Case 1: Serum Lab Values

Question 1

What is serum?

Answer 1

Blood plasma lacking clotting factors

Question 2

Substances that ionizes when dissolved in polar solvent.

Answer 2

Electrolytes

Question 3

High sodium

Answer 3

hypernatremia

Question 4

What causes hypernatremia?

Answer 4

Decreased total body water (burns, excessive sweating, diabetes insipidus), increased intake of sodium (diet/IV), or decreased renal clearance of sodium (hyperaldosteronism), Cushing Syndrome (excess cortisol; occurs with increased calcium).

Question 5

Low sodium

Answer 5

hyponatremia

Question 6

What causes hyponatremia?

Answer 6

Increased body water (excessive intake, CHF), decreased intake of sodium (diet/IV), or increased sodium loss (diarrhea, vomiting, renal insufficiency).

Question 7

What is the major cation within the cell?

Answer 7

Potassium

Question 8

What is the major extracellular cation?

Answer 8

Sodium

Question 9

What can cause hypokalemia

Answer 9

Deficient dietary intake, deficient IV intake, burns, GI disorders, hyperaldosteronism, renal artery stenosis, trauma, surgery

Question 10

How does renal artery stenosis cause hypokalemia?

Answer 10

It decreases renal blood flow, stimulating aldosterone, which leads to a loss of potassium

Question 11

What symptoms can hypokalemia cause?

Answer 11

Decreased contractility in all types of muscle (weakness, paralysis, arrhythmias, colicky pain, etc)

Question 12

What is the major extracellular anion?

Answer 12

Cl (primary purpose is to maintain electric neutrality with sodium)

Question 13

True or false: Hyper/hypochloremia commonly occurs without any other serum chemistry abnormalities.

Answer 13

False; often occurs in parallel with shifts in bicarbonate or sodium levels

Question 14

What can cause hyperchloremia?

Answer 14

Dehydration, metabolic acidosis (because loss of bicarb), Cushing syndrome (excess cortisol secretion; sodium will be too high as well)

Question 15

How does chloride help buffer the blood?

Answer 15

When CO2 (and H+) levels in blood rise, bicarb moves from inside cells into blood to buffer. Chloride moves into the cells to maintain electrical neutrality

Question 16

When aldosterone causes sodium reabsorption, ______ follows to maintain electrical balance.

Answer 16

chloride

Question 17

TCO2 is the concentration of ____ ____ in the peripheral blood and uses ______ CO2, not arterial. It is essentially a measurement of ___________.

Answer 17

total CO2; venous; bicarbonate

Question 18

________ is the second most important anion in extracellular blood in regards to electrolyte neutrality.

Answer 18

Bicarbonate

Question 19

Most of the CO2 in blood is in the form of ________.

Answer 19

bicarbonate

Question 20

Levels of bicarbonate are regulated by the _______.

Answer 20

Kidneys

Question 21

Venous TCO2 blood values can give a rough estimate of bicarbonate concentration, but because they are affected by ____ in the laboratory are not very accurate. Primarily used as a rough guide for acid-base balance.

Answer 21

Air

Question 22

Indications for measuring total CO2 (TCO2)?

Answer 22

1) Evaluate pH status

2) Assist in evaluating electrolytes

Question 23

Indications for measuring serum chloride?

Answer 23

To assist in evaluating electrolytes

Question 24

What are the indications for measuring serum calcium levels?

Answer 24

1) Evaluate parathyroid function
2) Evaluate calcium metabolism
3) Monitor patients with renal failure or transplantation, hyperparathyroidism, and certain malignancies.
4) Monitor calcium levels following blood transfusion.

Question 25

What can cause elevated serum glucose?

Answer 25

Diabetes mellitus, stress, Cushing syndrome are most common

Question 26

What can cause low serum glucose?

Answer 26

Insulinoma (insulin released without regard to biofeedback mechanisms), hypothyroidism, hypopituitarism, Addison's disease (diminished cortisol production), liver disease, glycogen storage diseases, carnitine deficiency (or other block of beta oxidation), insulin overdose (most common)

Question 27

What is creatinine used to evaluate?

Answer 27

Renal function (glomerular filtration rate)

Question 28

True or false: Creatinine level is impacted drastically by hepatic function.

