Blood Therapy
Should the PRBCs be diluted before administration to ensure rapid infusion?
You can add 60-100 mls of 0.9% saline to help it infuse faster
How is FFP administered?
Must be thawed in water bath with agitation, which can take approx 30 mins. After thawing FFP stored at 1-6 C and must be transfused within 24 hrs. FFP should be administered through a component administration set with a 170 um filter.
What is the incompatibility risk of typed blood, screened blood, and fully cross-matched blood?
99.8% safe, 99.94% safe, and 99.95% safe respectively
Is it necessary to administer ABO-specific platelets?
No because platelet concentrates contains few RBCs. However, the administration of pooled platelet compoenets of various ABO types can transfuse plasma containing anti-A/or anti-B, resulting in human leukoctye antigen (HLA) antibody formation.
What is the relationship between oxygen extraction ratio (02ER) and anemia?
As the Hct decreases below normal, there is a decrease in systemic oxygen delivery, but the O2ER increases which helps maintain a constant oxygen uptake in the tissues. The point at which the compensatory increase in O2E begins to fail corresponds to an O2ER of 0.5 (50%). Many institutions use this value as a transfusion trigger, when this information is available.
What is the cardiovascular effect of acute anemia in an otherwise healthy patient?
Basic CO can rise 5-fold to maintain oxygen delivery. As plasma volume increases, the Hct decreases, resulting in reduction in blood viscosity and PVR. HR does not increase in the absence of hypovolemia. Redistribution of blood flow to the heart and brain occurs with increased tissue oxygen extraction.
How does a healthy heart compensate for anemia during hemodilution?
By redistribution of blood flow to the coronary circulation. Under basal conditions the heart already has a high ER (50-70%)
Which data may be useful in determining a RBC transfusion threshold?
CO, arterial & mixed venous oxygen, and the whole-body ER
What are the potential complications of intraoperative blood salvage (IBS)?
Cost, contamination, removal of essential blood componenets (clotting factors & platelets), and air embolism. 1. Reinfusion of materials that might remain after the washing process such as fat, microaggregates, air red cell stroma, free hemoblobin, heparin, bacteria, tumor, and debris from a contaminated surgical field. 2. Massive air embolism have been reported. 3. Dilutional coagulopathy is associated with large volume IBS because washing removes clotting factors and most of the platelets. DIC-like coagulopathy has also been reported
What is critical oxygen delivery?
Critical oxygen delivery is the point at which oxygen delivery is no longer capable of supporting cellular respiration because ER exceeds a critical threshold, and O2 consumption becomes directly proportional to oxygen delivery. Progressive lactic acidosis results from cellular hypoxia.
What is the difference in volume and components between FFP and cryoprecipitate?
Cryo has much more fibrinogen. FFP (225 ml) contains 1 U/ml of all procoagulants and 3-4mg/ml of fibrinogen. A single donor unit of cryo (10 ml) contains 80-145 Units of VIII, 250 mg fibtinogen, vWF, XIII, and fibronectin
How is cryo prepared and administered?
Cryo is prepared from a unity of FFP. It is the cold-insoluable precipitate that forms when a bag of FFP is thawed at 1-6 C. This cold-insoluable material is removed following centrifugation and immeditaely frozen at -18 C and can be stored for up to 1 year. Cryo must be transfused rapidly and within 4-6 hours of thawing if given to replace factor VIII levels. Units are usually pooled and should be given through a 170 um filter.
What is the formula to calculate oxygen delivery?
DO = CO[(Hb X 1.39)SaO2 + 0.003 PaO2]
What is a massive transfusion?
Defined as the transfusion of blood approximately equal to the total body blood volume within 24 hours. In a normal adult, this is approximately 10 units.
What is ER?
Defines what fraction of the total oxygen delivered is consumed or extracted by the tissues; ER = O2 consumption/O2 delivery. In healthy adults, ER is usually 25%, but may increase to 70-80% during maximal exercise in well-trained athletes.
How are platelet pheresis units prepared?
Donating plasma - returns RBCs while siphoning all the plasma
How should dilutional coagulopathy from massive packed cell transfusion be treated?
