Glossary of Blood Management Terms

Index: A | B | C | D | E | F | G | H | l | K | L | M | N | O | P | R | S | T | V | Z |

A [TOP]

AABB: The American Association of Blood Banks is a knowledge-based organization that is focused on improving health through advancing the science and practice of transfusion medicine and cellular therapies to optimize patient and donor care and safety.

ABCP: The American Board of Cardiovascular Perfusion is the certifying body for cardiovascular perfusionists in the United States.

Acute Normovolemic Hemodilution (ANH): Acute normovolemic hemodilution (ANH) is a blood conservation modality used in the operating room by anesthesiologists. Whole blood is drained by gravity into blood collection bags containing anticoagulant. As blood is collected, asanguineous fluid, either colloid and/or crystalloid, is infused to maintain hemodynamic stability and “normovolemia.” This process tends to dilute the patients’ blood, hence the term “hemodilution.” On completion of the surgical procedure, the patient’s whole blood is reinfused. Other terms used are acute isovolemic hemodilution and intraoperative autologous donation (IAD). ANH creates a personalized blood bank for patients, since fresh whole blood contains red blood cells, coagulation factors and platelets.

Adhesives: Human-derived or synthetic products that can be used in surgery to support the body’s ability to clot and reduce bleeding (see also Thrombin‘).

Advanced Directive: Is a legal document giving instructions as to the type and degree of medical care to be administered in the event that the person signing the document becomes mentally incompetent during the course of a terminal illness, or becomes permanently comatose (persistent vegetative state). State legislatures have enacted so-called Death with Dignity laws to protect the rights of patients to refuse medical care, including life-prolonging and palliative care in terminal illness, as well as to clarify the role of physicians and indemnify them against the accusation of euthanasia or physician-assisted suicide when they withhold such care in compliance with patients’ wishes. These laws spell out strict procedural requirements, including the need for the signing of an advance directive to be duly witnessed, and make it easier to revoke an advance directive than to establish one. When an advance directive provides instructions for the types of care the patient does or does not want to receive, it is known as a living will. When it names another person to make such decisions, it is known as a durable power-of-attorney for health care decisions. An advance directive can contain both types of instruction. An agent making end-of-life decisions on behalf of a patient is required to follow the patient’s instructions, interpreting them when necessary in the light of the patient’s personal philosophy, religious beliefs, and ethical values, and with due consideration for the likelihood that the patient will regain competency or will recover.

Advanced Transfusion Practices: Transfusion alternatives available to treat patients without the use of donor blood.

Albumin: A type of simple protein, varieties of which are widely distributed throughout the tissues and fluids.

Allogeneic: Describes the genetic differences between two individuals.

Allogeneic Blood: Blood that is donated from a person other than oneself. (Also known as banked or homologous blood) The term is typically used for biological material taken from different individuals of the same species. Two or more individuals are said to be allogeneic to one another when the genes at one or more loci are not identical.

Alloimmunized: The creation of immunity due to the development of antibodies.

Alveolocapillary Membrane: The pulmonary diffusion barrier where oxygen is exchanged.

Anemia: Any condition in which the number of red blood cells per mm3, the amount of hemoglobin in 100 ml of blood, and/or the volume of packed red blood cells per 100 ml of blood are less than normal; clinically, generally pertaining to the concentration of oxygen-transporting material in a designated volume of blood. Anemia is frequently manifested by pallor of the skin and mucous membranes, shortness of breath, palpitations of the heart, soft systolic murmurs, lethargy, and fatigability.

Antianemic: Pertaining to factors or substances that prevent or correct anemic conditions.

Antifibrinolytic: Denoting a substance that decreases the breakdown of fibrin; e.g., aminocaproic acid.

Antihypertensive agents: Indicating a drug or mode of treatment that reduces the blood pressure of individuals with high blood pressure.

Apheresis: A technique in which blood products are separated from a donor and the desired elements collected and the rest returned to the donor.

Autologous Blood Transfusion: Blood that the donor has donated previously and then receives back, usually during surgery.

Autotransfusion: A process when a person receives their own blood for a transfusion, instead of banked donor blood. Blood can be pre-donated before a surgery, or can be collected during and after the surgery using a device commonly known as the Cell Saver. The Cell Saver is utilized in surgeries where there is expected

B [TOP]

Bicarbonate: A central buffering agent in blood.