Answer 28

False

Question 29

Decreased BUN can indicate___________.

Answer 29

Liver dysfunction (urea is synthesized in the liver), protein depletion, overhydration, pregnancy

Question 30

Increased BUN can indicate_______.

Answer 30

Renal dysfunction (urea is excreted by kidneys), hypovolemia, CHF, MI, shock, burns, starvation (excess protein breakdown), sepsis

Question 31

What would you get BUN levels to evaluate?

Answer 31

Renal and liver function, hydration status, protein breakdown

Question 32

What would you order a serum creatinine to evaluate?

Answer 32

GFR of kidneys (kidney function)

Question 33

What would high levels of serum Total Protein indicate?

Answer 33

Infection, inflammation, cancer, or dehydration

Question 34

What can low levels of serum Total Protein indicate?

Answer 34

Kidney or liver disease, malnutrition, blood loss.

Question 35

Total protein includes ________ and ______, which constitute most of the protein within the body.

Answer 35

Albumin and globulin

Question 36

Albumin is formed within the ________ and makes up _____% of the total protein.

Answer 36

liver; 60%

Question 37

What are the two major functions of albumin?

Answer 37

To maintain colloidal (i.e., protein-exerted) osmotic pressure and transport blood constituents (e.g., drugs, hormones, and enzymes).

Question 38

Increased albumin levels can be caused by what?

Answer 38

Dehydration

Question 39

Decreased albumin levels can be caused by what?

Answer 39

Malnutrition (lack of amino acids for synthesis), liver disease (preventing synthesis of albumin), pregnancy (albumin levels decline during pregnancy), GIT and kidney pathologies (causing protein loss), overhydration, inflammatory diseases

Question 40

What is a serum bilirubin test used to evaluate?

Answer 40

Liver function

Question 41

Bilirubin metabolism begins with the breakdown of RBCs (mostly in the ______) to heme and globin. Heme is then catabolized to _______, and then to ________ _________. In the ______, unconjugated (or indirect) bilirubin is linked to a __________ molecule to form _______ bilirubin, which can then be excreted via the _____ ______ and the bowel.

Answer 41

spleen; biliverden; unconjugated bilirubin; liver; glucuronic; conjugated; bile duct

Question 42

Buildup of bilirubin in body tissues causes _______.

Answer 42

Jaundice

Question 43

What causes jaundice in many newborns?

Answer 43

Immature liver that lacks the enough conjugating enzymes to allow bilirubin to be excreted.

Question 44

If bilirubin levels in a newborn are greater tha 15 mg/dL, what is the danger?

Answer 44

Unconjugated bilirubin will cross the BBB and cause encephalopathy (kernicterus).

Question 45

How is jaundice in newborns often treated?

Answer 45

Light therapy

Question 46

If jaundice is caused by indirect (unconjugated) bilirubin, what is the likely cause?

Answer 46

Hepatic dysfunction or sickle cell anemia, other hemolytic disease, or hematoma that overloads liver's ability to process indirect bilirubin,

Question 47

What type of bilirubin will be elevated in jaundice caused by hepatic dysfunction?

Answer 47

Indirect (unconjugated) bilirubin

Question 48

What type of jaundice is caused by bile duct obstruction, gall stones, or something else preventing excretion?

Answer 48

Direct (conjugated)

Question 49

What is alkaline phosphatase used to detect?

Answer 49

Diseases of the liver and bone

Question 50

________ _______ enzymes line the biliary collecting system in the liver and are excreted with bile.

Answer 50

Alkaline phosphatase

Question 51

The most frequent extrahepatic source of alkaline phosphatase is ____.

Answer 51

Bone

Question 52

Young children have increased alkaline phosphatase levels because ______.

Answer 52

their bones are growing

Question 53

New bone growth is associated with increase _______ ________ levels in serum.

Answer 53

alkaline phosphatase

Question 54

What are some bone conditions that could cause increased Alk Phos?

Answer 54

Paget disease, healing fracture, RA, and hyperparathyroidism.

Question 55

The isoenzyme ______ would be high if high alkaline phosphatase is due to a liver condition.

Answer 55

ALP1

Question 56

The isoenzyme ______ would be high if high alkaline phosphatase is due to a bone condition.

