LRS vs Citrate: Friend or Foe?

Imagine that you have a patient who requires a simultaneous administration of a blood product and LRS, however it has only one available peripheral catheter because the second catheter is being used for a CRI medication.

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

The majority of us will confidently say that you cannot do that because LRS is a calcium-containing fluid that is incompatible with citrate due to risks of chelation and clot formation. In theory, this makes a 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.

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 clinically relevant dilutions between 5:1 and 2:1. 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 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.

Another way to look at this question is to consider the concentration of calcium in LRS and compare it with the serum calcium concentration. LRS contains 1.5 mmol/L (3 mEq/L), which is only slightly above the normal concentration of ionized calcium in healthy dogs and cats. If this concentration of calcium in LRS resulted in clot formation, each blood transfusion would have led to a thrombotic storm as soon as it came into contact with recipient’s blood. And we know that it doesn’t happen.

In veterinary emergency and critical care, patients require intensive management with multiple procedures being simultaneously performed. Changing fluid bags from LRS to normal saline or other solutions with zero calcium content may be time consuming and not supported by current evidence.

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.

Author: Igor Yankin

Igor is the creator of VetEmCRIT.com. He is a clinical assistant professor of Veterinary Emergency and Critical Care Medicine at the Texas A&M University.