Hematologic Disorders Flashcards
The transfussion trigger
A loss of more than 30% - 40% requires RBC transfusion to restore oxygen-carrying capacity
In the case of massive transfusion (>50% blood volume replaced w/in 24 hrs) RBC may need to be accompanied with FFP and platelets in what ratio?
1:1:1
A hct of 28-30% may be appropriate transfusion trigger in what patients?
Unstable coronary syndromes
In what ways does Thalassemia differ from IDA?
Presence of a family hx of thalassemia;
Iron stores & ferritin are normal or increased;
RBC production is maintained or even disproportionately high
How do you confirm the diagnosis of Thalassemia?
Hb electrophoresis which determines the types of globin chains present
What is the result of the inability of a G6PD deficient RBC to protect itself from oxidative damage
Hemolysis
Events that precipitate new or aggravate preexisting hemolysis in G6PD deficiency include:
Infection, metabolic conditions like DKA, certain drugs, & ingestion of fava beans
Anesthetic risk is largely a funciton of the _________ and _____ of G6PD deficiency anemia
Severity & acuity
Primary causes of macrocytic anemia in adults
Folic acid & B12 deficiency
Folic acid & B12 are essential for?
DNA synthesis
What is affected first by folic acid and B12 deficiency
High-turnover tissues such as bone marrow (unable to complete cell division. The marrow becomes megaloblasitc & macrocytic red cells are released into the circulation)
Sustained exposure to _________ can produce an impairment of vitamin B12 activity
Nitrous oxide
Sustained hypoxia results in?
Compensatory increase in RBC mass and Hct
Tissue oxygen delivery is maximal at Hct of _____ & Hgb of ____
33%- 36%; 11-12
How do higher Hcts with polycythemia affect oxygen delivery?
Increase in blood viscosity slows blood flow and decreases oxygen delivery
When Hct rises above ______, whole-blood viscosity increases exponentially affecting blood flow especially in small blood vessels sucha s capillaries with low flow/shear rates
55%- 60%
Prior to surgery, pts with hemophilia A, factor VIII level must be brought close to normal with an infusion of ________. This should be given ______ prior to surgery
DDAVP; 30-90 min
One unit of single-donor apheresis platelets is equivalent to a random-donor pool of ______ units of platelets
4-8
Random and single donor platelets do not need to be _____ compatible
ABO
The differential diagnosis of thrombocytopenia is best organized according to the physiology of:
- Platelet production;
- Distribution in the circulation;
- Platelet destruction
Platelet production disorders may be caused by _________ or _________ in the bone marrow
Megakaryocyte hypoplasia or aplasia
Inherited autosomal recessive;
The thrombocytopenia initially severe (<30,000 platelets) but gradually improves to normal by 2;
Often have bilateral radial anomalies & abnormalities of other bones may occur
Congenital hypoplastic thrombocytopenia with absent radii (TAR syndrome)
Immune-mediated HIT occurs b/w days ______ of heparin use
5 and 10
4Ts system for diagnosing HIT:
The degree of Thrombocytopenia;
The Timing of the platelet reduciton;
The presence of Thrombosis or other sequlae;
The presence of other causes of Thrombocytopenia
What are the 2 types of HIT?
Early onset that occurs in pts exposed to heparin w/in the previous 3 months;
Delayed onset that appears after heparin is discontinued
Thrombocytopenia unrelated to drug exposure, infection, or autoimmune disease.
High level of platelet destruction tht is balanced by high marrow production of platelets that have better-than-normal funciton
Autoimmune idiopathic thrombocytopenic purpura (ITP)
Because platelets are dysfuncitonal, the ___________ does not predict bleeding risk
Absolute platelet number
Tx with ______ may imporve a mild to moderate platelet defect, especially if the risk of bleeding is relatively minor
Desmopressin
As a general rule, sufficient platelet transfusions to increase the percentage of normally functioning platelets to about _______ of all platelets should be sufficient to provide adequate overall platelt function for surgery
10% - 20%
