Frozen and Deglycerolized Red Blood Cells

Summary of Changes

- Updates on current operational employment of frozen and deglycerolized red blood cells (RBCs).
- Update on quality metrics that must be met to produce deglycerolized RBCs.
- General administrative updates.

BACKGROUND

Frozen red blood cells are important in the military trauma system to maintain blood reserves in challenging operational environments. There are many clinical and operational limitations to using frozen red cells, but they remain an essential capability. However, whole blood is always preferable to using deglycerolized Red Blood Cells (DRBC). The idea behind a frozen blood (DRBC) reserve is twofold in the civilian system: 1.) to freeze units of rare blood types for later use by patients with special transfusion needs and 2.) managing special transfusion circumstances. For the military, the Navy is the primary user of DRBC to meet the needs of isolated maritime operational units with a Food and Drug Administration (FDA) licensed product, provide a licensed product when no other option exists, and for contingency reserves. Glycerol is the additive that is used to protect the RBCs from the effects of freezing. When the blood is thawed, the glycerol is removed, and the product is referred to as DRBC. The introduction of an automated, functionally closed system for glycerolization and deglycerolization of RBCs improved the operational practice and decreases the risk of bacterial contamination of the blood. The first operational frozen blood bank was established in 1956 at Chelsea Naval Hospital (Boston), in part to determine the practicality of frozen blood usage aboard Navy ships. In 1966, under Department of Defense (DoD) direction, the Navy Bureau of Medicine and Surgery established the first frozen blood bank in a combat zone at Naval Station Hospital, DaNang, Republic of South Vietnam. Over a 7-month period, 465 DRBC units were transfused to severely injured casualties. In the 1980s, the DoD froze 68,000 RBC units. Those units were pre-positioned throughout several geographic Combatant Commands in direct support of current and future military medical contingency operations. As of October 2023, just under 950 units of DRBC have been transfused to under 400 casualties. This compares to over 360,000 units of other blood products. (Table 1.) While DRBC have a role in transfusion therapy, they are less commonly used than other blood products and from an operational standpoint, have more of a use on hospital ships and amphibious warships in denied maritime environments. Navy hospital ships (USNS Comfort and USNS Mercy) and amphibious war ships routinely deploy with a standard amount frozen blood reserves roughly proportional to casualty holding capacity (Table 2). Aircraft carriers do not have DRBCs, although some have up to 5 units of stored whole blood generated from the ship’s crew. All the ships in table 2 have a routine walking blood bank (WBB) capability, but no stored platelets.

Table 1. Patient transfusions by blood product type

DRBCs are derived from 450 ml of whole blood collected in Citrate/Phosphate/Dextrose (CPD) or Citrate/Phosphate/Dextrose/Adenine (CPDA-1) collection bags. DRBCs can also be made from additive solution Red Blood Cell (RBC) units such as CPD/AS-1, CPD/AS-5 or CP2D/AS-3 if these are first centrifuged to concentrate the RBCs to hematocrit of about 75%. The RBCs are stored for up to 6 days at 1 – 6 °C before being frozen in a cryoprotectant (40% weight/volume glycerol) and stored in the frozen state at minus 65 °C or colder, for up to 10 years. 1

Once it is determined that they will be needed for transfusion, the frozen RBCs are thawed. They are then deglycerolized by sequential washing with hypertonic (12%) saline followed by normal (0.9%) saline mixed with 0.2% glucose. Following deglycerolization, units are re-suspended in AS-3 additive solution and stored at 1-6°C, until ready for transfusion. DRBCs must recover at least 80% of the RBCs present from the original unit. Units suspended in AS-3 are FDA-approved for transfusion for up to 14 days when processed on the Haemonetics Automated Cell Processor ACP215 (Figure 1), an FDA 510(k)-cleared, closed processing system device. DRBCs are licensed under the respective Service Blood Program licenses.1, 2 All U.S. hospital ships and amphibious warships (LHA, LHD, LPD) with DRBC have ACP215.

Table 2. Standard Stored DRBC Reserves on U.S. Ships

FRBC storage and DRBC processing are organic to select naval vessels (Table 2), some garrison medical treatment facilities (MTFs), and Service blood depots in the European Command, Africa Command, and Indo-Pacific Command areas of responsibility. Deployed MTFs and Medical Detachment Blood Support units do not have the organic mission or capability to store and process frozen RBCs. Use of this capability is based on operational necessity. Upon completion of the deglycerolization process, the produced DRBCs are typically provided to Role 2 and higher MTFs due to the 14-day shelf life.