Clinical Chemistry > Electrolytes > Flashcards

Electrolytes Flashcards

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1
Q

Anions move toward anode or cathode?

A

Anode

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2
Q

Cations move toward anode or cathode?

A

Cathode

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3
Q

Na, Cl, K are important for which processes?

A

Volume + osmotic regulation

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4
Q

K, Mg, and Ca are important for which processes?

A

Mycocardial rhythm and contractility

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5
Q

Mg, Ca, and Zn are important cofactors for what?

A

Enzyme activation

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6
Q

Ca and Mg are important for which process?

A

Blood coagulation

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7
Q

Water
Percent body wt?
How much in intra/extracellular compartments?
How is it controlled?

A
  • 40-75% of human body wt
  • 2/3 intracellular and 1/3 extracellular
  • Controlled by maintaining electrolyte/protein concentration in compartments
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8
Q

Osmolality
Definition?

A
  • Physical property of solution based on concentration of solute (mmol) per kg solvent (w/w)
  • Related to changes in properties of solution relative to pure water (decrease in fp and vapor pressure)
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9
Q

Osmolality
Clinical significance?

A
  • Hypothalamus responds to it
  • Affects plasma sodium conc.
  • Regulation of sodium + water controls blood volume
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10
Q

From which specimen(s) do we measure osmolality?

A

Serum or urine

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11
Q

Anti-diuretic hormone (ADH) is now called _____
Function?

A
  • Arginine vasopressin (AVP) hormone
  • Functions to promote water reabsorption in renal tubule of kidneys (aka stimulates thirst)
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12
Q

Diabetes insipidus
General mechanism?
Symptom?

A
  • Pituitary gland produces insufficient AVP, meaning body can’t reabsorb water, so that water gets excreted into lots of urine
  • Symptom: constant thirst
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13
Q

Function of Renin-Angiotensin-Aldostorone System?

A

Helps control blood pressure

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14
Q

Other factors affecting blood volume

A
  1. Atrial natriuretic peptide released by myocardial atria in response to vol expansion->promotes Na and water excretion
  2. Volume receptors independent of osmolality stimulate AVP release
  3. GFR increases with overhydration (vol expansion) and decreases with dehydration (vol depletion)
  4. Increase in plasma sodium increases urine sodium and water excretion, and vice versa (ceterus paribus)
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15
Q

How to calculate osmolality?

A
  • Uses glucose, BUN, and Na values
  • (2 X Na) + (glucose/20) + (BUN/3)
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16
Q

How to calculate osmolal gap?

A
  • Gap= Measured osmolality - calculated osmolality
  • Gap should be less than 5-10
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17
Q

Define osmolal gap

A

Difference between calculated and lab-determined osmolality

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18
Q

Sodium ion
Percent of extracellular fluid (ECF)?
Determines what parameter of plasma?
Conc. in ECF compared to intracellular?
How to prevent sodium equilibrium?

A
  • 90% ECF
  • Largely determines plasma osmolality
  • ECF Na+ > Intracellular Na+
  • ATPase ion pumps (active transport) prevents sodium equilibrium
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19
Q

How is sodium ion regulated?

A
  • Intake of water in response to thirst
  • Water excretion
  • Blood volume status
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20
Q

Sodium Reference Range

A

135-145 mmol/L

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21
Q

Serum sodium levels in hyponatremia

A

Sodium < 135 mmol/L
Sodium < 120 mmol/L clinicaly sig

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22
Q

Serum sodium levels in hypernatremia

A

Sodium > 145 mmol/L
Sodium > 160 mmol/L leads to death

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23
Q

Specimens for sodium measurment?

A
  • Serum
  • Plasma
  • Whole blood
  • Urine
  • Sweat
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24
Q

Common symptoms in hyponatremia Na+ btwn 120-135 mmol/L?

