Fresh frozen plasma

Fresh frozen plasma (FFP), as defined by the American Association of Blood Banking (AABB), is plasma separated from whole blood and stored in a –18 °C or colder freezer within the time frame required by the anticoagulant or collection process, typically within 6 hours (if ACD is the anticoagulant) to 8 hours (if the anticoagulant is CPD, CP2D, or CPDA-1) of blood collection. Plasma frozen at ≤ –65 °C can be stored for 7 years after collection (AABB 2011). FFP contains essentially all of the hemostatic proteins, albumin, and globulin as the plasma from which it was prepared. Veterinary studies have shown retention of functional hemostatic proteins in FFP units for up to 1 year of storage (Wardrop and Brooks 2001; Wilson et al. 2008).

FP24

Plasma frozen within 24 hours after collection (FP24) is typically prepared from whole blood that has been stored at 4–6 °C for up to 24 hours before centrifugation. The separated plasma is then stored at –18 °C or colder. When used clinically in human patients, the product has slightly to moderately decreased concentrations of factor VIII (O’Neill et al. 1999; Smith et al. 2000; Cardigan et al. 2005) and factor V (Cardigan et al. 2005). Plasma prepared from whole blood stored at room temperature, rather than refrigeration for 24 hours, has also been investigated in people and shows up to 20% reduction of factor VIII, with other coagulation factors comparable to FFP (Alhumaidan et al. 2010). A concern of this method is the risk of bacterial contamination, but significant microbial growth does not occur during the first 24 hours in human platelets stored at room temperature (Ezuki et al. 2007) and the freeze-thaw process used with plasma would be expected to disrupt most microbes.

A study in dogs suggested that canine whole blood units stored at room temperature for up to 24 hours, followed by processing to plasma and freezing, still retained therapeutic coagulation protein and hemostatic protein content. Small aliquots of plasma frozen in plastic tube segments at –80 °C were used in the study, which might not mimic conditions for plasma unit storage. A direct comparison of factor concentrations between FFP and FP24 was not performed in this study (Walton et al. 2014).

Frozen plasma

Frozen plasma (FP) refers to FFP units stored for longer than 1 year or thawed FFP units stored under refrigeration for more than 24 hours before transfusion (now termed thawed plasma) (Brooks 2010). The term FP is not commonly used in the human field. FP is a source of albumin and globulins. Hemostatic proteins retain variable activity in FP and the product may not supply replacement levels of the most labile coagulation factors such as factors V and VIII (Allain et al. 1983). A study evaluating canine plasma units collected from greyhound blood donors and stored at –30 °C for 5 years showed that the plasma (FP) was hemostatically active as demonstrated by thromboelastography; prothrombin times (PT) and activated partial thromboplastin times (aPTT) also remained within respective reference intervals. However, significant decreases were noted in factor VIII and factor X activities of the FP as compared to fresh plasma samples (Urban et al. 2013).

Thawed plasma

Thawed plasma is prepared from FFP or FP24 by thawing the unit at approximately 37 °C and storing the liquid component at 1–6 °C for up to 5 days (Benjamin and McLaughlin 2012). In humans, the activities of factors II, VII, IX, X, and fibrinogen are comparable to those found in FFP or FP24, while factor VIII shows the greatest degree of degradation (Downes et al. 2001). Extension of the storage time up to 10 days still maintained what were considered therapeutic levels of factors V and VIII in one study using human thawed plasma, although levels were reduced from day 0 (Tholpady et al. 2013).

Liquid plasma

Liquid, never frozen plasma for transfusion can be separated from whole blood at any time during storage and stored at 1–6 °C for up to 5 days after the expiration date of the whole blood (Kakaiya et al. 2011). Liquid plasma (LP) can be deficient in labile factors, but one study using human plasma separated and refrigerated within 24 hours of blood collection showed that at least 50% of activity of factors V, VII, VIII, VWF, and Protein S were maintained by day 15 (Gosselin et al. 2013). Another study comparing 5-day-old never frozen LP to FFP thawed and refrigerated for 5 days showed better endogenous thrombin potential in the LP (Matijevic et al. 2013). LP is transfused for immediate treatment of acute hemorrhage and for reversal of warfarin effects in people. Its major use is in high volume trauma centers, where plasma needs to be immediately available with no thaw time that would delay administration. A study using canine LP processed routinely after whole blood collection showed that the PT and aPTT remained within reference intervals after refrigerated storage up to 14 days. No significant differences for factors V and VIII were noted between the refrigerated LP at 14 days and plasma frozen at –20 °C within 2 hours of collection and thawed at 14 days. Aerobic and anaerobic bacterial cultures obtained on days 7 and 14 for the refrigerated LP and on day 14 from the thawed frozen plasma yielded no growth. The study indicated that refrigerated storage of canine LP might be useful, particularly in high volume emergency clinics (Grochowsky et al. 2014).