Blood Coagulation: The process of forming a blood clot where the soft, coherent, jelly-like red mass resulting from the conversion of fibrinogen to fibrin, thereby entrapping the red blood cells (and other formed elements) within the coagulated plasma.

Blood Component: A therapeutic component of blood intended for transfusion (e.g., red cells, granulocytes, platelets, plasma, cryoprecipitate, cyrosupernatant plasma) that can be prepared using the equipment and techniques available in a blood centre.

Blood Component Sequestration or Aphaeresis: Like acute Normovolemic hemodilution, blood is removed from a patient at the start of surgery. The blood is fractionated into its primary components of plasma, platelets and red blood cells. Each component is given back to the patient during surgery as needed with the ideal being that the platelets and plasma are left for the end of the procedure. Because of the time that is required to pull the blood out and to fractionate it, this procedure is generally reserved for major blood loss procedures where significant blood loss is almost guaranteed (for example cardiac surgery).

Blood Fractions: Are components that make up whole blood. They consist of major and minor fractions. Major fractions include RBC, WBC, plasma and platelets. Minor blood fractions include albumin, cryo, immune globulin and clotting factors.

Blood Product: Is any therapeutic product derived from human blood or plasma, and produced by a manufacturing process that pools multiple units (usually more than 12) e.g. human serum albumin, immunoglobulin preparations, and coagulation products (factors VIII and IX, fibrinogen, anti-thrombin III, etc.).

Blood Transfusion: The process of administering blood or blood components from one person into the circulatory system of another. Blood transfusions can be life-saving in some situations, such as massive blood loss due to trauma, or can be used to replace blood lost during surgery.

Blood Viscosity: Is the thickness of blood. Is the resistance of blood to flow because of a shearing force.

Blood Volume: Is the total amount of blood in a person’s body.

“Bloodless” Medicine and Surgery: Medical or surgical treatment without the use of banked (stored) allogeneic blood or primary blood components.

Bone Marrow: The soft, pulpy tissue filling the medullary cavities of bones in which the stroma primarily contain the developmental stages of erythrocytes, leukocytes, and megakaryocytes.

C [TOP)

Capillaries: The tiniest blood vessels in the body.

Carbaminohemoglobin: Carbon dioxide bound to hemoglobin; approximately 20% of the total content of carbon dioxide in blood is combined with hemoglobin in this manner.

Cerebral Oximetry: a noninvasive technology that continuously monitors cerebral tissue oxygen saturation, which is a sensitive index of global cerebral oximetry.

Chelates: A complex formed through chelation that is a complex formation involving a metal ion and two or more polar groupings of a single molecule; thus, in heme, the Fe2+ ion is chelated by the porphyrin ring. Chelation can be used to remove an ion from participation in biological reactions, as in the chelation of Ca2+ of blood by EDTA, which thus acts as an anticoagulant.

Clotting Factors: Clotting factors are plasma that guides the thinning and clotting of blood. Many are known only by Roman numerals (1-13). Their simple names contradict the importance of their role in clotting. One of the clotting factors, factor XI, contributes to the formation of an enzyme that plays an important role in the development of a protein called fibrin, a key clotting agent in the blood.

Clotting Time: Is the time required for you to stop bleeding or for your blood to clot.

Coagulation: Coagulation is a complex physiological cascade of enzymatic reactions in response to an injured blood vessel that result in a fibrin clot.

Coagulation Factor: Any of the various plasma components involved in the clotting process. There are 13 “factors” in the blood that can make it clot.

Coagulopathy: is a defect in the body’s mechanism for blood clotting, causing susceptibility to bleeding.

Colloids: A type of nondisfusable intravenous fluid used to maintain circulation volume in the body. Examples are albumin, dextran, hetastarch, tetrastarch, and gelatin (not available in the US).

Complement Cascade: Eleven specific enzymatic proteins occurring in normal serum which interact and destroy (not all complements destroy) foreign cells.

Connective Tissue: The supporting or framework tissue of the body, formed of fibrous and ground substance with more or less numerous cells of various kinds; it is derived from the mesenchyme, and this in turn from the mesoderm; the varieties of connective tissue are: areolar or loose; adipose; dense, regular or irregular, white fibrous; elastic; mucous; and lymphoid tissue; cartilage; and bone; the blood and lymph may be regarded as connective tissues the ground substance of which is a liquid.

