Exam 3 (Electrolytes) Flashcards
1
Q
Cations vs Anions
A
Cations: positively charged particles
Anions: negatively charged particles
2
Q
What are electrolytes?
A
Soluble substances (ions or minerals that have a charge) found in liquid serum or plasma
3
Q
What are the general overall functions of electrolytes?
A
Coagulation, Energy production, cell metabolism, skeletal/cardiac muscle function, volume and fluid gradients between cells/blood/tissues
4
Q
Humans are predominantly ______, making up ______% of body weight.
A
Water; 50-75%
5
Q
Water % ______ with age.
A
Declines
6
Q
Do women or men have less % water?
A
Women
7
Q
Do obese people have less or more water than non-obese people?
A
Less
8
Q
Intracellular fluid and % of total water
A
Fluid found inside of all cells - appx 66% of total water weight
9
Q
Extracellular fluid + 2 groups; % of total water?
A
Fluid found outside of cells that can be broken into 2 groups:
Intravascular: found in vasculature; plasma portion of whole blood
Interstitial: fluid surrounding the cells
10
Q
Active transport
A
Moves substances against concentration gradient and requires ATP
11
Q
Passive transport
A
AKA diffusion; moves substances with the concentration gradient and requires no ATP
12
Q
What is the major extracellular cation?
A
Sodium
13
Q
What is largely responsible for the osmolality of plasma?
A
Sodium
14
Q
What is the reference range for serum sodium?
A
135-145 mmol/L
15
Q
How many Na ions are pumped out of the cell for every 2 K ions in the cell?
A
3 Na per 2 K
16
Q
What is plasma sodium heavily regulated by?
A
water intake and loss of water through sweat and renal functions
17
Q
If plasma sodium osmolality is high, what occurs?
A
Hypothalamic thirst centers in the brain drive increased water consumption and ADH is released to increase water reabsorption from urine
18
Q
What is hyponatremia usually due to?
A
Increased sodium loss (decreased aldosterone, K deficiency)
Increased water retention (renal failure, nephrotic syndrome)
Water imbalance (excessive water intake, increased ADH)
19
Q
What is a critical sodium level?
A
Hyponatremic <120 mmol/L
20
Q
How are sodium levels regulated?
A
Water intake and water loss (aldosterone increases sodium reabsorption and ADH increases water reabsorption)
21
Q
Signs and symptoms of Hyponatremia
A
GI distress, neurological symptoms (weak, headache, seizure, ataxia)
22
Q
What is Hypernatremia caused by?
A
excessive water loss (diabetes insipidus, diarrhea, profuse sweating)
increased sodium retention (increased aldosterone)
Decreased water intake
23
Q
Is Hypo or Hypernatremia more critical?
A
Hyponatremia
24
Q
How can we detect sodium levels in the lab?
A
Serum/plasma (lithium heparin tube, green top) using Ion Selective Electrodes (ISE)
Can also test urine
25
Does hemolysis impact sodium levels? Why?
Not really because sodium is located outside of cells
26
Direct vs Indirect ISE
Direct ISE uses undiluted sample using whole blood
Indirect ISE uses diluted sample using plasma or serum
27
What is the major intracellular cation?
Potassium
28
Functions of potassium in the body
Regulation of neurons for action potentials, heart contractions, ICF volume, Hydrogen ion regulation, skeletal muscle contractions
29
How are potassium levels related to Sodium and Hydrogen ions?
If K ions decrease, ICF increases Na and H levels which decreases ECF levels of Na and H (leads to hyponatremia and alkalosis of blood pH)
30
What is the normal reference range for serum K?
3.5-5.1 mmol/L
31
What is potassium regulated by?
The renal system with tubular secretion and absorption (Nearly all K is reabsorbed in the PCT)
32
What are the 3 influences of potassium distribution between the ICF, ECF, and urine?
Na/K pumps, Insulin, and Catecholamines
33
How does exercise affect potassium levels?
Potassium is released from skeletal muscles during exercise due to firing multiple action potentials which could raise potassium levels greatly
34
Does hemolysis affect potassium levels?
Yes
35
What can hypokalemia lead to?
Decreased muscle contractions leading to paralysis and decreased HR
36
What can cause hypokalemia?
Renal dysfunction, cellular loss due to alkalosis or insulin overdose, decreased intake of fluid, gastrointestinal loss
37
What can hyperkalemia lead to?
Increased action potentials (cells are easier to excite) leads to muscle fatigue, paralysis, arrhythmia, death because muscle cells cannot repolarize properly
38
What are the causes of hyperkalemia?
