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Director of Marketing, Temperature Management, Smiths Medical ASD, Inc., (formerly Level 1, Inc.), Rockland, MA
To the Editor:
We wish to respond to a recent series of articles that were published in Anesthesia & Analgesia.
Barcelona et al. (1) compared the Hemonetics RIS (Braintree, MA) to the Level 1 Model 1000 Fast Flow Fluid Warmer configured with the D-50 disposable set. The D-50 disposable set has the slowest flow rate and lowest heat exchanger surface area of all the four different models of disposable sets available from Smiths Medical. A more equitable comparison would be the Level 1 D-300 disposable set, which does provide the highest flow rate and largest heat exchanger capacity. We do not believe that the comparisons accurately reflect the performance range of the Level 1 devices. We would welcome a fair comparison between the two types of equipment using comparable testing conditions.
Dr. Comunale (2) compared the Belmont Instrument FMS 2000 (Billerica, MA) with ultrasonic air detection to a Level 1 device without air detection. It is important to note that Smiths Medical offers an ultrasonic air detector and line clamp for use with all Level 1 warmers to provide additional protection against IV air embolism. All Level 1 fast flow disposable sets incorporate a gas vent designed to vent microbubbles released during the warming process. The gas vent is not designed to function as an air embolism prevention device.
Similarly, Eaton et al. (3) discussed the air elimination capabilities of the Level 1 and Arizant Medical’s Ranger (Eden Prairie, MN) on initial use with saline as the infused fluid. The authors reported that the Level 1 device had superior warming capability, while the Ranger device had superior air elimination capabilities. Again, this comparison was performed using a Level 1 device that was not equipped with the ultrasonic air detector and line clamp. One must remember that after many units of blood or plasma have been infused, hydrophobic air escape membranes may become clogged, compromising the device’s air elimination capabilities. Smiths Medical offers an active electromechanical device, which has an integral tube clamp that shuts off flow if air is detected within the fluid path and prevents air being delivered to the patient. An electromechanical device may provide superior performance over time as compared to a passive device, where air elimination performance may degrade after multiple units of blood products have been administered.
We believe that the currently offered Level 1 device is a cost-effective method of providing warmed fluids to patients with superior flow rates to manual methods. When equipped with additional air detection capabilities, the Level 1 warmers are optimal pressure infusion devices. The air detectors and line clamps can be used with any Level 1 Fast Flow Fluid Warmer.
References
Chicago, IL
In Response:
In response to Ms. Schecter’s comments regarding the recent upgrades available for the Level 1 system; we are aware that D-100, D-300 disposables, and the new ultrasonic air detection component now exist. However, at the time of our research (2 years ago), none of aforementioned advancements were available. Even at the time that our article was accepted for publication (August 2003), the ultrasonic air detector had not yet been U.S. FDA approved. We would welcome the support of Level 1 Inc. to compare the now available upgraded systems with other devices.
We have used but not yet studied the D-100 and D-300 disposable systems that claim higher flow rates and better warming capabilities than the D-50. However, even with more rapid flow rates, the disadvantage of the Level 1 that is not overcome is the lack of reservoir into which multiple blood components and crystalloid can be combined for continual rapid transfusion during times of critical blood loss.
The new ultrasonic air detection and elimination component does appear to be much more sophisticated and should greatly improve the safety of the Level 1 device. If Level 1, Inc. has evidence that the new device is superior at preventing air embolization, then we suggest that previously purchased Level 1 devices be recalled and retrofitted with the new air detection system at no or minimal cost. This would be an ethical gesture to improve patient safety.
Department of Anesthesiology, University of Rochester School of Medicine and Dentistry, Rochester, NY California Pacific Medical Center, San Francisco, CA
In Response:
We appreciate the comments of Laurie Schechter for Smiths Medical but cannot agree with her conclusions. First, Ms. Schechter points out that our comparisons were done with a Level 1 device not equipped with the ultrasound air detector/line clamp. At the time of our study (1), the detector/clamp was not yet available, and so we could not have included such a device. We would further argue that using a pressure infusion device (PID) so equipped would not be a relevant comparison. Although new Level 1 devices are now shipped with this device, there are still hundreds if not thousands of older devices without such clamps being used in hospitals across the country. The detector/clamp is being offered as a retrofit for old devices, but at a cost over $3,000, approximately 60% of the price of the original PID. Many hospitals will find it difficult to fit all their devices with the safety upgrade. It could be argued that the device should be offered as a safety measure free of charge, or at least at cost.
Second, Ms. Schechter states that the air elimination abilities of a hydrophobic membrane may degrade over time, especially after the transfusion of multiple units of blood or plasma. Indeed this had been our clinical observation using the Level 1 device prior to initiating the study, and is the reason for our study design incorporating a measure of air elimination both before and after the "transfusion" of three units of packed red blood cells. We noted no difference whatsoever in air elimination after blood transfusion with either device. Although we used only 3 units of blood, they were expired units, which have a high content of devitalized red cells and are more likely to cause obstruction. Additionally, the Ranger disposable incorporates a 150-micron filter in the drip chamber that should keep aggregates from coming into contact with the hydrophobic membrane and changing its performance. The Level 1 disposable has the membrane and filter in the same component, making it more likely that performance will degrade during transfusion.
Third, Ms. Schechter states that with the air detector/line clamp in place, the Level 1 is now an "optimal" PID. We would not characterize a PID that may abruptly stop itself at any time as "optimal." An optimal PID should safely and continuously deliver blood and fluids at physiologic temperature at high rates, should be affordable and have low operating costs, and should be easily and quickly set up for use. We argue that there is no such optimal PID currently commercially available.
Reference
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