Coumadin TM (Warfin): An anticoagulant that causes your clotting time to be prolonged. Used after surgeries when there is concern about clots forming and causing problems.

CPB: Cardiopulmonary Bypass.

CPD: Citrate Phosphate Dextrose, and anti-coagulant additive.

Cryoprecipitate: A plasma blood fraction used to treat deficiencies of Factor VIII, and fibrinogen in the treatment of Hemophilia A. The product is made by thawing frozen plasma at 4°C which results in a precipitate. This precipitate is removed and is named “cryoprecipitate”.

Crystalloids: A type of intravenous fluid made up of various dissolved salts and sugars. These fluids are used to help maintain circulating blood volume.

D [TOP]

Deoxygenated Blood: Is blood that’s low in oxygen because it has released it to the body tissues.

Deoxyribonucleic Acid (DNA): The type of nucleic acid containing deoxyribose as the sugar component and found principally in the nuclei (chromatin, chromosomes) and mitochondria of animal and plant cells, usually loosely bound to protein (hence the term deoxyribonucleoprotein). It’s considered to be the autoreproducing component of chromosomes, including many viruses, and the repository of hereditary characteristics. Chromosomes are composed of double-stranded DNA; mitochondrial DNA is circular.

Desmospressin: shortens the prolonged activated partial thromboplastin time and the bleeding time. These effects probably result from the increases in factor VIII and vWF, which play a rate-accelerating role in these global tests of intrinsic coagulation and primary hemostasis.

Dextran: An intravenous fluid used as a plasma volume expander.

Diffusion: The random movement of particles from an area of greater concentration to one of a lower concentration.

Diphosphoglycerate: A chemical in the blood that attaches to the hemoglobin molecule and helps the hemoglobin release oxygen to the tissues and grab oxygen in the lungs.

Disseminated Intravascular Coagulation (DIC): A hemorrhagic syndrome that occurs following the uncontrolled activation of clotting factors and fibrinolytic enzymes throughout small blood vessels; fibrin is deposited, platelets and clotting factors are consumed, and fibrin degradation products inhibit fibrin polymerization, resulting in tissue necrosis and bleeding.

DNA: Abbreviation for deoxyribonucleic acid.

E [TOP]

ECMO: Extracorporeal Membrane Oxygenation.

Electrocautery: Cauterizes tissue using electric current to reduce or stop bleeding.

Endothelium: A layer of flat cells lining especially blood and lymphatic vessels and the heart. Bleeding occurs when these cells are torn or ruptured until a clot forms.

Erythroblasts: The first generation of cells in the red blood cell series that can be distinguished from precursor endothelial cells.

Erythrocyte: A mature red blood cell. It contains hemoglobin and oxygen.

Erythroid Progenitor Cells: A cell that will become a red blood cell.

Erythropoiesis: The formation of red blood cells.

Erythropoietin: A sialic acid-containing protein that enhances red cell production by stimulating formation of proerythroblasts and release of reticulocytes from bone marrow; it is formed by the kidney and liver, and can be detected in human plasma and urine. Its function is to stimulate the bone marrow to produce more red blood cells.

Extracorporeal Circulation: Diversion of blood flow through a circuit located outside the body but continuous with the bodily circulation.

F [TOP]

Factor IX: Participates in the clotting of blood. It is found in the plasma. Required for the formation of intrinsic blood thromboplastin and affects the amount formed (rather than the rate). Deficiency of factor IX causes hemophilia B.

Factor Vll: Is essential for blood to clot. It is found in the plasma. It accelerates the conversion of prothrombin to thrombin, in the presence of tissue thromboplastin, calcium, and factor V.

Factor VIII: Participates in the clotting of the blood by forming a complex with factor IXa, platelets, and calcium and enzymatically catalyzing the activation of factor X. It is found in the plasma. Deficiency of factor VIII is associated with classic hemophilia A. A deficiency of factor VIII can lead to impaired blood coagulation.

Factor XII: Participates in the clotting of blood, also known as plasma thromboplastin antecedent. It is found in the plasma. Deficiency of factor XI results in a hemorrhagic tendency and is caused by an autosomal recessive gene.

