Blood Warmer

OVERVIEW

• devices that warm blood during or prior to administration

USES

• Used with rapid transfusion rates (e.g. >50 mL/kg/hr), in already hypothermic patients or rare conditions where cold fluid delivery is problematic (e.g. cold agglutinins)
• massive transfusion (avoid hypothermia)

DESCRIPTION

Three main types/methods:

• Water-bath warmers
• Dry heat plate warmers
• Intravenous fluid tube warmers

Water-bath warmers

• warms IV fluid with prewarmed water; maximum temperature is 38°C and whilst cheap the system is inefficient at high infusion rates.

Dry heat plate warmers

• increases heat transfer capability of the material and enables an increase in temperature up to 41°C
• the IV fluid is warmed in a cassette between the heat plates.

Intravenous fluid tube warmers

• An outer layer allows warm water to circulate down one side and then up into a reservoir that surrounds this
• Tubing is heavy and long and only efficient at low flow rates (20–30 mL/min)
• Each requires a specially designed IV tube warmer coil
• fluid heating rate is a function of the power of the heating device

This means that although IV fluid warmers are the most efficient low flow rates, if higher flow rates are necessary a device using a dry heat plate is more effective at higher flow rates (because the metals used are more effective conductors than the fluids used in other systems)

METHOD OF USE

• routine warming of blood is not necessary
• If warming is clinically indicated a specifically designed commercial device should be used with both visible and audible alarms, to ensure that the blood is not heated above 41°C
• Blood warmers must be regularly serviced and maintained, as they can be very dangerous if they malfunction
• Blood should never be warmed by any other method

COMPLICATIONS

• Overheating of blood (risk of haemolysis)
• Air embolism