In vitro effects of thawing fresh-frozen plasma at various temperatures

Thawing fresh-frozen plasma (FFP) in South Africa is uncontrolled because the plasma is issued frozen from the blood bank and thawing techniques and temperatures are at the discretion of the clinician. Following anecdotal reports of disseminated intravascular coagulation (DIC) developing in patients who received FFP thawed in an uncontrolled manner, the effects of various thawing temperatures on coagulation parameters were studied. Fifteen adult units of FFP were each divided into 4 satellite units by the South African Blood Transfusion Service before freezing at -25 degrees C. These bags were then defrosted in a waterbath at 22 degrees C, 37 degrees C, 45 degrees C and 60 degrees C, respectively, and removed as soon as they had thawed. Samples were collected for measurement of International Normalized Ratio (INR), prothrombin time (PT), partial thromboplastin time (PTT), fibrinogen, and D-dimers. These tests were done according to standard operating procedures. FFP samples were also used in place of agonist in platelet aggregation studies to assess whether the FFP could induce platelet aggregation. Results were analyzed with the percentage similarity model. Using this method the percentage similarity (%sim) of each bag thawed at each temperature with the same donor's bag thawed at 37 degrees C was calculated. The mean, standard deviation, and percentage coefficient of variation of the percentage similarities were then derived. Data sets were also compared using the Wilcoxon test. The fibrinogen values remained stable at 22-45 degrees C (%sim = 97-99%) while there was a significant decrease in fibrinogen levels at 60 degrees C compared with 37 degrees C (p<0.001, %sim = 75%). INR and PTT values were highest in the bags thawed at 60 degrees C (%sim = 114% and 110%, respectively) with the difference between the INR levels at 60 degrees C compared with 37 degrees C showing statistical significance (p<0.05). D-dimers were high at all temperatures tested with widely ranging results at each temperature. The FFP did not induce platelet aggregation at any of the thawing temperatures. In summary, INR and PTT values increase at a thawing temperature of 60 degrees C compared with 37 degrees C. D-dimers are elevated in thawed FFP. Fibrinogen levels are markedly decreased in FFP thawed at 60 degrees C compared with that thawed at 37 degrees C. FFP should be thawed at 37 degrees C in a strictly controlled environment.