Body Fluids and Electrolytes Flashcards
(195 cards)
1
Q
What are electrolytes?
A
Molecules that dissociate into charged ions in water, carry electrical current
Anions or cations
2
Q
What are anions?
A
Negatively charged ions
Move to the anode (positive pole)
3
Q
What are examples of anions?
A
Chloride
Bicarbonate
Phosphate
4
Q
What are cations?
A
Positively charged ions
Move to the cathode (negative pole)
5
Q
What are examples of cations?
A
Sodium
Potassium
Magnesium
Calcium
6
Q
What are the functions of electrolytes?
A
Maintain osmotic pressure and water balance Maintain pH Regulate heart and muscle function Redox reactions Enzyme cofactors/activators
7
Q
What interference should be avoided for electrolyte analysis? Why?
A
Hemolysis
Increased K
Decreased Na and Cl by dilution
8
Q
Why should serum/plasma be separated from cells quickly?
A
Otherwise K will be released into plasma and falsely increase results
9
Q
What might cause falsely increased K before collection?
A
Exercise
Pumping fist
Hemoconcentration due to extended tourniquet use
10
Q
How is water distributed in the body?
A
Intracellular fluid (70%)
Extracellular fluid (30%)
- Plasma (20%)
- Interstitial fluid (80%)
11
Q
How does osmosis work?
A
Water moves across semi-permeable membranes into the compartment with a higher concentration of non-diffusible particles
12
Q
How is water control mainly achieved by the kidneys?
A
By ADH
13
Q
What happens during a concentrated state?
A
Hypernatremia
Hyperosmolality (more solutes)
Hypovolemia (low water volume)
14
Q
What happens during a diluted state?
A
Hyponatermia
Hyposmolality (less solutes)
Hypervolemia (high water volume)
15
Q
How is water balance monitored?
A
CNS osmoregulators
Baroreceptors in kidneys
Baroreceptors in heart and blood vessels
Adrenal cortical cells
16
Q
How does aldosterone help water regulation?
A
Increases sodium resorption and potassium excretion during hyponatremia/hyposmolality
Decreases sodium resorption and potassium excretion during hypernatremia/hyperosmolality
17
Q
How does ADH help water regulation?
A
When osmolality rises ADH is released stimulating the resorption of water to dilute the blood
When osmolality lowers ADH is suppressed in order to secrete excess water
18
Q
What is sodium?
A
Dominant electrolyte in ECF
Major extracellular cation
19
Q
What does sodium do?
A
Major role in plasma osmolality and water balance
20
Q
Where is sodium high? Low?
A
Very low in cells due to Na/K pump
High in ECR
21
Q
How are sodium levels regulated?
A
Filtered by kidneys then reabsorbed as controlled by aldosterone
22
Q
What stimulates aldosterone release? From where?
A
Released from the adrenal cortex in response to:
Low osmolality
Low sodium
High potassium
Low cardiac output
23
Q
What is potassium?
A
Major intracellular cation
24
Q
Where is potassium high? Low?
A
High in cells
Low in fluids
25
How are potassium levels regulated?
Filtered by kidneys then reabsorbed the excreted again
26
How does aldosterone affect potassium levels?
Lowers potassium
| Increase sodium resorption means potassium excreted in exchange
27
How might potassium be lost from cells?
```
Dehydration - follows water out
Acidosis - displaced by H+
Cellular breakdown (crush injuries, protein breakdown)
```
28
How might potassium be gained in cells?
Alkalosis - moves into cell as H+ leaves
29
What does potassium do?
Regulating cell membrane potentials (neuromuscular excitability)
30
What happens if potassium is imbalanced?
Cardiac arrythmias
| Muscle weakness
31
What is chloride?
Major extracellular anion
32
How are chloride levels regulated?
Filtered by kidneys the reabsorbed
| Follows sodium passively and "pumped" back in
33
What does chloride do?
Maintains electroneutrality
Retained if cations are increased
Lost if anions are increased
34
What is the anion gap formula?