During massive transfusion of PRBCs, patients receive only a small residual plasma volume (50 ml), which contains clotting factors. Investigations of patients receiving large-volume isovolemic transfusion suggest that clinically significant dilution of fibrinogen; factors II, V, & VIII; and platelets will occur after volume exchange of approximately 140%, 200-230%, and 230% (1.4, 2, 2.3 blood volumes) respectively. Resusitation from hypovolemia will result in reaching these thresholds at small percentage volume exchanges. Treatments include cryoprecipitate (fibrinogen), FFP (clotting factors), and platelet transfusions.
What is the rational for acute hemodilution?
During surgery, the patient will lose blood at a lower hematocrity and the fresh whole blood withdrawn immediately prior to surgery will be available for reinfusion. This procedure may reduce total red cell volume loss, enhance maximum allowable blood loss before blood transfusion, as well as reduce the need for transfusion of allogeneic blood.
What is the most common complication of massive transfusion?
Traditional answer: dilutional thrombocytopenia. In current practice, this may not be true when PRBCs are used for massive transfusion. It has been shown that co-ag factors [FFP] are necessary after 12 U, and platelet therapy is required after receiving 20 U PRBC.
Describe the process of intraoperative autotransfusion.
Intraoperative autotransfusion is defined as the reinfusion of patient blood salvaged during the operation. Red "cell savers" collect and anticoagulate the salvaged blood with citrate or heparin as it leaves the surgical field, filter to remove debris and clots, wash with saline, and concentrate RBCs by centrifugation, and the concentrate is then reinfused to the patient suspended in saline in aliquots of 125-225 ml with an Hct of 45-65%
Which solutions are considered "incompatible" with PRBCs?
LR (theoretical clot formation due to calcium) and 5% dextrose in water and 0.2% saline and pasmanate
What is the normal blood volume in adults, children, infants, and neonates?
Men 75 Women 65 Infants 80 Full-term neonates 85
What is the most common blood group? What percentage of the population is Rh positive?
Most common is O. 45% of caucasians, 49% African Amers, 79% American Indians, & 40% of Asians are blood type O. Approximately 85% of the population is Rh positive.
Which clotting factors are most likely to be decreased as a result of massive transfusion?
Factors V & fibrinogen. With the use of PRBCs, fibrinogen levels decrease significantly in contrast to the use of whole blood, in which fibrinogen levels remain unchanged unless DIC is present. Factor VIII is probably stored in endothelial cells and released during surgical stress.
What are indicators of inadequate oxygen delivery to tissues?
Hypotension, decreased urine output, and altered mental status. Laboratory indicators include acidosis, worsening base deficit, anion gap, and lactate levels.
What are potential problems with massive blood transfusion?
Hypothermia, thrombocytopenia, hypokalemia, hyperkalemia, dilution of clotting factors, acidosis, ARDS, pulmonary edema, hypocalcemia, hypomagnesemia, hepatitis, or other infectious diseases
What are the three phases of type and crossmatch of blood?
Immediate, incubation, and antiglobulin. 1. The 1st phase combines recipient serum and donor cells to test ABO group compatibility at room temp. Also identifies MN, P, and Lewis incompatibilities (approx 5 mins). 2. 2nd phase - incubates the products from the first in albumin at 37 C, enhancing incomplete antibodies. This phase primarily detects antibodies in the Rh system. 3. The last phase is the indirect antiglobulin test. Antiglobulin serum is added to the previously incubated test tubes. This phase aids in the detection of incomplete antibodies in Rh, Kell, Duffy, and Kidd systems.
How much does the transfusion of 1 U of platelets increase the platelet count?
In an adult, 1 U of platelet concentrate generally increases the platelet count by ~ 5,000-8,000/mm3
In isovolemic hemodilution, what mechanisms serve to maintain oxygen delivery?
Increase in CO, redistribution of blood flow to organs with greater oxygen requirements, increased O2 extraction, and decreased hemoglobin O2 affinity.
What is the reason for decreased hemoglobin O2 affinity in anemia?
Increased 2,3 DPG. In chronic anemia, increased oxygen extraction by tissues produces increased concentration of deoxygemoglobin in the RBC, which stimulates the production of 2,3 DPG and lowers the affinity of hemoglobin A for oxygen
What causes coagulopathy in massively transfused patients?
Multifactoral etiology: dilutional thrombocytopenia, depletion of co-ag factors (V, VIII, & fibrinogen), and DIC. Risk factors include the volume of blood given and the duration of hypotension and hypoperfusion. Hemolytic transfusion reaction also causes coagulopathy and should be considered.
What happens to the oxygen transport during hemodilution?
