2015 L6 Case 5 Car Crash Guy

Hypovolemic Shock

A condition resulting from a sudden decrease in blood volume leading to severe drop in blood pressure and insufficient blood supply to organs.

Restoring Haemodynamic Stability

• Pro-coagulant drugs e.g. transexamic acid

• Saline

• RBC

• FFP

Packed Red Blood Cells (PRBC)

Blood product consisting of red blood cells with most plasma removed; used for transfusions.

• 40g of haemoglobin

• RBC suspended in anticoagulant/nutrient solution (acid citrate dextrose)

• patients may have special requirements

  • CMV (cytomegavirus) for babies

  • irradiated to prevent TA-GvHD

  • antigen negative

Disseminated Intravascular Coagulation (DIC)

A serious disorder in which the proteins that control blood clotting become overactive, leading to excessive clotting and bleeding.

Tranexamic Acid

A medication that inhibits plasminogen activation and prevents the breakdown of blood clots.

• antifibrinolytic agent

  • fibrin clot broken by plasmin

  • plasmin = the active form of plasminogen - usually activated alongside coagulation cascade, also a serine protease

• prevents conversion of plasminogen and plasmin

  • synthetic lysine analogue

  • irreversibly binds to 5 lysine receptors on plasminogen

Blood Stats

• Humans with a body weight of 60kg usually have around 4 to 5L of blood

• RBC transfusion rec if > 30% of blood volume is lost or haemoglobin < 80g/L

History of Blood Transfusions

• 1818: first human-human transfusion by James Blundell

• 1901: Karl Landsteiner demonstrates main blood groups

Fresh Frozen Plasma (FFP)

Plasma that has been frozen and stored; contains coagulation factors necessary for blood clotting.

• single donor (250-300ml) and frozen within 6hrs

• contains plasma with all normal proteins e.g. fibrinogen, FVIII, other coagulation factors and antibodies

• Stored at -30 degrees, shelf life of 2 yrs

• Thawed in controlled environment, can be stored ↑ to 24hrs at 4 degrees

Coomb's Test aka Crossmatch Procedure

A test used to determine if the patient's body has alloantibodies against transfused blood cells.

1. recipient serum obtained containing antibodies

2. donor blood sample added to tube with serum

3. recipient’s antibodies target donor’s RBCs form antibody-antigen complexes

4. anti-human antibodies e.g. Coomb’s antibodies added

5. POSITIVE RESULT = agglutination of RBC occurs because human antibodies are attached to RBC

Rhesus Factor

An antigen found on the surface of red blood cells; significant in blood transfusion compatibility.

• Discovery by Karl Landsteiner in 1937

• Second major group of proteins found on cell surface

ABO Blood Group

• Each blood group has different proteins/antigens on their surface

• ABO locus located on Chr9, contains 7 exons

• ABO gene encodes for glycotransferase

• Main alleles for ABO locus: A, B, O

Saline Infusion

A common procedure in emergency care to increase blood volume and raise blood pressure without carrying oxygen.

Blood Group O

• O allele due to frameshift mutation in exon 6 > loss of enzymatic activity

• Lacks A or B antigens

• Expresses H antigen, the precursor for all other antigens

Blood Group A

• A allele of ABO locus encodes for glycosyltransferase

• Bonds α-N-acetylgalactosamine onto the H surface

Blood Group B

• B allele of ABO locus encodes for a glycotransferase

• Binds α-D-galactose to H antigen

Blood Group AB

• Heterozygotes for A and B allele produce AB blood

• Consists of both antigens, often in in various quantities

RhDCE

• Rh system consists of 50 antigens, but most important are D, C, c, E, e

• 5 antigens are products of the RHD and RHCE genes

• RhD most clinically significant

Hemolytic Transfusion Reaction

A serious and potentially life-threatening response to transfusion, caused by the recipient's immune system attacking the transfused red blood cells.

