LRS vs Citrate: Friend or Foe?

Imagine having a patient who needs simultaneous administration of a citrated blood product and Lactated Ringer’s solution (LRS), but there is only one available peripheral catheter.

Can you administer citrated donor blood or plasma and LRS at the same time?

Conventionally, this practice is discouraged because LRS is a calcium-containing fluid that may be incompatible with citrate due to the risks of calcium chelation and clot formation. Once LRS exceeds the chelating capabilities of the citrate in the stored blood that may result in clot formation, which makes perfect sense. However, as we all know, theory and practice are not the same in clinical medicine. Therefore, let’s explore the evidence to answer this very practical question.

The common recommendation to avoid simultaneous administration of LRS and citrated blood products is based on the paper published in 1975 by Ryden and Oberman (Ryden et al; Transfusion 1975) who demonstrated that trace amounts of clot could be obtained from intravenous tubing at a whole blood to LRS volume ratio of 1:1 at room temperature. Fibrin clots were seen when the flow rate was slow (60 drops per minute). In that study, gross clot formation was observed at a blood:LRS volume concentration of 1:5 at a temperature of 37°C. To achieve this ratio, a 10 kg dog should be receiving LRS at a rate of 125 ml/hr and a simultaneous blood transfusion at a rate of 25 ml/hr through the same catheter.

Cull and colleagues (Surg Gynecol Obstet. 1991) studied the compatibility of Ringer’s lactate solution and citrate phosphate dextrose (CPD)-preserved packed erythrocytes to evaluate the safety of using Ringer’s lactate solution as a diluent in the emergency setting. They diluted aliquots of CPD-preserved packed red cells with either Ringer’s lactate or normal saline solutions in ratios between 5:1 to 1:20 (packed red cells to crystalloid). Then, they examined the solution for clot formation at intervals up to two hours. No clot formation occurred in the dilutions between 5:1 and 2:1 (blood:LRS). There was no difference in flow rates between packed red cells diluted with Ringer’s lactate compared with normal saline solutions. The authors concluded that Ringer’s lactate solution can ONLY be safely used as a packed red cell diluent in patients requiring rapid blood transfusions.

Lorenzo and colleagues (Am J Surg. 1998) performed another experiment. They rapidly mixed whole blood and packed red blood cells with normal saline or LRS. These solutions were put through a filter and the authors compared the infusion time, filter weight, and clot formation between the two solutions. They found no significant differences in infusion time or filter weight using whole blood or packed cells with normal saline or LRS. There was also no significant difference in clot formation between the two solutions mixed with anticoagulated blood. The authors of this paper recommended blood bank guidelines be revised to allow the use of LRS in the rapid transfusion of PRBC.

The Bottom Line

Simultaneous administration of LRS and citrated blood products MAY lead to clot formation, depending on the ratio and rate of administration. Only rapid administration of blood products with simultaneous administration of LRS at much lower rates may be relatively safe. Ideally, the blood product administration rate should exceed LRS administration rate by at least a factor of 2 to 5 (i.e. 2:1 to 5:1 ratio of blood administration rate to LRS rate).  For example, if a 10-kg dog is receiving citrated whole blood at 50 ml/hr, LRS administration rate should not exceed 25 ml/hr, and ideally be even lower (e.g. 10 ml/hr). Alternatively, NaCl 0.9% could be used in all cases to avoid any risks associated with clot formation.

References

1. Compatibility of common IV solutions with CPD blood. Ryden et al; Transfusion. 1975.
2. Compatibility of packed erythrocytes and Ringer’s lactate solution. Cull et al.; Surg Gynecol Obstet. 1991.
3. Can Ringer’s Lactate Be Used Safely with Blood Transfusions? Lorenzo et al; The American Journal of Surgery, 1998.