Over a wide range of hematocrits, isovolemic hemodilution is self-correcting. The decrease in carrying capacity is matched by improvements in oxygen transport due to improved blood flow to the tissues.
A patient's oxygen delivery is impaired by severe anemia. What are the compensatory mechanisms?
Oxygen delivery is determined by arterial oxygen content and CO. In severe anemia, arterial O2 content is decreased. The compensatory mechanisms are to increase tissue oxygen extraction and CO.
How is platelet concentrate prepared and how many platelets are in a platelet transfusion?
Platelet concentrate is prepared from whole blood within 8 hours of collection. AFter the collection of approximately 500 ml of whole blood into collection bags containing citrate based antico-ag preservative solution, the blood is centrifuged. Following centrifugation, the PRP is separated into an attached empty satellite bag. This PRP is centrifuged and separatedinto 1 U platelet and 1 U plasma. Each unit of platelets contains ~ 5.5 X 10^10 platelets in 50-70 mL of plasma. An adult dose pack of platelets contains 6-7 U of platelet concentrate.
How are platelets administered?
Platelets may be stored at room temp for up to 5 days with continuous gentle agitation to prevent aggregation. Must use a 170 um filter.
List 3 ways of collecting autologous blood for transfusion?
Predonation, intraoperative isovolemic hemodilution using blood withdrawal & simultaneous volume replacement with cell-free subsititutes, and perioperative blood salvage during and immediately after surgery
How is FFP prepared?
RBCs removed from whole blood, then remaining platelet-rich plasma (PRP) separate into platelets & plasma. FFP is frozen within 6 hours of donation.
What are the relative contraindications to autologous blood donation?
Severe aortic stenosis, severe left main coronary artery disease, hypertrophic cardiomyopathy, active bacterial infection, or low blood volume.
What is a type & screen and how is it performed?
Type and screen is ABO-Rh typing and antibody screening. ABO typing is performed by testing RBCs for A and B antigens, and the serum for A and B antibodies. Recipient serum is mixed with commerically type O RBCs and incubated. If no agglutination is observed, the screen is negative. If the screen is positive, serum is tested using selected reagent RBCs to identify the antibodies present.
How can you estimate blood volume to be removed preoperatively when you are using normovolemic hemodilution/autotransfusion technique to reduce the loss of red cells intraoperatively?
V = EBV [(Hct i - Hct f)/Hct avg] where V is the volume to be removed
What is the effect of normovolemic hemodilution to a hematocrit of 28% from 41% on HR, BP, and CO in healthy elderly patients?
Stroke volume increases with HR, and BP remains unchanged. Venous return, right atrial pressure, and CO are increased secondary to decreased viscosity & SVR and increased contractility. There is a reduction in O2 delivery as a result of the failure to fully compensate for lowered O2-carrying capacity by an increased CO. O2 delivery is max'd in the hematocrit range of 35-45%.
What should be done if the type and screen report indicates screen positive?
The blood bank performs and antibody identification, and sets aside 2 RBC U that lack the corresponding antigens. This is done in advance of surgery.
What is the primary reason for increase in CO with isovolemic hemodilution?
The rise in CO is related mainly to decrease in blood viscosity and enhanced sympathetic stimulation. As Hct decreases, a reduction in viscosity causes a decrease in PVR and increase in SV, so that CO rises without an increase in blood pressure
What values may indicate significantly impaired oxygen delivery?
There is no safe level of mixed venous oxygen, but acutely ill patients are at risk when SVO2 <0.6-0.65 and O2ER exceeds 65-75%. Reduction of total oxygen consumption <50% indicates significantly impaired oxygen delivery. Blood lactate concentration is an unreliable indicator of tissue hypoxia.
What is acute normovolemic hemodilution (ANH)?
This is a point-of-care method of autologous blood procurement. The term ANH refers to the removal of blood from a surgical patient immediately before or just after induction of anesthesia (1-1.5 L, to a hematocrit of 27-33%), and replacement with asanguinous fluid to maintain normovolemia. The removed blood is stored a CPD bag at room temp up to 6 hours to preserve platelet function and later reinfused. ANH is employed to reduce the need for allogeneic blood and to avoid potential transfusion associated complications. An additional potential advantage of ANH is improvement in tissue perfusion as a result of decreased viscosity. The presence of malignancy or wound infection may contraindicate blood recovery during surgery (cell saver), but not ANH.
