Introduction

A walking blood bank is hardly a new concept. In fact, they have existed since World War I and were used routinely until after the Vietnam War. It was not until the 1960s that blood donations were broken down into red blood cells, plasma, and platelets. With the advantages of longer storage time, improved blood safety, and ability to more effectively use each donation, blood component therapy became the standard and the use of whole blood nearly disappeared.

Since the conflicts in Iraq and Afghanistan, however, whole blood has come back into fashion, particularly in the military. Whole blood has been shown to be at least as effective as transfusing blood products in a 1:1:1 ratio of packed red blood cells, thawed fresh frozen plasma, and five pack of platelets and has the advantage of being available in every human. Setting up a walking blood bank is a practical and efficient way to obtain whole blood quickly in circumstances where the use of stored blood is not feasible.

Preparation

In order to start a walking blood bank, several questions need to be answered. First, is there a need? Weighing the likelihood of massive hemorrhage or a mass casualty event versus the availability of stored whole blood can give a good indication as to whether the effort to build a blood bank will be worthwhile. Next, what protocol fits that need? The military has several and a few exist on the civilian side as well, but each will need adjustment based on specific circumstances. One of the biggest debates is whether to use a low titer O positive approach or aim for type-specific blood. O type blood is the universal donor, but all O blood contains some A and B antibodies; low titer donors have low amounts of these antibodies and are less likely to cause a transfusion reaction. It is not always possible to test for low titer donors, however, so some advocate for prioritizing type-specific blood if available, although this is falling out of favor.

And finally, leadership will need to approve the process, sufficient numbers need to volunteer as donors, and staff needs to agree on both necessity and protocols in order to create a successful walking blood bank.

Selection

The screening process is arguably the most crucial step in establishing a walking blood bank. Ideally, screening for ABO and Rh typing, viruses, and titer levels occurs before potential donors travel, when there is access to a full lab. Blood obtained in the routine setting is tested for HIV, hepatitis B, hepatitis C, human t-lymphotropic virus, syphilis, cytomegalovirus, and others so if these labs can be obtained for potential donors before traveling to the remote environment, the likelihood of blood borne pathogen transfer decreases. The military tests all members before deployment.

Even if there is pre-testing, however, there is still a need for confirmatory testing on site, particularly for ABO typing. There is a known error in people self-reporting blood type and even military dog tags are incorrect 4% of the time, which could lead to a potentially devastating hemolytic reaction. Each person registered in the blood bank should have confirmatory testing of blood type using an Eldon card or other typing test. There are also point-of-care tests (Figure 2) that do not require a lab for HIV, hep B, hep C and malaria that can be collected from each participant in military walking blood banks.

This information is then compiled into a database for easy access and clarity to be readily available when the blood is needed. In some instances, a computer-based system is used. In others, a simple binder or file folder contains each person’s data and their point-of-care tests, organized by blood type for easy use.

Activation

Notifying potential donors is easy if you are in a small group in a small area. It is significantly more difficult if you are spread out across a military base or a large expedition. Most walking blood banks are activated in a similar fashion to a code blue medical emergency. As soon as the medical team lead decides more blood will be needed than is available or if a patient meets massive hemorrhage criteria, the code is activated (Figure 3).

Once the donor verifies their information, staff places a large bore needle, connects the collection bag, and places it on the ground. The bag is supposed to be frequently mixed so one practice is to have the donors gently rock the bag with their foot as it is filling. The goal is to fill the bag to 450 mL, which can be achieved either by either using a scale to reach 585 grams, or more practically, have paracord or a zip tie pre-measured to 6.5 inches wrapped around the bag and have the donors kink the tubing to stop flow once it reaches that circumference.

Recommendations are that only one unit of whole blood be taken from a single donor, though this can be stretched to two units if absolutely necessary. There have been several studies to see if there is impaired performance after donation, and all have shown no decrease in physical abilities afterward, so the larger amount can be considered.

If the donated blood is not used within eight hours, it can be stored at 1-6° C (~34-36° F) and then becomes stored whole blood. It lasts 21 days in anticoagulant CPD containing bags and 35 days in CPDA-1 bags. Fresh whole blood should not be used after 24 hours if not refrigerated.

Transfusion

The actual transfusing of the blood to the patient is probably the most straightforward part of the process. The blood type of both the donor and the patient must be verified before administering. The bag infuses by gravity. Infusion reactions, as listed in Figure 6, must be monitored for closely.