Ferritin: An iron-protein complex, containing up to 23% iron, formed by the union of ferric ions with apoferritin; it is found in the intestinal mucosa, spleen, bone marrow, reticulocytes, and liver, and regulates iron storage and transport from the intestinal lumen to plasma.

Fibrin: An elastic filamentous protein in the blood that cannot be dissolved and which forms clots along with platelets. It is composed from fibrinogen, which under influence of thrombin forms fibrin monomers that polymerise to fibrin polymers. The polymers form threads and a network that binds the surrounding fluid. Under influence of factor XIII the fibrin polymers interconnect through a binding of a glutamine and a lysine side chain and become as such insoluble.

Fibrinogen (Factor I): A protein of the blood that is necessary for the blood to clot.

Fibrinoysis: The process of splitting fibrin into smaller pieces as the blood clot is being dissolved.

Fresh Frozen Plasma: The fluid portion of one unit of human blood that has been centrifuged, separated and frozen solid at -18°C (-0.4°F) (or colder) within 8 hours of collection.

G [TOP]

Gammaglobulin: A protein precipitated from plasma (or serum).

Glycoprotein IIb/IIIa: a platelet surface receptor that is target by a class of drugs known as G IIb/IIIa inhibitors that inhibit and prevent platelet aggregation and thrombus formation.

H [TOP]

Haptoglobin: A group globulins in human serum that combine with hemoglobin, preventing hemoglobin loss in the urine.

Heart-Lung Pump: The heart-lung pump is used in heart surgery to recirculate and oxygenate the patient’s own blood. At a crucial point during heart surgery, the surgeon will direct the patient’s blood from the heart to the pump through tubing. The pump circulates the blood until the time when the surgeon is ready to redirect it back to the patient. This recirculation of blood allows the surgeon time to work on the vessels and the heart without the full flow of blood.

Hematinic: An agent that improves the quality of blood by increasing the number of erythrocytes and/or the hemoglobin concentration.

Hematocrit: Percentage of the volume of a blood sample occupied by red blood cells.

Hematology: The medical specialty that pertains to the anatomy, physiology, pathology, symptomatology, and therapeutics related to the blood and blood-forming tissues.

Hematopoietic Agents: Natural or artificial chemicals used to stimulate blood-cell growth and development.

Heme: The porphyrin chelate of iron in which the iron is Fe(ll) (or Fe2+); the oxygen-carrying, color-furnishing, prosthetic group of hemoglobin.

Hemochromatosis: A disorder of iron metabolism characterized by excessive absorption of ingested iron, saturation of iron-binding protein, and deposition of hemosiderin in tissue, particularly in the liver, pancreas, and skin; cirrhosis of the liver, diabetes (bronze diabetes), bronze pigmentation of the skin, and, eventually heart failure may occur; also can result from administration of large amounts of iron orally, by injection, or in forms of blood transfusion therapy.

Hemodilution: Removal of a specific amount of blood during surgery, replaced with intravenous (IV) fluids, and returned after surgery. This means the blood loss during surgery will contain less erythrocyte (red blood cells) and more water. Doing so will effectively reduce the amount of blood lost during surgery. This technique is only applicable in large surgery in which a high quantity of blood loss is expected.

Hemoglobin (Hgb): The protein found in red blood cells that transports oxygen from the lungs to the tissues where the oxygen is readily released and C02 from the tissues to the lungs where it is released.

Hemolytic Disease of the Newborn: A condition resulting from differences between the fetus’s blood group and that of the mother’s.

Hemophilia: An inherited disorder of blood coagulation characterized by a permanent tendency to hemorrhages spontaneous or traumatic, because of the result of a missing or a low amount of one of the clotting factors.

Hemorrhagic Disorder: Excessive or abnormal bleeding as a result of a disorder of the blood coagulation system.

Hemostatic Drug Therapy: Medications that assist with the clotting functions of blood. They make the blood clot better, which in large surgery or wounds with large amounts of blood loss, is necessary to prohibit further blood loss.

Hemostasis: The arrest of bleeding.

Heparin: A drug used to prevent blood from clotting.

Heparin Resistance: the failure to reach a certain ACT value after administration of heparin.

Hetastarch: An IV fluid used as a volume expander.

HITT: Heparin Induced Thrombocytopenia. Is the development of low platelet count due to the administration of various forms of heparin.

