Perfline |  |
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There have been recent reports regarding several episodes of water-to-blood leaks in blood cardioplegia units. These incidents have prompted all of us to review our safety protocols and make sure that every heat exchanger is fully tested before use, regardless of being part of an integrated oxygenator or any other device inserted in the cardiopulmonary bypass circuit.
Heat exchangers in general are built of two materials: metal (stainless steel, aluminium) and plastic polymers (polyester, polyurethane). Metal can be made as thin as possible to improve conductance, but must be thick enough to resist to pressures exerted on both sides. Usually pressures in the water path are higher than in the blood path which determines a water to the blood direction of a leak.
Manufacturers have their own protocol to test the integrity of every heat exchanger produced before the final procedures to deliver to end users.
In the USA, the FDA recommends testing the heat exchangers using water and subjecting the device to 1,5 times the maximum recommended pressure for six hours to determine fi a water to blood leak will occur.
Water to blood leak is a dreadful complication capable to produce hemolysis, interstitial fluid accumulation, sepsis, and multiple organ failure.
Hamilton et cols have reported an excellent revision of heat exchangers tests and risks:
Testing of heat exchangers in membrane oxygenators using air pressure. Hamilton C, Seidler R, Kind R, Tosok J, Upterfofel J. Perfusion 2006;21:105-107 April 6, 2008 11:31 am - Rio de Janeiro, Brazil |
Richard Seyhlham | |
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Water-to-blood leaks is an almost always lethal complication of cardiopulmonary bypass. In the old times of bubble oxygenators it used to be a not so rarely seen accident and the results were always severe sepsis and multiple organ failure. Even when the water reservoirs were carefully maintained, the leaks were a source of lethal outcomes.
Best solution for this problem resides in the bonstruction of heat-exchangers with a low pressure water path. Blood path having a higher pressure than water pressure will eliminate the complications of water-to-blood leaks. Any perforation will allow only a blood-to-water leak and serve as an indicator of its occurrence. A closer work with the industry will serve as a great stimulus for the design of such heat-exchangers.
Other than that, I presume, we will be always prone to be suprised by one of these severe and fatal accidents. April 28, 2008 10:40 am - Turkey |
Kalay Subram | |
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This is an important matter. Trying to overcome the chances of having water leaking into blood there are a few alternatives studies with thermoelectric heating. This, if successful will eliminate the need to use water as a source of thermal energy to warm or cool the blood in the oxygenators. April 29, 2008 10:24 am - India |
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