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Clin Lab Med Unit 1 > CMP & Electrolyte Abnormalities > Flashcards

CMP & Electrolyte Abnormalities Flashcards

1
Q

Tests that make up the CMP

A
  • Glucose
  • Renal function: BUN, Creatinine, BUN/Cr ratio
  • Electrolytes: Na, K, Cl, CO2

Total protein

Albumin

Ca

Liver: ALP, ALT, AST, Total bilirubin

(* indicates test that are part of the Basic Metabolic Panel)

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2
Q

________ is involved in energy metabolism

A

Glucose

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3
Q

Glucose is regulated by ________ hormones

A

Pancreatic hormones:

Insulin released in response to HIGH blood glucose

Glucagon released in response to LOW blood glucose

Glucose levels are influenced by multiple factors

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4
Q

DDx for HYPERglycemia

A 
Diabetes
Gestational diabetes
IV Dextrose infusion
Drugs (steroids, etc)
Stress (trauma, illness, infection etc)
Endocrine disorders (Cushings, Acromegaly)
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5
Q

Why does stress lead to hyperglycemia?

A

Trauma, illness, infection, burns etc lead to increased catecholamine release by the adrenal gland, which raises blood glucose

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6
Q

DDx for HYPOglycemia

A

Drugs (insulin overdose)

Starvation

Endocrine disorders (Addison Disease, Hypopituitarism)

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7
Q

In evaluating blood glucose for diabetics, correlate levels according to …

A

Time of day obtained (fasting, casual, post-prandial, etc)

Note: post-prandial = 2 hours after a meal

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8
Q

What does BUN measure?

A

Blood Urea Nitrogen measures the amount of Urea formed in the liver as a by-product of protein metabolism

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9
Q

Urea is made in the ______ and excreted by ________.

A

Made in the liver, excreted by the kidneys

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10
Q

BUN is an indirect measurement of _________________ and ______________.

A

Metabolic function of the liver and excretory function of the kidney

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11
Q

Severe primary liver diseases _________ BUN

A

Decrease

2˚ decreased urea synthesis

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12
Q

Nearly all primary renal diseases will _______ BUN

A

Increase

2˚ reduced urea excretion

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13
Q

How does hydration status affect BUN?

A

Dehydration concentrates BUN, thus RAISING it

Overhydration dilutes BUN, thus LOWERING it

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14
Q

An upper GI bleed will _______ BUN levels

A

Increase

Blood overloads the gut with protein, thus the BUN goes up

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15
Q

How does protein intake affect BUN?

A

Low protein diets lower BUN

High protein diets raise BUN

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16
Q

Catabolic product of creatine phosphate

A

Creatinine (Cr)

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17
Q

Because it is excreted entirely by the kidneys, ______ is a measurement of renal function

A

Creatinine

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18
Q

Creatinine is interpreted in conjunction with…

A

BUN

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19
Q

Creatinine can be used as an approximation of …

A

Glomerular filtration rate (GFR)

Inverse relationship between Cr and GFR

Generally, a doubling of Cr suggests a 50% reduction in GFR

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20
Q

Why must we interpret Creatinine with regards to GFR with caution?

A

Serum CR levels are influenced by muscle mass, protein intake, certain drugs, and unstable critically ill patients

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21
Q

Factors increasing levels of Creatinine (Cr)

A

Acute Kidney Injury (multiple etiologies)
Chronic Kidney Disease
Rhabdomyolysis
Dehydration

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22
Q

Factors decreasing levels of Creatinine (Cr)

A

Debilitation
Muscular Dystrophy
Myasthenia Gravis

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23
Q

The BUN/Cr ratio is helpful in determining cause of ____________.

A

Acute Kidney Injury

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24
Q

Normal BUN/Cr ratio

A

~10-20/1 (if BUN = 10, Cr=~1)

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25
Q

BUN/Cr ratio > 20:1 suggests…

A

Prerenal cause of AKI

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26
Q

BUN/Cr ratio ~10:1 suggests…

A

Intrinsic renal AKI

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27
Q

What BUN/Cr ratio might we expect for postrenal AKIs?

A

Varies!

Variations in ratio are due to the extent and overlap of etiologies

Hx and Phys Ex are important

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28
Q

How is the Chloride (Cl) test used?

A

In the evaluation of electrolyte and acid-base disturbances.

Hypo- and hyperchloremia rarely occur alone - usually accompany shifts in sodium and bicarbonate

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29
Q

How is the CO2 test used?

A

In the evaluation of electrolyte and acid-base disturbances

CO2 is an indirect measurement of bicarbonate (HCO3), which indicates pH.

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30
Q

HCO3 is regulated by the _________

A

Kidneys!

Excretion or retention of bicarbonate pending acid-base disturbance

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31
Q

The total protein is a combination of what?

