Test 4 Flashcards
What is the most abundant trace element?
Iron
What is ferritin?
Storage form of iron
Decreased plasma ferritin is the earliest indication of what?
Iron deficiency
What does transferrin do?
Transports iron from GI tract to the bone marrow and other organs
Where is transferrin synthesized?
In the liver
Each transferrin molecule transports how many iron atoms?
two
What are some causes of increased serum iron?
Hemolytic anemias, thalassemias, hepatitis, excessive transfusions, iron poisoning (vitamin overdose)
What are some causes of decreased serum iron?
Insufficient dietary iron, bleeding, malabsorption, and infection or chronic disease
What is hemochromatosis?
A recessive genetic disorder where excess iron accumulates in tissues from increased GI absorption
What is treatment for hemochromatosis?
Therapeutic phlebotomy
What are the main steps iron tests follow?
Dissociate Fe from transferrin
Reduce Fe from ferric to ferrous
Add ferrozine to make a colored compound
Measure colored product by spectrophotometry
What specimen is needed for iron testing?
Serum with no hemolysis or has been in a tube with anticoagulants that bind iron (EDTA and Sodium Citrate)
What is the TIBC?
Total Iron Binding Capacity is an estimate of transferrin concentration
What does TIBC measure?
How much iron could be transported in the plasma by transferrin (not how much iron the patient has)
TIBC is an ________ measurement of transferrin.
Indirect
What are the steps for TIBC testing?
- Add excessive amount of iron to serum to saturate transferrin.
- Add MgCO3 to remove unbound iron
- Centrifuge specimen to get the MgCO3 to the bottom
- Take the supernate and test that for iron
What 3 components are in an iron profile?
Total iron, TIBC, % iron saturation
% Iron Saturation = ?
Total Iron / TIBC X 100
What does the % Iron saturation measure?
Measures how full transferrin is
What are the usual results for total iron, TIBC, and %Fe Sat in a person with iron deficiency?
Total iron decreased
TIBC increased
% Fe Sat decreased
What are the usual results for total iron, TIBC, and %Fe Sat in a person with hemochromatosis?
Total iron increased
TIBC decreased
% Fe Sat increased
What are the usual results for total iron, TIBC, and %Fe Sat in a person with infection/cancer?
Total iron decreased
TIBC decreased
% Fe Sat increased
What are the usual results for total iron, TIBC, and %Fe Sat in a person with hemolysis?
Total iron increased
TIBC normal
% Fe Sat increased
What is step 1 and 2 in the formation of bilirubin?
- RBCs are eaten by spleen. Hgb is catabolized into amino acids, iron, and heme
- Heme ring is broken open and converted to unconjugated bilirubin
What are steps 3 and 4 in the formation of bilirubin?
- RE cells in the spleen secrete the unconjugated bilirubin into the plasma, where bilirubin is bound by albumin.
- Albumin - bilirubin complex travels to liver
What are steps 5 and 6 in the formation of bilirubin?
- Hepatocytes conjugates bilirubin with glucoronic acid by UDPG enzyme
- Conjugated bilirubin is secreted into bile duct
What are step 7 and 8 in the formation of bilirubin?
- GI bacterial normal flora converts conjugated bilirubin into urobilinogen
- Urobilinogen may be excreted into stool, reabsorbed in plasma, or excreted in the urine.
What is UDPGs main job?
Conjugating bilirubin
What two things can increased plasma bilirubin indicate?
Increased RBC catabolism or decreased hepatic conjugation with excretion of bilirubin
What is jaundice?
Yellowing of the skin and sclera from increased bilirubin
What does icteric mean?
Plasma/serum with yellow color from increased bilirubin
At what range in numbers does jaundice start showing?
2.5 - 3.0 mg/dL
What causes prehepatic jaundice?
Excess RBC destruction or increased unconjugated bilirubin
What causes hepatic jaundice?
Defective liver function
Defective hepatocyte uptake
Cholestasis (impaired hepatic transport)
What causes post hepatic jaundice?
Impaired ability of liver to excrete bile into the GI tract
What happens in Crigler - Najar syndrome?
Hepatocytes lack UPDG enzyme and cannot conjugate bilirubin
What is Gilbert’s syndrome?
30-50% deficiency of UPDG and decreased conjugation
What is physiological jaundice of the newborn?
Babies are born with immature liver and have temporary deficiency of UDPG
What is hemolytic disease of the newborn?
Mother newborn blood group incompatibility
Most common cause of HDNB?
O mom with A baby or rh negative mom with rh positive baby
What happens in HDNB?
Maternal IgG antibodies cross the placenta and attack fetal RBCs
What is kernicterus?
Permanent brain damage from excess free bilirubin penetrating blood brain barrier
What is the total bilirubin when kernicterus occurs
> 20 mg/dL
What is the treatment of HDNB
Uv light or exchange transfusion
What is cirrhosis
Irreversible structural damage (scaring) of the liver
What reagent is used in bilirubin techniques
Diazotized sulfanilic acid
What type of bilirubin needs an accelerator?
Unconjugated
What is an acid?
Any substance that yields a H+ in H2O
What is a base?
Any substance that yields OH- in H2O
K = ?
Dissociation constant
Product / reactant
What does pK equal?
-log of the dissociation constant
What is the pK?
Numerical expression of a substances ability to dissociate to prince H+ and OH- ions
What is a buffer?
Any substance that resists change in ph
Strong acids have a _____ dissociation constant.
High
Weak acids have _____ disassociation constants.
Low
What is considered acidosis in terms of pH?
< 7.35
What is considered alkalosis in terms of pH?
> 7.45
The most effective buffer system is?
The Carbonic-Acid Bicarbonate System
What are good buffers?
Weak acids
What is the Henderson-Hasselbach equation?
pH = pK (6.1) + log (HCO-3/H2CO3)
What regulates H2CO3?
Lungs (respiratory)
What regulates HCO3?
Kidneys
The ratio of (HCO3/H2CO3) must remain at?
20 to 1
What does compensation do?
Compensation corrects pH whenever it falls out of normal range
What is primary compensation?
When one organ causes a pH problem and the “other” organ corrects it
What is secondary compensation?
When the offending organ fixes its own problem
What is respiratory acidosis?
Decreased respiratory activity which causes increased CO2/H2CO3 in the plasma
What is the primary compensation for respiratory acidosis?
Kidneys increase H+ excretion and HCO-3 reabsorption
What is metabolic acidosis?
Decreased plasma bicarbonate concentration
What is the primary compensation for metabolic acidosis?
Hyperventilation - lungs decreases CO2
What is respiratory alkalosis?
Decreased CO2
Common causes of respirator alkalosis
Hyperventilation and aspirin overdose
What is the primary compensation for respiratory alkalosis
Kidneys compensate by increasing excretion of HCO3- And increasing reabsorption of H+
What is metabolic alkalosis?
Increased bicarbonate
Primary compensation of metabolic alkalosis
Linda compensate by decreasing respirations and increasing carbonic acid
What is the pH of metabolic acidosis (increased or decreased)
Decreased
What is the ph for metabolic alkalosis
Increased
