Chapter 24 - Blood Therapy

Seth Christian, MD MBATulane Anesthesiology

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)

Practice Guidelines for Perioperative Blood Transfusions and Adjuvant Therapies

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• RIsk of fatal outcome due

to blood transfusion is remote but possible.

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