Decreased renal excretion (renal failure)
Cellular shift (blood acidosis, hemolysis)
Increased intake
Collection error
39
How does improper collection affect potassium levels?
It can increase them because of increased hemolysis (cells release their contents into the blood stream)
40
Signs of hyperkalemia
Muscle weakness, tingling, numbness, because cells are not contracting appropriately -- can lead to cardiac arrest
41
What is the most abundant extracellular anion?
Chloride
42
What is the function of Chloride?
Maintains osmolality, blood volume, electroneutrality between ECF and ICF, plays a role in regulating HCO3 and Na levels
43
What is the common route of elimination of chloride?
Via the kidneys and the skin as sweat
44
What is the reference range for Chloride levels in serum?
98-107 mmol/L
45
What is the chloride shift?
When bicarb leaves the RBC to buffer the blood pH, Cl goes into the RBC to maintain electrical charge
46
What are chloride diseases similar to and why?
Sodium level diseases because chloride passively follows sodium
47
What is the second most abundant extracellular anion?
Bicarbinate [HCO3]
48
What does HCO3 play a role in ?
Regulating and transporting CO2 from tissues and blood to the lungs
Blood pH regulation
49
Normal Serum HCO3 levels? This is identical to which levels?
22-29 mmol/L; identical to CO2 levels
50
Blood Alkalosis: HCO3 levels, CO2 levels, leads to what
HCO3 levels increased, CO2 levels decreased, leads to the body increasing HCO3 secretion which increases H ions in blood and hypoventilation due to decreased CO2 levels
51
Blood Acidosis: CO2 levels, HCO3 levels, leads to what
Increased CO2 levels, decreased HCO3 levels, leads to kidneys increasing HCO3 tubular reabsorption and increased H ion secretion which can cause hyperventilation due to increased CO2
52
What type of conditions are ideal for CO2 samples?
Anaerobic because if sample is uncapped, CO2 can evaporate and decrease
53
Two most common ways to measure pCO2 in lab
ISE and enzymatic methods
54
Calcium is predominantly stored where? Where is the remainder?
Bone; remainder is an extracellular cation in ECF
55
Disease associated with increased HCO3?
Blood alkalosis
56
Disease associated with decreased HCO3?
Blood acidosis
57
What is the mean ionized Ca level?
1.18 mmol/L
58
Calcium levels are vital for?
cardiac/skeletal contractions, coagulation cascade function, and neuronal firing
59
Where can calcium be in the blood?
Freely circulating as ionized calcium, bound to albumin/proteins, or bound to anions like HCO3
60
How is calcium regulated in the body?
PTH increases blood calcium by acting on bone resorption and the kidneys (tubular reabsorption of Ca), Vitamin D increases blood Ca to enhance PTH effect
Calcitonin decreases blood Calcium levels by inhibiting PTH and Vitamin D for bone remodeling. Increases renal excretion of Calcium
61
T/F: Blood ionized calcium levels in neonates are usually higher at birthday and rapidly decline after 1-3 days.
True
62
What is hypocalcemia caused by?
Hypoparathyroidism, Vitamin D deficiency
63
Signs/Symptoms of hypocalcemia
Neurological, muscular, cardiac issues and coagulation issues
64
What is hypercalcemia due to?
Hyperparathyroidism, Increased vitamin D
65
How can improper collection of ionized calcium affect results?
Increased pH due to decreased CO2 in the tube will decrease ionized calcium as calcium binds to albumin
66
How is total calcium vs ionized calcium measured in the lab?
Total calcium measured by CPC
Ionized calcium measured by ISE
67
What is the second most abundant intracellular cation?
Magnesium
68
Where is Mg stored?
Mostly in bone and muscle, and a trace amount found in RBCs and blood
69
Reference range for serum Magnesium
0.66-1.07 mmol/L
70
Function of magnesium
Functions as an essential cofactor for many enzymes involved in processes like glycolysis, cell signaling, metabolism
71
How is magnesium regulated?
Magnesium is predominantly acquired from dietary sources and regulated by the kidneys where reabsorption occurs in the PCT and loop of Henle
72
What can cause hypomagnesemia?
Often seen in hospitalized patients in ICU due to increased excretion (kidney disorders), decreased absorption, decreased intake, and pregnancy
73
Signs of hypomagnesemia
Most asymptomatic until Mg levels drop below 0.5 mmol/L
74
What is hypermagnesemia caused by?
Very rare condition but most commonly caused by renal failure (GFR less than 15 mL/min)
Can also be caused by decreased excretion, increased intake, bone cancer, dehydration
75
How do we test for magnesium in the lab?
