Aluminum: The Hidden Danger in Blood Warmers

Recently, there have been growing concerns from regulatory agencies, such as the FDA, as to the safety of aluminum containing medical devices, especially those involved with the infusion of fluids into patients. Just this past year, the FDA has recalled six intravenous fluid warming products due to evidence showing increased levels of aluminum. According to the FDA, “Exposure to toxic levels of aluminum may not be easily recognized and exposure effects may cause serious adverse events including death”. Some manufacturers have provided a potential solution by using coated aluminum surfaces. While these solutions certainly show improvement, they still release detectable levels of aluminum into infused fluids. The question is, are these levels safe or not? In this article, I will unfold some information about the recent recalls, the risk in aluminum, and other safety considerations regarding blood/fluid warmer. But I would like to start by making it clear to the reader that —

I’m not an expert, just an informer. First let me say that I am no expert in the field of toxicology, therefore it is beyond me to say for certain the safety of aluminum based warmers. That job I leave to regulatory agencies such as the FDA. However, once I reviewed the evidence and recalls put out by the FDA, I felt that I needed to make sure other providers are aware of the risks and recent recalls of these products. We should trust the sophisticated and rigorous medical approval system that we have in place. Therefore, it is my viewpoint that aluminum-based heaters that are regulatory cleared must be 100% safe to use. Nonetheless, we as critical care paramedics, nurses, and physicians must, as a minimal requirement, understand the risks associated with this method of warming. We owe it to our patients to be as well informed and up to date with the risks of certain treatments we provide, especially given the growing number of recalls of aluminum based warming devices.

Peer reviewed research of the risks. Aluminum toxicity can lead to a plethora of diseases ranging from Alzheimer’s, autism, breast cancer, to pancreatitis and pneumonia just to name a few (Igbokwe, 2019). In infants, aluminum toxicity is associated with impaired neurological development (Bishop, 1997). What’s even more alarming is that aluminum can also cause decreased iron absorption and anemia. Imagine trying to infuse blood products to correct anemia, and exposing your patient to toxic aluminum that causes the problem you are trying to reverse! Recalls of blood/fluid warmers due to the potential of aluminum leaching are typically identified as Class I recalls. These are the most serious as they are for devices that may cause serious injury or death! Patients most at risk are pediatric patients, specifically neonates and infants, pregnant women, geriatric populations, and those with decreased renal function or on dialysis.

Why manufacturers like to use aluminum in fluid warmers. Aluminum is used in a wide spectrum of medical devices, and when compared to other materials, it’s easy to see why. Aluminum has a large strength-to-weight ratio. This means that aluminum compared to other materials is stronger and lighter. Aluminum is also a good thermal conductor. In addition, aluminum is very malleable, thus it can be formed to almost any specification. Aluminum is a plentiful material as well; in fact, it is the most abundant metal in earth’s crust, making it very cost effective. All these reasons are why we find aluminum, not just in medical equipment, but in our everyday lives. It’s a good, plentiful, strong material that has countless applications. However, this article seeks to explain why using aluminum may not be the best option with respect to blood/fluid warmers.

Advancements in analytical technology have changed the stance on aluminum. If aluminum is unsafe, then why did the FDA approve of its use in fluid warmers initially? The answer is basically “you don’t know what you don’t know”. Regulatory agencies such as the FDA are only as good as the technology they have available to them. In recent years, advancements in technology have enabled regulators to measure more accurately the levels of aluminum produced from blood warmers that use that material. Keep in mind that when the FDA approved aluminum containing medical devices, it was before sensitive testing instruments were used to detect the minimum allowable limits of aluminum that is set forth today. This means that there was no way of knowing if these devices were leaching aluminum or not into the infused fluids. Therefore, these devices were developed, approved, and put on the market. Only until recently are regulatory agencies capable of measuring the threshold limits produced by these products, and the results — for some of these devices — are concerning.

