Fluid warmer

Abstract: Hypothermia in trauma patients is generally considered an ominous sign, although the actual temperature at which hypothermia affects survival is ill defined. In this study, the impact of body core hypothermia on outcome in 71 adult trauma patients with Injury Severity Scores (ISS) greater than or equal to 25 was analyzed. Forty-two per cent of the patients had a core temperature (Tc) below 34 degrees C, 23% below 33 degrees C, and 13% below 32 degrees C. The mortality of hypothermia patients was consistently greater than those who remained warm, regardless of index core temperature. Mortality if Tc less than 34 degrees C = 40%, less than 33 degrees C = 69%, less than 32 degrees C = 100%, whereas mortality if Tc greater than or equal to 34 degrees C = 7%, and greater than or equal to 32 degrees C = 10%. Mortality and the incidence of hypothermia increased with higher ISS, massive fluid resuscitation, and the presence of shock. Within each subgroup (i.e., greater ISS, massive fluid administration, shock) the mortality of hypothermic patients was significantly higher than those who remained warm. No patient whose core temperature fell below 32 degrees C survived.

Abstract: An apparatus for heating parenteral fluids for intravenous delivery to a patient. The apparatus includes a disposable cassette which in one presently preferred embodiment is made up of a unitary member which is divided to form a serpentine flow path by a plurality of path separators. Thin, flexible metallic foil membranes are sealingly joined to the unitary member on the upper and bottom surfaces thereof to form an enclosed, fluid-tight serpentine flow path between the plurality of path separators. The entire periphery of the unitary member and the thin, flexible heat conductive foil membranes are sealingly held by a framework. The disposable cassette slides between first and second heating blocks which contact the thin, flexible heat conductive foil membranes so as to provide heat transfer to fluid flowing in the serpentine flow path. The heating blocks are designed to provide a gradation of heat energy such that more heat energy is available for transfer to the parenteral fluid at the inlet end of the serpentine flow path than is available for transfer to the parenteral fluid at the outlet end of the serpentine flow path.

Abstract: An in-line fluid warmer for heating parenteral fluids, particularly blood, supplied from a fluid container through a flexible supply conduit. The fluid warmer includes a box-like enclosure containing a heated plate having a sinuously-shaped groove configured to accept and hold a length of the supply conduit in heat transfer relationship with the plate. A pair of temperature sensors monitor the actual temperature of the plate. One of the temperature sensors controls a voltage controlled oscillator, while the other is used to determine maximum permissible plate temperature. The voltage controlled oscillator supplies proportional control to the heated plate up to a predetermined temperature of 37° C. for warming blood. In the event that the temperature of the plate exceeds the predetermined temperature, or in the event that component failure occurs, or in the event the maximum permissible temperature of the plate is exceeded, oscillation from the voltage controlled oscillator ceases, and the heater is de-energized. Consequently, the parenteral fluid such as blood is protected from overheating.