Electrolyte/Acid Base Disorders Flashcards
1
Q
Functions of the kidney?
A
- Primarily responsible for regulation of fluid and electrolyte balance (maintenance and regulation)
- Secretion of hormones that participate in regulation of systemic/renal hemodynamics, RBC production, Metabolism of Ca++, phosphorus & bone
2
Q
Maintenance of the kidney?
A
Maintains constant extracellular environment so cells can function
3
Q
Regulation of kidney?
A
Regulates excretion of water and solutes (Na+, K+, H+)
4
Q
Hormones secreted by kidney for regulation of hemodynamics?
A
Renin, prostaglandins, bradykinin, erythropoietin
5
Q
Common electrolytes in electrolyte disorders?
A
Na+, K+, Mg, Ca+, Phosphorus (P), Chloride (Cl), Bicarb (HCO3)
6
Q
Where are electrolytes found?
A
Serum
7
Q
What are electrolytes?
A
Chemicals that are dissolved in water –> producing ions that enable flow of electrical signals through body
8
Q
What do ions aid in?
A
Nerve excitability, endocrine secretion, membrane permeability, body fluid buffering, controlling movement of fluid between compartments
9
Q
How do ions enter the body?
A
Digestive tract (90%)
10
Q
How are ions excreted?
A
Kidneys (small amount lost through sweat/feces)
11
Q
What does serum osmolality measure?
A
Body’s electrolyte-water balance (measured by labs)
12
Q
What are the primary circulating solutes?
A
Sodium salts (Cl, HCO3), glucose, urea
13
Q
The osmolality of extracellular fluid and intracellular fluid are approximately ______?
A
Equal
14
Q
What is tonicity a measure of?
A
Effective osmotic pressure gradient; the water potential of two solutions separated by semipermeable cell membrane
(relative concentration of solutes dissolved in solution that determine direction/extent of diffusion)
15
Q
Tonicity is influenced only by what solutes?
A
Solutes that cannot cross the cell membrane (exert an effective osmotic pressure)
16
Q
What are the three classifications of tonicity?
A
Hypertonic, Hypotonic, Isotonic
*used to compare osmolarity of cell to osmolality of extracellular fluid around it
17
Q
Hypertonic fluid/electrolyte disorders cause what?
A
Fluid/H2O to flow out of cell (dehydrate)
18
Q
Hypotonic fluid/electrolyte disorders cause what?
A
Fluid/H2O to flow into cell (overhydrate)
19
Q
What happens to fluid/electrolyte balance in dehydration?
A
Serum osmolality increases leading to:
Hypertonic dehyration or Hypotonic dehydration or Isotonic dehydration
BY release of ADH
20
Q
What happens to fluid/electrolyte balance in excessive water intake?
A
Serum osmolality decreases leading to: hypervolemia
21
Q
What is the anion gap?
A
Difference between measured cations and anions in serum, plasma, or urine
22
Q
Serum anion gap formula?
A
Serum AG = measured cations - measured anions
OR
Serum AG = Na - (Cl + HCO3)
23
Q
Serum anion gap (AG) is used in the differential diagnosis of what?
A
Metabolic acidosis
24
Q
What does a high/increased AG indicate?
A
Metabolic acidosis**, hyperalbuminemia, hyperphosphatemia, lab error
25
What does a low/decreased AG indicate?
Lab error**, hypoalbuminemia, hyperkalemia, hypercalcemia, hypermagnesia, lithium toxicity
26
Sodium is a ______ _______ of ECF?
Major cation
27
Sodium is responsible for 50% of the osmotic pressure gradient existing between what?
ICF and ECF
28
How is Na+ excreted?
Kidneys
29
How much sodium is typically consumed daily in the western diet?
130-160 mmol
30
What occurs in hyponatremia?
Dec. serum osmolality: water moves from ECF to ICF
31
Hyponatremia is typically associated w/ what?
Excess water accumulation (dilutes Na+) or diuretic use (inc. water and Na+ excretion)
32
Early clinical manifestations of acute hyponatremia?
Nausea and malaise (125-130 mEq/L)
33
Delayed clinical manifestations of acute hyponatremia?
Headache, lethargy, obtundation, seizure, resp. arrest (115-120 mEq/L)
34
Severity of symptoms of hyponatremia reflects what?
Degree of cerebral involvement/over-hydration and edema
35
What is a concern with excessive cerebral edema as a result of hyponatremia?
Herniation of the brain
36
Clinical manifestations of chronic hyponatremia?
cerebral adaptation allows for pts to be relatively asx
If sx: fatigue, N/V, dizziness, gait disturbance, confusion, lethargy
37
Causes of Hyponatremia?
