Page 80 - JSOM Spring 2023

2–5 days. However, if the only donors available have recently However, a life-saving transfusion should never be denied if a
taken an NASID, their blood should be collected and used due blood warmer is not available, such as in a field transfusion
to the life-saving benefits of transfusion. setting.

There are two minor issues associated with donors on TRT: To minimize the effect of transfusion-induced hypothermia, a
polycythemia and increased hemolysis during storage. Polycy- cold stored transfusion could be administered at a slower rate
themia, an increased number of RBCs and therefore a higher (if possible) than a warmed (or fresh) unit. However, the trans-
hematocrit compared to normal, can pose a problem because fusion should always be completed within four hours. Addi-
the higher hematocrit is accompanied by a relatively lower tionally, the TCCC guidelines suggest that keeping LTOWB
plasma volume. Hematocrit is the percent of whole blood outside of a climate-controlled container (like a cooler) may
made up of RBCs, so the more RBCs present, the lower the be acceptable so long as the product is finished infusing into
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relative plasma volume in the donor’s whole blood. One study the patient within four hours of spiking the bag. If it be-
found that donors on TRT had mean hemoglobin concen- comes clear that a patient will require a transfusion, the unit
trations that were significantly higher than demographically can be removed from the cooling device and placed at am-
matched donors who were not taking this therapy (mean ± bient air temperature (assuming that ambient temperature is
standard deviation (SD), 17.8 ± 1.44 versus 15.6 ± 1.37g/dL, greater than 1–6°C) while the patient is being prepared for
31
respectively; p<.0001). However, another study found a sim- the transfusion. This way, the unit will not be as cold at the
ilar mean hemoglobin concentration amongst donors on TRT time of infusion as it would have been had it been removed
of 17.3g/dL (range 13.4–20.5g/dL), with calculated hemato- from the cooler immediately before the infusion began. Note
crit values ≥54% in 25% of these donors. While this should that all blood warmers should be validated before use. Im-
32
not impact the blood collection process itself, the relatively provising a blood warmer, such as by putting the unit near
smaller amount of plasma in the collected whole blood unit a radiator or surrounded by chemical hand warmers, might
could result in having a slight excess of unchelated citrate in inadvertently overheat the unit leading to hemolysis, which
the unit. This could potentially contribute to hypocalcemia in can cause severe harm to the recipient. That said, warming
the recipient. However, given the urgent and life-saving nature methods that do not involve concentrated, focused heating
of battlefield transfusions and the ability to administer sup- may be safe (e.g., any heat source that is significantly above
plemental calcium, the potential that these units might slightly body temperature should be avoided – if the heat source is hot
contribute to hypocalcemia should not prevent their adminis- to the touch, do not use it). To date, several field-expedient
tration. Furthermore, a polycythemic unit that contains more plasma thawing techniques have been evaluated, although it
RBCs than usual might actually be of benefit to a bleeding is unclear if these techniques would be suitable for warming
40
recipient. RBCs and cold stored LTOWB. Again, a life-saving transfu-
sion should never be withheld if the unit cannot be warmed
There have been reports that testosterone itself has direct ef- before infusion.
fects on RBCs. These include perturbations in RBC metabolism
and susceptibility to hemolysis, as well as higher concentra- Conclusion
tions of testosterone in the liquid component of the RBC unit
compared to donors not on TRT, as expected. 33–35 However, The questions that were answered in this manuscript came
these in vitro findings need in vivo correlation to determine if from the austere battlefield experience of combat medics and
there are detrimental issues for the recipient. Given the short highlight the challenges they have faced in resource limited set-
interval between collection and transfusion of FWB units from tings. These recommendations have taken this experience into
a walking blood bank, any issues that develop as a result of account with the goal of providing the best possible opportu-
TRT during prolonged cold storage are probably irrelevant. nity of saving the life of a fellow Servicemember. These recom-
mendations are not meant to contradict the current standard
of care and treatment protocols. Rather, they are aimed at pro-
Transfusing Cold Units Without
Using a Fluid Warmer viding options when there are seemingly none.

The infusion of cold stored blood can reduce body tempera- Disclosure
ture, thereby further aggravating the hypothermia associated The authors have indicated they have no financial relation-
36
with trauma. In a study of patients with massive bleeding, ships relevant to this article to disclose.
the rate of the decline in temperature depended on the vol-
ume of blood infused and the rate of infusion. The authors Disclaimer
37
observed a <1.5°C decrease in esophageal temperature until The opinions or assertions contained herein are the private
about 1800mL of cold blood had been infused (approximately views of the author and are not to be construed as official
3.5 units of LTOWB). In another study on patients undergoing or as reflecting the views of the Department of the Navy, the
knee replacement, one group received blood through a blood Department of the Army, the Department of Defense, or the
warmer while the other group received blood that had been United States Government
removed from refrigeration and placed at room temperature
for 15–20 minutes. This study, although conducted in dras- Author Contributions
38
tically different circumstances than the austere setting of pre- RN, TS, MO, JL, ML, MH, AG, and CS all provided oper-
hospital trauma care, demonstrated a small but significantly ational understanding and determined the pertinent clinical
higher nasopharyngeal temperature amongst those who re- questions to be reviewed. AG, CS, AC, and MY analyzed, in-
ceived warmed blood compared to the control patients. Thus, terpreted and provided clinical advice regarding the topics be-
when an approved blood warmer is available it should be used ing reviewed. All authors read, contributed to, and approved
in a patient who is predicted to receive a massive transfusion. the final manuscript.

78 | JSOM Volume 23, Edition 1 / Spring 2023