Blood conservation: glossary of terms

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, asanguinous 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 retransfused. 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.

Advance Directive
A document in which a capable person sets out what, how or by whom health care decisions are to be made in the event that he or she is not capable of making health care decision on his /her own. Two types of advance directives are instruction directives and proxy directives.

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.

Alloimmunization
Development of antibodies in response to foreign substances such as antigens. Allogeneic blood transfusion introduces a multitude of foreign antigens and living cells into the recipient that will persist for a variable time. A recipient who is immunocompetent often mounts an immune response to the donor antigens, resulting in a variety of clinical consequences depending on the blood cells and specific antigens involved. The antigens most commonly involved are human leukocyte antigens, granulocyte-specific antigens, platelet-specific antigens and RBC-specific antigens.

Anemia
Anemia is derived from Greek, (an-haîma) meaning "without blood." It is defined as a qualitative or quantitative deficiency of hemoglobin, a molecule inside red blood cells (RBCs). As hemoglobin carries oxygen from the lungs to the tissues, anemia leads to hypoxia (lack of oxygen) in organs. The three main classes of anemia include excessive blood loss (acute or chronic), excessive blood cell destruction (hemolysis) or deficient red blood cell production. Anemia is the most common disorder of the blood.

Antibody
Antibodies (also known as immunoglobulins) are gamma globulin proteins that are found in blood or other bodily fluids, and are used by the immune system to identify and neutralize foreign objects, such as bacteria and viruses. They are typically made of basic structural units - each with two large heavy chains and two small light chains - to form, for example, monomers with one unit, dimers with two units or pentamers with five units. Antibodies are produced by a kind of white blood cell called a B cell. There are several different types of antibody heavy chain, and several different kinds of antibodies, which are grouped into different isotypes based on which heavy chain they possess. The 5 antibody isotypes known as IgA, IgD, IgE,IgG and IgM. They are each named with an "Ig" prefix that stands for immunoglobulin, and differ in their biological properties, functional locations and ability to deal with different antigens.

Antifibrinolytic
A pharmaceutical agent that inhibits fibrinolysis (the splitting up or dissolution of blood clot). Coagulation and fibrinolysis are natural biologic functions in blood. By inhibiting fibrinolysis, coagulation is theoretically enhanced. By enhancing coagulation or minimizing the effects of excess fibrinolysis, surgical hemorrhage in the presence of fibrinolysis may be reduced. Examples include aprotinin (serine protease inhibitor) and epsilon aminocaproic acid, tranexamic acid (lysine analogs).

Antigen
An antigen (from antibody-generating) or immunogen is a molecule that sometimes stimulates an immune response. The word originated from the notion that they can stimulate antibody generation. Antigens are usually proteins or polysaccharides. This includes parts (coats, capsules, cell walls, flagella, fimbrae, and toxins) of bacteria, viruses, and other microorganisms. Lipids and nucleic acids are antigenic only when combined with proteins and polysaccharides. Non-microbial exogenous (non-self) antigens can include pollen, egg white, and proteins from transplanted tissues and organs or on the surface of transfused blood cells. An allergen is a substance that causes the allergic reaction. The (detrimental) reaction may result after exposure via ingestion, inhalation, injection, or contact with skin. Cells present their antigens to the immune system via a histocompatibility molecule. Depending on the antigen presented and the type of the histocompatibility molecule, several types of immune cells can become activated.

Argon Beam Coagulator
A surgical tool that uses a beam of ionized argon gas to conduct a high-frequency electric current to stop bleeding of tissues. The beam of argon forms an electrical bridge between the instrument and the tissue; this conducts an electrical current in order to cause superficial electrocoagulation with a penetration depth of 0.5 mm.

Autologous Blood Product
An autologous blood product describes a patient's own blood or blood component. There are several methods for collecting autologous blood; blood that is pre-donated by the patient prior to surgery, is called pre-deposit autologous blood donation (PABD) or collected during a surgical procedure called intraoperative autologous donation (IAD). Blood collected from the surgical field, that is washed and concentrated by centrifugation is terms cell salvage.

