Penn State Health Milton S. Hershey Medical Center Hershey, Pennsylvania, United States
Background/Case Studies: Hydroxocobalamin, an FDA-approved drug for treating cyanide poisoning, inhibits nitric oxide synthase and has been used off-label to curb hypotension in refractory vasoplegic syndrome, a potential complication of cardiopulmonary bypass. However, hydroxocobalamin may cause transient skin erythema. It may also cause plasma discoloration and chromaturia due to its deep red color. Recent literature identifies at least 11 substances and conditions which may discolor plasma and mimic hematuria in transfusion reaction evaluations or interfere with other laboratory testing.
Study
Design/Methods: Case report. A 75-year-old man received packed red blood cells, platelets, and cryoprecipitate during cardiopulmonary bypass for surgery to address severe multivessel coronary artery disease. Hydroxocobalamin was administered for vasoplegia part-way through the procedure. Upon removal of the sterile surgical field, the patient was noted to have diffuse, non-blanching erythema and edema. Diphenhydramine and solumedrol were administered for a possible allergic reaction. A transfusion reaction evaluation was submitted to the blood bank. A timeline of pertinent vital signs is shown in Table 1.
Results/Findings: The blood bank’s investigation included a direct antiglobulin test (DAT), which was negative, and a visual inspection of pretransfusion and posttransfusion blood tubes, which showed red discoloration of the supernatant in the posttransfusion specimen only. The clerical check showed no errors. The transfusion reaction was signed out as a possible allergic transfusion reaction, since it was unclear if the symptoms were ultimately due to medications used for intubation, a transfused blood product, or a known side effect of the administered hydroxocobalamin. Conclusions: This case illustrates hydroxocobalamin as a potential mimic of hemolysis in transfusion reaction evaluations. Given the negative DAT in the context of a relatively hemodynamically stable patient, the red-colored supernatant of the posttransfusion specimen was attributed to the hydroxocobalamin and not evidence of immune-mediated hemolysis.
Importance of research: Recognition of potential mimics of hemolysis during transfusion reaction evaluations is important to avoid misdiagnosis and potential patient mismanagement. In this case, we illustrate a case where hydroxocobalamin administration resulted in red discoloration of the supernatant in a posttransfusion blood specimen.