Homologous Blood Product: Blood product obtained from a donor other than the patient. These can be divided in packed cells (red blood cells), thrombocytes, plasma (the watery fluid of the blood without the cells), clotting factors.

Hormone: A chemical substance formed in one organ or part of the body and carried in the blood to another organ or part.

Hypercoagulable Disorders: Disorders or diseases characterized by abnormally increased coagulation.

Hypervolemia: Abnormally increased volume of blood.

Hypovolemia: A decreased amount of blood in the body.

I [TOP]

IBBM: International Board of Blood Management.

Immunoglobulins: One of a class of structurally related proteins, antibodies. Classified (in order of relative amounts present in normal human serum) as IgG (80%), IgA (10-15%), IgM (5-10%), IgD (less than 0.1%), and IgE (less than 0.01%).

Intraoperative: Is during surgery or within surgery.

Intra-operative Blood Cell Recovery and Reinfusion: The process of collecting blood lost during surgery and returning it to the patient after being appropriately processed.

Iron: A metallic element that occurs in the heme of hemoglobin, myoglobin, transferrin, ferritin, and iron-containing porphyrins.

Iron Therapy (oral and intravenous): Therapy with high doses of Iron, a mineral essential for the formation of red blood cells, especially for the formation of hemoglobin. This therapy is used in iron depletion anemia and before surgery, in which large amounts of blood loss are expected, to enhance the condition of the patient and the hemoglobin level. It is frequently combined with erythropoietin. The use of this therapy effectively reduces the risks of blood loss by increasing the oxygen transport capacity of the blood.

K [TOP]

Kidney: One of the paired organs that excrete urine. The kidneys are bean-shaped organs (about 11 cm long, 5 cm wide, and 3 cm thick) lying on either side of the vertebral column, posterior to the peritoneum, about opposite the twelfth thoracic and first three lumbar vertebrae.

L [TOP]

Leukocytes: White blood cells, or leukocytes, are cells of the immune system defending the body against both infectious disease and foreign materials.

M [TOP]

Major Blood Fractions: The major components of whole blood – red blood cells, white blood cells, plasma, platelets.

Microsampling: Technique that restricts the quantity or frequency of blood sampling for lab tests. In many cases, a complete run of tests can be done from only a few drops of blood. Typically, small vials are used for blood collection.

Mini-Circuit: CPB circuits that offer potential advantage in terms of reduced size and priming volume.

Minor Blood Fractions: Substances found in whole blood albumin, cryoprecipitate, immuneglobulin, clotting factors.

MUF: Modified Ultrafiltration.

Myelodysplastic Syndromes: A syndrome that in time may develop into overt leukemia. It is characterized by bone marrow dysfunction manifested by anemia, neutropenia, and thrombocytopenia.

N [TOP]

Non-wash Device: A system used during surgery to collect, filter, and reinfuse the patient’s blood back into the body.

Normal Saline: In medicine, normal saline (NS) is the commonly-used term for a solution of 0.9% of NaCI, or about 300 mOsm/L; It is also known as physiological saline or isotonic saline.

Normochromic: Being normal in color; referring especially to red blood cells that possess the normal quantity of hemoglobin.

O [TOP]

Oxygenated Blood: Is blood that is carrying oxygen.

Oxyhemoglobin: Hemoglobin in combination with oxygen, the form of hemoglobin present in arterial blood, scarlet or bright red when dissolved in water.

P [TOP]

Pentastarch: An IV fluid used as a blood volume expander.

Perfusion: The flow of blood through capillaries.

Peripheral Vascular Resistance: The resistance to flow of blood in the systemic circuit.

Phagocytic Cells: A cell possessing the property of ingesting bacteria, foreign particles, and other cells. Phagocytes are divided into two general classes: 1) microphages, polymorphonuclear leukocytes that ingest chiefly bacteria; 2) macrophages, mononucleated cells (histiocytes and monocytes) that are largely scavengers, ingesting dead tissue and degenerated cells.

Plasma: The fluid portion of the blood minus the red blood cells and white blood cells, and platelets.

Plasma Free Hemoglobin: Hemoglobin found in plasma due to rupture of red blood cells.

Plasminogen: An inactive form of plasmin, which is an enzyme in the blood that helps dissolve blood clots.

Platelet Rich Plasma (PRP): A concentrated source of autologous platelets, PRP contains and releases at least seven different growth factors that stimulate bone and soft tissue healing. Platelet-rich plasma is an alternative source of growth factors to promote wound healing.

