Lab Med: CMP and Electrolytes Flashcards
Which tests monitor renal function?
BUN
Cr
BUN/Cr ratio
Which tests measure electrolytes and pH?
Na
K
Cl
CO2
What are considered the liver tests?
ALT
AST
ALP
Total Bili
Which tests monitor synthetic function of the liver?
albumin
platelets
PT/INR
A basic metabolic panel consists of what labs?
glucose
BUN, Cr, BUN/Cr ratio
Na, K, Cl
CO2
What is the most common acute cause of hyperglycemia?
Physiologic stress (trauma, illness, infx, burn, surgery, etc)
Which endocrine disorders can cause hyperglycemia?
Cushings, Acromegaly
Cushings causes hyperglycemia through what mechanism?
excess cortisol production results in increased glucagon release
Acromegaly causes hyperglycemia through what mechanism?
increased HGH is secreted, which causes increased glucagon release
What drug class can cause hyperglycemia?
steroids
What are three common causes of hypoglycemia?
insulin OD
starvation
Addision’s, Hypopituitarianism
Which electrolytes rise with kidney dysfunction?
K, PO4, Mg
Urea is formed in the ______ and excreted by the ______
formed in liver
excreted by kidneys
This test is an indirect measurement of the liver’s metabolic function and the excretory function of the kidney
BUN
Severe primary liver diseases have what effect on BUN?
decreased BUN due to decreased urea synthesis
Primary renal diseases do what to BUN?
increase BUN secondary to reduced urea excretion
Dehydration does what to BUN?
concentrates BUN, increases serum BUN
how does an upper GI bleed lead to increased BUN?
blood overloads gut with protein
What conditions lead to increased BUN?
primary renal diseases
dehydration
UGIB
high protein diet
What conditions lead to a decreased BUN?
Severe primary liver diseases
overhydration
low protein diet
What makes creatinine a specific measure of renal function?
creatinine is excreted 100% by the kidneys
Cr can be used as an approximation of what physiologic process?
GFR
Describe the relationship between GFR and Cr
inverse
What is the main cause of increased Cr?
AKI
list your DDx for increased Cr…
AKI
CKD
Rhabdo
Dehydration
list your DDx for decreased Cr
debilitation
muscular dystrophy
myasthenia gravis
An acute kidney injury results in a rapid _____ in GFR
AKI = rapid decrease of GFR
Bun/Cr ratio is helpful in determining what?
cause of AKI
A BUN/Cr of 20:1 or higher indicates…
prerenal AKI
A BUN/Cr of 10:1 indicates
intrinsic renal AKI
The following would classify as what type of AKI?
hypovolemia
CHF
vascular resistance changes
prerenal
What is the main cause of intrinsic AKI?
acute tubular necrosis from IV contrast
The following would classify as what type of AKI?
ureteral stones
bladder outlet obstruction
BPH
Urethral Stricture
postrenal
Hyper/hypochloremia usually accompanies a shift in what two measures?
sodium and bicarb
CO2 is an indirect measure of…
HCO3/bicarb
What regulates HCO3 retention or secretion?
kidneys
The following conditions affect what… albumin or globulin?
liver disease
edematous states
protein losing conditions
nutrition status
albumin
The following conditions affect what… albumin or globulin?
immune disorder
cancer
globulin
By what mechanism does albumin keep fluid within the vascular space?
maintains osmotic pressure
A patient presents with increased albumin… what can you immediately include in your DDx?
dehydration
When albumin is low, what happens to globulin and why?
elevated to maintain normal total protein
What is the MC cause of hypoalbuminemia?
liver disease
What is the complete list of DDx for hypoalbuminemia?
Liver disease
Crohns/celiac/protein losing enteropathies
nephrotic syndrome/protein losing nephropathies
burn
malnutrition/malabsorption
inflammatory disease
what is the cause of edema in nephrotic syndrome?
decreased albumin causes decreased osmotic pressure
Patients presenting with normal total protein with hypoalbuminemia and increased globulin should be considered for what conditions?
chronic liver disease
collagen vascular diseasae/lupus
patients with increased total protein with increased globulin fraction should be considered for…
multiple myeloma
what two diagnostics indicate multiple myeloma?
M-spike
bence jones proteinuria
what are the transaminases?
ASP
ALT
Which liver tests measure injury to hepatocytes?
AST, ALT
which liver tests measure injury to the bile ducts/bile flow?
ALP, total bili
Which is more specific to the liver, AST or ALT?
