SAFETY TIPS: Anticipating Adverse Events by Gary Grist RN CCP Emeritus

Perfusion safety is the avoidance of unnecessary incidents that result in adverse patient outcomes. These incidents usually involve 1) malfunctioning or defective equipment or disposables, 2) communication failure between healthcare professionals, 3) human error or incorrect execution of procedures and probably most importantly 4) the failure to anticipate adverse events. As regards number 4, I would like to discuss two safety tips that I used to anticipate adverse events.


Oxygenators have been known to fail during bypass.  Either it fails to oxygenate, or it fails to remove CO2 adequately.  Sometimes both problems occur simultaneously.  Over the years I have seen perfusionists address these problems by first increasing the sweep gas blender FiO2 and then increasing the sweep gas flow.  After each action, valuable time is taken to evaluate the success of the action. If those interventions fail, the perfusionist will then trouble shoot the sweep gas circuit; searching for an obvious mechanical problem or a hard-to-find leak. But by this time, often the blood exiting the oxygenator is black and/or the CO2 will approach 100 mmHg. At that point the trouble shooting time is up and the decision must be made to change the oxygenator during CPB.

Usually when an oxygenator fails and it is sent back to the manufacturer, no defect in the unit can be found.  Of course, the manufacturer is biased when making its evaluation of the oxygenator.  A manufacturing flaw of a single oxygenator could result in a recall of that entire lot; an expensive action on the part of the manufacturer.

After seeing this scenario play out in my own program and in other programs over time, I decided to take a different tack.  At the first sign of an oxygenator failure, pure oxygen should be supplied to the unit from an independent gas circuit and reliable gas source.  Pure oxygen flowing into a failing oxygenator from a separate source would immediately indicate if the unit was failing or if the sweep gas circuit was defective.

Initially I kept a new piece of PVC tubing readily available at the pump side utility cart. This tubing was long enough to reach from the oxygenator to the oxygen spigot on the anesthesia machine. There were two problems with this. 1) The flow meter on the spigot was too gross to fine tune the gas flow to maintain a proper CO2 and pH level. I ran a pediatric program where even a gas flow of 500 mls/min could be too high. 2) The anesthesiologist was often too busy to prioritize the need for sweep gas flow and adjust it whenever asked.

The solution was to obtain an independent gas source and circuit over which the perfusionist had complete control.  I mounted a full oxygen E tank with the appropriately sized flowmeter on the pump utility cart within arm’s reach of the pump. A short piece of fresh PVC tubing could then be connected between the flowmeter and the oxygenator at the first sign of an oxygenator failure.  No time is wasted trouble shooting the regular sweep gas circuit, but rather this method provided a definitive and immediate confirmation if the oxygenator was failing.

I believed (and still believe today) that most oxygenator failures are actually a sweep gas circuit failure of some type: a cracked connector, bad seals on a vaporizer, a malfunctioning blender, aging tubing that is stretched out of shape and no longer snugly fits on the connectors or gas port of the oxygenator. I have actually witnessed a connector spontaneously cracking, a sweep gas tube unexpectedly falling off the gas port of an oxygenator, a seal leaking in a vaporizer and a blender malfunction during CPB.

For decades I also incorporated a mechanical pressure gauge into each regular sweep gas circuit. Before CPB, the sweep gas circuit was clamped and pressurized to 200 mmHg for at least 30 seconds.  Any drop in the pressure would trigger a maintenance action before CPB commenced.  This process was an early checklist item so the system could be changed if needed before the extracorporeal circuit was setup.


My second safety tip is to have a battery powered centrifugal pump (c-pump) on a small rolling cart.  This unit should also be stored nearby the CPB pump and immediately available to the perfusionist.  The cart should allow the c-pump to be rolled near the oxygenator and arterial pump and positioned at the correct height to facilitate the transfer of the arterial pump tubing to the c-pump.