Autologous Blood
Autologous refers to cells, tissues or even proteins that are either reimplanted or given back to the same individual as they come from. Autologous blood is therefore blood that is collected and transfused to the same individual. Some advantages of autologous blood type will always match, even with a rare blood type or antibody type. The risk of exposure to infectious disease such as hepatitis or HIV from blood is eliminated. The risk of allergic reactions is reduced. Disadvantages are higher cost due to individualized processing, record-keeping, management and increased blood wastage.

Autotransfusion
Autotransfusion is a term that is loosely used to describe the use or transfusion of any autologous blood product. However, traditionally, the term “autotransfusion” is the collection of blood from an active bleeding site and reinfusion of that blood into the same patient for the maintenance of blood volume. Several commercial devises that perform autotransfusion are available. There are three types of systems; un-washed filtered blood, discontinuous flow centrifugal and continuous flow centrifugal. The unwashed systems are popular because of their perceived inexpense and simplicity. Washed systems require a properly trained and clinically skilled operator. Collected blood is washed and then concentrated by centrifugation. Autotransfusion is particularly useful when blood loss during surgery is substantial and can eliminate or reduce the need for allogeneic blood. The term “cell-saver” is used for one commercial device. Autotransfusion is also known as intraoperative blood salvage. There are new commercial systems that collect blood from the surgical area postoperatively, and then wash or filter that blood for reinfusion. These are designed for patients undergoing cardiac or orthopedic surgery.

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 apheresis
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 Product
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.).

Bone and Tissue Donation/Transplantation
Bone and tissue are used in certain surgical procedures. It is standard practice for extensive testing and purging of blood to be done on all organs and tissue.

Bone can be donated postmortem, but also during life. More specific bone of people receiving a total hip arthroplasty can be used for donation procedures. If someone agrees to donate the bone to the bone bank he/she is extensively tested before the bone can be used.

A family conference regarding the patient's choice of organ donation and/or transplantation is advisable and is recommended before the patient enters the hospital.

Bone Marrow
The soft tissue inside bones where blood cells are formed. Most of it is in the long bones. The tissue is active during the whole life and has a large overcapacity. The removal of the marrow from one bone to place prosthesis or repair a bone through intramedullary devices will not jeopardize the function of the bone marrow as blood forming organ.

Capacity
A capable patient must be able to understand: the condition for which the treatment is proposed; the nature and purpose of the treatment; the risks involved in undergoing the treatment; and the risks involved in not undergoing the treatment. Any assessment of capacity includes a determination as to whether or not the patient's ability to consent or dissent is affected by his/her medical condition(s). A person is presumed to be capable unless assessed as being incapable by an attending physician, in consultation with a psychiatrist as necessary, or deemed to be incapable by the court under the provisions of the Guardianship Act or the Incompetent Persons Act. Where a patient's capacity is difficult to assess, or is not agreed upon by those providing health care to the patient or the family of the patient, or there is dispute as to who has the right to make substituted health care decisions for the patient, a psychiatrist's assessment as to the patient's capacity is required.

Clotting Factors
Clotting factors are plasma that guide 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.

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

Colloids
A type of nondisfusable intravenous fluid used to maintain circulation volume in the body. Examples are albumen, dextran, hetastarch, 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.

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.

Dextran
An intravenous fluid used as a plasma volume expander.

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

Electrosurgery
The passage of very high frequency electrical current through tissue to create a desired surgical effect. Specialized "pencils" or electrodes and a generator are used to deliver electrical energy to 'cut' tissue and/or coagulate blood. Unlike electroacautery, the tip of the electrosurgery instrument itself is not heated.

Endoscope
A tube-like device that allows physicians to view the internal structures of the digestive tract and other body cavities without traditional open surgery.

Erythropoietin (EPO)
Erythropoietin (EPO) is a growth hormone. 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.

Fibrin
A protein essential for the clotting of blood. 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.

Folic acid
A member of the vitamin B complex that is necessary for red blood cell production. It can be recommended almost universally in any case of anemia. A deficiency of this acid is the cause of megalobalstic anaemia. In the first trimester of pregnancy this acid prohibits the occurrence of spina bifida in the fetus.

