Aluminium release by coated and uncoated fluid-warming devices.
Fluid-warming devices are recommended when infusion rates are >500 ml/h (in adults) to reduce peri-operative hypothermia. Surface contact systems often use a heated aluminium plate, either with a bio-compatible coated such as parylene or uncoated aluminium in direct contact with the intravenous fluids being administered. Aluminium is thought to be toxic in humans due to the aluminium oxide radicals depleting mitochondrial Fe2+ and promoting the generation of oxygen radicals which cause oxidative damage and intrinsic apoptosis.
The authors compared a coated (Fluido compact) and uncoated (Enflow) disposable fluid warming device infusing normal saline and balanced electrolyte solution at 2, 4 and 8 ml/h with each device both heated and unheated.
There was a rise above baseline in aluminium concentration with the Fluido that was not rate dependent. This occurred with both solutions. Similar aluminium concentrations were seen with the use of normal saline in the Enflow. However, there was a “striking increase” in aluminium levels when balanced electrolyte solution was infused through the Enflow, particularly at lower flower rates, with increased time of infusion and with the device heated.
The authors concluded that there are unacceptably high levels of aluminium when balanced electrolyte solution is passed through an uncoated warming device, especially when it is warmed. The actual clinical effect of short term exposure remains unclear, as does the threshold of a “safe“ aluminium concentration. Chronic aluminium exposure is known to cause complications such as neurological impairment in preterm infants and osteomalacia in adults on total parenteral nutrition.
As we all know, the uncoated Enflow device has been withdrawn from use at least temporarily. This would seem particularly prudent in paediatric practice where we are more likely to use lower flow rates and look after potentially fragile brains.
Reviewed by: Dr Stephanie Aplin