Keywords
autologous platelet-rich plasma - cell saver - patient blood management - retrograde autologous priming - autologous blood transfusion
Introduction
In 2019, approximately 10.85 million units of whole blood and red blood cell (RBC) units and more than 2.2 million apheresis and whole blood-derived platelet units were transfused in the United States.[1] While blood donors have declined, the blood supply and demand are narrowing. In addition, allogeneic blood transfusion-associated complications are becoming a major concern. It is common for aortic surgeries to require more blood transfusions due to cardiopulmonary bypass (CPB), as it requires anticoagulation with high doses of heparin and causes hemodilution, systemic inflammation reaction, and hypothermia. Patients undergoing ascending aorta and aortic arch repair may require massive blood transfusions due to deep hypothermia circulatory arrest (DHCA) and prolonged interactions with CPB. Changes of both quality and quantity of coagulation factors and platelets trigger coagulopathy and bleeding after CPB. Emphasizing and addressing blood conservation is always required. Patient blood management (PBM) not only reduces blood transfusions but also improves clinical outcomes. Its goal is to maintain an adequate hemoglobin level for oxygen carrying capacity, improve and accelerate hemostasis, minimize blood loss, reduce allogeneic blood transfusion and transfusion-associated complications.
PBM is a multidisciplinary, perioperative strategy. It involves the three perioperative periods: (1) preoperative management of RBC volume, correcting anemia, holding anticoagulation and antiplatelet medications, and optimization of coagulation abnormalities; (2) intraoperative management of minimizing blood loss with surgical techniques, coagulation and anticoagulation, hemodilution transfusion strategies, prevention and therapy of fibrinolysis with tranexamic acid, auto-blood transfusion, and surgical hemostasis; and 3) Postoperative management of avoiding unnecessary iatrogenic blood loss, such as excess blood draws.[2]
Autologous blood salvage is recycling patient's blood in the surgical field or purposed removal of patient's circulating blood temporally, reinfusing it back to the patient at the conclusion of surgery. Autologous blood salvage significantly reduces blood bank transfusions and does not produce red cell antibodies from alloimmunization. Autologous blood transfusion is one of the most effective and important methods of blood conservation used in cardiac and major aortic surgeries. Its primary goal is to reduce (or avoid) allogeneic blood transfusion (and associated transfusion complications), improve clinical outcomes and reduce blood shortage and healthcare costs.
There are many advantages of auto blood donation/transfusion. These include: 1) Prevents transfusion transmitted disease; 2) Prevents red cell alloimmunization; 3) Preserves the resource of blood donors; 4) Protects patients' own blood components and alloantibodies; 5) Prevents some adverse transfusion reactions; and 6) Is more cost-efficient than allogeneic blood.
Disadvantages include: 1) Risk of bacterial contamination; 2) Wastage of blood not transfused; 3) Can cause perioperative anemia and increase likelihood of transfusion; and 4) Acute anemic induced organ ischemia.
Current intraoperative autologous blood conservation techniques include autologous cell salvage, autologous platelet-rich plasma (aPRP), acute normovolemic hemodilution (ANH), and retrograde autologous priming (RAP).
Autologous Blood Salvage as Cell Salvage/Cell Saver
The first auto blood transfusion was reported by Highmore for postpartum hemorrhage in 1874.[3] Since the concept of autologous blood transfusion was first introduced, there has been great research and development of technologies focused on safety, feasibility, popularity, convenience, and cost effectiveness. Haemonetics (Braintree, Massachusetts) introduced the “cell saver” in 1974, the first commercial device for open surgery that collects blood from the surgical field and reinfuses those RBCs back to that patient. There are several cell saver devices used perioperatively today. The most popular are the Cell Saver Elite® (Haemonetics, Braintree, Massachusetts), Sorin Xtra® Autotransfusion System (UK), the autoLog® Autotransfusion System (Medtronic, Santa Rosa, California) and the C.A.T.S.® plus Continuous AutoTransfusion System (Germany).
