Plus-Hex CLINICAL
post-transfusion bacterial sepsis , which would be detrimental to patients . If at all concerned , test units for bacterial contamination prior to transfusing .
Storage lesions
Figure 3 . Storage of PRBCs .
Although little research in this area has been conducted within veterinary literature , it is presumed that these mechanisms are similar with canine patients , reiterating the importance of following strict aseptic techniques during the blood donation process and wearing gloves at all times when handling blood products . The presence of bacteria within a blood unit at collection is concerning but the proliferative rate of the bacteria while in storage , which could potentially lead to septic complications if administered , should also be contemplated ( Hillyer et al ., 2003 ).
Miglio et al . ( 2016 ) conducted a study to identify bacterial microorganisms in whole blood products and revealed that low amounts of bacteria had no clinical significance or effect on triggering a transfusion reaction . Nevertheless , the authors suggested that storing blood products for shorter periods of time would benefit patients by reducing the amount of time bacteria are given to proliferate .
Of the units that tested positive for bacterial contamination in the Miglio et al . ( 2016 ) study , none showed any gross visual changes . In contrast , in a study conducted by Stefanetti et al . ( 2016 ), all four contaminated PRBC units showed distinct colour changes from light red to dark red and almost black appearance . These units tested positive for the bacteria Serratia liquefaciens and Pseudomonas spp . ( both of which are commonly found in the environment and on patients ' skin ) on the 20th , 31st and 32nd day of storage – which are towards the latter end of the recommended storage time .
The contrast in these two studies clearly demonstrates that visual changes are not always apparent , so RVNs need to remain vigilant and should regularly inspect units in an attempt to detect any changes . The findings of bacteria in older units also suggests that the current guidelines of storing PRBC units for 42 days may need evaluating as , even though these studies suggest that low-yield bacteria do not induce a transfusion reaction , older units still have the potential to induce
In human and veterinary medicine , there have been growing concerns about the age of PRBC units and the risk of a transfusion reaction due to RBC storage lesions ( SLs ). These are biochemical and biomechanical changes that occur during PRBC storage , which compromise function and stability when transfused to a patient ( Hann et al ., 2014 ). Wilson et al . ( 2017 ) aimed to describe the biochemical changes that occur in canine PRBCs during a 42-day storage period . Unfortunately , the study had a very small sample size , weakening the significance of its findings . However , many of the findings did correlate with current human review literature ( D ' Alessandro et al ., 2015 ). Continually increasing concentrations of both ammonia and lactate were seen during storage , alongside a decrease in pH and glucose . Conversely , the concentration of potassium was considerably lower in canine PRBCs compared with human PRBCs . Nevertheless , all concentrations of the tested analytes changed significantly , many within the first 21 days of storage , which may have considerable effects if transfused to a critically ill patient .
The clinical impact of these changes in certain disease conditions is yet to be fully understood . However , due to hepatic involvement in the clearance of lactate from the body and the conversion of ammonia into the less toxic urea , veterinary surgeons and RVNs should be cautious about administering older PRBC units to patients with hepatic disease . It may be sensible to transfuse fresher blood to these patients , as well as to patients with metabolic disturbances , to reduce the risk of worsening the condition by transfusing blood with increased concentrations of lactate .
Within the past 10 years , two retrospective studies have sought to determine whether the age of PRBC units , and possible SL processes within , increase the risk of a patient suffering an acute transfusion reaction and whether they have an effect on mortality and morbidity rates . Hann et al . ( 2004 ) retrospectively analysed 3,095 dogs that had received PRBC for various clinical conditions and found no difference in mortality rates of patients that received fresher versus older PRBC units in the overall canine population . However , it was noticed that patients with pre-occurring haemolysis ( e . g . immune-mediated haemolytic anaemia ), were more at risk of not surviving to discharge ( P = 0.024 ). This coincides with the more recent study by Maglaras et al . ( 2017 ), which , in addition , suggests that patients receiving older units are more at risk of developing transfusion-related reactions , with fever ( 12.3 %) and transfusion-related haemolysis ( 6.3 %) being the most common . These did not necessarily lead to death of the patient .
Volume 37 ( 4 ) • September 2022
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