Healthcare Provider
A healthcare provider is a medical or allied health professional who offers services for the prevention, treatment, and management of illness and the preservation of mental and physical well-being.

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.

One of the people who distinguished themselves in this field was Professor Jacob Jongbloed from Utrecht, the Netherlands. He wrote an article in 1948 that stated "the surge for a mechanical heart, an artificial heart, so to speak, is pending". He meant his own finding, the Heart-lung machine. With this device it would be possible to have the heart depleted of blood during surgery, to make surgery to the heart itself possible. This would clear the way for technically demanding surgery to the inside of the heart, like the valves. The circulation of blood would not be disturbed during the surgery for it would be detoured through the heart-lung machine. The machine could also be used for those patients with an acute heart disease. In these cases it should take over the heart function during the recovery period.

Hemodilution
Removal of a specific amount of blood during surgery, replace with intravenous (IV) fluids, and returned after surgery. This means the blood loss during surgery will contain less erythrocytes (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
The pigment in red blood cells which carries oxygen and carbon dioxide to or away from the tissues. This molecule is dependant on iron for its function.

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.

Hetastarch
An IV fluid used as a volume expander.

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.

Human Albumin
Albumin is the major protein comprising plasma. Donated plasma is used for making albumin solutions which can be used for expansion of the blood volume.

Immunoglobulins
Antibodies produced in the lymphatic cells to combat infections or other invading substances.

Intra-operative Blood Salvage
The process involves recovery of blood shed during a surgical procedure or in the postoperative period. The blood is generally filtered, washed and returned back to the patient. In postoperative blood salvage, the blood is frequently returned without the washing step.

Intra-operative Blood Salvaging
Process of collection your blood lost during surgery, washing, filtering and re-infusion of red blood cells.

Intra-Operative Cell Salvage
The process involves recovery of blood shed during a surgical procedure. The blood is generally filtered, washed and returned to the patient.

Post-operative blood salvage
The process involves recovery of blood shed in the postoperative phase after large surgery through the wound drains. It is then filtered and returned to the patient.

Invasive Procedure
An invasive procedure is defined as any procedure excluding venipuncture and IV therapy which involves puncture or incision of the skin or insertion of an instrument or foreign material into the body, including, but not limited to, percutaneous aspirations and biopsies, cardiac and vascular catheterizations, internal laser procedures, endoscopies, angioplasties, and implantations.

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.

Laparoscope
A device similar to an endoscope that is used to view internal structures of the abdominal cavity. The laparoscope is a telescopic rod lens system, that is usually connected to a video camera. Also attached is a fiber optic cable system connected to a 'cold' light source (halogen or xenon), to illuminate the operative field. The laparoscope is inserted through a small incision via a 5 mm or 10 mm trocar; other specialized surgical instruments may be inserted via adjacent nearby small incisions to perform surgical interventions. The abdomen is essentially blown up like a balloon (insufflated); elevating the abdominal wall above the internal organs like a dome, in order to create a working and viewing space. This type of surgery is also known as laparoscopic surgery, also called minimally invasive surgery (MIS), bandaid surgery or keyhole surgery, and differs from the larger incisions needed in traditional surgical procedures. Laparoscopic surgery includes operations within the abdominal or pelvic cavities, whereas keyhole surgery performed on the thoracic or chest cavity is called thoracoscopic surgery.

Laser
A laser is a device that emits light (electromagnetic radiation) through a process called stimulated emission. The term "laser" is an acronym for Light Amplification by Stimulated Emission of Radiation. An electric current is passed through a tube that contains an amplifying medium, usually a gas or solid material, which serves to intensify the energy. This energy is emitted as a narrow light beam which, when focused through a microscope, will either cut, burn, or dissolve various tissues. Different types of lasers emit specific colors of light and are usually named for the amplification materials used. For instance, the carbon dioxide laser is called a CO2 laser, while the YAG laser contains a solid material made up of yttrium, aluminum, and garnet. The argon laser is filled with argon gas that produces blue/green wavelengths.