Core Mechanism of Cell Salvage Devices
Cell saver utilization begins at the time of surgical incision and continues until the end of surgery. ([Fig. 1]) It must be used during CPB, which is replaced by pump suction. Collected blood from the surgical field is collected by suction catheter and sent to a reservoir with continuous flow of anticoagulant fluid to prevent the suctioned blood from clotting. Then, mixed with anticoagulant, the shed blood (heparin or citrate) in the reservoir is washed and concentrated by the cell saver, which can recycle between 55–70% of RBCs in each surgery.[4]
Fig. 1 Timeline of open-heart surgery. The time of each autologous blood conservation technique is different. Abbreviations: ANH, acute normovolemic hemodilution; aPRP, autologous platelet rich plasma; CPB, cardiopulmonary bypass; CVICU, cardiovascular intensive care unit; DHCA, deep hypothermia circulatory arrest; GA, general anesthesia; RAP, retrograde autologous priming.
Several sizes of volume of the centrifuge bowl are commercially available with a conical- or cylindrical-shaped centrifuge chamber. Centrifugal forces at 5,000 rpm for cell saver processing separate RBC from plasma and wash solution. Common bowl sizes are 225–250 ml for adults, with smaller bowls at 125 ml. The smallest is 55–57 ml for pediatric surgery.
Processing 225 ml of cell saver blood requires 500–750 ml of shed blood. The 125 ml cell saver requires 250–400 ml of shed blood for adequate filling. In other words, processing 225 ml of the patient's own RBC, as one unit of cell saver, will lose 250–500 ml shed blood into the waste bag. Substantial volume deviations are due to differences in patient RBC volume. Unfortunately, all coagulation factors, platelets, plasma proteins and other plasma contents are unable to be retrieved and are washed out into the waste bag.
Hemolysis may accrue due to over-suction force of the suction tip. If sterile unbalanced solution is used for surgical washing, hemolysis can be severe. In addition, residual heparin is often mentioned as a risk of giving too much salvaged blood. Studies show that 99.8% of the heparin is removed in the wash process.
Indication and Contraindication
Intraoperative cell saver has become a requirement in most open cardiac surgeries and major aortic surgeries to decrease risk of exposure to allogeneic transfusions. It is one of the most important methods of blood conservation. It starts after surgical incision and ends upon completion of surgery. Collected blood can be returned to the CPB-pump reservoir during the CPB. ([Fig. 2]) Cell salvaged blood does not induce immunological challenges to patients, and recycling their own concentrated and functional RBCs back can reduce allogeneic blood transfusion. Cell salvaged blood can be stored at room temperature for a short time in the operating room, if RBCs are not immediately needed.[4] Cell salvage is especially important for patients with rare blood types or Jehovah's Witnesses, who do not accept allogeneic blood transfusion. (Most Jehovah's Witness patients accept CPB and intraoperative cell saver.) In these cases, the modification of circulatory system between cell saver and the patient must be established.
Fig. 2 Diagram of intraoperative cell saver, the preservation of the patient's own red blood cells.
There are situations that require special precautions while significant infection with septicemia is rare in surgical patients, there is evidence that a leukoreduction filter can reduce the bacterial load by 98–99%.[5] In general, the benefits and risks of cell salvage are dependent on the patient's medical condition and the type of surgery. Careful cell washing combined with leukoreduction filters is safer in many circumstances.
RBC quality with cell saver blood has always been questioned. Quality measures in comparing salvaged RBCs and banked RBCs were summarized by Frank and colleagues.[6] The salvaged RBCs have normal levels of 2, 3-DPG, with a normal hemoglobin-oxygen dissociation curve.[7] Increased RBC membrane deformability, and lower level of hemolysis and red cell fragility, are achieved when limited lower surgical suction forces used (<150 mm Hg).[8] Also, free hemoglobin level from cell saver blood cells is lower than stored RBC (1% threshold regulated by FDA). Both cell saver blood and banked RBCs can reach an average hematocrit of 55–70%.
Benefits and Disadvantages
The benefits of using cell saver are that it reduces allogeneic blood transfusion and avoids transfusion-associated complications, such as transfusion-transmitted infections, transfusion reaction, anaphylaxis, acute lung injury, acute or delayed hemolysis, alloimmunization, immunosuppression, hyperkalemia, hypocalcemia, acid-base disturbance, coagulopathy physical hypothermia, microembolism, air embolus, circulatory overload, and iatrogenic administration of incorrect blood. Cell salvage is an important technique in current PBM, among multimodal methods used to reduce allogeneic transfusion.
