5. Fluid, Electrolyte, and Acid-Base Balance Flashcards
1
Q
60-40-20 rule
A
- 60% of body weight = total body weight (TBW) - 40% of body weight = intracellular fluid (ICF) - 20% of body weight = extracellular fluid (ECF)
2
Q
What is ECF composed of?
A
- interstitial fluid (spaces between cells) - intravascular - lymphatics - transcellular (joint, intraocular, and CSF)
3
Q
Describe whether each electrolyte is found more in ICF or ECF - Na - Cl - Ca - K - Mg
A
- Na = ECF - Cl = ECF - Ca = ECF - K = ICF - Mg = ICF
4
Q
1L of water weighs how much?
A
1kg or 2.2 lbs
5
Q
Hydrostatic vs osmotic/oncotic pressure
A
- hydrostatic: fluid pushed out of space due to pressure against walls - osmotic/oncotic: proteins pull/attract water back into space
6
Q
4 factors in fluid homeostasis
A
- intake - absorption - distribution - excretion
- intake
- absorption
3.
7
Q
Describe each of the following: - capillary hydrostatic pressure - capillary oncotic pressure - interstitial hydrostatic pressure - interstitial oncotic pressure
A
- capillary hydrostatic pressure: pushing force of water out of vessels into interstitial space - capillary oncotic pressure: attraction of water from interstitial space into vessels - interstitial hydrostatic pressure: pushing of water from interstitial space into vessels - interstitial oncotic pressure: attraction of water from vessels into interstitial space
8
Q
What type of pressure is blood pressure?
A
capillary hydrostatic pressure -> pushing against the vessels
9
Q
What forces favor filtration?
A
capillary hydrostatic pressure and interstitial oncotic pressure -> both move water out of vessels
10
Q
What forces oppose filtration?
A
capillary oncotic pressure and interstitial hydrostatic pressure -> both move water into vessels
11
Q
Name 4 factors in the absorption of fluid
A
- ADH - RAAS - ANP - renal function
12
Q
What primarily regulates water balance?
A
antidiuretic hormone (ADH); aka vasopressin
13
Q
Describe the steps of the ADH system
A
- increase in plasma osmolarity or decrease in fluid volume -> ADH secretion (hypothalamus/ p. pituitary) -> decreased water excretion and increased renal water retention -> increased circulating fluid volume -> decreased osmolarity -> decreased ADH
14
Q
What is another method the body uses to raise fluid volume or decrease plasma osmolarity other than ADH?
A
thirst -> increase fluid intake
15
Q
What does RAAS stand for?
A
Renin-Angiotensin-Aldosterone System
16
Q
Describe the RAAS system
A
decreased renal perfusion (decreased plasma volume) -> renin secreted -> Ang I -> Ang II -> ADH (water absorption) and Aldosterone (salt reabsorption) -> increased blood volume
17
Q
What secretes renin and when?
A
juxtaglomerular cells when BP is low
18
Q
What converts angiotensin I to angiotensin II and where?
A
angiotensin-converting enzyme (ACE) in the pulmonary vessels
19
Q
What releases aldosterone and what stimulates it release?
A
released from the adrenal cortex; stimulated by Ang II or directly by increased plasma K
20
Q
What produces ANP and BNP?
A
ANP: atria BNP: ventricles
21
Q
What causes production of ANP and BNP?
A
cardiac distention (ECF volume increased, Na and H2O retention, increased BP)
22
Q
What will ANP and BNP do?
A
- decrease RAAS - increase GFR - increase Na and water excretion (natriuresis and diuresis) - vasodilation (decrease BP)
23
Q
3 lab tests used to measure renal function
A
- GFR - serum creatinine - serum BUN
24
Q
What is the minimum normal urine output?
A
30 mL/hr
25
Normal blood osmolarity
275-295 mosm/Kg
26
high serum osmolarity means what?
too many particles compared to plasma -\> dehydration
27
low serum osmolarity means what?
not enough particles compared to plasma -\> overload of fluid
28
high urine osmolarity means what?
concentrated urine -\> dehydration
29
What is responsible for the ECF water balance
Na
30
What will isotonic IV solution do?
remain in vessels -\> add to blood volume
31
Ex of isotonic IV solution
normal saline or 0.9% NaCl
32
What will hypertonic IV solution do?
contains high Na -\> will pull fluid from cells into vessels (useful in cerebral edema)
33
Ex of hypertonic IV solution
3-5% normal saline
34
What will hypotonic IV solution do?
contains low Na -\> fluid will be pulled into the tissues from the vessels
35
Ex of hypotonic IV solution
0.45% normal saline
36
What will happen to a cell in the following solutions: isotonic, hypotonic, hypertonic?
- isotonic: equal movement of water in and out of cell - hypotonic: less concentration in fluid -\> fluid moves into cell -\> cell ruptures - hypertonic: more concentration in fluid -\> fluid moves out of cell -\> cell shrinks
37
What does filtration depend on (4)?
