In other words, the student need not be thoroughly prepared for this life or death event.  It is as if the instructor does not feel that the student will ever have to deal with this issue. In a 2016 YouTube video, the instructor tells the student to seek help, preferably another perfusionist, but “any ‘body’ will do as long as it has a heartbeat” (4). In a last YouTube example (2017), two perfusionists are changing a pediatric oxygenator during a real case (5). Even with two perfusionists, the procedure takes over four minutes, and air gets pumped up the arterial line when CPB is resumed. I hope that the exercise was being performed on an animal and not a child; the video does not say.

There are some glaring problems with these instructional videos.  Nobody is wearing gloves.  An experienced perfusionist knows that opening packages, using clamps, prepping, cutting tubing and pushing it on a blood port or connector is more difficult and takes more time when wearing gloves which are usually ill-fitting and wet with fluid or blood spillage.  Secondly, nobody in the videos says what the student is supposed to do when there IS NO HELP available.  I am not writing this to criticize, demean or ridicule the instructors in these videos. I apologize if I have offended them. They are doing their best and at least have the courage to post their videos in public for anyone to examine.  What I am trying to do is to get the entire perfusion community to adopt a new safety standard for oxygenator change out; the PRONTO procedure.

*I want to thank Bob Groom for his contributions to this article.

**When I was working on perfusion failure modes and effects analyses (FMEAs) to share with the perfusion community, Bob Groom suggested that I include a management step on critical failures that required PTSD counseling to be available for the perfusionist involved.  I think it was this particular change out incident that prompted the suggestion.

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Perfusion Theory is an educational platform for the Oxygen Pressure Field Theory (OPFT). August Krogh’s theoretical concept of the oxygen pressure field is explained and then applied to clinical applications in perfusion practice.