A
  • Headache
  • Nausea
  • Vomiting
  • Fatigue
  • Confusion
  • Muscle cramps
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25
Symptoms in hyponatremia Na+ < 120 mmol/L?
- Headache - Restlessness - Lethargy - Seizures - Brain-stem herniation - Respiratory arrest - Death
26
Causes of hypernatremia?
- Excess water loss - Decreased water intake - Increased intake or retention
27
Hypernatremia symptoms?
**FRIED SALT** Fever Restlessness (irritable) Increased fluid retention/BP Edema Decreased urinary output/dry mouth Skin flushed Agitation Low-grade fever Thirst
28
**Potassium** Conc intracellular fluid (ICF) vs ECF? Functions?
- Intracellular K+ 20 times greater than ECF - Functions: regulate neuromuscular excitability, heart contraction, ICF volume, H+ conc
29
Potassium regulation
- Kidneys regulate potassium balance - Potassium uptake from ECF into cells normalizes: acute rise in plasma potassium due to increased intake - Exercise increases plasma potassium - Hyperosmolality decreases plasma potassium - Cellular breakdown releases potassium into ECF so avoid hemolysis of samples
30
Factors that influence potassium distribution
1. Inhibition of **Na+ K+ ATPase** pump 2. **Insulin** promotes potassium ions entering muscle and liver 3. **Catecholamines** promote cellular entry of potassium
31
High WBC manifests as which condition?
Pseudo-hyperkalemia (false increase in potassium levels)
32
Serum potassium ref range
3.5-5.1 mmol/L
33
Urine 24 hr potassium reference range
33-86 mmol/d
34
Causes of hypokalemia
- GI loss (vomiting, malabsorption) - Renal loss (diuretics, nephritis, acute leukemia) - Cellular shift (alkalosis or insulin overdose) - Reduced intake
35
Hypokalemia signs and symptoms
**A SIC WALT** Alkalosis Shallow respirations Irritability Confusion/drowsiness Weakness/fatigue Arrhythmias Lethargy Thready pulse
36
Causes of hyperkalemia
- Decreased renal excretion (renal failure, diuretics) - Cellular shift (acidosis, muscle/cell injury, chemo, leukemia, hemolysis) - Increased intake - Artifactual (sample hemolysis, thrombocytosis, prolonged tourniquet use or excessive fist clenching)
37
Hyperkalemia sign and symptoms
**MURDER** Muscle cramps Urine abnormalities Respiratory distressed Decreased cardiac contractility EKG changes REflexes
38
**Chloride ion** Majority conc. found where? Functions? Absorbed by?
- Major extracellular ion - Functions: maintains osmolality, blood volume, and electric neutrality Ingested in diet and almost completely absorbed by intestinal tract
39
Chloride clinical applications
- Hyperchloremia - Hypochloremia
40
Specimens for measuring chloride
Serum Plasma Urine Sweat
41
Ref range for chloride in plasma/serum
98-107 mmol/L
42
Ref range for urine chloride (24 hr)
110-250 mmol/d
43
Bicarbonate (HCO3-) makes up what percent of CO2? What about this percentage makes it "special?"
90% of CO2, which is special because it means that it can correlate closely with total CO2 on metabolic panel
44
**Bicarb** Abundance? Where? Function? Regulation? Clinical applications?
- Second most abundant anion in ECF - Functions to buffer blood - Regulation: reabsorbed by proximal (85%) and distal (15%) tubules in kidneys - Metabolic acidosis may reduce bicarb
45
Determinations of CO2
- Serum or plasma specimens - ISE and enzymatic methods
46
Total CO2 equation
Total CO2 = CO2 (g) + HCO3- + H2CO3
47
Reference range for venous CO2 in plasma or serum?
22-29 mmol/L
48
Describe chloride-bicarbonate exchange
Chloride in Bicarb out Mediated by one exchange protein
49
**Magnesium** Abundance? Where? Functions? Regulation?
- Fourth most abundant cation in body, second intracellularly - Functions: glycolysis, transcellular ion transport, neuromuscular transmission, synthesis of carbs/proteins/lipids/nucleic acids, and release of/response to certain hormones **(cofactor for 300+ enzymes)** - Regulation: controlled mainly by kidneys (reabsorb in deficiency/excrete excess
50
Magnesium reference range in serum?
0.66-1.07 mmol/L
51
General causes of hypomagnesemia?
- Increased renal excretion (glomerulonephritis) - Increased endocrine excretion (hyperthyroidism) - Increased drug-induced excretion (diuretics, Abx) - Reduced absorption - Reduced intake - Misc (pregnancy, excess lactation)
52
General causes of hypermagnesemia?
- Decreased excretion (hypothyroidism) - Increased intake (enema) - Misc (dehydration, bone carcinoma)
53
What conc of Mg2+ causes death?
Mg2+ > 5.0 mmol/L
54
**Calcium** Distribution? Functions? Regulation?
- Distribution: 99% body Ca2+ in bone, 1% in blood/other ECF - Functions: **Essential for myocardial contraction**, maintaining normal ionized levels during surgery, and in critically ill patients - Regulation: by PTH, **Vit D**, and calcitonin. Blood-ionized Ca2+ closely regulated with mean conc 1.18 mmol/L
55
Causes of hypocalcemia
- Primary hypoparathyroidism - Vit D deficiency - Hypomagnesemia - Hypermagnesemia - Hypoalbuminemia - Acute pancreatitis - Renal disease - Rhabdomyolysis
56
Causes of hypercalcemia
- Primary hyperparathyroidism - Hyperthryoidism - Increased Vit D - Benign familial hypocalciuria - Malignancy - Multiple myeloma - Milk alkali syndrome - Thiazide diuretics - Prolonged immobilization
57
**Phosphorus/Phosphate** Found where? Functions? Regulation?
- Found everywhere in living cells, 80% found in bone/20% in soft tissues/serum plasma <1% - Functions in lots of biochem processes - Regulation: may be absorbed in intestine from dietary sources, released from cells into blood, and lost from bone
58
**Lactate** Found where? Clinical applications? Regulation?
- By-product of emergency mechanism that makes small amount of ATP when hypoxic - Clinical apps: metabolic monitoring of critically ill pts - Regulation non-specific; Rapid rise when O2 delivery decreases below critical level
59
Type A (anaerobic) causes of lactic acidosis?
- Shock - Heart failure - Asphyxia - Carbon monoxide poisoning
60
Type B (aerobic) causes of lactic acidosis
- Systemic disease (diabetes, neoplasia, hepatic failure, renal failure) - Drugs (ethanol/methanol, salicylate overdose, inborn errors of metabolism)
61
Explain metabolic effects of hypoxia and cellular consequence
Lactic acid accumulation -> cell death
62
Anion gap definition + equation
Difference between **unmeasured anions** and **unmeasured cations** AG = [Na + K] - [Cl + HCO3]
63
Anion gap reference range
10-20 mmol/L
64
Anion gap usefulness
- Indicate increase in 1+ anions in serum - QC for analyzer used to measure electrolytes
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