Can latent heat safely warm blood? – in vitro testing of a portable prototype blood warmer

Mark P Mcewen,David Roxby

doi:10.1186/1471-227x-7-8

Abstract

BackgroundTrauma/retrieval patients are often in shock and hypothermic. Treatment of such patients usually involves restoring their blood volume with transfusion of blood (stored at 2°C – 6°C) and/or crystalloids or colloids (stored at ambient temperature). Rapid infusion of these cold fluids can worsen or even induce hypothermia in these patients. Warming of intravenous fluids at accident sites has traditionally been difficult due to a lack of suitable portable fluid warmers that are not dependent on mains electrical or battery power. If latent heat, the heat released when a liquid solidifies (an inherently temperature limiting process) can warm intravenous fluids, portable devices without a reliance on electrical energy could be used to reduce the incidence of hypothermia in trauma patients.MethodsRapid infusion of red cells into patients was timed to sample typical clinical flow rates.An approved dry heat blood warmer was compared with a prototype blood warmer using a supercooled liquid latent heat storage material, to warm red cells whilst monitoring inlet and outlet temperatures. To determine the effect of warming on red cell integrity compared to the normal storage lesion of blood, extracellular concentrations of potassium, lactate dehydrogenase and haemoglobin were measured in blood which had been warmed after storage at 2°C – 6°C for 1 to 42 days.ResultsA prototype latent heat fluid warmer consistently warmed red cells from approximately 4°C to approximately 35°C at typical clinical flow rates. Warming of stored blood with latent heat did not affect red cell integrity more than the approved dry heat blood warmer.ConclusionUsing latent heat as an energy source can satisfactorily warm cold blood or other intravenous fluids to near body temperature, without any adverse affects.

Highlights

Trauma/retrieval patients are often in shock and hypothermic
Fluid warmer testing Most of the red cells (RC) warmed with latent heat were in batches of 4 – as would occur if a retrieval patient required approximately 1100 mL of RC
Testing reported in this paper found that the warm blood outlet temperature from a latent heat fluid warmer did not exceed the phase change temperature of the latent heat storage material, even during times of flow cessation

Summary

Introduction

Trauma/retrieval patients are often in shock and hypothermic Treatment of such patients usually involves restoring their blood volume with transfusion of blood (stored at 2°C – 6°C) and/or crystalloids or colloids (stored at ambient temperature). Rapid infusion of these cold fluids can worsen or even induce hypothermia in these patients. At trauma sites it is common to transfuse red cells that have been stored and transported at 4°C and/or colloid/ crystalloid fluids at ambient temperature This administration of cold intravenous fluids has been identified as one of the main factors that contribute to the high incidence of hypothermia in the trauma population [1]. At retrieval or accident sites electrical energy is generally only available in the form of batteries

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