A

Albumin + Globulin

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32
Q

Fractionation of total protein is used to diagnose, evaluate, and monitor:

A

Liver disease, edematous states, protein-losing conditions, nutrition status, immune disorders, and cancer

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33
Q

Albumin is synthesized in the ________

A

Liver

Measurement reflects synthetic function of the liver

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34
Q

Albumin helps maintain ____________

A

Osmotic pressure

Keeps fluid within the vascular space
Transports hormones, enzymes, and drugs

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35
Q

Increased albumin is associated with ….

A

Dehydration

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36
Q

Globulin represents non-albumin proteins, produced mainly in …

A

Bone marrow and lymph tissues

They are the building blocks for antibodies, acute-phase reactants, transport

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37
Q

The three groups of globulins

A

Alpha
Beta
Gamma

38
Q

________ is often elevated when albumin is low to maintain normal total protein levels

A

Globulin

39
Q

DDx for Hypoalbuminemia

A

Liver Disease

Protein-losing enteropathies (Crohn’s, Celiac)

Protein-losing nephropathies (Nephrotic Syndrome)

Burns

Malnutrition/malabsorption

Inflammatory diseases (globulins increase causing albumin to decrease)

40
Q

Normal total protein with low albumin and normal/increased globulin

A

Chronic liver disease

Collagen vascular disease (Lupus)

41
Q

Increased Total Protein with increased globulin fraction

A

Multiple Myeloma

SPEP (Serum protein electrophoresis) will demonstrate “M-spike” and you’ll see Bence-Jones proteins in urine

42
Q

Hepatocellular injury will effect…

A

AST and ALT

43
Q

Cholestatic injury (to bile ducts and/or bile flow) will effect…

A

ALP and Total billirubin

44
Q

Enzyme found in liver, cardiac and skeletal muscle, as well as kidney and brain

A

Aspartame Aminotransferase (AST)

Injury or disease affecting these tissues release AST into the bloodstream with resultant rise in AST

45
Q

Enzyme found predominantly in the LIVER; lesser quantities in kidneys, cardiac, and skeletal muscle

A

Alanine Aminotransferase (ALT)

Injury or disease affecting the liver will release ALT into the bloodstream with resultant rise in ALT

46
Q

______ is more specific to the liver than ______

A

ALT more specific than AST

Because it’s got an L. Duh

47
Q

Enzyme predominantly found in liver, biliary tract, and bone

A

Alkaline Phosphatase (ALP)

Excreted in Bile, therefore conditions that obstruct the flow of bile can increase ALP

48
Q

______ is used primarily to detect hepatobiliary and bone disorders

A

ALP

49
Q

AST & ALT > ALP reflective of …

A

Hepatocellular injury

50
Q

ALP > AST & ALT reflective of…

A

Cholestatic injury

51
Q

________ is the most frequent extrahepatic source of ALP

A

Bone

52
Q

An isolated elevated ALP in the absence of other liver test abnormalities or H/P to suggest live disease) should raise suspicion for …

A

Extrahepatic cause, especially conditions with high bone turnover

Physiologic growth in children/adolescents
Healing fractures
Bone metastasis

53
Q

The 3rd trimester of pregnancy can also give rise to …

A

Isolated elevated ALP

54
Q

Total bilirubin =

A

Unconjugated (indirect) and Conjugated (direct) bilirubin

55
Q

Excess hemolysis will …

A

Increase unconjugated bilirubin

56
Q

Steps in the Bilirubin process

A

1) Hemolysis in the spleen (RBC —> Heme —> Unconjugated bilirubin)
2) Unconjugated bilirubin, bound to albumin, is transported to the liver for uptake
3) In the liver, unconjugated bilirubin is conjugated via enzymes
4) Conjugated bilirubin is excreted through the biliary ducts into the duodenum

57
Q

Discoloration of body tissues caused by abnormally high levels of bilirubin

A

Jaundice

Can result in a defect in any stage of bilirubin metabolism

58
Q

Bilirubin is interpreted in conjunction with …

A

AST, ALT, ALP

59
Q

DDx for unconjugated hyperbilirubinemia

A

Excess hemolysis, impaired hepatic bilirubin uptake (HF), impaired bilirubin conjugation (Gilbert Syndrome)

60
Q

DDx for conjugated hyperbilirubinemia

A

Hepatitis, drugs/toxins, liver infiltrations (TB), biliary obstruction

61
Q

What test results might you see in hepatocellular damage?

A

Disproportionate elevation of AST/ALT compared to ALP

Serum Bilirubin may be elevated

62
Q

What test results might you see in cholestatic damage?

A

Disproportionate elevation in ALP compared to AST/ALT

Serum bilirubin may be elevated

63
Q

Why do we measure Ca in the blood?