Na - [Cl + HCO3]
or
[Na + K] - [Cl + HCO3]
35
What causes the anion gap?
Anions in the sample not measured such as albumin, proteins, phosphate, etc
36
What causes an increased anion gap?
Displacement of Cl by other anions
| Low Cl is not accounted for by an increase in HCO3 or decrease in cations
37
What are examples of things that cause an increased anion gap?
Ketones
Lactic acid
Toxic ingestions (alcohol, salicylate)
38
Is a decreased anion gap possible?
Not really, maybe hypoalbuminemia
| Usually test issue
39
What is bicarbonate?
Major buffer base of plasma
| The form most CO2 is transported as in plasma
40
How are bicarbonate levels controlled?
Filtered by kidneys
Converted to carbonic acid and CO2
CO2 enters cells and is used to create new HCO3 when it moves into the blood
41
What is magnesium?
Second most abundant intracellular cation
42
What does magnesium do?
Enzyme activator
Influences nerve control
Influences neuromuscular contration
Formation of bones and teeth
43
Where is most magnesium found?
65% in bones and teeth
| 30% in intracellular fluid
44
How is magnesium found in blood?
30% protein bound
Ionized form is active
45
How is magnesium regulated?
PTH regulates plasma levels by increasing resorption
46
Where is calcium found in the body?
99% bones and teeth
47
How does calcium travel in the blood?
50% free, ionized, active
45% bound mostly to albumin
5% in complexes
48
What is ionized calcium levels dependent on?
Dependent on plasma protein and pH levels
Reduced in alkalosis and when there is increased plasma proteins
49
What does calcium do?
Enzyme activator (coagulation)
Muscle contraction
Influences membrane permeability
Influences cell motility
50
What happens when calcium is elevated?
Muscle weakness
| Loss of neuromuscular excitability
51
What happens when calcium is decreased?
Increased muscle excitability
Spasms
Cardiac arrhythmia
52
How is calcium absorbed into the body?
Requires activated vitamin D in intestine
53
What causes decreased calcium absorption?
High pH
| High phosphate level
54
How is calcium regulated?
PTH and calcitonin
55
How does PTH affect calcium blood levels?
PTH is secreted when calcium is low
It increases reabsorption by kidneys and breakdown of bone by osteoclasts
56
How does calcitonin affect calcium blood levels?
Calcitonin is secreted when calcium is high
It decreases kidney reabsorption and simulates osteoblasts to increase bone synthesis (inhibits osteoclasts)
57
What is phosphorus?
Major intracellular anion
| Component of many molecules like ATP
58
Where is most phosphorus found?
80% in bones
59
How is phosphorus absorbed?
Vitamin D increases absorption and kidney resorption
60
What affects phosphorus levels the most?
PTH
| Which decreases phosphorus by increasing excretion
61
What acts conversely with calcium?
Phosphorus
62
Which electrolytes are mostly in ECF?
Sodium and chloride
63
Which electrolytes are mostly in ICF?
Potassium, magnesium, and phosphorus
64
What is fluid depletion?
Loss of fluid
65
What causes fluid depletion?
Vomiting/diarrhea
Burns
Decreased intake
Sweating/high temperature
66
What are electrolyte findings in water depletion?
Increased sodium and osmolality
| Decreased urine volumeW
67
What is diabetes insipidus?
Decreased ADH causes less water to be reabsorbed by kidneys
| Urine is very dilute but large quantities
68
What is fluid excess?
Increased fluid
69
What causes fluid excess?
Failure of homeostasis
Increased intake
Increased ADH
70
What can fluid excess cause?
Edema, accumulation of interstitial fluid causing swelling
71
What causes hypernatremia?
Decreased plasma water
or
Increased plasma Na
72
When might hypernatremia be seen?
Dehydration
Diabetes insipidus
Primary hyperaldosteronism (increased resorption of Na)
Excess intake
73
What causes hyponatremia
Increased plasma water
or
Decreased plasma Na
74
When might hyponatremia be seen?