Significant disadvantages of cell salvage include loss of clotting factors and platelets. Cell salvage saves RBC from collected whole blood. Theoretically, the more cell saver RBC received, the more coagulation factors and platelets are lost, the more bleeding, and the worse coagulation. Therefore, when large amounts of salvaged blood are transfused, hemodilutional coagulopathy may be induced, worsening the bleeding due to a deficiency in clotting factors. Platelet insufficiency then begin to occur after approximately one-half the patient's blood volume has been shed and processed.[9] Eventually, the patient needs more transfusion of platelets, fresh frozen plasma, or replacement of other sources of coagulation factors. ([Fig. 2]) There are safety concerns in cases with gross bacterial contamination in the cell saver circuit system.[6]
In summary, for open heart and major aortic surgeries, it should be the routine to use cell salvage to minimize allogeneic blood transfusions. This is an important blood conservation strategy in PBM. However, with reinfusion of washed erythrocytes of more than 4 units (225ml/unit) of cell salvaged blood, coagulopathy from loss of coagulation factors and platelets and by reinfusion hemodilution must be considered.
Mortified Cell Salvage Techniques
The mortified cell saver technique ([Fig. 3]) is designed for open thoracoabdominal aortic aneurysm (TAAA) repair with active left heart to distal aortic shunt techniques. These procedures may be accompanied by massive blood loss in a short period. The average cell saver volume for TAAA II and III procedures is 45–65 units at our institution, which includes more than 1,000 cases. The maximum recorded was 208 units. Blood volume replacement is critical to maintaining hemodynamic stability and oxygen-carrying capacity for preventing organ hypoperfusion and ischemia. In this situation, there is no time to wash out collected blood from the surgical field and return it to the patient to maintain effective blood volume intraoperatively. Also, it is unrealistic to solely use blood from the blood bank, and poor clinical outcomes are associated with large volume allogeneic blood transfusion. Last, with mortified cell salvage washout occurs of all the clotting factors, platelets, and other plasma components, which are necessary for hemostasis and blood colloid osmotic pressure and electrolytes balance, as well as immunoglobins against infection.
Fig. 3 Diagram of mortified cell salvage technique. Partial bypass as active left heart to distal aortic shunt. Cell salvage devices combine cell saver with fluid management system (FMS). Blood is collected from the surgical filed, runs through a 40-μm screen filter on the cell saver, and is directly sent postfiltering to FMS reserve with the second filter, warming, and then deairing before transfusing back to the patient.
The core mechanism of mortified cell salvage devices combines cell saver with the fluid management system (FMS). Blood is collected from the surgical field, flows through the 40 μm screen filter on the cell saver, and postfiltered blood is sent directly to FMS reserve with the second filter, warming, and de-airing before transfusing back to the patient. The system uses citrate for the anticoagulant so that calcium replacement is needed.
Overall, the mortified cell saver is a great blood conservation technique for persevering all plasma components and reducing allogeneic blood transfusion.
Retrograde Autologous Priming (RAP)
Retrograde Autologous Priming (RAP)
Hemodilution is a major risk factor for perioperative anemia and perioperative transfusions. All current blood conservation guidelines strongly recommend implementing strategies to minimize hemodilution during cardiac surgery. These strategies may include the use of miniaturized CPB circuits (mini-circuits) with decreased priming volume, RAP of the CPB circuit, and modified hemofiltration. RAP of the CPB circuit is not a new technique and is very much time-restricted. The purpose of RAP in clinical practice is to avoid further hemodilution when full flow pump has begun. It is most beneficial for small body surface areas using the RAP technique to avoid significant hemodilution and to reduce the risk of using RBC as primer to avoid acute anemia.[10] A review of published reports identified small body size (low preoperative RBC volume) is associated with increased intraoperative blood transfusion. An evidence-based review[11] in adult patients with CPB suggests that reducing hemodilution during open heart surgery, including reduction of prime volume, is valuable in reducing allogeneic blood transfusion. Many meta-analyses have concluded that RAP significantly reduces allogeneic blood transfusion by avoiding hemodilution.