Leukocytes
White blood cells, or leukocytes, are cells of the immune system defending the body against both infectious disease and foreign materials. There are several different types of white blood cells. Granulocytes (polymorphonuclear leucocytes): leukocytes characterized by the presence of differently staining granules in their cytoplasm when viewed under light microscopy. These granules are membrane-bound enzymes which primarily act in the digestion of endocytosed particles. There are three types of granulocytes: neutrophils, basophils, and eosinophils, which are named according to their staining properties. Agranulocytes (mononuclear leucocytes): leukocytes characterized by the apparent absence of granules in their cytoplasm. Although the name implies a lack of granules these cells do contain non-specific azurophilic granules, which are lysosomes. The cells include lymphocytes, monocytes, and macrophages.

Meticulous Surgical Techniques
Using surgical instruments or techniques that prevent or minimize blood loss. One such approach, the Halstedian surgical technique, for cancer surgery aims at meticulous removal of all cancer tissue, while minimizing blood loss.

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.

Microwave coagulating scalpel
A device that employs microwave energy to perform similar activity to that of electrocautery, but is capable of cauterizing greater areas of tissue at one time. Microwave Tissue Coagulation System (MTCS) is designed to coagulate soft tissue using a surface contact applicator. The system consists of an applicator, external microwave generator, vacuum pump, and a cooling fluid pump and tubing. The desired power and delivery time are set manually by the operator. The applicator is a specifically designed to deliver microwave energy at the frequency and power levels that the generator outputs. This technology has been primarily used for hepatic and urologic surgery.

Minimally Invasive Surgery
Allows surgical repair through small incisions such as for example, laparoscopic surgery.

Normal Saline
In medicine, normal saline (NS) is the commonly-used term for a solution of 0.9% of NaCl, about 300 mOsm/L, also known as physiological saline or isotonic saline. NS is used frequently in intravenous drips for patients who cannot take fluids orally and have developed or are in danger of developing dehydration or hypovolemia. Variations of the concentration of sodium in the solution exist such as half-normal saline (0.45% NaCl) or hypertonic saline (3 or 5% NaCl).

Platelet Rich Plasma
Tissue adhesives (glues) made with a patient’s own blood; or for orthopedic procedures, these adhesives can be mixed with bone or coral.

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

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

Radiosurgery
Conventional radiation treatment for cancer exposes tumors and surrounding tissue to repeated low doses of radiation over an extended period. Radiotherapy employs a single highly focused beam of radiation to perform tissue destruction. Stereotactic radiosurgery is an image-guided non-invasive procedure whereby multiple precisely targeted, highly focused beams of radiation intersect at the tumor location to deliver a large dose of radiation to the tumor or lesion with minimal radiation to adjacent normal tissue. Radiation is concentrated on the target by moving the energy source and firing from many directions or by simultaneously firing multiple beams from a static array of radiation sources.

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.

Red Blood Cells
Red blood cells (also called erythrocytes) serve two important functions:
  1. Carry oxygen from the lungs to cells in all parts of the body. Oxygen helps cells obtain energy from food.
  2. Take carbon dioxide back to the lungs from the cells; carbon dioxide is released as a waste product of cell processes
Ringer's Lactate
An IV solution used primarily for volume expansion during acute blood loss.

Substitute Decision Maker
A person with the legal authority to make a health care decision on behalf of an incapable person (see definition of capacity) in the following order of priority: a guardian appointed by the court; a proxy named in an advanced directive (i.e. a person authorized to give consent under the Medical Consent Act); a souse or common-law partner (if cohabitating in a conjugal relationship); an adult child; a parent or a person who stands in loco parentis; an adult brother or sister; any other adult next-of-kin; and the Public Trustee. Other than a proxy, a guardian and the Public Trustee, a substitute decision maker must have been in personal contact with the incapable person over the preceding twelve months.

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

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, pancreas) are losing blood. The mixture is sprayed or painted on the organ(s) during surgery to stop or slow blood loss.

Treatment
The application of medical care to cure diseases, heals injuries, or ease symptoms.

Volume Expanders
Intravenous fluids made with water, salts, sugars or starched that help maintain the correct amount if fluid in the blood vessels
  • Crystalloids – normal saline, lactated Ringer’s solutions
  • Colloids – albumin, hetastarch
White Blood Cells
Colorless blood cells that fight infection.