```
Diuretic medication (decreased resorption)
Excessive sweating
Renal conditions
Hypoaldosteronism/Addison's Disease
Severe vomiting and diarrhea
Acidosis
Decreased intake
Syndrome of inappropriate ADH secretion (water retention)
```
75
What is pseudohyponatremia?
Electrolyte exclusion effect
Increased protein or lipid reduce water component
Apparent decrease in all electrolytes using indirect methods (dilution)
76
What is hyperkalemia?
Elevated potassium
77
What causes hyperkalemia?
```
Crush injuries
Metabolic acidosis (pH decreases K increases due to displacement from cells and H+ excreted over K)
Hypoaldosteronism/Addison's Disease (Na secreted over K)
```
78
What causes hypokalemia
```
Hyperaldosteronism (Na reabsorbed, K excreted)
Metabolic alkalosis (K excreted over H+)
Vomitting/diarrhea
```
79
What causes hypochloremia?
Displacement by other anions (ketoacidosis, lactic acidosis, metabolic alkalosis)
Associated with Na loss
- Hypoaldosteronism/Addison's Disease
- Vomiting/diarrhea
80
What causes hyperchloremia?
Dehydration
Increased salt intake
Decreased bicarbonate
- Respiratory alkalosis (CO2 lost, Cl moves out of cells to compensate for lost anions [HCO3])
81
What is the sweat chloride test?
Diagnoses cystic fibrosis
| Chloride and sodium levels markedly elevated (> 60 mmol/L)
82
What causes hypermagnesemia?
Usually due to magnesium infusion especially with renal impairment
Also seen in renal failure
83
What causes hypomagnesemia?
Severe vomiting/diarrhea
Drug therapy
Malnutrition
84
What causes hypercalcemia?
Hyperparathyroidism (increased PTH = increased calcium)
Excessive vitamin D
Multiple myeloma
85
What causes hypocalcemia?
```
Hypoparathyroidism (decrease PTH = decreased calcium)
Protein loss (nephrotic syndrome)
Chronic hypomagnesemia
```
86
What causes hyperphoshatemia?
Acute or chronic renal failure (impaired excretion)
Increased intake
Lymphoblastic leukemia
87
What causes hypophospatemia?
Hyperparathyroidism (Increased PTH = increased excretion)
88
How is sodium typically analyzed?
ISE typically glass membrane
Sometimes differential potentiometry using dry film dual ISE electrode slides (Vitros)
89
What causes interference in sodium analysis?
```
Severe hemolysis (dilution)
Hyperlipidemia/hyperproteinemia in indirect methods
```
90
What are the reference ranges for sodium in serum, urine, sweat, and CSF?
Serum: 135-150 mmol/L
Urine 40-220 mmol/day (24 hr)
Sweat 10-40 mmol/L
CSF 135-150 mmol/L
91
How is potassium usually measured?
ISE usually valinomycin membrane
Sometimes differential potentiometry using dry film dual ISE electrode slides (Vitros)
92
What might cause interference in potassium measurement?
Hemolysis (K release from cells)
Excessive time on cells
Hyperlipidemia/hyperproteinemia in indirect methods
93
What is the reference range for potassium?
3.5-5.0 mmol/L
94
How is chloride usually measured?
ISE typically a sliver chloride/silver sulphide membrane
95
What is something to note about a chloride ISE?
It will detect all halogens not just chloride
Samples with bromide containing drugs will interfere
96
What are other ways that chloride can be measured?
```
Colormetric titration (amperometric)
Mercuric thiocyanate (photometric)
```
97
How does colormetric titration work?
An electrochemical titration of chloride ions with silver ions to form AgCl
One all the chloride ions are used silver ions are present in excess
This results in a change of conductivity detected by electrodes which stop the reaction
Time is proportional to chloride concentration
98
What are interferences with chloride measurement?
Other halogens
Hyperlipidemia/hyperproteinemia with indirect methods
99
How does the mercuric thiocyante method work?
