Case 1: Serum Lab Values Flashcards
What is serum?
Blood plasma lacking clotting factors
Substances that ionizes when dissolved in polar solvent.
Electrolytes
High sodium
hypernatremia
What causes hypernatremia?
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).
Low sodium
hyponatremia
What causes hyponatremia?
Increased body water (excessive intake, CHF), decreased intake of sodium (diet/IV), or increased sodium loss (diarrhea, vomiting, renal insufficiency).
What is the major cation within the cell?
Potassium
What is the major extracellular cation?
Sodium
What can cause hypokalemia
Deficient dietary intake, deficient IV intake, burns, GI disorders, hyperaldosteronism, renal artery stenosis, trauma, surgery
How does renal artery stenosis cause hypokalemia?
It decreases renal blood flow, stimulating aldosterone, which leads to a loss of potassium
What symptoms can hypokalemia cause?
Decreased contractility in all types of muscle (weakness, paralysis, arrhythmias, colicky pain, etc)
What is the major extracellular anion?
Cl (primary purpose is to maintain electric neutrality with sodium)
True or false: Hyper/hypochloremia commonly occurs without any other serum chemistry abnormalities.
False; often occurs in parallel with shifts in bicarbonate or sodium levels
What can cause hyperchloremia?
Dehydration, metabolic acidosis (because loss of bicarb), Cushing syndrome (excess cortisol secretion; sodium will be too high as well)
How does chloride help buffer the blood?
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
When aldosterone causes sodium reabsorption, ______ follows to maintain electrical balance.
chloride
TCO2 is the concentration of ____ ____ in the peripheral blood and uses ______ CO2, not arterial. It is essentially a measurement of ___________.
total CO2; venous; bicarbonate
________ is the second most important anion in extracellular blood in regards to electrolyte neutrality.
Bicarbonate
Most of the CO2 in blood is in the form of ________.
bicarbonate
Levels of bicarbonate are regulated by the _______.
Kidneys
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.
Air
Indications for measuring total CO2 (TCO2)?
1) Evaluate pH status
2) Assist in evaluating electrolytes
Indications for measuring serum chloride?
To assist in evaluating electrolytes
What are the indications for measuring serum calcium levels?
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.
What can cause elevated serum glucose?
Diabetes mellitus, stress, Cushing syndrome are most common
What can cause low serum glucose?
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)
What is creatinine used to evaluate?
Renal function (glomerular filtration rate)
True or false: Creatinine level is impacted drastically by hepatic function.
False
Decreased BUN can indicate___________.
Liver dysfunction (urea is synthesized in the liver), protein depletion, overhydration, pregnancy
Increased BUN can indicate_______.
Renal dysfunction (urea is excreted by kidneys), hypovolemia, CHF, MI, shock, burns, starvation (excess protein breakdown), sepsis
What would you get BUN levels to evaluate?
Renal and liver function, hydration status, protein breakdown
What would you order a serum creatinine to evaluate?
GFR of kidneys (kidney function)
What would high levels of serum Total Protein indicate?
Infection, inflammation, cancer, or dehydration
What can low levels of serum Total Protein indicate?
Kidney or liver disease, malnutrition, blood loss.
Total protein includes ________ and ______, which constitute most of the protein within the body.
Albumin and globulin
Albumin is formed within the ________ and makes up _____% of the total protein.
liver; 60%
What are the two major functions of albumin?
To maintain colloidal (i.e., protein-exerted) osmotic pressure and transport blood constituents (e.g., drugs, hormones, and enzymes).
Increased albumin levels can be caused by what?
Dehydration
Decreased albumin levels can be caused by what?
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
What is a serum bilirubin test used to evaluate?
Liver function
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.
spleen; biliverden; unconjugated bilirubin; liver; glucuronic; conjugated; bile duct
Buildup of bilirubin in body tissues causes _______.
Jaundice
What causes jaundice in many newborns?
Immature liver that lacks the enough conjugating enzymes to allow bilirubin to be excreted.
If bilirubin levels in a newborn are greater tha 15 mg/dL, what is the danger?
Unconjugated bilirubin will cross the BBB and cause encephalopathy (kernicterus).
How is jaundice in newborns often treated?
Light therapy
If jaundice is caused by indirect (unconjugated) bilirubin, what is the likely cause?