ALT
Where is ALP found?
liver, biliary tract, bone
if a patient presents with increased ALP in the presence of otherwise normal labs, what should you suspect?
bone pathology
What is on your list of DDx for AST/ALT > ALP?
liver drug toxicity
viral hepatitis
alcoholic and non-alcoholic liver disease
cirrhosis
infiltrative liver disease, tumor
genetic liver disorder
biliary cholestasis (obstruction)
What is the list of DDx for elevated ALP?
biliary obstruction
hepatitis, cirrhosis, infiltrative liver disease
drug toxicity
What is a common cause for increased ALP in children and adolescents?
physiologic growth
What are the broad two reasons for extrahepatic ALP elevation?
high bone turnover
3rd trimester pregnancy
what test can be ordered to distinguish between liver and bone etiology for isolated ALP elevation?
ALP isoenzymes
increased unconjugated bili is caused by…
hemolysis
HF
Gilbert syndrome
increased conjugated bili is caused by…
hepatitis
drugs
TB/liver infiltration
biliary obstruction
Calcium has an inverse relationship with…
phosphorus
of the 1% of calcium not in bone, what percent is free/ionized?
50%
of the 1% of calcium not in bone, what percent is bound to albumin?
40%
this form of calcium is free to participate in cellular function, and is the most accurate measurement of serum calcium…
ionized Ca
When serum albumin is low, what should you expect calcium level to be?
low
PTH is stimulated by falling blood Ca levels. PTH secretion from the parathyroid has what effects?
stimulates Ca release from bone
increases Ca uptake in kidneys and GI
Calcitonin is stimulated by rising blood Ca levels. When it is released by the thyroid, calcitonin has what effect?
stimulates ca deposition in bone
reduces GI and Kidney uptake of Ca
What is responsible for 90% of cases of hypercalcemia?
hyperparathyroidism and malignancy
A patient presents with the following S/S… what is this suspicious for?
- decreased neuromuscular function
- shortened QT
- Nephrolithiasis, polyuria, polydipsia
- constipation
Hypercalcemia
How do you manage hypercalcemia?
tx underlying cause
volume expansion
calcitonin, bisphosphates
What is the most common cause of hypocalcemia?
hypoalbuminemia
when you see hypoalbuminemia, what should you do to dx hypocalcemia
calculate corrected Ca
when should you check serum ionized calcium
only if dx of hypocalcemia is in doubt after calculating corrected Ca
What causes hypocalcemia from large blood transfusions
chelation of calcium to citrate additives
Hypomagnesemia causes hypocalcemia because…
Mg deficiency inhibits PTH activity
Renal failure causes hypocalcemia through what mechanism?
phosphorus retention leads to reciprocal loss of Ca
A patient presents with the following… what do you suspect?
parasthesias
hyperactive DTRs
Carpopedal spasm
Chvosteks sign
Trousseau sign
prolonged QT
Hypocalcemia
The tapping of facial nerve resulting in contraction of facial muscles is known as…
chvostek’s sign
occlusion of brachial artery for 3 minutes inducing carpal spasm is known as…
trousseau’s sign
How do you manage mild hypocalcemia?
Severe?
mild: oral calcium +/- Vitamin D
Severe: IV Calcium gluconate
What is the most important regulator of serum phosphate?
kidneys
Phosphate has an inverse relationship with what electrolyte?
calcium
What is the most common reason for hyperphosphatemia?
renal failure
What is the full list of DDx for hyperphosphatemia
renal failure
hypoparathyroidism
hypocalcemia
exogenous phosphate
What is the number one reason for hypophosphatemia?
malnutrition/malabsorption
Cellular shift is when a mediator drives electrolytes into a cell. What are two common causes of cellular shift derived hypophosphatemia?
insulin
refeeding syndrome
hypophosphatemia can be caused by…
malnutrition/malabsorption
hyperparathyroidism
chronic alcoholism
severe vomiting/diarrhea
cellular shift
Severe hypophosphatemia manifests with what sxs?
muscle weakness
rhabdo
seizures
how do you treat hyperphosphatemia
treat underlying cause
how is hypophosphatemia treated?
treat underlying cause
phosphate repletion as appropriate
magnesium levels are intimately tied to which electrolytes?
calcium and potassium
hypomagnesemia can contribute to what two conditions?
refractory hypocalcemia and hypokalemia
What are the two most common causes of hypermagnesemia?
renal insufficiency
large Mg load
The following can do what to magnesium levels?
Malnutrition/absorption
severe diarrhea
alcoholism
cellular shift
cause hypomagnesemia
Hypermagnesemia presents with…
decreased DTRs
Bradycardia
Hypotension
Hypomagnesemia presents with…
tetany
cardiac arrhythmias/torsades
How should hypermagnesemia be treated?
stop magnesium containing meds
isotonic fluids and loop diuretics
dialysis
IV calcium
How should hypomagnesemia be treated?
asymptomatic: oral Mg
symptomatic: IV Mg