Answer 56

ALP2

Question 57

What are some liver conditions that could cause high Alkaline Phosphatase?

Answer 57

Cirrhosis, bile obstruction, liver tumor

Question 58

AST is used to screen for what?

Answer 58

Hepatocellular disease

Question 59

______ is an enzyme that is found in high concentrations in highly metabolic cellular tissue (especially liver, heart, and skeletal muscle).

Answer 59

AST

Question 60

What causes a high AST level in serum?

Answer 60

Lysing of cells from highly metabolic tissue (liver, skeletal muscle, heart). Amount of AST is related to number of damaged cells.

Question 61

If liver disease is chronice, AST levels will ________. If liver cellular injury is not chronic, AST levels will be cleared from blood within ______ days

Answer 61

Be persistently elevated; 3-7 days

Question 62

What can cause increased AST levels?

Answer 62

Liver damage, muscle damage, hemolytic anemia, acute pancreatitis

Question 63

What can cause low AST?

Answer 63

Acute renal disease, pregnancy, chronic dialysis, diabetic ketoacidosis.

Question 64

AST

Answer 64

Aspartate Aminotransferase

Question 65

ALT

Answer 65

Alanine Aminotransferase

Question 66

What is ALT used to evaluate?

Answer 66

Liver function

Question 67

In jaundiced patients, increased ALT will indicate ________ as the cause, rather than ___________.

Answer 67

liver rather than RBC hemolysis

Question 68

ALT is found mostly in _______.

Answer 68

liver

Question 69

In comparing ALT and AST, ______ is more specific for hepatocellular dysfunction.

Answer 69

ALT

Question 70

What can cause significantly increased levels of ALT?

Answer 70

Hepatitis and hepatic necrosis

Question 71

What can cause moderately increased levels of ALT?

Answer 71

Liver conditions other than viral hepatitis (which causes very high ALT)

Question 72

If your ALT to AST ratio is less than one, what is the most likely cause?

Answer 72

Viral hepatitis

Question 73

What is an amylase test used to screen for? For what symptom is it usually ordered?

Answer 73

Pancreatitis; acute abdominal pain

Question 74

True of false: serum amylase is a very specific test for pancreatitis.

Answer 74

False; other conditions--such as bowel perforation--can cause pancreatic digestive enzymes to leak into the peritoneum and be picked up by blood vessels. Mumps can also caused increased amylase (because of amylase in salivary glands).

Question 75

What can cause elevated lipase levels?

Answer 75

Pancreatic or kidney diseases (lipases are excreted by the kidneys).

Question 76

If lipase levels are very elevated (5-10x), the cause is probably the ______.

Answer 76

pancreas

Question 77

If lipase levels are less than 3x normal, the cause is probably outside of the _____.

Answer 77

pancreas (i.e., kidneys, intestinal diseases, salivary gland conditions)

Question 78

Common causes of hyperglycemia

Answer 78

Diabetes mellitus, acute stress response (infection, burn, surgery), Cushing syndrome, renal failure (glucagon is normally excreted by kidneys), glucagonoma, corticosteroid use

Question 79

Glucagon is autonomously secreted, without regard to biofeedback mechanisms (causing hyperglycemia).

Answer 79

glucagonoma

Question 80

Insulin is autonomously secreted, without regard to biofeedback mechanisms (causing hypoglycemia).

Answer 80

insulinoma

Question 81

Common causes of hypoglycemia

Answer 81

Insulinoma, Hypothyroidism, Hypopituitarism, Addison disease, Liver disease, Insulin overdose, starvation

Question 82

What is a serum lactic acid test used for?

Answer 82

To quantify the degree of tissue hypoxemia associated with shock or vascular occlusion.

Question 83

What is serum calcium used to evaluate?

Answer 83

parathyroid function and calcium metabolism

Question 84

Does the serum calcium measure ionized Ca, protein(albumin)-bound Ca, or both?

Answer 84

Both

Question 85

How should low serum albumin affect serum Ca?

Answer 85

Ca should also be low

Question 86

About how much serum calcium is bound to protein?

Answer 86

1/2

Question 87

What should you suspect if serum calcium is normal but serum albumin is low?

Answer 87

Hypercalcemia

Question 88

A decrease in blood pH causes ____________ Ca levels.

Answer 88

Increased