We use Ranger blood warmers in OR and sometimes other locations (but Belmonts for rapid infusion). I have been presented a question asking if we can still use them for blood because they warm the blood to 41C, but UpToDate says that blood shouldn't be warmed above 40C. I see no references listed in UPToDate to support their 40C requirement.

We test the alarms on Ranger blood warmers, and they must alarm by 43C.

From the Ranger Service manual:

"The Ranger blood/fluid warming system is designed to warm blood, blood products, and liquids and deliver these at flow rates from KVO to 500 mL/min. At these flow rates, the device maintains fluid output temperatures ranging from 33°C to 41°C (Note: This is for room temperature fluids only). It takes less than two minutes to warm up to the 41°C ±1 set point temperature. The alert points on the Model 245 are 43°C ±1 and 46°C [+3, -2°C]."

The 2002 AABB Guidelines for the Use of Blood Warming Devices says "The effectiveness of a blood warmer is limited by the flow rate of the infusion and the heating technology of the device in use. Most do not delivery normothermic (37C) fluids at very rapid flow rates--most reach a temperature of only 33 C to 36 C."

These devices are FDA approved for blood transfusion, right?

Can anyone supply an answer to the question of why (or why not) they are okay to use according to manufacturer's instructions, but UpToDate says not to warm blood above 40C?

Aside from the obvious reason why blood shouldn't be warmed to 40C, why would you need 40C blood? I think rbcs starts to lyse around that temperature. Why would you want lysed blood? Sorry, I am not familiar with these Ranger blood warmers, I am just curious. Good luck

All I'm finding are studies indicating there is no medically significant difference with transfusions up to 43C or possibly higher. I haven't seen any source giving a specific temperature. AABB Standard 3.8 only states "Warming devices shall be equipped with a temperature sensing device and a warning system to detect malfunctions and prevent hemolysis or other damage to blood or blood components."

After a significant amount (too much) of digging it I found an article on uptodate (https://www.uptodate.com/contents/hemolytic-transfusion-reactions?sectionName=Non-immune%20hemolysis&search=blood%20warmer%2040C&topicRef=7084&anchor=H809056280&source=see_link#H809056280) that references the 40C requirement and links to this article https://pubmed.ncbi.nlm.nih.gov/1310923/

If you actually read the abstract though it specifically states that "Significant haemolysis and increased fragility were not observed at any temperatures after incubation for 4h."