Mercuric thiocyanate and ferric nitrate added
Chloide reacts with mercuric thiocyanate to form precipitate mercuric chloride
Thiocyanate ions react with ferric ions to form red ferric thiocyante
Ferric thiocyante is measured at 480nm
Proportional to Chloride
100
What are the reference ranges for chloride in serum, urine, sweat, and CSF?
Serum 98-108 mmol/L
Urine 110-250 mmol/L (24hr)
Sweat 0-40 mmol/L
CSF 120-130 mmol/L
101
How is bicarbonate usually analyzed?
ISE usually gas-permeable silicone rubber membrane
(pH electrode)
Acid reagent added to convert all forms to CO2
102
What is the reference range for bicarbonate?
22-30 mmol/L
103
What will cause interference with chloride?
Remaining on cells
| Hemolysis (dilution)
104
What are 4 methods that can be used for magnesium analysis?
Calagmite
Formazan (vitros)
Methylthymol blue
Enzyme
All spectrophotometric
105
How does the calagmie method work?
Calagmite reacts with magnesium at an alkaline pH to form calagmite-magnesium complex
Measured at 532 nm
106
How does the Formazan method work?
Formazen dye binds magnesium
Measured at 660nm
107
How does the methythymol blue method work?
Magnesium binds with the chromogen to form a colored complex
108
How does the enzyme method work?
Magnesium and ATP react to eventually form NADPH
NADPH is measured at 340nm
Proportional to magnesium
109
What interferes with magnesium analysis?
Hemolysis (released from cells)
Leaving on cells
EDTA, citrate, and oxalate anticoagulants which bind magnesium
110
What is the reference range for magnesium?
0.65-1.05 mmol/L
111
What are methods that can analyze calcium?
O-Cresolphtalein complexone method
Arsenazo III method
Both spectrophotometric
112
How does the O-Cresolphthalein complexone method work?
Calcium combines with the ortho-cresolphthalein complexone at alkaline pH to form a purple chromophone
Measured at 575nm
113
How does the Arenazo III method work?
Dye combines with calcium to form colored complex
Measured at 660nm
114
What causes interference with calcium analysis?
Magnesium in o-cresolphthalein method (eliminated with another reagent)
Extended tourniquet use
EDTA and oxalate anticoagulants remove calcium
115
What is the reference range for ionized and total calcium?
Ionized 1.15-1.35 mmol/L
| Total 2.10-2.60 mmol/L
116
What are critical calcium levels?
Ionized < 1.75 > 3.25 mmol/L
Total < 0.85 > 1.50 mmol/L
117
How is phosphorus analyzed?
Ammonium phosphomolybdate complex measured at 340nm
or
further reduced into heteropolymolybdate blue and read at 660nm
118
What is the reference range for phosphorus?
0.80 - 1.50 mmol/L
Higher in children and newborns
119
What interferes with phosphorus analysis?