Diuretic use**, diarrhea, CHF, Liver and renal dz, SIADH
Chronic diseases that cause retention of sodium and fluid: body retains more water than Na+ (dilutes Na+ conc.)
38
Diagnostic testing for Hyponatremia?
CBC, CMP, urine osmolality (24 hrs), Mg, Phos
39
Treatment of hyponatremia depends on what?
The cause
40
Treatment of hyponatremia?
H2O restriction, Sodium and water repletion SLOWLY
-Vaptans: nonpeptide vasopressin antagonist (interfered w ADH) *useful for hypervolemic, hyponatremia secondary to CHF/Liver failure
41
What is hypernatremia?
Inc. serum osmolality, water movement from ICF to ECF
*most often d/t water depletion
42
Clinical manifestations of hypernatremia?
Early/mild: thirst, weakness, nausea, loss of appetite
Severe: confusion, lethargy, muscle twitching, intracerebral hemorrhage
43
Causes of hypernatremia?
Vomiting, diarrhea, DI (unreplaced water loss), dehydration (pts w/ dementia, end of life/failure to thrive), severe exercise or seizure (water loss into cells), overload of Na+/hypertonic solution
44
Hypernatremia is seen in those with impaired ability to do what?
Impaired ability to obtain water or experience thirst
45
Treatment of hypernatremia?
If due to water loss (dehydration) or hypovolemia (Na+ and water loss): determine etiology, calculate water deficit, fluid repletion (D5W)
46
How to calculate water deficit?
Plasma Na = (total body Na + total body K)/TBW
47
Potassium is a major ________ _______?
Intracellular cation
48
What does Potassium help establish?
Resting membrane potential in neurons and muscle fibers
49
Effect of potassium on osmotic pressure?
Very little effect (unlike Na+)
50
What maintains potassium gradients between ICF and ECF?
Sodium-potassium pumps in cell membranes
51
How is potassium excreted?
Kidneys
52
Recommended adult daily consumption of potassium?
4700mg
53
Hypokalemia typically results from what?
Unreplenished GI or urinary loss of K+
54
Symptom severity of hypokalemia is directly related to what?
Degree/duration of K+ reduction
55
Clinical manifestations of hypokalemia (<3.0mEq/L)?
Muscle weakness (LE to UE), muscle cramps, rhabdo, N/V/D and ileus, Cardiac arrhythmias/EKG abnormalities***
56
Cardiac arrhythmias with hypokalemia?
PAC's, PVC's, sinus brady, AV block, Vtach, Vfib
57
Characteristics EKG findings associated with hypokalemia?
ST depression, decreased T wave amplitude, increased amplitude of U wave, prolonged QT interval
58
Causes of hypokalemia?
Vomiting, diarrhea, diuretics (non-K+ sparing), DKA
59
Diagnostics for hypokalemia?
Hypo-K and Hypo-Mg concurrent loss, CMC, CMP, Mg, Phos, EKG, ABG, serum ketones
60
Assume what with hypokalemia tx?
Intracellular and extracellular K+ is equal
61
Management methods for hypokalemia?
-Careful monitoring in repletion to avoid hyperkalemia (overcorrection risk increases w/ renal insuff.)
-Determine Cause & replete IV or PO
62
Preparations for repletion of K+ in hypokalemia?
Potassium chloride preferred in most cases (IV, PO)
63
Treatment for mild-mod hypokalemia (3.0-3.4 mEq/L)?
K+ 10-20 mEq BID (tabs, liquid, or K+ rich foods)
+/- potassium sparing diuretic
64
Treatment for severe hypokalemia (<2.9mEq/L)?
Admit
K+ 20 mEq PO
10-20 mEq/hr in 100-200mL saline (K-rider)
65
What is transient correction of hypokalemia?
OK for several hours and then drops (most exogenous K+ taken into cells)
66
What is hyperkalemia?
-Impaired urinary K+ excretion by CKD, meds
-Inc. K+ release from cells (DKA)
67
Hyperkalemia is rare in most healthy individuals due to what?
Cellular and urinary response mechanisms to prevent excess K+ accumulation in ECF
68
Clinical manifestations of hyperkalemia (>7.0 mEq/L)
Muscle weakness/paralysis, cardiac arrhythmias/EKG changes
69
Characteristic EKG changes with hyperkalemia?
Peaked T-waves, Shortened QT interval
70
Causes of hyperkalemia?