Colorimetric methods for total serum Mg using calmagite and formazan dye that form red complex and read at 532 and 660nm. Mg is greatly affected by hemolysis because it is an intracellular ion.
76
What is the predominant intracellular anion?
Phosphorous/Phosphate
77
Where is phosphate/phosphorous predominantly found in the body?
Bone, soft tissue, and then serum/plasma
78
What is the function of phosphate?
Major anion involved in many metabolic processes and genetic material (DNA and RNA's backbone)
79
Reference range for serum phosphate levels in adults
0.81-1.45 mmol/L (lower than children)
80
How is phosphate regulated?
The kidneys, vitamin D, and PTH.
(High PTH lowers phosphate levels in exchange for calcium)
(High vitamin D increases phosphate levels and calcium levels)
81
What is hypophosphatemia caused by?
Usually a complication of DKA, COPD, cancer, IBS, alcoholism
Hyperparathyroidism
Vitamin D deficiency
82
What is hyperphosphatemia caused by?
Renal disease
Hypoparathyroidism
Increased vitamin D
83
How do we test for phosphorous in the lab?
Formation of ammonium phosphomolybdate complexes using PO4 from patient that are read at 340 and 600-700 nm
84
Does hemolysis affect phosphorous levels?
Yes because it is intracellular.
85
When are lactate levels higher in the body? Why?
During strenuous exercise or hypoxic situations. This occurs because in these situations, NADH accumulates faster than NAD+ causing excess H ions in the blood and favor the reaction of pyruvate into lactate and lactic acids
86
How is lactate regulated in the body?
There is no formal regulation because it is a byproduct of hypoxic conditions. When oxygen levels are low, lactate levels increase in tissue creating muscle fatigue and weakness.
87
How is lactate removed from the body?
The liver removes excess lactate in the blood by converting it back to glucose via gluconeogenesis
88
Type A lactic acidosis
Hypoxic conditions that increase lactic acid like MI, CHF, pulmonary edema
89
Type B lactic acidosis
metabolic conditions that increase lactic acid like diabetes mellitus, infections, leukemia, liver diseases, and toxins
90
How is lactate measured in the lab?
Coupled enzymatic reactions that may be read spectrophotometrically to assess color change intensity
91
What is the anion gap?
The difference between unmeasured anions and unmeasured cations
92
The anion gap uses _______ ions to determine increased or decreased ______ ions.
measured; unmeasured
93
What is an increased anion gap caused by?
Increased unmeasured anions such as PO4, SO4, ketones, methanol, ethanol, ethylene glycol, aspirin, lactic acid
94
What is a decreased AG caused by?
Decreased unmeasured anions (hypoalbuminemia) or increased unmeasured cations (hypercalcemia or hypermagnesemia) very rare.
95
What are the measured ions in the anion gap?
K, Na, Cl, HCO3
96
What is the formula for anion gap?
AG = (cations) - (anions)
so, AG = (Na + K) - (Cl + HCO3)
97
What is reference range for anion gap?
10-20 mmol/L
98
Osmolality
# moles per kg of water
99
How is osmolality measured in the lab (most commonly)?
Freezing point depression
100
Osmolarity
# moles per L of water
101
Excessive water intake will ______ plasma osmolality.
Decrease
102
Decreased water consumption will ______ plasma osmolality.
Increase
103
Loss of ADH production
Neurogenic
104
Loss of ADH response
Nephrogenic
105
What does the RAAS system respond to? What does the RAAS system ultimately stimulate?
Decreased blood volume. It ultimately stimulates vasoconstriction, release of ADH, and release of aldosterone to increase blood volume and blood pressure.
106
Describe the RAAS system:
Renin secreted from kidneys in response to decreased blood volume/pressure (hyponatremia). Renin stimulates angiotensinogen to angiotensin I. Angiotensin I travels to the lungs where ACE converts Angiotensin I into Angiotensin II which causes vasoconstriction, ADH and aldosterone release.
107
What does AVP and ANP do?
Work to decrease blood pressure/volume (found in the heart). Opposite system than RAAS
108
What is the formula for osmolality?
2 Na + glucose/20 + BUN/3
109
What is the formula for osmolal gap?
295 (which is normal osmolality value) - osmolality value calculated
110
What impact would diabetes insipidus have on Na levels and why?
Diabetes insipidus patients lose more water in urine due to defective ADH leading to increased sodium levels in the blood.
111
Which cation functions to regulate skeletal and heart muscle contraction?
Calcium and potassium
112
What are 3 sources of error with potassium testing?
hemolysis, prolonged tourniquet use, and excessive exercise
