In Vivo Viability of Platelets Stored in Whole Blood at 4°C

Background:  Trauma surgeons have suggested that the optimal transfusion support for actively bleeding patients may be a 1:1:1 ratio of red cells, plasma and platelets (plts).  Therefore, the only reason to give component therapy – rather than whole blood (WB) – for these patients may be because of the poor post-transfusion survivals of plts stored at 4°C.  However, for trauma/surgical patients, even short plt survivals may be sufficient to allow the surgeon enough time to repair the injury.  We report the “first ever” data on the post-storage viability of plts stored at 4°C beyond 3 days.  In the studies to be reported here, plts were stored within WB for up to 22 days at 4°C.

Study Design/Methods:  Normal subjects donated a unit of WB that was stored at 4°C either for 12 days with mixing only at the end of storage or for 10, 15, or 22 days with end-over-end rotation of the WB throughout storage.  After storage, a plt concentrate was prepared from the WB using standard centrifugation procedures.  At the end of WB storage, the donor donated a 40 ml blood sample from which fresh plts were prepared.  The autologous stored and fresh plts were radiolabeled with ¹¹¹In or ⁵¹Cr, respectively, before simultaneous transfusion into their donor.  Serial post-transfusion blood samples were collected to determine stored versus fresh plt recoveries and survivals.  Our pre-defined acceptance criteria were:  1) stored plt recoveries should average ≥50% of the same donor's fresh plt recoveries; and 2) plt survivals should average ≥1 day.

Results/Findings:  When the WB was mixed only at the end of storage, plt yields in the WB were just 48% of baseline values with average plt counts of 4.6 ± 2.0 x 10¹⁰.  This amount of plt loss was considered unacceptable (Table).  In contrast, with continuous end-over-end rotation of the WB during storage, plt yields after 15 days were 76% of baseline values and plt counts averaged 7.6 ± 1.4 x 10¹⁰ (well within FDA guidelines that require 5.5 x 10¹⁰ plts/concentrate prepared from WB).  Radiolabeled autologous plt recoveries averaged 27 ± 11% (49 ± 16% of fresh) and survivals averaged 1.2 ± 0.4 days (16 ± 1% of fresh); i.e., our pre-defined plt acceptance criteria were met.  Storage for 22 days gave unacceptable results.

Conclusion:  Plt concentrates stored at 4°C for up to 3 days have been FDA approved for use in thrombocytopenic patients since the 1970's.  These plts had autologous plt recoveries of 40 ± 5% and survivals of 1.0 ± 0.1 days (S.E.) (Br J Haematol 1976;34:403-419).  The FDA has recently approved the use of 3-day 4°C stored apheresis plts for actively bleeding patients.  Our data may suggest that plts stored within WB at 4°C for up to 15 days may provide similar post-storage plt viability as plt concentrates or apheresis plts stored for ≤3 days.  Red cells and plasma derived from CP2D WB stored for 21 days at 4°C are already licensed.  Therefore, for actively bleeding patients who need all three components (red cells, plasma, and plts), WB stored for up to 15 days may provide effective quantities of all the needed components.

AUTOLOGOUS YIELDS, RECOVERIES, AND SURVIVALS OF PLATELETS STORED IN WHOLE BLOOD AT 4°C

Storage Time (Days)	N	Rotation	WB PLT COUNTS x 1010		Post-Storage Yield (% of Baseline)	PLT RECOVERIES (%)			PLT SURVIVALS (Days)
			Baseline	Post-Storage		Fresh	Stored	% of Fresh	Fresh	Stored	% of Fresh
12	7	Mixed at end of storage*	9.4 ± 2.4	4.6 ± 2.0	48 ± 12	50 ± 15	22 ± 8	48 ± 29	8.3 ± 1.6	1.8 ± 0.6	23 ± 10
10	10	Continuously during storage**	9.5 ± 2.1	7.2 ± 1.6	77 ± 10	50 ± 10	26 ± 7	51 ± 7	8.1 ± 1.1	1.3 ± 0.3	16 ± 4
15	10	Continuously during storage**	10.0 ± 1.0	7.6 ± 1.4	76 ± 10	55 ± 11	27 ± 11	49 ± 16	8.0 ± 0.1	1.2 ± 0.4	16 ± 1
22	3	Continuously during storage**	12.9 ± 1.9	9.2 ± 0.7	73 ± 15	56 ± 12	14 ± 4	25 ± 5	7.7 ± 0.6	0.8 ± 0.3	10 ± 3
Data reported as average ±1 S.D.  *WB units were hand mixed only at the end of storage before plt counting. **WB units were continuously rotated end-over-end during storage.