Inc. potassium release from cells: DKA***, succinylcholine, exercise, rhabdo, crush injury
Reduced urinary excretion: acute & chronic kidney disease
71
Diagnostic testing for hyperkalemia?
EKG, CBC, CMP, Mg, Phos, consider ABG and serum ketones
72
Management of hyperkalemia?
-Calcium antagonizes membrane actions of hyperkalemia (stabilizes cardiac tissue)
-Insulin (w/ IV glucose) drives extracellular K+ into cells
-Inhaled beta-agonists (Albuterol)
-Remove K+ from body: IV diuretics (+/- IV saline), Polystyrene sulfonates (Kayexalate PO), hemodialysis (ESRD)
73
Hypomagnesemia occurs in what % of hospitalized populations?
12%
74
Symptoms of hypomagnesemia are typically associated with what?
Concurrent hypokalemia, hypocalcemia and/or metabolic acidosis
75
Causes of hypomagnesemia?
GI loss/diarrhea, chronic PPI use, Renal loss (loop/thiazide diuretics, nephrotoxic drugs), alcohol (secondary to urinary excretion, diarrhea, dietary deficiency), Hypercalcemia
76
Most of the body's magnesium stores are where?
Intracellular, 60% in bone
77
Extracellular magnesium can be ionized (free) or bound to what?
Protein
78
Magnesium helps to maintain what?
Normal nerve and muscle function, blood glucose control, BP regulation, contributes to construction of bone
79
Magnesium is required for what?
Energy production
80
What does magnesium help transport across cell membranes?
Calcium and potassium
81
Diagnostic testing for hypomagnesemia?
EKG, CMC, CMP, Mg, Phos, consider ETOH
82
Treatment for hypomagnesemia?
Identify cause, IV/PO repletion
83
Hypermagnesemia is uncommon in the absence of what?
Mg+ repletion or kidney disease
84
Clinical manifestations of hypermagnesemia?
Nausea, flushing, headache, lethargy, comnolence, hypocalcemia, absent deep tendon reflexes, hypotension, bradycardia, muscle paralysis, apnea, resp. failure, heart block
85
Causes of hypermagnesemia?
Kidney disease/failure (no Mg regulation other than urinary excretion), Mg infusion/repletion
86
Diagnostic testing for hypermagnesemia?
EKG, CBC, CMP, Mg, Phos
87
Treatment of hypermagnesemia?
Determine cause, prevention, improve renal elimination by loop diuretics and IV saline or hemodialysis
88
99% of calcium is found where?
Bone and teeth
89
1% of calcium is in the serum and is required for what?
Vascular function, muscle function, nerve transmission
90
Serum calcium is regulated and does not fluctuate with what?
Dietary intake
91
The body uses what as a reservoir to maintain constant Ca concentration?
Bone
92
45% of calcium in the serum is bound to what?
Albumin
93
The 40% of calcium in the serum not bound to albumin is ____ _____ ______?
Ionized free calcium (not bound to proteins)
94
Average recommended daily intake of calcium varies with what?
Age (most adults 1000-1300mg)
95
Hypocalcemia values must be corrected if patients have what?
An abnormal albumin level
96
How to calculate corrected calcium?
Corrected calcium = measured total Ca + 0.8 (4.0 - serum albumin)
97
Clinical manifestations of acute hypocalcemia?
Tetany** (HALLMARK), fatigue, hyperirritability, anxiety, QT prolongation
Trousseau's and Chvosteks's signs
98
What is Trousseau's sign?
Induction of carpal spasm by inflation of BP cuff
99
What is Chvosteks's sign?
Contraction of the ipsilateral facial muscles elicited by tapping facial nerve anterior to the ear
100
Causes of hypocalcemia?
Vitamin D/ phosphate influence on serum calcium, hypoalbuminemia (pseudo-hypocalcemia), Hypoparathyroidism due to excision, Vit D deficiency, CKD, Sepsis
101
Diagnostics for hypocalcemia?
EKG, CBC, CMP, Mg, Phos, Ionized Ca
102
Treatment of hypocalcemia?
Determine cause
Severe: IV calcium gluconate (over 10-20 min*** NEVER FASTER)
Mildly symptomatic/chronic: PO calcium gluconate
103
Is hypercalcemia common?
No, relatively uncommon
104
Causes of hypercalcemia?
Primary hyperparathyroidism and malignancy (90% of cases), Drug-induced hypercalcemia
105
Clinical manifestations of hypercalcemia?
No specific manifestation, depends on cause
106
Diagnostics for hypercalcemia?