- normal serum albumin/protein - normal fluid level - normal heart function - normal BP = controlled peripheral vascular resistance (PVR)
38
Explain how fluid moves in the arterial and venous sides of circulation
- arterial side of capillary: hydrostatic pressure greater than oncotic pressure -\> fluid moves to interstitial space - venous side of capillary: oncotic pressure in capillary greater than hydrostatic pressure -\> fluid moves into circulation
39
Pathophysiology of edema (3)
- increased capillary permeability (proteins moves to interstitial space) - low levels of serum proteins - hydrostatic pressures increased due to venous obstruction, Na or water retention
40
list some causes of edema
- CHF - liver and renal failure - venous or lymphatic obstruction - inflammation - malnutrition - trauma/tissue injury
41
edema limited to site of trauma
local edema
42
edema over a larger area of the body due to liver or renal failure
generalized edema
43
Describe third spacing and 3 places it can occur. What is the most common cause?
- too much fluid shifts to a nonfunctional area - can occur in an interstitial space, pleural space, or pericardial space - most commonly due to burns
44
Non-pitting vs pitting edema
- Non-pitting: swollen cells due to increased ICF volume - Pitting: increased interstitial fluid volume
45
T/F: A loss or gain of saline affects the volume of both ICF and ECF
False; saline is confined to the extracellular compartment -\> does not affect volume of the intracellular compartment
46
Causes of isotonic fluid loss
- hemorrhage - wound drainage - severe diaphoresis - hyposecretion of aldosterone
47
How does serum Na change in isotonic fluid loss and excess
will see Normal serum Na
48
Clinical presentation of isotonic fluid loss
- orthostatic hypotension - tachycardia - weight loss - decreased skin turgor and slow capillary refill - low urine output - hypovolemic shock
49
Clinical presentation of isotonic fluid excess
- hypertension - weight gain - edema - signs of CHF - may have increased urine output
50
Causes of isotonic fluid excess
- fluid excess of IV solution - hypersecretion of aldosterone
51
Tx of isotonic fluid excess
- diuretics - reduce rate of isotonic fluid administration - investigate: what is kidney function?
52
Cause of hyponatremia
- excessive hypotonic IV - excess water intake (includes psychogenic polydipsia, tap water enemas, and NG irrigation) - vomiting/diarrhea - fresh water drowning - SIADH
53
occurs when there is a loss of Na without a significant loss of water (pure Na deficit)
isovolemic hyponatremia
54
occurs when total body Na level increases -\> leads to increase in TBW and dilution of Na in extracellular space
hypervolemic hyponatremia
55
occurs w/ a loss of TBW but there is a greater loss of Na; extracellular volume is decreased
hypovolemic hyponatremia
56
occurs when there is intake of large amounts of free water or replacement of fluid loss w/ IV 5% dextrose in water (dilutes Na)
dilution hyponatremia (water intoxication)
57
What will happen to serum Na and cells with hyponatremia?
low serum Na and cellular swelling
58
Clinical presentation of hyponatremia and why?
- confusion, lethargy, coma - headache, weight gain - nausea - seizure, weakness, muscle twitching - decrease in Na concentration changes the cell's ability to depolarize and repolarize normally -\> alters APs of neurons and muscles - will also see cerebral edema (causes many neurological changes)
59
Most important way to determine if someone is retaining fluid or losing fluid
Daily weights
60
Normal Na level
135-145 mEq/L
61
Causes of hypernatremia
- chronic diarrhea, vomiting and fever (water loss) - no access to water (decreased thirst) - diabetes insipidus - drowning in salt water - tube feedings - diaphoresis and diuresis - primary hyperladosteronism - Cushing syndrome
62
What will happen to serum Na with hypernatremia?
elevated serum Na
63
clinical manifestations of hypernatremia and why?