A minority of patients having cardiac procedures (15–20%) consume more than 80% of the blood products transfused at operation.[12] Blood must be viewed as a scarce resource that carries risks and benefits. Many preoperative and perioperative interventions are likely to reduce bleeding and blood transfusion.
Core Mechanism of RAP
As a blood conservation technique, RAP is an efficient, well-tolerated and inexpensive technique that reduces intraoperative allogeneic red cell transfusion in cardiac surgical patients.
First described in 1960 by Panico and Neptune,[13] the modifications of RAP technique of the CPB circuit were popular until the late 1990s. The RAP technique varies, depending upon the pump configuration and the CPB circuit design, which vary at different centers. The RAP technique describes retrograde direction prime displacement through the aortic cannula and an antegrade direction of prime displacement.
RAP starts when activated clotting time reaches more than 400 seconds after heparin has been administered. Approximately 150–200 ml of the patient's blood from the aorta is used to replace the priming solution after ascending aorta cannulation is completed. Then, venous blood slowly drains from the connected IVC/SVC cannula line. The venous side of the circuit is drained slowly, replacing the crystalloid priming volume by filling the circuit with the patient's blood. The time for retrograde priming procedure is ∼3–5 minutes before the onset of full CPB. During this time, it is important to maintain a constant level in the venous reservoir and patient hemodynamic stability with careful hemodynamic monitoring. Arterial blood gas analyses are needed to closely monitor hemoglobin (Hb)/HCT concentration and lactate level.
RAP admitted with BSA <1.5 m2 in small adult patients has significant benefits in reducing over hemodilution on CPB, as well as subsequent hemodilution-inducing coagulopathy and bleeding to achieve the goal of reducing total blood transfusion.[14] In addition, the RAP technique also benefits patients with BSA of more than 1.7m2, as it can be used safely on a wide range of patient sizes.
Benefits and Disadvantages
There are several concerns regarding potential for hypotension and concomitant need for vasopressors during the removal of the blood volume during RAP processes to maintain normotension. Some cases may need termination of RAP, due to hemodynamic instability. Although hypotension associated with RAP occurs transiently, it may increase risk of organ malperfusion, resulting in acute kidney injury, stroke, or myocardial injury, with long-term impact.
In summary, RAP and antegrade autologous priming should be considered as part of a blood conservation strategy in cardiovascular surgery during CPB to avoid hemodilution and reduce allogeneic blood transfusions.
Acute Normovolemic Hemodilution (ANH)
Acute Normovolemic Hemodilution (ANH)
ANH is a blood conservation strategy aimed at avoiding the use of allogenic blood products, decreasing allogeneic blood transfusion, and preventing blood borne diseases and transfusion reaction. ANH is often combined with all other techniques in blood conservation practice. It requires the adoption of a standardized, multidisciplinary blood transfusion policy. ANH is appropriate for selected patients with normal initial hemoglobin levels who are expected to lose two or more units of blood (typically ≥1000 mL) during surgery. The technique is also focused on the patient safety. Meta-analysis, including the largest cardiac surgery population, demonstrate a reduction of RBC transfusion compared with standard care in cardiac surgery, CABG, and valve surgery.[15] Compared with RBC from the blood bank, ANH is drawn from patient's own whole blood and contains both of RBC and hemostatic capacity.
Core Mechanism of ANH
ANH as a blood conservation technique was first used in 1946. It became widely used in clinical practice as far back as the 1970s, when it was described in detail by Stehling and Zauder.[16]
[17] It was initially used in cardiac surgery but later expanded to other surgical fields, such as orthopedic, vascular, neurologic, and thoracic. The ANH technique involves hemodilution, which is characterized by an increase in cardiac output and decrease in total peripheral resistance and blood viscosity, reflex vasodilation, and changes in the regional regulation of blood flow. It improves tissue perfusion and oxygenation and may be useful in the management of cross-clamping hypertension,[18] compared with cell saver, which lacks some of the potential benefits of ANH, such as reduced risk of suction-induced hemolysis and transfusion of autologous whole blood. However, questions remain as to whether ANH usage truly benefits the high-risk cardiac patient population.[19]
[20]
ANH involves the removal of whole blood shortly after induction of anesthesia and large bore of central venous cannulation, established before surgery. At the same time, an equivalent volume of balanced solution (crystalloid and/or colloid fluid) is replaced to compensate acute circulation volume loss and to maintain normovolemia. The appropriately diluted blood reduces the loss of components of blood during surgery. ANH technique is also used to reduce blood viscosity during CPB and improve blood flow, thus overcoming hemodilution and the lowered blood oxygen-carrying capacity.
