pseudoreaction


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Related to pseudoreaction: Order of reaction, Rate law

pseudoreaction

 [soo″do-re-ak´shun]
a false or deceptive reaction; in intradermal skin tests, a reaction not due to the specific test substance but to protein in the medium employed in producing the toxin.

pseu·do·re·ac·tion

(sū'dō-rē-ak'shŭn),
A false reaction; one not due to specific causes in a given test.

pseudoreaction

/pseu·do·re·ac·tion/ (-re-ak´shun) a false or deceptive reaction; a skin reaction in intradermal tests that is not due to the specific test substance but to protein in the medium employed in producing the toxin.

transfusion reaction

Blood transfusion reaction, incompatibility reaction Transfusion medicine Any untoward response to the transfusion of non-self blood products, in particular RBCs, which evokes febrile reactions that are either minor–occurring in 1:40 transfusions and attributed to nonspecific leukocyte-derived pyrogens, or major–occurring in 1:3000 transfusions and caused by a true immune reaction, which is graded according to the presence of urticaria, itching, chills, fever and, if the reaction is intense, collapse, cyanosis, chest and/or back pain and diffuse hemorrhage Note: If any of above signs appear in a transfusion reaction, or if the temperature rises 1ºC, the transfusion must be stopped; most Pts survive if < 200 ml has been transfused in cases of red cell incompatibility-induced transfusion reaction; over 50% die when 500 ml or more has been transfused; TF mortality is ± 1.13/105 transfusions Clinical Flank pain, fever, chills, bloody urine, rash, hypotension, vertigo, fainting
Transfusion reactions
Immune, non-infectious transfusion reactions  
• Allergic Urticaria with immediate hypersensitivity
• Anaphylaxis Spontaneous anti-IgA antibody formation, occurs in ± 1:30 of Pts with immunoglobulin A deficiency, which affects 1:600 of the general population–total frequency: 1/30 X 1/600 = 1/18,000
• Antibodies to red cell antigens, eg antibodies to ABH, Ii, MNSs, P1, HLA
• Serum sickness Antibodies to donor's immunoglobulins and proteins
Non-immune, non-infectious transfusion reactions  
• Air embolism A problem of historic interest that occurred when air vents were included in transfusion sets
• Anticoagulant Citrate anticoagulant may cause tremors and EKG changes
• Coagulation defects Depletion of factors VIII and V; this 'dilutional' effect requires massive transfusion of 10 + units before becoming significant
• Cold blood In ultra-emergent situations, blood stored at 4º C may be tranfused prior to reaching body temperature at 37º C; warming a unit of blood from 4 to 37º C requires 30 kcal/L of energy, consumed as glucose; cold blood slows metabolism, exacerbates lactic acidosis, ↓ available calcium, ↑ hemoglobin's affinity for O2 and causes K+ leakage, a major concern in cold hemoglobinuria
• Hemolysis A phenomenon due to blood collection trauma, a clinically insignificant problem
• Hyperammonemia and lactic acid Both molecules accumulate during packed red cell storage and when transfused, require hepatorenal clearance, of concern in Pts with hepatic or renal dysfunction, who should receive the freshest units possible
• Hyperkalemia Hemolysis causes an ↑ of 1 mmol/L/day of potassium in a unit of stored blood, of concern in Pts with poor renal function, potentially causing arrhythmia
• Iron overload Each unit of packed RBCs has 250 mg iron, potentially causing hemosiderosis in multi-transfused Pts
Microaggregates Sludged debris in the pulmonary vasculature causing ARDS may be removed with micropore filters
Pseudoreaction Transfusion reaction mimics, eg anxiety, anaphylaxis related to a drug being administered at the same time as the transfusion
Infections transmitted by blood transfusion
• Viruses B19, CMV, EBV, HAV, HBV, HCV, HDV, HEV, Creutzfeldt-Jakob disease, Colorado tick fever, tropical viruses–eg Rift Valley fever, Ebola, Lassa, dengue, HHV 6, HIV-1, HIV-2, HTLV-I, HTLV-II
• Bacteria Transmission of bacterial infections from an infected donor is uncommon and includes brucellosis and syphilis in older reports; more recent reports include Lyme disease and Yersinia enterocolitica  Note: Although virtually any bacteria could in theory be transmitted in blood, the usual cause is contamination during processing rather than transmission from an infected donor
• Parasites Babesiosis, Leishmania donovani, L tropica, malaria, microfilariasis–Brugia malayi, Loa loa, Mansonella perstans, Mansonella ozzardi, Toxoplasma gondii, Trypanosoma cruzi

pseu·do·re·ac·tion

(sū'dō-rē-ak'shŭn)
A false reaction; one not due to specific causes in a given test.

pseudoreaction

a false or deceptive reaction; in intradermal skin tests, a reaction not due to the specific test substance but to protein in the medium employed in producing the toxin.