If the arterial pump fails, then the perfusionist should quickly transfer to the c-pump.  If the primary pump is a roller pump, then the pump boot should be severed and attached to the centrifugal pump head, priming it quickly from the venous reservoir.  If the primary pump is a centrifugal pump, the pump head (if still operational and compatible with the emergency c-pump) should be transferred to the emergency c-pump. If the pump heads are not compatible, tubing should be severed and transferred.

Hand cranking is not a solution to a failed arterial pump.  During hand cranking, if immediate trouble shooting is unsuccessful, there is no choice but to change out the pump.  There are the problems of finding and fetching a replacement pump, removing the old pump, installing the new pump with the pump boot or centrifugal head correctly positioned for use.  Even with help, this is a difficult chore.  And for a perfusionist working alone, this cannot be done rapidly enough to prevent death or disastrous injury to the patient.

I once had an engineer from one of the major manufacturers visit me.  She was curious about how I liked my new pumps purchased from her company.  I said that I had several areas of concern.  One was that the power and telemetry connections to each pump from the instrument stack were difficult to detach and reattach should the arterial pump need to be changed out.  And once the change out was made, the pump still needed to be ‘assigned’ within the computer system of the instrument stack.  All this took a lot of time and, in an emergency, it could be disastrous for the patient.  She then told me not to worry because these pumps were designed never to fail.  I thought to myself; “What was the last project you worked on….the Titanic?”

Then she noticed that I had placed clear, rigid plastic screen covers over each touch screen on the pumps, and hinged them with a piece of tape so they could be lifted to access the screens. She wondered what those were for.  I told her that the touch screens were vulnerable to being smashed by a dropped clamp or medication vial; they had no protection.  If the screen were smashed during a case it might be difficult to control the pump. She wondered out loud why anyone would deliberately drop a clamp or med vial on one of the screens.  At this point in our conversation I thought that the pump was well designed for normal function, but the manufacturer had given less than adequate thought to safety if a failure should occur.


Some perfusionists would say that an oxygenator or arterial pump failure are rare occurrences; too rare to worry about with such elaborate preparations as I have described.  I respond with this; airline crashes are much rarer by several magnitudes of order.  But would you ride on an airliner that had no emergency wing exits? Likewise, I think patients needing CPB would hesitate if they believed that not all safety precautions possible were taken to protect them from a perfusion accident. But patients are not privy to that kind of detailed information. Patients understand that they may die if their surgery is unsuccessful, but no patient believes they will die as a result of a pump accident. Wing exits are mandated by law, but there are no mandates for perfusion safety.  So perfusionists must protect their patients by using every safety precaution possible. We must be responsible as a profession to set safety standards wherever we see a potential problem; anticipating adverse events even if they are rare. Every hospital has E tanks and flowmeters that can be obtained by the perfusionist. And older battery powered c-pumps are readily available at a cheap price.  So costs are really no excuse not to implement these practices.

If the decision is made to adopt the safety precautions I have described (or maybe something even better) then they should be practiced frequently.  For example, after a case but before tear down, see how fast the sweep gas system can be changed over to the E tank as if the oxygenator or sweep gas circuit were failing. This is a good time to make sure that the E tank is full and has the correct flowmeter and that the tubing is long enough. Or see how quickly implementation of the emergency c-pump can be made as if the arterial pump had failed. This is a good time to check for proper emergency pump function including the battery and proper positioning near the oxygenator. (The chief perfusionist should consider picking a random time for these practice exercises which is unknown to the staff to see if they are really prepared.)

If there are three staffers, these exercises should be done three times yearly; once for each staffer or four times for four staffers, etc.  Then document the practice exercise so that it can be demonstrated to future assessors and litigants the awareness of these risks and that the program is prepared to address them safely.  For perfusionists working alone, it is even more important to adopt these suggestions and practice them even more frequently.

In perfusion the quality of safety is measured by the lack of accidental death or injury in addition to providing focused and successful care. If incidents of these types never occur at your program, do not consider preparing for them a waste of time and resources. Consider yourself and your patients fortunate and your program a safe one.

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.

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