Platelets: The small colorless disks in circulating blood which aid in blood clotting.

Polycythemia: An increase above the normal in the number of red cells in the blood.

Postoperative Blood Cell Recovery and Reinfusion: The process of collecting blood lost after surgery, and returning it to the patient after being appropriately processed.

Predonation: Donating your own blood prior to surgery. This practice may not reduce your risk of receiving ablood transfusion and may actually increase that risk because predonating makes the patient anemic, (see alsoAutologous Blood).

Pre-operative: before surgery takes place.

Post-operative: after surgery takes place.

Protein: Macromolecules consisting of long sequences of amino acids. Protein is three-fourths of the dry weight of most cell matter and is involved in structures, hormones, enzymes, muscle contraction, immunologic response, and essential life functions.

R [TOP]

RAP (Retrograde autologous priming): A technique for reducing hemodilution by removing crystalloid from the CPB circuit backwards from the aortic cannulation site.

Recombinant: In a laboratory setting, a cell or organism that has received genes from different parental strains.

Recombinant Erythropoietin: Erythropoietin made in the laboratory.

Recombinant Factor VIIa: A clotting factor which is manufactured through recombinant protein technology rather than from an allogeneic blood product. It is used to control bleeding and promote coagulation of blood.

Recothrom: Recombinant thrombin from a human source.

Red Blood Cells: Red blood cells (also called erythrocytes or RBCs) serve two important functions: they carry oxygen from the lungs to cells in all parts of the body and take carbon dioxide back to the lungs from the cells. Carbon dioxide is released as a waste product of cellular metabolism.

Reticulocytes: A young red blood cell. Such cells become more numerous during the process of active blood regeneration.

Ringer’s Lactate: An IV solution used primarily for volume expansion during acute blood loss.

S [TOP]

Sickle Cell Anemia: An autosomal recessive anemia characterized by crescent- or sickle-shaped erythrocytes and accelerated hemolysis, due to substitution of a single amino acid (valine for glutamic acid) in the sixth position of the *-chain of hemoglobin the gene of which is on chromosome 11. Develop “crisis” episodes of severe pain due to microvascular occlusions, bone infarcts, leg ulcers, and atrophy of the spleen associated with increased susceptibility to bacterial infections, especially streptococcal pneumonia.

Stem Cell: A cell capable of forming all the cells in a person’s blood system.

Surface coating in CPB: coating on or in the extracorporeal circuit which reduces complement activation of the blood when it comes into contact with the circuit.

Synthetic Erythropoietin: A hormone that stimulates production of red blood cells in your bone marrow.

T [TOP]

Tetrastarch: 3rd generation Hydroxethyl starch which falls under the category of colloidal volume expanders with lower molecular weight.

Thrombotic: Relating to, caused by, or characterized by clotting within a blood vessel.

Thrombin: Human-derived or synthetic products that can be used in surgery to support the body’s ability to clot and reduce bleeding (see also Adhesives).

Thrombelastography (TEG) is a method of testing the efficiency of coagulation in the blood. It was first developed by the German Dr.Hellmut Hartert at University of Heidelberg School of Medicine in 1948. It is especially important in surgery and anesthesiology.

Tissue Adhesives: Tissue Adhesives or surgical glue are a combination of the fibrinogen and thrombin mixed with the drug aprotinin. Tissue adhesives can be helpful in trauma when specific organ(s) (liver, spleen, and pancreas) are losing blood. The mixture is sprayed or painted on the organ(s) during surgery to stop or slow blood loss.

Transferrin: A non-heme globulin of the plasma, capable of acting as an iron-transporting protein.

V [TOP]

VAD: Ventricular Assist Device.

Vascular System: The cardiovascular and lymphatic systems collectively better known as the circulatory system.

Volume Expanders: Intravenous fluids made with water, salts, sugars or starched that help maintain the correct amount if fluid in the blood vessels (ie. the crystalloids – normal saline, lactated Ringer’s solutions and the colloids –tetrastarch, albumin, hetastarch).

VVA: Venous Vacuum Assist.

W [TOP]

White Blood Cells: Colorless blood cells that fight infection.

Z [TOP]

Z-Buff: Zero-balanced Ultrafiltration.