Increased concern over aluminum containing warmers evident by 3 FDA recalls of 6 warming devices in just 6 months. Since March of this year there have been three separate recalls on fluid warmers that contain aluminum. The FDA has warned that the aluminum used in the heating elements is leaching into the fluids and being infused into patients. In March of 2021 ThermaCor 1200 disposable sets were recalled. The customers were notified of a Toxicological Assessment that there was potential aluminum leaching into fluids. Later, Eight Medical International’s Recirculator disposables were recalled in July of this year. The most recent recall was of 4 Smith Medical’s Level 1 configurations for the same reason, leaching of aluminum. This is on top of yet another global recall of the enFlow device in 2019. With so many recalls in such a short period, it does raise concern that blood warmers containing aluminum in their heating elements pose a potential risk to patients. You can read the FDA’s Letter to Health Care Providers on the recent recalls here.

Researchers find that coated aluminum may not prevent leaching. Manufacturers of blood/fluid warmers with aluminum heaters often make a distinction between uncoated and coated aluminum heaters. The latter (i.e. coated aluminum) is expected to be safer for patients, compared with non-coated aluminum. This makes sense. However, even blood/fluid warmers that utilize coated aluminum may pose a risk to patients. In June of 2019, researchers found that aluminum was still detectable in fluids infused with devices that use coated aluminum. The study compared aluminum release of coated and uncoated fluid-warming devices. The results of the study found that while aluminum release was less in coated devices, it still was elevated above baseline. In fact, the researchers stated that “our methodology does not have the ability to differentiate between the concentrations we measured and the FDA threshold.”(Perl, 2019).

Manufacturers may be predisposed to maintain the status quo. Despite the recent recalls, the default claim of manufacturers that use aluminum heaters is that the aluminum remains below the acceptable limits set forth by regulatory agencies. However, the accuracy of this claim is debatable, and the data that is used to defend these claims is often open for contradicting interpretations. At least in one recent case, the Canadian FDA publicly refuted such a claim proposed by Smiths Medical. Without getting into the specifics of this particular case, it’s easy to understand why manufacturers may resist a change. It goes without saying that they must trust that their solution is 100% safe in order to commercialize it. However, is it possible that this high level of confidence may also be fueled by some sort of an ‘organizational predisposition’? Let me try to explain: these manufacturers assumed significant risks and invested millions of dollars to overcome the demanding regulatory barriers that stand between any medical device innovation and the marketplace. Even after commercializing the product, they had to invest significant budgets in continuous engineering and regulatory affairs. Therefore, they need to see positive returns following these huge investments, otherwise future innovation might suffer. Certainly, a very complex and delicate situation that manufacturers must contend with.

Other associated risks of blood/fluid warming. It should be noted that warming fluids does come with other risks besides aluminum leaching. Let’s review some of these other risks:

