oa Southern African Journal of Anaesthesia and Analgesia - Evaluation of red blood cell stability during immersion blood warming : research article
<I>Introduction:</I> The practice of warming blood for transfusion by immersion into a waterbath has been investigated. <br><I>Objective:</I> To find the maximum waterbath temperature at which blood can be heated effectively without effecting the red blood cell functional and structural integrity. <br><I>Method:</I> Blood, three days after donation (fresh blood), with CPD anticoagulant, was warmed at 37°C, 43°C, 45°C, 47°C, 50°C and 55°C for 10, 20, 30 and 60 minutes and analysed for haemolysis. In addition, the biochemical markers were done on the blood after 34 days of storage at 4°C (old blood). Temperature increase within the blood unit being warmed by immersion in warm water is non-uniform, with the outer part showing the largest temperature increases. This was examined at waterbath temperatures of 45°C and 47°C and represented graphically. Temperature decrease in a stainless steel bucket filled with 10 liters of warm water (45°C and 47°C), commonly used in theatre to heat blood, was analyzed and is graphically displayed. Results and discussion: Only minor biochemical changes resulted from warming up to 47°C for 1 hour. The values of the free haemoglobin in old blood corresponded to the significant changes of fresh blood after being heated at 50°C for 30 minutes (p<0.001). The change of the haematocrit in old unheated blood was much higher than the significant changes caused by heating the fresh blood at 55°C. The value of potassium of old blood corresponded to the value after heating fresh blood at 55°C for 30 minutes, even though the potassium already increased significantly at 50°C after 60 minutes (p<0.01). The value of lactate hydrogenase in old blood corresponded to the significant increase after heating fresh blood at 55°C for 60 minutes, while this marker already increased significantly at 50°C after 20 minutes exposure (p<0.001). The results suggest that immersion warming of fresh blood for 1 hour at 47°C and below do not cause red cell damage. A limitation of immersion warming is that warming of the blood within the unit is not uniform, with a temperature gradient as big as 5°C to 10°C between the inner and outer parts of the unit. There is also a lag time of 30 to 40 minutes between the inner and outer parts to reach the same temperature in a thermostatically controlled waterbath. The temperature of the bucket of warm water in theatre decreased rapidly. <br><I>Conclusion:</I> It is safe to heat blood in a bucket of warmed water in theatre at a confirmed initial temperature of 47°C, as only the outer part of the unit is exposed to this temperature for a short while.
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