- confusion, lethargy, coma - seizure - fever - dry mucous membranes - hyperreflexia - pulmonary edema - CNS signs due to brain cells shrinking and Na can't cross BBB; also due to alterations in membrane potential
64
occurs w/ loss of free water and near normal body Na concentration
isovolemic hypernatremia
65
occurs where there is loss of Na accompanied by a greater loss of body water
hypovolemic hypernatremia
66
rare and occurs when there is increased TBW and greater increase in total body Na level
hypervolemic hypernatremia
67
normal K levels
3.5-5.0 mEq/L
68
4 factors that enhance cellular uptake of K
- insulin - epinephrine - aldosterone - alkalosis (K is lo)
69
4 factors that enhance K release
- acidosis (H+ takes over cells) - cell lysis - strenuous excersice - increased ECF osmolarity
70
causes of hyperkalemia
- excess K intake - diuretics - large blood transfusions - decreased renal excretion - Addison's disease (decreased aldosterone) - crush injuries and burns (cell lysis)
71
Clinical signs of hyperkalemia
- muscle weakness/paralysis - cardiac dysrhythmias/arrest - hypopolarization (lowering) of RMP (easier to excite) - anxiety, numbness/tingling, N/V/D
72
EKG signs of hyperkalemia
- flattened P wave - prolonged PR interval - tall, peaked, T wave - bradycardia
73
Causes of hypokalemia
- anorexia or NPO - diuretics - V/D - NG suction - intestinal drainage
74
Clinical signs of hypokalemia
- hyperpolarization (increasing) of RMP - muscle weakness/paralysis - paralytic ileus - dysrhythmias
75
EKG signs of hypokalemia
- sinus bradycardia - ventricular tachycardia - AV block - low T wave
76
Normal total Ca level
9-11 mg/dL
77
Normal ionized Ca level
4.5-6 mEq/L
78
Causes of hypercalcemia
- hyperparathyroidism (increased PTH secretion) - immobilization (stimulation breakdown of bones) - leukemia - diuretics
79
Clinical signs of hypercalcemia
- weakness and CNS depression - decreased NM excitability
80
Causes of hypocalcemia
- dietary deficiency (vitamin D) - laxative abuse - diarrhea - pancreatitis - malabsorption
81
Clinical signs of hypocalcemia
- cramps and seizures - increased NM excitability
82
What is trousseau sign
- identifies hypocalcemia - inflate BP cuff on arm and will see flexion at wrist (carpal spasm)
83
What is Chovstek sign
- identifies hypocalcemia - tap the facial nerve anterior to the ear to elicit ipsilateral facial contraction
84
Normal Mg level
1.5-2.5 mEq/L
85
causes of hypermagnesemia
laxatives and antacids
86
Clinical signs of hypermagnesemia
- decreased reflexes - muscle weakness - drowsiness - respiratory depression - cardiac arrhythmias
87
causes of hypomagnesemia
alcoholism, poor nutrition, and malabsorption
88
Clinical signs of hypomagnesemia
- muscle cramps/spasm - tetany - seizures - hyperactive reflexes - cardiac arrhythmias
89
Normal Pi levels
2.5-4.5 mg/dL
90
causes of hypophosphatemia
- alcoholism - malabsorption - diarrhea - DKA - diuretics - antacids - dialysis
91
Clinical signs of hypophosphatemia
- anorexia - malaise - paresthesias - muscle weakness - decreased reflexes - confusion - impaired cardiac function
92
causes of hyperphosphatemia
- phosphate containing enemas - crushing injury - adrenal insufficiency - hypoparathyroid disease
93
Clinical signs of hyperphosphatemia
- increased NM excitability - Ca deposits in body tissues - hypocalcemia
94
Which electrolyte imbalances will cause weakness/poor muscle tone?
- hyperkalemia - hypokalemia - hypercalcemia - hypermagnesemia
95
Which electrolyte imbalances will cause twitchy/crampy muscles?
- hypocalcemia - hypomagnesemia
96
Major plasma buffer system
carbonic acid (weak acid) H20 + CO2 -\> H2CO3 -\> HCO3 + H+
97
How are CO2 and H2O produced and removed?
produced by aerobic metabolism; blown off by lungs
98
How are HCO3 and H+ produced and removed?
produced by anaerobic metabolism; regulated by kidneys
99
How does Hb act as an intracellular blood buffer?
binds with H+ and CO2
100
What acts as buffers in ICF?
phosphate and proteins
101
Normal blood pH
7.35-7.45
102
Normal blood PaCO2
35-45 mmHg
103
Normal blood HCO3 (bicarb)
22-26 mEq/L
104
causes of metabolic acidosis
- loss of base or addition of acid - DKA - lactic acidosis - EtOH poisoning
105
What is the compensation of metabolic acidosis?
hyperventilation (respiratory compensation) -\> excrete more CO2
106
Clinical presentation of metabolic acidosis
- N/V/D - confusion/coma - Kussmaul breathing (deep and rapid)
107
causes of metabolic alkalosis
- addition of base or loss of acid - vomiting (loss of acid) - antacid tablets (gain HCO3) - diuretics (volume contraction)
108
What is the compensation of metabolic alkalosis?
hypoventilation (respiratory compensation) -\> retain more CO2
109
Clinical presentation of metabolic alkalosis
- increased NM irritability - tetany - seizures - confusion - lethargy - coma
110
Respiratory acidosis compensation
decreased ventilation -\> CO2 goes up -\> kidneys increase HCO2 regeneration and acid excretion
111
causes of respiratory acidosis
CNS depression, airway obstruction, pneumonia, PE, COPD
112
Clinical presentation of respiratory acidosis
- headache - lethargy - confusion - tremors/seizures - cardiac arrhythmias
113
Respiratory alkalosis cause and compensation
increased ventilation (hyperventilation) -\> CO2 decreases -\> kidneys decrease acid excretion
114
Clinical presentation of respiratory alkalosis
- diaphoresis - NM irritability - carpopedal spasms - tingling around fingers/mouth - seizures/coma
115
What is the relationship between calcium and phosphate?
extracellular concentrations are inversely related -\> both regulated by the same hormones
