Do not mix pRBC infusion with hypotonic solution (i.e D5W).Why?
The hypotonic solution has a lower osmolarity, will shift into the RBCs, causing swelling and then lysis.
Mixing of pRBC infusion with Ringer Lactate (RL) is not recommended by the AABB. Simultaneous use of 0.9% Normal Saline is the only recommended isotonic solution. Why?
This stems from a 1975 study that initially demonstrated formation of clots in vitro when whole blood was mixed with RL (ionized calcium catalyzing the coagulation cascade).
Another study has demonstrated this effect, however also showed no clotting depending on the ratio (1:1 vs. 1:2 or 1:5) used. Other studies ,  support this.
NOTE:A more recent study has found it to be safe. If you have any questions about transfusion practice at your hospital, consult your blood bank medical director.
S. E. Ryden, H. A. Oberman. Compatibility of Common Intravenous Solutions with CPD Blood. Transfusion. 1975 May-Jun;15(3):250-5.
Cull DL, Lally KP, Murphy KD. Compatibility of packed erythrocytes and Ringer’s lactate solution. Surg Gynecol Obstet. 1991 Jul;173(1):9-12.
Lorenzo M, et al. Can Ringer’s lactate be used safely with blood transfusions? Am J Surg. 1998 Apr;175(4):308-10.
Albert K, et al. Ringer’s lactate is compatible with the rapid infusion of AS-3 preserved packed red blood cells. Can J Anaesth. 2009 May;56(5):352-6. doi: 10.1007/s12630-009-9070-5. Epub 2009 Apr 2
Levac B, et al. Ringer’s lactate is compatible with saline-adenine-glucose-mannitol preserved packed red blood cells for rapid transfusion. Can J Anaesth. 2010 Dec;57(12):1071-7. doi: 10.1007/s12630-010-9396-z. Epub 2010 Oct 5.