Lansteiner’s Law

Whenever an antigen is not present on red cells, the corresponding antibody will be found in the plasma

• If you have A, you have anti-B antibodies in plasma

• If you have B, you have anti-A antibodies in plasma

• If you have O, you will have both anti-A and anti-B in your plasma

• If you are blood group AB you will have no anti-A or anti-B

Safe Transfusions

Cell Salvage

A technique to collect and reinfuse a patient's own blood lost during surgery.

Antigen

A substance that induces an immune response, especially the production of antibodies.

Antibody

A protein produced by the immune system to recognize and neutralize foreign substances such as pathogens or incompatible blood.

Transfusion Labs

• Ensures availability for transfusions, investigates

  • patient blood group

  • if patient has reactive antibodies

• Ensures blood is safe, either by electronic issue and crossmatch

  • electronic issue = Laboratory Information Management System (LIMS) determined

  • crossmatch = to detect the presence of antibodies in the recipient against the red blood cells of the donor, preventing hemolytic anaemia

Finding Blood Groups

• Lab tests = antibody-antigen reactions

• Pt RBC (no plasma) incubated with specific antibodies (anti-A and anti-B) - if agglutination occurs, reaction is positive

  • if pt is Type A, they’d have positive reaction with anti-A

• Pt plasma (no cells) incubated with known antigens (A or B cells) - reverse group

  • pt with Type A would have anti-B antibodies in their plasma, positive agglutination would occur against B cells

O neg as a universal donor

• potentially 600 diff antigens on RBC that can cause response

• giving pt O neg without testing for other antigens only done in emergencies

• its possible that pt who has never been transfused may have an antibody against one of these by chance

• multiple transfused patients risk developing of antibody

Crush Syndrome

A condition that can occur after a major crush injury, leading to muscle and tissue damage, potential renal failure, and electrolyte imbalance.

Compartment Syndrome

A serious condition that occurs when there is increased pressure within a muscle compartment, leading to reduced blood flow, nerve damage, and muscle necrosis.

Antibody Screening

• test for blood compatibility against 600 antigens

• patient plasma incubated with cells of known antigen makeup

• agglutination against cell = antibody present in plasma that has reacted against antigen

Electronic Issue

• prior to blood transfusion, individual must submit 2 samples for blood grouping and antibody screening

• if blood group is confirmed and antibody screen is negative, computer will issue comptable units to pt

Acute Hemolytic Transfusion Reaction

Occurs when the immune system attacks transfused red blood cells, resulting in their destruction. This reaction is typically caused by ABO incompatibility.

• other causes of widespread haemolysis of RBC can be caused by the presence of very rare antigens thats never tested

• free haemoglobin then causes renal damage (nephrotoxicity, glomeruli destruction > haematuria

• hepatoxicity, Fe in haem can produce ROS which damage liver

• rampant coagulation aka DIC

• fragmented RBC = damage-associated molecular patterns, causes immune response (fever)

FFP Complications

• Fluid overload: when FFP administered at large volumes > heart failure/pulmonary edema esp in patients with preexisting cardiac conditions

• Immunosuppression: FFP may contain antibodies that suppress pt’s immune response

• nvCJD from donors with infected with prion responsible

• Viral infection e.g. HepB, HepC and HIV

• Haemolysis if incompatibility or if FFP improperly handled FFP C

Methylene Blue Treatment of FFP

• nvCJD is a prion disease

• treatment for everyone before 1996 who is susceptible

• when exposed to UV, meth blue will produce ROS aka free radicals that can denature prions

Cryoprecipitate

• Made by freezing donor plasma in blast freezer then thawing at 4 degrees, causing plasma proteins e.g. VIII and fibrinogen to precipitate out - removal of more water from cryo

• Plasma transferred to another bag and precipitate is refrozen and stored at 30 degrees

• Prevents fluid overload as there is less water

• Good for pt with trauma so they have coagulation factors for clotting