Whole blood collection is from a large bore central venous catheter, draining by gravity by placing the blood collection bag below the patient's body under the operation table. The collection bag is pretreated with citrate-phosphate-dextrose solution to prevent blood clot formation.
The amount of autologous blood collected, from a volume of 270–600 ml, is dependent on the patient's red blood volume and systemic medical condition. The whole blood collection bag with anticoagulant is stored in the operating room at room temperature and re-transfused to the patient at the end of surgery after surgical bleeding is controlled.[21] Replacement calcium is necessary when using citrate-anticoagulant induced hypocalcemia.
Indication and Contraindication
The indication should be very restrictive for the ANH technique, depending on patients' RBC volume and predicted estimate blood loss. Most anesthesiologists perform ANH with preoperative Hct >33%, PLT >100 × 109/L, normal prothrombin time PT, PTT, and normal cardiopulmonary function.[10]
Safety and Efficacy of ANH
ANH technique is used only in healthy adults having surgery with anticipated blood loss. It can effectively reduce intraoperative blood loss due to hemodilution and sparing small volume of whole blood. It has also proven safe and useful for cancer surgeries.[20] However, ANH is limited in cardiovascular patients with preexisting medical conditions, especially cardiac and renal function.
Underlying infections, such as endocarditis, also may not be suitable. Hemodynamic stability must be closely monitored during blood harvest and effective volume replacement accomplished. Inadequate management of the hemodilution technique will increase risks of organ malperfusion and organ ischemic injury. In open heart surgery, additional hemodilution with the primer of CPB can lower hemoglobin further, which can cause hemodynamic instability and organ ischemia. The efficacy of ANH in decreasing allogeneic blood requirements remain controversial during cardiac surgery. Höhn and colleagues in a prospective, randomized study in 2000, suggested that hemodilution is not an effective way to reduce allogeneic blood transfusion in elective cardiac surgical patients compared with using standard, intraoperative cell saving combined with antifibrinolytic medication.[22]
[23]
[24]
Advantages and Disadvantages
ANH advantages include: 1) Hemodilution by crystalloid or colloidal liquids reduces the blood concentration in total blood circulation volume during surgery; 2) It can preserve fresh whole blood, in which not only RBC but also platelet function and coagulation factors and other blood components are spared from surgical damage, and medications affect; 3) Collection and transfusion of ANH are a simple operation, cost effective, with easy storage—and ANH can be performed safely under the direction of the cardiovascular anesthesiologist; and 4) For a special population of patients, ANH is particularly suitable, such as patients with Rh D negative traits, difficulty in crossmatching blood due to irregular antibodies, and difficult ABO blood typing.
ANH disadvantages include: 1) Hypovolemia-induced hemodynamic instability, requiring the administration of large volumes of crystalloid; 2) Risk of bacterial contamination and clotting in the collected bag; 3) Inadequate anticoagulant; 4) Increased likelihood of transfusion due to perioperative anemia and factors such as platelet hemodilution; 5) Acute anemia-induced organ ischemic; 5) Inadequate amount of coagulator factors and platelets for hemostasis; and 6) Wastage of blood from not being transfused.
For patients undergoing cardiac surgery requiring CPB, ANH results in significant improvements of activated partial thromboplastin time, fibrinogen, and hemoglobin values. However, the true clinical significance is questionable. In the absence of ongoing surgical bleeding, there appears to be normalization of coagulation tests (excluding fibrinogen) following CPB.