Hepatic dysfunction or sickle cell anemia, other hemolytic disease, or hematoma that overloads liver’s ability to process indirect bilirubin,
What type of bilirubin will be elevated in jaundice caused by hepatic dysfunction?
Indirect (unconjugated) bilirubin
What type of jaundice is caused by bile duct obstruction, gall stones, or something else preventing excretion?
Direct (conjugated)
What is alkaline phosphatase used to detect?
Diseases of the liver and bone
________ _______ enzymes line the biliary collecting system in the liver and are excreted with bile.
Alkaline phosphatase
The most frequent extrahepatic source of alkaline phosphatase is ____.
Bone
Young children have increased alkaline phosphatase levels because ______.
their bones are growing
New bone growth is associated with increase _______ ________ levels in serum.
alkaline phosphatase
What are some bone conditions that could cause increased Alk Phos?
Paget disease, healing fracture, RA, and hyperparathyroidism.
The isoenzyme ______ would be high if high alkaline phosphatase is due to a liver condition.
ALP1
The isoenzyme ______ would be high if high alkaline phosphatase is due to a bone condition.
ALP2
What are some liver conditions that could cause high Alkaline Phosphatase?
Cirrhosis, bile obstruction, liver tumor
AST is used to screen for what?
Hepatocellular disease
______ is an enzyme that is found in high concentrations in highly metabolic cellular tissue (especially liver, heart, and skeletal muscle).
AST
What causes a high AST level in serum?
Lysing of cells from highly metabolic tissue (liver, skeletal muscle, heart). Amount of AST is related to number of damaged cells.
If liver disease is chronice, AST levels will ________. If liver cellular injury is not chronic, AST levels will be cleared from blood within ______ days
Be persistently elevated; 3-7 days
What can cause increased AST levels?
Liver damage, muscle damage, hemolytic anemia, acute pancreatitis
What can cause low AST?
Acute renal disease, pregnancy, chronic dialysis, diabetic ketoacidosis.
AST
Aspartate Aminotransferase
ALT
Alanine Aminotransferase
What is ALT used to evaluate?
Liver function
In jaundiced patients, increased ALT will indicate ________ as the cause, rather than ___________.
liver rather than RBC hemolysis
ALT is found mostly in _______.
liver
In comparing ALT and AST, ______ is more specific for hepatocellular dysfunction.
ALT
What can cause significantly increased levels of ALT?
Hepatitis and hepatic necrosis
What can cause moderately increased levels of ALT?
Liver conditions other than viral hepatitis (which causes very high ALT)
If your ALT to AST ratio is less than one, what is the most likely cause?
Viral hepatitis
What is an amylase test used to screen for? For what symptom is it usually ordered?
Pancreatitis; acute abdominal pain
True of false: serum amylase is a very specific test for pancreatitis.
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).
What can cause elevated lipase levels?
Pancreatic or kidney diseases (lipases are excreted by the kidneys).
If lipase levels are very elevated (5-10x), the cause is probably the ______.
pancreas
If lipase levels are less than 3x normal, the cause is probably outside of the _____.
pancreas (i.e., kidneys, intestinal diseases, salivary gland conditions)
Common causes of hyperglycemia
Diabetes mellitus, acute stress response (infection, burn, surgery), Cushing syndrome, renal failure (glucagon is normally excreted by kidneys), glucagonoma, corticosteroid use
Glucagon is autonomously secreted, without regard to biofeedback mechanisms (causing hyperglycemia).
glucagonoma
Insulin is autonomously secreted, without regard to biofeedback mechanisms (causing hypoglycemia).
insulinoma
Common causes of hypoglycemia
Insulinoma, Hypothyroidism, Hypopituitarism, Addison disease, Liver disease, Insulin overdose, starvation
What is a serum lactic acid test used for?
To quantify the degree of tissue hypoxemia associated with shock or vascular occlusion.
What is serum calcium used to evaluate?
parathyroid function and calcium metabolism
Does the serum calcium measure ionized Ca, protein(albumin)-bound Ca, or both?
Both
How should low serum albumin affect serum Ca?
Ca should also be low
About how much serum calcium is bound to protein?
1/2
What should you suspect if serum calcium is normal but serum albumin is low?
Hypercalcemia
A decrease in blood pH causes ____________ Ca levels.
Increased