EDTA, citrate, and oxalate
| Hemolysis (released from cells)
120
List the 4 ions commonly referred to as electrolytes
Na, K, Cl, HCO3
121
State the importance of selecting a proper anticoagulant for the collection of samples for electrolyte measurement
Ammonium or lithium heparin preferred
Anticoagulants with Na or K will falsely increase results
122
List the two main mechanisms that control water balance
Voluntary intake
| Urinary output
123
Name the source tissue that secretes renin
Juxta-glomerular apparatus of the kidneys
124
Describe ADH with regards to source, stimulus for release, target tissue, action, and result
```
S: posterior pituitary
R:increased plasma osmolarity
T: distal renal tubules
A: water resorption by tubules
R: water conservation, concentrated urine
```
125
Describe aldosterone with regards to source, stimulus for release, target tissue, action, and result
```
S: adrenal cortex
R: renin secretion during hypovolemia
T: kidneys
A: sodium resorption
R: hypernatermia and hyperosmolality during hypovolemia
```
126
Name the major extracellular and intracellular cations and their importance in body funtion
Extracellular: Na (water balance)
Intracellular: K (neuromuscular excitability), Mg (enzymes, nerves, neuromuscular, bones and teeth)
127
State the effect of plasma H+ ion concentration (pH) on potassium levels
Acidosis causes K to be displaced from cells as H moves in
128
State the calculation used to determine anion gap
[Na + K] - [Cl + HCO3]
129
State what an increased anion gap can indicate
Displacement of Cl by other anions
Acidosis
Toxic ingestion
130
State what a decreased anion gap can indicate
Hypoalbuminemia
Usually measurement issue
131
List the approximate distribution of calcium in the plasma, and indicate which is the active form
50% free/ionized = active
45% bound to protein
5% in complexes
132
State the affect of increased protein levels on ionized calcium levels
Lowers ionized calcium
133
State the affect of decreased pH on ionized calcium levels
Increased ionized calcium
134
State the physiological affects of both increased and decreased calcium
Increased: muscle weakness, arrhythmias
Decreased: muscle excitability, spasms, arrhythimias
135
List the two hormones involved in calcium regulation and their actions
PTH: increases blood calcium levels (increases calcium reabsorption, increased bone breakdown)
Calcitonin: decreases blood calcium levels (increases bone creation, calcium excretion)
136
List the common lab findings associated with fluid depletion
Increased Na, osmolality, urea, Hct
Decreased urine volume
137
Briefly describe diabetes insipidus
Decreased ADH causes failure to concentrate urine
High urine output with low SG and no glucose
138
List three causes associated with hypernatremia
Dehydration
Decreased water intake
Hyperaldosteronism
139
List three causes associated with hyponatremia
Vomiting/diarrhea
Hypoaldosteronism
Inappropriate ADH secretion
140
List 3 causes associated with hyperkalemia
Crush injuries
Metabolic acidosis
Hyperaldosteronism
141
List 3 causes associated with hypokalemia
Hyperaldosteronism
Metabolic alkalosis
Vomiting/diarrhea
142
State the effect on electrolyte measurements caused by excessive lipids or proteins in samples, and which methods are more affected
Cause apparent decrease in all electrolytes in indirect methods
Due to excess solids
143
State the 3 conditions that can cause displacement of chloride ions by other anions
Ketoacidosis
Lactic acidosis
Metabolic alkalosis
144
Name the condition assessed by measuring sweat chloride and the typical finding
Cystic fibrosis
> 60 mmol/L
145
State 1 major cause of hyper and hypomagnesemia
Magnesium product infusions
Malnutrition
146
State two major causes of hypercalcemia and hypocalcemia
Hyperparathyroidism, excessive vitamin D
Hypoparathyroid
Protein loss
147
State the type of membrane used for sodium ISEs
Glass
148
State the type of membrane used for potassium ISEs
Valinomycin
149
State the type of membrane used for chloride ISEs
Silver chloride / silver sulphide
150
State the type of membrane used for bicarbonate ISEs
Silicone rubber
151
State the effect on potassium levels if the sample is hemolyzed or allowed to sit on cells
Potassium increased due to release from cells
152
State the potential interference that can be experienced with chloride ISEs
Bromide containing drugs
Electrode measures all halides
153