Confirm dx, Measure PTH, Vit D levels
107
Treatment of hypercalcemia?
Tx underlying cause
108
If normal or low PTH with hypercalcemia, assume what dx?
Malignancy
109
Phosphorous is an essential mineral and makes up what % of someone's total body weight?
1%
110
Phosphorous is present in which cells?
All of them
111
85% of phosphorous is found where?
Bones & teeth, DNA, RNA
112
Phosphorous and what ion are interrelated?
Calcium
113
Phosphorous and calcium metabolism is regulated by what?
Vit. D and PTH
114
Phosphorous is excreted by what?
Kidneys (w/ renal failure levels rise)
115
Where is phosphorous absorbed?
Small intestines
116
Phosphorous can be found in many ____ and _____?
Foods and additives
117
Causes of hyperphosphatemia?
Acute or chronic kidney disease, acute phosphate load: tumor lysis, rhabdo, exogenous phosphate
118
Treatment of hyperphosphatemia?
Determine cause, IV normal saline, May require dialysis
119
Causes of hypophosphatemia?
Increased insulin secretion (when treating DKA), poor absorption (anorexia, alcoholism, chronic diarrhea, short gut synd.), Hyperparathyroidism, Vit D deficiency
120
Treatment of hypophosphatemia?
Determine cause (may only require tx of underlying cause), repletion often not necessary
121
What is the physiology of acid-base status?
Humans generate large amounts of acids daily --> must be excreted, expired, metabolized, or buffered
122
Acid-base is maintained by what?
Normal pulmonary excretion (CO2), Metabolic utilization of acid, Renal excretion of acid
123
Acid-base is aseessed by measuring what?
Components of bicarb-carbon dioxide buffer system in the blood
124
Measuring pH is measuring which ions?
H+ ions (balance = regulation of H+ ions)
125
Concentration of H+ ions in the body has a ____ range for optimal cellular function?
narrow *small deviations in either direction carries significant morbidity and mortality
126
Buffer system defense mech. of the body in acid-base balance?
HCO3
127
Respiratory system defense mech. of the body in acid-base balance?
CO2 (expire)
128
Renal system defense mech. of the body in acid-base balance?
Reabsorbs HCO3, excretes H+
129
CO2 formed during cellular respiration combines with H2O to form what?
Carbonic acid
130
What are carbonic acid disscoates?
HCO3 and H+ ion (pH)
131
a pH of <7.35 (acidemia) and inc. PaCO2 indicates what?
Resp. Acidosis
132
a pH of <7.35 (acidemia) and dec. HCO3- indicates what?
Metabolic Acidosis
133
a pH of >7.45 (alkalemia) and dec. PaCO2 indicates what?
Resp. Alkalosis
134
a pH of >7.45 (alkalemia) and inc. HCO3- indicates what?
Metabolic Alkalosis
135
How to measure acid-base?
ABG (arterial or venous)
1. identify/monitor acid-base
2. measure PaO2 and PaCO2
3. assess response to tx
4. detect abnormal hemoglobins**
136
Contraindications of measuring acid-base w/ ABG?
Local infection, thrombus, abnormal anatomy, severe PVD, anti-coagulation pts (relatively C/I)
137
How to interpret ABG?
Look at pH (acidotic, alkalotic, normal?), look at HCO3 and CO2 --> determine if metabolic or resp.
138
Low pH w/ High CO2 ABG?
respiratory
139
Low pH w/ Low HCO3 ABG?
metabolic
140
High pH w/ Low CO2 ABG?
respiratory
141
High pH w/ High HCO3 ABG?
metabolic
142
What indicates compensation?
If CO2 and HCO3 are both high or both low
if pH normal: full compensation
if pH abnormal: partial compensation
143
Causes of metabolic acidosis?
Lactic acidosis (DKA), Ketoacidosis (ETOH), Ingestions (methanol, ethylene glycol, ASA), Loss of HCO3 (diarrhea), Dec. renal excretion (CKD)
144
Causes of metabolic alkalosis?
GI loss (excess vomiting/diarrhea, laxative abuse), Renal loss (diuretics)
145
Causes of respiratory acidosis?
Dec. central respiratory drive (overdose, encephalitis, CVA), Dec. NM respiratory drive (metabolic disorders), Short/shallow breathing (PE, pulm vascular dz, COPD, interstitial lung disease)
146
Causes of respiratory alkalosis?
CNS (pain, hyperventilation, anxiety/panic, drug withdrawal), Pulmonary (COPD, interstitial lung disease, pneumothorax, pneumonia), High altitude
