chapter 24 - blood therapy
Post on 11-Jan-2016
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Overview of Perioperative Blood
Transfusion and Adjuvant Therapies• Transfusion Medicine (T&S, T&C, Emergency transfusion, Storage)
• Transfusion Thresholds
• Blood Components (PRBC, Plt, FFP, Cryo)
• Complications and Risks
• Miscellaneous (autologous transfusion, cell-saver, normovolemic hemodilution)
Type and Screen• Type - the donor erythrocytes do not
have major antigens (A, B, Rh) that will react with antibodies in the recipient blood
• O negative blood - does not have any antigens, so it is the universal donor
• Screen - the donor erythrocytes do not have common antigens that will react with antibodies in the recipient blood
• T&S blood is recommended for procedures in which transfusion is unlikely, but possible (lap choly, TAH)
• Risk of Significant Transfusion Reaction = 1 in 10,000 units transfused
Type and Cross• Cross-match - donor
erythrocytes are introduced to the recipient's plasma
• Major cross-match checks for IgG antibodies (Duffy, Kell, Kidd)
• T&C blood should be reserved for procedures in which transfusion is expected
• Risk of Significant Transfusion Reaction = 1 in 1,000 units transfused
Emergency Transfusion
• It takes 5 minutes to perform a partial cross-match (donor erythrocytes introduced to recipient plasma, centrifuged and observed for agglutination
• Once 2 units of O-negative PRBC are transfused, subsequent transfusions should continue with O-negative blood
Blood Storage• Temperature - 1 to 6 deg
C
• ADP (adenine, dextrose, phosphate)
• Adenine: fuel for ATP production/survival
• "Young blood" - < 14 days is associated with better outcomes.
Decision to Transfuse
• BP, HR, UOP, O2, EKG, AGB, SvO2.
• Hgb <= 6 almost always require transfusion
• Hgb = 8 may be threshold for patients not at risk of ischemia
• Hgb = 10 may be threshold for patients at risk of ischemia (COPD, CAD, rapid bleeding).
• Hgb > 10 g/dl rarely require transfusion
Decision to Transfuse
• Transfusion greater than 10 does not substantially increase O2 delivery
• "The exact Hgb value at which CO increases (compensatory) varies among individuals and is influenced by age, chronicity, and sometimes anesthesia"
Decision to Transfuse
• Hypotension and tachycardia are likely, but may be blunted by anesthesia or other drugs
• Compensatory vasoconstriction may conceal the signs of acute blood loss until at least 10% of blood volume is lost
• Healthy patients may be able to lose 20% of blood volume before signs of hypovolemia occur.
PRBCs• 250 - 300 ml with Hct
~70-80
• Cell Saver - Hct usually ~ 50
• Mix with NS (not hypotonic or LR)
• Ca++ may cause clotting
Platelets• Probably not required unless
platelet count is less than 50,000
• Consider transfusing 1 pooled unit (6 pk) for every 6 units of PRBC in large transfusions
• Bacterial contamination is most likely to occur in platelet concentrates
• Platelet related sepsis incidence is as high as 1 in 5000 transfusions
• Desmopressin 20 mcg may be given for qualitative platelet disorders
Fresh Frozen Plasma• All coagulation factors
except platelets
• Probably not necessary unless PT is > 1.5 times normal or INR > 2
• Warfarin reversal, heparin resistance
• FFP of 10-15ml/kg will achieve 30% of most plasma factor concentrations
Cryoprecipitate• The fraction of plasma that
precipitates when FFP is thawed
• High concentrations of Factor VIII, fibrinogen
• Indicated for Hypofibrinogenemia and Hemophilia A
• Consider transfusion if fibrinogen less than 100 mg/dl
• Not recommended for patients with unstable coronary artery disease because ultralarge vWF multimers released by DDAVP can aggregate platelets and increase risk of infarction
Complications• Hyperthermia, increased airway pressures, and/or
change in urine output/color may be suggestive of transfusion reaction
• Febrile reaction: most common (0.5-1%) as a result of recipient antibodies to donor antigens on leukocytes or platelets
• Allergic reaction: also associated with pruritis and urticaria, bronchospasm
• Slow the infusion and give antipyretics for febrile reaction; give antihistamines, bronchodilators, and stop infusion for allergic reaction
Complications• Hemolytic reactions: typically a
result of wrong blood type
• Lumbar and substernal pain, fever, chills, dyspnea, and skin flushing
• Free hemoglobin in plasma or urine, acute renal failure and DIC occur
• Discontinue transfusion and maintain urine output with IVF, mannitol and lasix
• Alkalinization of urine with bicarb and steroids are of unproven value
Autologous Blood Transfusions
• Predeposited autologous donation (PAD):
• More expensive and not very effective at reducing allogenic blood transfusion
• Patients for elective surgery with high likelihood of transfusion may donate 10ml/kg of blood every 5-7 days if Hgb > 11g/dL up to a maximum of 3 units
Autologous Blood Transfusion
• Infection or malignancy is a contraindication to blood intraop blood salvage (cell saver)
• Normovolemic hemodilution: early intraop donation and intravascular volume replacement with crystalloids to Hct of 27-33%
• Fewer RBC per millimeter of blood loss during surgery
Complications• Incidence of infection from
blood transfusions has markedly decreased
• HCV transmission decreased from 1 in 10 to less than 1 in 1 million transfusions since 1980
• Nucleic acid technology responsible for improved viral testing
• HBV, HTLV, CMV, Malaria, Creutzfeldt-Jakob
TRALI• Non-cardiac exudative
pulmonary edema in the absence of left atrial hypertension that occurs within 6 hours of transfusion
• Exclusion of female donors and fresher blood (< 14 days) decreases risk
• Stop transfusion, send off fluid from ETT, CBC, CXR, and notify blood bank so that other units may be quarantined
Transfusion Related Immunomodulation
• Long-term prognosis in cancer surgery is unclear, but there is a suggestion of a correlation between tumor recurrence and blood transfusions
• Leukoreduction reduces incidence of nonhemolytic febrile transfusion reactions and transmission of leukocyte-associated viruses
• Leukoreduction to prevent cancer recurrence is more speculative
Metabolic Abnormalities
• pH decreases, K increases, and 2,3-DPG decreases with duration of storage.
• Metabolic acidosis and hyperkalemia rarely occur even in massive transfusions
• Less 2,3-DPG increases affinity of Hgb for Oxygen, and potentially decreases tissue oxygen delivery
• Citrate metabolism to bicarbonate may contribute to metabolic alkalosis
• In anhepatic phase of liver transplant, citrate is not metabolized and it binds to calcium in blood causing hypocalcemia
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