List the spectrophotometric methods used for chloride analysis
Mercuric thiocyanate
154
List the spectrophotometric methods used for magnesium analysis
Calagmite
Formazan
Methylthymol blue
Enzymatic
155
List the spectrophotometric methods used for calcium analysis
O-cresolphthalein complexone
| Arsenazo III
156
List the spectrophotometric methods used for phosphate analysis
Ammonium phosphomolybdate
157
List the electrolytes that are falsely increased due to hemolysis or increased time on cells
Mostly K
| Mg, PO4
158
State the reference range for sodium
135 - 150 mmol/L
159
State the reference range for potassium
3.5 - 5.0 mmol/L
160
State the reference range for chloride
98 - 108 mmol/L
161
State the reference range for bicarbonate
22 - 30 mmol/L
162
State the reference range for total calcium
2.10 - 2.60 mmol/L
163
State the reference range for ionized calcium
1.15 - 1.35 mmol/L
164
State the reference range for magnesium
0.65 - 1.05 mmol/L
165
State the reference range for phosphate
0.80 - 1.50
166
TRUE OR FALSE
An electrolyte is a substance that dissociates into ions in water and is also able to conduct an electrical current
True
167
TRUE OR FALSE
Magnesium is important in reactions of the coagulation system
False
Calcium is
168
TRUE OR FALSE
Water acts as a lubricant as a component of joint fluids and mucous
True
169
TRUE OR FALSE
Potassium is the most concentrated ion in the extracellular fluid
TRUE OR FALSE
Sodium is
170
TRUE OR FALSE
Potassium is important in re-establishing resting membrane potentials in muscles and neurons
True
171
TRUE OR FALSE
Anabolic reactions in our cells generate about 250 mL of water per day
True
172
TRUE OR FALSE
The thirst center is located in the juxta-glomerular apparatus
False
hypothalamus
173
TRUE OR FALSE
Sodium on creates much of the osmotic pressure in body fluid
True
174
TRUE OR FALSE
Vasopressin is also known as antidiuretic hormone
True
175
TRUE OR FALSE
In dehydration plasma osmolality is low
False
High
176
Aldosterone does which of the following
a. vasodilator
b. increases aldosterone
c. increases sodium resorption
d. activates angiotensinogen
e. increases water resorption
c. increases sodium resorption
177
Rennin does which of the following
a. vasodilator
b. increases aldosterone
c. increases sodium resorption
d. activates angiotensinogen
e. increases water resorption
d. activates angiotensinogen
178
Antidiuretic hormone does which of the following
a. vasodilator
b. increases aldosterone
c. increases sodium resorption
d. activates angiotensinogen
e. increases water resorption
e. increases water resorption
179
Atrial natriuretic peptide does which of the following
a. vasodilator
b. increases aldosterone
c. increases sodium resorption
d. activates angiotensinogen
e. increases water resorption
a. vasodilator
180
Angiotensin II does which of the following
a. vasodilator
b. increases aldosterone
c. increases sodium resorption
d. activates angiotensinogen
e. increases water resorption
b. increases aldosterone
181
TRUE OR FALSE
Chloride helps maintain the electropositivity of the ECF
False
Shifts back and forth, often allowing Na movement to maintain electroneutrality
182
TRUE OR FALSE
Potassium is excreted by the proximal tubules
False
Distal tubules
183
TRUE OR FALSE
Sodium concentration in the plasma is normally about 105 mmol/L
False
135-150 mmol/L ~142 mmol/L
184
TRUE OR FALSE
In ketoacidosis there is usually an anion gap
True
185
TRUE OR FALSE
Diabetes insipidus is due to increased aldosterone
False
Decreased ADH
186
TRUE OR FALSE
Pseudohyperkalemia is seen in grossly lipemic serums
False
Pseudohypokalemia
187
TRUE OR FALSE
Parathyroid hormone decreases renal excretion of phosphate
False
PTH decreases resorption by kidneys
188
TRUE OR FALSE
Absorption of calcium is dependent upon activated vitamin D
True
189
TRUE OR FALSE
Plasma magnesium is regulated by thyroxine
False
PTH promotes tubular resorption of Mg
190
TRUE OR FALSE
Calcitonin decreases blood calcium
True
191
TRUE OR FALSE
A danger of dextrose infusion is hyperphosphatemia
False
Hypophospatemia by dilution
192
TRUE OR FALSE
The ISE for potassium has a cellulose membrane
False
Valinomycin
193
TRUE OR FALSE
Severe hemolysis will decrease the serum sodium level
True
194
TRUE OR FALSE
The Vitros uses an ISE slid method for measuring chloride
True
195
TRUE OR FALSE
The CX uses colormetric methods for measuring Mg, Ca, and P
True
