Reliability of modern microwave ovens to safely heat intravenous fluids for resuscitation.
OBJECTIVE
To determine if intravenous fluid heated in modern microwave ovens is warmed to a consistently safe temperature, as has been advocated in a number of texts and journals.


METHODS
Five, 1L bags of normal saline in Viaflex (Baxter Healthcare, Old Toongabie, NSW, Australia) containers were heated for 2 min on high setting in 16 different microwave ovens. The output power ranged from 650 to 1,000 W. All microwave ovens were equipped with electronic timers and turntables. Initial and final temperatures were recorded with a TestoTerm 1100 electronic thermometer (Dade Behring, Lane Cove, NSW, Australia), accessing the centre of the fluid via the injection port. The average and standard deviation for each measurement was determined for each microwave oven.


RESULTS
In nine out of the 16 microwaves (56%) tested, the fluid had reached an average final temperature greater than 42 degrees C and thus was greater than the recommended maximum temperature for the heating of intravenous fluids. All microwave ovens with an output power of greater than 900 W overheated the fluids. However 13/16 microwaves (81%) had a temperature range less than 3 degrees C, thus if correctly calibrated could be appropriate for heating intravenous fluid for resuscitation.


CONCLUSIONS
The increased output power of modern microwave ovens can lead to overheating of resuscitation fluids, if the simple algorithm currently recommended is followed, leading to potentially serious complications. Microwave heating of intravenous fluid could be a safe, simple, cheap and effective means of heating intravenous fluids for resuscitation, but care needs to be taken to calibrate individual machines to ensure a safe temperature is reached.
Delaney
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Emergency Department, Gosford Hospital, New South Wales, Australia. drtoze@hotmail.com
D006358:Hot Temperature; D006801:Humans; D008872:Microwaves; D012151:Resuscitation / Q000379:methods*; D012965:Sodium Chloride / Q000627:therapeutic use
D012965:Sodium Chloride