Hematologic System

Question 1

What is the most common cause of transfusion-related mortality?

Answer 1

It is due to neutrophilic immune response

Transfusion-related acute lung injury (TRALI) is the most common cause of transfusion-related mortality, causing more deaths than acute hemolytic reactions from ABO blood type error.

TRALI involves an immune response of recipient antibodies directed against donor human leukocyte antigens (anti-HLA) or human neutrophil antigens (anti-hak) and causes an influx of neutrophils into the lungs, with subsequent activation of neutrophils and release of inflammatory mediators with the development of increased pulmonary microvascular permeability

Question 2

What is the most frequent cause of acute hemolytic reactions?

Answer 2

Clerical error

Question 3

Infectious complications related to blood transfusions is usually caused by what source?

Answer 3

Bacterial infection

Due to storage at room temperature to maintain platelet function. Gram-negative bacteria are frequent causes of transfusion-associated sepsis as well.

Question 4

What precaution should be taken in a patient with an IgA deficiency prior to administration of blood products?

Answer 4

Washing product

Anti-IgA antibodies may develop in patients who lack IgA, and the administration of blood products can cause anaphylaxis.

Washing blood products with normal saline removes as much of the contaminating IgA as possible.

Question 5

What factor is missing in patients with Christmas Disease?

Answer 5

a.k.a. Hemophilia B, which is missing Factor IX

Question 6

What is the most common cause of transfusion-related mortality? describe.

Answer 6

Transfusion-related acute lung injury (TRALI) causing more deaths than acute hemolytic reactions from ABO blood type error.
- TRALI involves an immune response of recipient antibodies directed against donor human leukocyte antigens (anti-HLA) or human neutrophil antigens (anti-HKA) and causes an influx of neutrophils into the lungs, with subsequent activation of neutrophils and release of inflammatory mediators with the development of increased pulmonary microvascular permeability

Question 7

At what percentage do patients become symptomatic with methemoglobinemia?

Answer 7

Patients are usually asymptomatic until levels of 15% are reached.

Question 8

What are the symptoms experienced with methemoglobinemia at 20-30%? 50%?

Answer 8

Dizziness and headache are seen at levels of 20-30%

Cardiac dysrhythmias and cardiac arrest occur at levels of 50% or higher

Question 9

How does chronic cocaine use effect platelets?

Answer 9

Chronic cocaine use is associated with thrombocytopenia

Question 10

What are the estimated blood volumes (EBV) for: premature infants, full-term infants, 3-12 month old children, and children older than 1 year?

Answer 10

Premature infants: 100mL/kg
Full-term infants: 90 mL/kg
3-12 month children: 80 mL/kg
Children > 1 year: 70 mL/kg

Question 11

What is the equation to calculate maximal allowable blood loss (MABL)?

Answer 11

MABL =

Estimated blood volume (EBV) x [(starting Hct - target Hct) / starting Hct]

Question 12

What is the goal in preoperative preparation of patients with Hemophilia A? How is it achieved?

Answer 12

The goal is to increase plasma Factor VIII activity to 100% at the start of a major surgical procedure, then maintain a trough level of 50-60% (max 75%) until discharge in 7-10 days.

Protocol:

• Obtain a baseline Factor VIII and inhibitor level
• 30 mins prior to surgical incision, give 50 mcg/kg (100%) factor VIII concentrate IV
• Repeat FVIII level 15-30 mins following infusion
• Post-op until discharge: 25 mcg/kg q 12 hrs, q am trough level (prior to infusion)
• Discharge: 50 mcg/kg q day x 1 week

Question 13

What is the half-life of Factor VIII?

Answer 13

12 hours

Question 14

Patients with sickle cell disease shift the oxyhemoglobin curve in which direction? What is the P50 of these patients?

Answer 14

A rightward shift making the P50 of these patients 31 mmHg (higher than the normal 26) due to the sickled red blood cell’s lower affinity for oxygen.

Question 15

What is included in the treatment of vonWillebrand disease?

Answer 15

1) Desmopressin (DDAVP), which stimulates the release of vWF
2) Blood products containing vWF and Factor VIII (i.e. Cryoprecipitate, Factor 8 concentrate, FFP)

[recombinant Factor VIII is not helpful because it does not contain vWF]

Question 16

For surgery with massive bleeding where the patient has received PRBCs and FFPs with continued bleeding, what product, when given, will stop the bleeding the fastest?

Answer 16

Recombinant Factor VIIa transfusion has a quick onset time of 10-20 minutes and only 5-10% serum levels of it is therapeutic to control massive bleeding.

Question 17

What is the likely diagnosis of a cyanotic patient with a normal PaO2, an elevated methemoglobin concentration by cooximetry, but does not respond to methylene blue tx?

Answer 17

Sulfhemoglobinemia, which causes a rightward shift of the oxyhemoglobin dissociation curve (unloading of oxygen to the tissues results in an increased tolerance of specific levels of sulfhemoglobin compared to methemglobin.)

Question 18

How is sulfhemogloinemia different from methemoglobinemia?

Answer 18

Unlike methemoglobin, which can be measured by conventional cooximetry, sulfhemoglobin must be measured by GAS CHROMATOGRAPHY

Also, sulfhemoglbin causes a right shift of the oxyhemoglobin dissociation curve. Methemoglobin causes a left shift

Question 19

Describe delayed hemolytic transfusion (DHTR)

Answer 19

Unlike an immediate transfusion reaction, patients with DHTR rarely develop hemodynamic instability, jaundice, and hemoglobinuria.

Occurs in o.2 - 2.6% of patients receiving transfusions

Most common manifestation of DHTR is a decrease in post-transfusion Hct due to a mild, gradual hemolysis

Onset of DHTR is 24 hrs to 21 days

It involves sensitization of the host to non-ABO blood groups (reactivation of latent antibody)

Question 20

Describe the mechanism of Graft vs. Host Disease

Answer 20

It is one of the most common causes of mortality associated with blood transfusion

It is thought to be due tot he proliferation of DONOR T-cells in the immunocompromised host

Though rare, it is associated with a high mortality (>90%)

Most patients are > 60 years of age and present with:

• fever
• rash
• liver dysfunction
• diarrhea
• pancytopenia

It usually manifests 1-6 weeks after the transfusion

Question 21

What is the purpose of plasmapheresis? (examples of diseases its used in)

Answer 21

It is a procedure used to remove pathologic components in the circulation and to replace abnormal or deficient proteins.

• Myasthenia Gravis (to remove autoantibodies to Ach receptors) in a myasthenic crisis
• Thyroid storm (to remove thyroid-stimulating autoantibodies)
• Donor-recipient ABO incompatibility

Question 22

What phase of the crossmatch process is used to detect Rh incompatibility?

Answer 22

The incubation phase

Question 23

What factor has the shortest half life?

Answer 23

Factor VII (3-6 hours)

Question 24

In acute hemorrhage and resuscitation, what is the first coagulation factor to reach a critically low level?

Answer 24

Fibrinogen