In summary, combined with intraoperative cell saver, ANH effectively prevents postoperative bleeding and anemia. It also provides a safe and effective autologous transfusion method as one of the options in cardiac surgery. However, the ANH technique for patients with high RBC volume and relatively normal cardiac function offers limited benefit in cardiac surgery.
Autologous Platelet-rich Plasma (aPRP) Harvest Technique
Autologous Platelet-rich Plasma (aPRP) Harvest Technique
The cell saver preserves RBCs only and loses all other blood components during the process. This technique alone could induce coagulopathy, due to the loss of coagulate factors and platelets. The ANH technique has limitations for cardiac surgery, even if it can preserve whole blood with hemodilution strategies to reduce blood loss and blood transfusion.
aPRP is modified from ANH and focuses on reserving coagulation components and restoring hemostasis after surgery. During aortic arch repairs, the aPRP technique includes true blood protection and blood component-sparing strategies to prevent issues, including systemic inflammation reaction from surgical trauma stimulation and platelet, complement activation, cellular activation during PUMP, cell injury from cardiotomy suction, hemolysis, heparin administration, and deep hypothermia.
The use of aPRP in cardiac surgery was first reported by Harke in 1977.[25] A decade later, Ferrari used aPRP via perioperative plasmapheresis, demonstrating reduced blood loss and need for allogeneic blood transfusions.[26] However, withdrawal of aPRP by plasmapheresis was cumbersome and expensive, requiring additional personnel. Ferrari analyzed the use of aPRP and demonstrated a benefit for those with high-risk of bleeding.[27] Since that time, others have reported conflicting results in the use of aPRP during cardiac surgery.[28]
[29]
[30]
[31]
[32]
In the late 2010s, Zhou and colleagues presented a study with high-risk patients undergoing ascending and transverse arch aortic repair or type A aortic dissection surgery using DHCA.[33] The use of aPRP was associated with less acute renal failure, decreased length of stay, and lower transfusion costs.[32]
[33]
[34] We adopted and, subsequently modified the use of aPRP as a component of our intraoperative blood conservation program during complex aortic surgery, such as ascending and transverse arch repair, using profound hypothermic circulatory arrest (PHCA).
Complex aortic surgery is often associated with bleeding, requiring transfusion of blood products. The need for transfusions can be attributed to thrombocytopathy as well as coagulation factor deficiencies associated with prolonged CPB and profound hypothermia. In addition, PHCA used during these repairs is associated with thermal dysregulation of the coagulation system, contributing to the coagulopathy. Traditional blood transfusion therapy is associated with adverse effects directly proportional to the amount transfused. Transfusion-related complications include allergic, anaphylactic, and hemolytic transfusion reactions, transfusion-related acute lung injury, transfusion-associated circulatory overload, acute respiratory distress syndrome, and ventilator-associated pneumonia, which can lead to significant morbidity and mortality after cardiac surgery.
Core aPRP Harvest Technique
Compared with ANH reserved whole blood, aPRP is focused on preserving coagulation factors and platelets and all the plasma components, except RBC. The harvest process includes harvesting whole blood, separation of whole blood into RBC and aPRP, volume replacement to maintain normal circulation volume, and transfusion RBC back to patient to harvest more aPRP volume.
Physiological volume compensatory mechanisms are smoother than ANH by reinfusion of RBC to avoid acute anemia-induced inadequate oxygenation at the tissue level and organ hypoxic injury, with the goal to avoid acutely reducing RBC concentration. Hematocrit changes are not significant. Cell savage and antifibrinolytic medications were used for standardized, intraoperative blood conservation techniques in all patients.
