Surface vs Core Temperature

Temperature monitoring is important when maintaining the quality of red blood cell products (RBCs). According to Food and Drug Administration (FDA) and American Association of Blood Banks (AABB) regulations RBC products must be kept within 1-10 ºC during transportation and 1-6 ºC during storage. Traditional methods of ensuring that these regulations are adhered to involve temperature sensitive indicators that display color changes at preset temperatures or infrared thermometers. These methods are limited to only monitoring the surface temperature of the blood product.

Blood products should ideally be monitored via a core (internal) temperature measurement. The surface temperature loosely approximates the core, but it can often be significantly higher than the true core temperature, especially during handling/transport.¹ Traditional monitoring options (chemical indicators and IR thermometers) fundamentally measure the surface temperature of blood products. Given their inability to measure core temperature, these devices may inappropriately suggest that a blood product has exceeded temperature parameters, thus contributing to inappropriate wastage.

A generic square placeholder image with rounded corners in a figure.

Ambient     Surface     Average Core

The difference between surface and core temperature measurements can be significantly different, particularly during transport.¹

Premature Triggering = Premature Wastage

Studies have shown that a blood product’s surface temperature can be several degrees higher than its true core temperature¹. Although this may seem like a small difference, this temperature delta can potentially result in a large number of “false-positive” wastage events. By monitoring core temperature, a blood product can be exposed to room temperature almost 4x longer than if surface temperature is used to trigger wastage. Given that each unit of wasted blood may cost over $300², switching to core temperature monitoring could represent a significant cost savings opportunity.

Measuring Core Temperature

Historically, there have been no commercially available options for monitoring a blood product’s core temperature, which is why surface temperature has been used as a surrogate. Exotag™ is a small and inexpensive device that adheres to blood products and continuously, non-invasively, and accurately monitors the core temperature. Exotag™ contains multiple temperature sensors that monitor heat gradients. A microprocessor uses this temperature data, in conjunction with advanced thermodynamic algorithms, to determine the true core temperature of the blood product.