To the Editor
In recent years, it has been well established that fluid warming is an important adjunct to the prevention of intraoperative hypothermia. However, recent investigations I have performed have led me to question whether the devices we use for fluid management are safe enough, particularly those involving pressure infusers. Most IV bags contain between 40 and 100 ml of air1 and too often this air is not removed before hanging the bag, particularly in moments of crisis.
A combination of an IV fluid bag with air and a pressure infuser presents a situation in which there is a high potential for air embolism. Larger air emboli may mechanically block the right side of the heart, constrict pulmonary arteries, decrease ventricular preload, and cause cardiovascular collapse. Even small emboli stimulate polymorphonuclear leukocytes and can cause extensive tissue damage.2 With the use of TEE, we have learned that the incidence of patent foramen ovale is about 25 %3,4 in normal healthy adults. Thus, there is the potential hazard for venous air crossing into the arterial circulation.
Manufacturers of pressure infusers warn that bags should be carefully de-aired and some provide air eliminators that, in my opinion, provide a false sense of security.
Hartsmannsgruber1 assessed the ability of one widely used air eliminator to actually eliminate air when presented with boluses in quantities typically found in a bag of saline that has not been de-aired. It was found that the air eliminator was ineffective with 50 to 90% of a 30 ml bolus of air passing through the eliminator when delivered under speeds typical of pressurized infusions at 300 mm mercury. In a similar test, I have observed 5 cc boluses of air pass directly through the air eliminator of a widely used rapid infuser when delivering saline from standard IV bags placed in the IV-bag compressor of the unit.5
I believe that the problem of air embolism from pressure infusers is more widespread than a limited number of literature reports would suggest. I personally am aware of a number of incidents, some fatal, that have resulted from air embolism delivered through pressure infusers. Charles Smith,6 indicates that he is aware of at least four institutions that have experienced massive air embolism associated with pressure infusers. Colleagues at other institutions have echoed these statistics as well. A recent search of the ASA Close Claims Study database found three cases that resulted in settlements of between $385,000.00 and $1,600,000.00. I believe there is definitely room for improvement in the safety profile of infusion devices which are capable of delivering large amounts of fluid at rapid rates and that we as anesthesiologists must demand better technology for the detection and elimination of air from IV lines. Manufacturers of IV solutions should remove air from IV solutions during manufacture. As well, anesthesiologists should work with device manufacturers to find alternatives to the current pressure infusers for situations where rapid infusion is necessary.
Mark E. Comunale, MD
Associate Anesthetist-in-Chief
Beth Israel Deaconess Medical Center
Boston
References
1. Hartsmannsgruber WB and Gravenstein N: Very limited air elimination capability of the level 1 fluid warmer. J. Clin. Anesth. 9:233-235, 1997.
2. Huang KZ and Lin YC: Activation of complement and neutrophils increases vascular permeability during air embolism. Aviat. Space Environ. Med. 68:300-305, 1997.
3. Meissner I, Whisnant JP, Khandheria BK, et al.: Prevalence of potential risk factors for stroke assessed by transesophageal echocardiography and carotid ultrasonography: The SPARC study. Mayo Clin. Proc. 74:862-869, 1999.
4. Heckmann JG, Niedermeier W, Brandt-Pohlmann M, et al.: Detection of patent foramen ovale. Med. Klin. 94:367-370, 1999.
5. Comunale ME: Comparison of the fluid warming and flow capabilities of the Belmont Instrument FMS2000 and the SIMS Level 1 1000. New York Postgraduate Assembly in Anesthesiology, 116, P9030, 1999.
6. Smith CE, for the ITACCS Seminar Panel: Principles of fluid warming in trauma. In: Smith CE, Rosenberg AD, Grande CM (Eds.). Massive Transfusion and Control of Hemorrhage in the Trauma Patient. International Trauma, Anesthesia and Critical Care Society, Baltimore, MD, 1999, pp. 30-34.