Currently, the collection of aPRP has been greatly simplified with a centrifugation process, using already present cell-saving devices. After administration of general anesthesia, we establish central venous access and place hemodynamic monitors including arterial line, a pulmonary artery catheter, and cerebral oximetry and perform transesophageal echocardiography (TEE). A balanced solution is given for volume replacement to maintain hemodynamic stability during aPRP harvest. About 300 ml (the centrifuge bowl capacity) of whole blood is collected from a large bore central venous access by gravity drainage. The collection bag is pretreated with citrate-phosphate-dextrose anticoagulant to prevent blood clot formation. Collected whole blood is then processed by an autologous transfusion system (Sorin Electa Essential, Sorin Group, Milan, Italy) into an aPRP and RBC components in the operation room. ([Fig. 4]) The RBC can be re-transfused back to the patient at any time to harvest more aPRP by repeating this process. The goal yield of aPRP is 5–10 ml/kg. The aPRP component is then stored at room temperature in a citrate containing bag. This process can be started after establishment of central venous access and is completed before surgical incision without increasing the operative time. The mean amount of aPRP collected for later infusion is 714 ± 184 ml. After aPRP collection, the autologous transfusion system is utilized for intraoperative cell salvage. There are no additional costs required as aPRP contains the patient's own coagulation factors, platelets, and all other cells and components, which has great hemostasis capacity.
Fig. 4 Autologous platelet-rich plasma (aPRP) separation diagram. Diagram of aPRP harvest technique focused on hemostasis and coagulation.
Indication and Contraindication
Indication and Contraindication
Indications for aPRP are surgeries with high risk of inducing coagulopathy, which would require additional blood transfusion. aPRP is always combined with cell saver for adult patients, age 18–80, with hemodynamically stable conditions and appropriate red blood volume with Hb >10 or Hct >30. Also included are patients who have not been exposed to heparin and are not on anti-GPIIb/GPIIIa agents (such as: Clopidogrel) for at least 3 days. A contraindication is patients with severe aortic stenosis, who are volume dependent for maintaining cardiac output. Great attention must be paid to avoid hypotension and organ ischemia. Patients with end-stage renal disease may have impaired platelet function. Therefore, aPRP may be chosen to preserve coagulation factors and plasma components. Contraindications include patients who have evidence of systemic infection, ASA classification of V or E, a known coagulation disorder, ventricular assist device, or trauma with multiple organ injuries and severe anemia (Hb < 8).
Safety of aPRP
The aPRP technique involves acute removal of patient blood volume. It can be performed in stages of 300ml each time, with extended, continuous hemodynamic monitoring. Invasive arterial pressure, central venous pressure, pulmonary artery pressure and continuous cardiac output measurement (pulmonary arterial catheter) and mixed venous O2 saturation (SvO2), ECG monitor (lead II and V5) with ST-segment analysis, urine output and cerebral oximetry and TEE are necessary. Arterial blood gas analysis for monitoring hematocrit and arterial lactate is performed, as needed, and intravenous replacement with balanced solution is preferred to maintain hemodynamic stability during aPRP harvest.
Advantages and Disadvantages
Advantages and Disadvantages
Blood transfusion is a balance with both risks and benefits. aPRP is one of the techniques within the blood conservation program which focuses on hemostasis by conservation of factors and platelets. Over the years, it has proven beneficial in reducing allogenic blood transfusions when used in combination with intraoperative cell saver (save RBC only) during cardiovascular surgery, especially complex aortic surgery using DHCA. However, low-risk surgical patients who have a low risk of needing blood transfusion are least likely to show great benefit from aPRP infusion.
A potential risk of PRP harvest is related to the harvesting procedure itself. The technique requires careful separation of fresh whole blood into components, maintaining closed circuit to prevent contamination, and anticoagulation in correct dosage to prevent clot formation and avoid citrate-induced hypocalcemia. Replacement of calcium is usually necessary after aPRP transfusion.
In summary, the use of aPRP reduced the use of allogenic blood transfusions by quickly restoring hemostasis at the conclusion of surgery. This meant less bleeding and reduced blood and blood product transfusion during ascending and transverse arch repair using PHCA. Overall, aPRP has proven to be a safe, time-saving, and cost-efficient blood protection and blood component-sparing strategy.
Conclusion
Intraoperative autologous blood transfusion techniques remain an important method in blood conservation strategies, as well as an effective and efficient tool in reducing allogeneic blood exposure in specific high-risk aortic surgeries. Intraoperative cell savers are considered a cost-effective tool for most cardiovascular procedures or other surgeries in which substantial blood loss is expected (>500 ml.) Although intraoperative blood conservation strategies have significant effects in reducing blood transfusions, safety issues remain. Further studies are warranted to deliver the most value to patients.