• Hemolysis. One risk is hemolysis due to the age of blood products given. This isn’t necessarily a risk associated only with warming blood products, but just a general risk overall. As the products age, red blood cells have a higher chance of rupturing. That’s why it’s important to infuse blood products before the expiration date.
• Excessive sheer force, turbulence, and cavitation. Hemolysis might be accelerated by suboptimal design of the fluid path of the warming element. You expect your blood/fluid line to be smooth and homogeneous, then why make exceptions for the warmer’s fluid path (or as it is often called, the cassette)? In other words, preferably the fluid path of the warmer should be designed in an ‘undisrupted’ fashion. That is, and to the extent possible, the fluid path design should avoid for example abrupt turns, connection points, and flow changes (e.g. from a wide to narrow carrier and vice versa) in order to minimize sheer force, turbulence, cavitation, and air bubble formation, to name just a few potential complications associated with high flows and elevated pressure. Why don’t you simply try to look under the hood of your chosen warmer?
• Over/under heating. Another risk is over/under heating the fluids/blood being infused. I believe that under heating is a bigger and more common issue especially with high flows and with intermittent flow methods. If your agency requires high flows or uses an infusion device that utilizes intermittent flow, most warmers cannot keep up with the job. If the warmer can’t physically warm the fluids to body temperature at the rate being infused, you’re introducing hypothermic fluids into your patient. Even room temperature fluids are far below body temperature, especially for severely sick patients suffering from shock.
• Aggressive heat transfer process. It seems logical that a relaxed heat transfer process from the heat exchanger to the blood/fluids is safer than an aggressive heat transfer process. Therefore, why not add this to your evaluation criteria? The most relaxed heat transfer mechanisms require a warming surface of 15-20 ml. We all love solutions with small priming volume, but we need to acknowledge that this may come at a ‘price’. And the price is a potentially aggressive heat transfer process from the heater to the blood, especially at elevated flows.
• Unavailability. One of the most prominent risks associated with your blood/fluid warmer over the past years is that you will not be able to use it since there is a shortage of disposable sets or a recall of the device. Ask users of enFlow, Level 1, ThermaCor, Thermal Angel, and several others to understand how frustrating this can get. And if there is one thing that COVID taught us, it is that complex solutions lead to complex supply chains and therefore to many months of lead times when the unexpected strikes. Therefore, make sure that the consumable of your solution of choice is simple enough to manufacture in large quantities, fast! Make sure that there are no chips that need to be placed into this consumable, otherwise you will be at the mercy of the market availability of chips, which is currently experiencing significant shortages.

A solution. Clearly the wrong answer to prevent aluminum leaching from blood/fluid warmers is to not utilize a warmer. Myself and other colleagues have written extensively about the importance of warming fluids, especially blood products in rapid transfusions. You can read some of those articles here .One practical solution to this problem is utilizing a warmer that is aluminum free in the first place, or, if you decide to use an aluminum warming solution, then do your due diligence about the solution. There are several prehospital and hospital solutions that are aluminum free, such as the Thermal Angel, Quantum, and Ranger, to name just a few. QinFlow’s Warrior is another excellent example of an aluminum-free warmer: it has battery and AC power sources and it therefore fits both prehospital and hospital settings. It has amazing performance levels, measured in maximum delivery rates. And as importantly, its per-use price is very competitive. You can read more about the Warrior here.

Summary & Conclusion. New, more sensitive, monitoring technology has made it possible for regulatory agencies to detect trace levels of aluminum, before unknown to us. Exposure to toxic levels of aluminum, according to the FDA, “may cause serious adverse events including death”. With that information, three recalls of 6 devices have been issued within the past few months over growing concern of elevated aluminum levels in fluids infused by products containing aluminum heating elements. We’ve seen that not even coated aluminum surfaces prevent leaching into fluids. The only way to ensure that zero aluminum is leaching into your patients is most probably to utilize solutions that are aluminum free. While there are several options out there, the QinFlow’s Warrior is a good place to start. Their fluid path is 100 percent aluminum free. They are also amongst the most cost efficient solutions on the market. A true win win. QinFlow’s disposable cassettes have a comfortable and gentle priming volume of 19mL. Finally, the Warrior is rugged enough to withstand high pressures of intermittent flow and can warm near freezing blood products to body temperature within seconds, safely!

***

Bishop NJ, Morley R, Day JP, Lucas A. Aluminumneurotoxicity in preterm infants receiving intravenous-feeding solutions. New England Journal of Medicine 1997;336: 1557–61

Igbokwe, I. O., Igwenagu, E., & Igbokwe, N. A. (2019). Aluminium toxicosis: a review of toxic actions and effects. Interdisciplinary toxicology, 12(2), 45–70. https://doi.org/10.2478/intox-2019-0007

Perl, T., Kunze-Szikszay, N., Bräuer, A., Quintel, M., Röhrig, A.L., Kerpen, K. and Telgheder, U. (2019), Aluminium release by coated and uncoated fluid-warming devices. Anaesthesia, 74: 708-713. https://doi.org/10.1111/anae.14601