A

Role in neurotransmission, muscle contraction, and blood clotting

64
Q

There is an inverse relationship between calcium and _______

A

Phosphorus

65
Q

99% of calcium is in the ______

A

Bone

66
Q

The remaining 1% of Ca in the ECF is distributed as:

A

50% free (ionized) - can participate in cellular function
10% complexed
40% protein-bound

67
Q

Which form of Ca in the ECF is physiologically active?

A

Ionized Ca

It is unaffected by serum albumin levels and free to participate in cellular function

68
Q

Complexed calcium can chelate with _________.

A

Citrate

Citrate is added to blood to prevent clotting

69
Q

When serum albumin is low, Calcium level will be…

A

Also low, because 40% of the ECF calcium is protein bound

Must look at the two together.

70
Q

Serum Total Calcium falls _____ for every 1 g/dL decrease in serum albumin

A

~0.8 mg/dL

Patients with hypoalbuminemia will need to have their total serum calcium concentration corrected for the abnormality in albumin

71
Q

Calculating Corrected Ca

A

Total serum Ca + 0.8(4.0 - serum albumin)

72
Q

Got a low Ca level?

A

Look at albumin, do a corrected Ca!

73
Q

If you get a high Calcium test, what’s the first thing you do?

A

Retest!

Always confirm a high Ca

74
Q

90% of cases of hypercalcemia are related to …

A

Primary hyperparathyroidism and malignancy

75
Q

Mechanism for high Ca in hyperparathyroidism

A

Bone reabsorption (Ca released from bone into blood) as a result of over production of Parathyroid Hormone (PTH)

76
Q

Second most common cause of hypercalcemia?

A

Malignancy

Mechanism: Tumor metastatic to bone can cause bone destruction and release Ca into bone

Mechanism: Cancer can produce PTH-like substance that drives calcium up (ectopic PTH)

77
Q

Clinical presentation of hypercalcemia

A

Decreased neuromuscular excitability —> muscle weakness, loss of muscle tone, lethargy, stupor, coma

CV: HTN, ECG abnormalities (short QT)

Renal: Polyuria, polydipsia, nephrolithiasis

GI: Anorexia, N/V, constipation

78
Q

DDx for hypocalcemia

A

Hypoalbuminemia

Large blood transfusion (citrate additives bind to Ca)

Hypomagnesemia (Mg deficiency inhibits PTH thus can be assoc. with refractory hypocalcemia)

Hypoparathyroidism

Renal failure (phosphorus retention and reciprocal loss of Ca)

Intestinal malabsorption/Vit D deficiency

79
Q

Clinical presentation of hypocalcemia

A

Increased neuromuscular excitability (tetany) —> parathesias, hyperactive reflexes, carpopedal spasms

CV: ECG changes (prolonged QT), arrhythmia, hypotension

80
Q

Carpopedal spasms and parasthesias are signs of …

A

Hypocalcemia

81
Q

Tapping facial nerve against the bone just anterior to the ear results in contraction of facial muscles

A

Chvostek’s sign (hypocalcemia)

82
Q

Occluding brachial artery for 3 minutes with BP cuff induces carpal spasms

A

Trousseau’s sign (hypocalcemia)

83
Q

Dietary phosphorus is absorbed in _____ and excreted by _____.

A

Small intestine; Kidneys

84
Q

DDx for hyperphosphatemia

A

Renal failure (increased b/c not being excreted)

Hypoparathyroidism (b/c low Ca means high PO4)

Hypocalcemia

Exogenous Phosphorus

85
Q

DDx for Hypophosphatemia

A

Malnutrition/malabsorption

Hyperparathyroidism

Chronic alcoholism

Severe diarrhea

Cellular shift (insulin, refeeding syndrome)

86
Q

Clinical presentation of hypophosphatemia

A

If severe (< 1.0 mg/dL0: muscle weakness and Rhabdomyolysis, seizures

87
Q

Magnesium is excreted by ________

A

Kidneys

88
Q

DDx Hypermagnesemia

A

Renal insufficency

Large Mg load (ingestion of Mg containing meds, IV Mg infusion for preeclampsia/eclampsia)

89
Q

DDx hypomagnesemia

A

Malnutrition/malabsorption

Severe diarrhea

Alcoholism

Cellular shift

90
Q

Clinical presentation of hypermagnesemia

A

Decreased DTRs, bradycardia, hypotension

91
Q

Clinical presentation of hypomagnesemia

A

Neuromuscular excitability (tetany)

Cardiac arrhythmias

92
Q

Mg is intimately tied to _________

A

Ca and K

Hypomagnesemia can contribute to refractory hypocalcemia and hypokalemia

Check and correct Mg deficit to fix Ca and K level!

Clin Lab Med Unit 1 (4 decks)

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