Cryoprecipitate-poor plasma

Cryoprecipitate-poor plasma (CPP), also known as cryopoor plasma or cryosupernatant/cryosuper, is made by thawing FFP at 1–6 °C, separating the cold-induced precipitate (cryoprecipitate) by centrifugation, and refreezing the remaining supernatant plasma at –18 °C or colder within 24 hours of thawing. CPP is significantly deficient in factor VIII, factor XIII, fibrinogen, and VWF, but retains albumin, other hemostatic proteins, and immunoglobulins (Benjamin and McLaughlin 2012). CPP can be used as a source of vitamin K-dependent coagulation factors (factors II, VII, IX, and X) and is stable for this purpose for at least 1 year of storage (Roback et al. 2010; AABB 2011).

Cryoprecipitate

Cryoprecipitate (CRYO) is prepared by slowly thawing FFP at temperatures between 1 and 6 °C until the plasma has a slushy consistency with a few ice crystals remaining. This is followed by centrifugation to sediment the cold-insoluble proteins, which appear as a white precipitate (Figure 4.4) within the thawed plasma (Kakaiya et al. 2011; Benjamin and McLaughlin 2012). The majority of the thawed plasma is removed, and the remaining CRYO fraction is then refrozen for storage within 1 hour of separation. A unit of CRYO prepared for human use must contain at least 80 IU of factor VIII and at least 150 mg of fibrinogen in a small amount of plasma, usually 5–20 mL (Benjamin and McLaughlin 2012). The unit definition of CRYO in veterinary medicine is variable among commercial blood banks, and should be defined based on the volume of starting FFP, or fibrinogen or factor content. CRYO contains fibrinogen, the VWF–factor VIII complex, factor XIII, and fibronectin (Benjamin and McLaughlin 2012). In comparison to the FFP from which it is derived, the process of cryoprecipitation can yield approximately 50–80% of the original factor activity, contained in a much smaller volume. This volume reduction is the major advantage of CRYO transfusion; therapeutic levels of factors are attained within minutes over the course of a single bolus infusion. The expiration date of CRYO is 1 year from the date of the original plasma collection, when stored at ≤ –18 °C. The product is often used for veterinary patients as a source of VWF and factor VIII. Lyophilized canine CRYO is available commercially (Animal Blood Resources International, Stockbridge, MI).

Platelet-rich plasma

Platelet-rich plasma is a platelet product and is discussed more extensively elsewhere in this textbook (see Chapter 5). It is prepared using a short, low g force centrifugation technique at room temperature, which separates the red blood cells but allows the platelets to remain suspended in the plasma.

Plasma derivatives, recombinant proteins, and pathogen-reduced plasma products

Plasma derivatives, most commonly albumin, immunoglobulins, and factor concentrates (factors VIII and VWF) have been isolated from plasma commercially for human use. Production techniques involve separation of proteins by Cohn’s fractionation (using varying temperatures, pH, and ethanol) or with chromatography and immunopurification (Thyer et al. 2006; Ofosu et al. 2008). The final protein concentrates are supplied as solutions or lyophilized powders with long (2–3 years) shelf-lives at room temperature. A lyophilized product of canine albumin is commercially available and is discussed in more detail in elsewhere in this textbook (see Chapter 7). Recombinant human factor VIII and IX products have also been developed to prevent and control hemorrhage in human hemophilic patients. These products do not prevent development of inhibitory alloantibodies, a severe complication of replacement therapy. Recombinant human factor VIIa (rhFVIIa) was developed for such patients with acquired coagulation inhibitors (Levy et al. 2006). At supra-physiologic levels, rhFVIIa generates thrombin by directly activating factor X on the surface of procoagulant platelets, independent of factors VIII and IX. Recombinant canine factor VIIa has been developed and was shown to be effective in a study involving a dog with hemophilia A (Knudsen et al. 2011); this product is not commercially available.

Plasma can be treated to inactivate microbial agents, thus lessening the potential transfer of such agents during transfusion. Pathogen-reduced human plasma products are in widespread use in many European countries. Pathogen-reduction techniques used for these products include solvent/detergent-treated plasma, methylene-blue-treated plasma, psoralen and ultraviolet light-treated plasma, and riboflavin and ultraviolet light-treated plasma. These products are for human use only and might not be available in the United States (Benjamin and McLaughlin 2012).