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Electrolytes Flashcards

1
Q

What are some of the s/s of severe hypophosphatemia?

A

effects are primarily related to impairment of cellular engery metabolism
-acute resp failure or failure to wean from vent
-impaired delivery to peripheral tissue
-left shift of oxyhemoglobin cure d/t 2,3-DPG depletion
-extreme muscle weakness
-hemolytic anemia
-impaired leukocyte and plt function

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2
Q

In a pt w/ re-feeding syndrome or who is a concern for re-feeding syndrome, what type of fluids should not be given?

A

IV dextrose containing fluids
-also high carbohydrate TF or TPN
-these lead to increased insulin levels which worsening hypophosphatemia d/t intracellular shifts of phosphate

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3
Q

What is TURP syndrome?

A

excessive absorption of irrigant fluid leanding to hypervolemia, hyponatremia, and low serum osmolality

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4
Q

At what level of hypermagnesemia are deep tendon reflexes lost?

A

10-14mEq/L
-at 5-10mEq/L will see prolonged PR interval and widened QRS
-at 15mEq/L SA/AV node blockade
-at 20mEq/L cardiac arrest

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5
Q

What is the total body water in males?

A

60% body weight

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6
Q

What is the total body water in females?

A

50-55% body weight

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7
Q

What is the total body water in a fetus?

A

90% body weight

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8
Q

What is the total body water in kids?

A

60-65% body weight

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9
Q

What is the total body water in the obese?

A

Up to 10-20% lower compared to similar age and gender

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10
Q

What are the main intracellular cations? Anions?

A

-potassium and magnesium
-phosphate, sulfate, proteins

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11
Q

What are the main exracellular cations? Anions?

A

-sodium
-chloride, bicarbonate, sulfate, proteins

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12
Q

What determines plasma osmolality?

A

ratio of plasma salutes and water

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13
Q

What is the normal range for plasma osmolality?

A

275-290 mOsm/kg
-mostly driven by Na+ w/ small contributions from glucose and BUN

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14
Q

How do you calculate osmolality?

A

Posm = 2x[Na] + (BUN/2.8) + (gluc/18)

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15
Q

What electrolyte derangement are seen in rhabdomyolysis?

A

due to myocyte breakdown
-hyperkalemia
-hyperphosphatemia
-hypocalcemia

also see:
-hypoalbumenia
-hyperuricemia

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16
Q

What electrolyte derangements are known to worsen digoxin toxicity?

A

-hypokalemia
-hypophosphatemia

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17
Q

What is the average volume made and amount of Na Cl K and HCO3 of the stomach?

A

1-2L
Na 59
K 9.3
Cl 89
HCO¬3 0-1

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18
Q

What is the average volume made and amount of Na Cl K and HCO3 of the duodenum?

A

100-2000mL
Na 105
K 5.6
Cl 99
HCO3 10

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19
Q

What is the average volume made and amount of Na Cl K and HCO3 of the ileum?

A

1-3L
Na 112
K 5
Cl 106
HCO3 15-20

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20
Q

What is the average volume made and amount of Na Cl K and HCO3 of the colon (diarrhea)?

A

500-1700mL
120
90
25
45

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21
Q

What is the average volume made and amount of Na Cl K and HCO3 of the bile?

A

500-1000mL
Na 145
K 5.2
Cl 100
HCO3 50

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22
Q

What is the average volume made and amount of Na Cl K and HCO3 of the pancreas?

A

500-1200mL
Na 142
K 4.6
Cl 77
 HCO3 70

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23
Q

With normal renal function and perfusion what is the principal regulator of serum osmolarity?

A

ADH

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24
Q

When both low plasma osmolarity and low blood volume/pressure are present which effect dominates control of ADH?

A

Low blood volume or pressure will cause an increase of ADH
-this is one of the ways hypovolemic hyponatremia occurs

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25
Why are the elderly more prone to alterations in sodium homeostasis?
Aging leads to reduced GFR which limits the ability to excrete a sodium load -makes them more prone to overexpansion of the extracellular fluid compartment -they also have impaired thirst mechanism and decreased ability to concentrate urine
26
What are causes of euvolemic hyponatremia?
-hyperlipidemia -hyperproteinemia
27
What are causes of dilutional (increased plasma osmolality) hyponatremia?
-hyperglycemia -mannitol
28
What are causes of hypovolemic hyponatremia?
-diuretics -plasma, GI, or skin fluid losses -CHF -hypoproteinemic states (cirrhosis, nephritis syndrome, malnutrition) -SIADH -endocrine disorders (hypothyroidism, hypoadrenalism) -meds (morphine, TCAs, indomethacin)
29
How much does Na drop for every 100mg/dL rise in glucose?
1.3mEq/L
30
What is the most common cause of hypovolemic hyponatremia?
Na losses
31
What urine studies are diagnostic for SIADH?
Uosm > 100 (maximally dilute urine) UNa > 30 (renal salt wasting) Serum osm < 280 Euvolemia (remember this is unregulated free water retention w/o adequate Na reabsorption)
32
At what Na plasma level do patients typically become symptomatic in hypernatremia?
Na > 160
33
What some causes of hypovolemic hypernatremia?
-fever -hyperventilation -burns -hypotonic fluid loss (perspiration, severe diarrhea) -excessive renal free water loss (hyperglycemia, mannitol)
34
What fluids should you give to treat hypovolemic hypernatremia?
-if hypovolemia is severe enough to cause tissue malperfusion = NS -if tissue perfusion is adequate = 0.5 NS or D5W
35
The recovery phase of which renal disorder can be characterized by high-output renal failure leading to severe hypernatremia?
acute tubular necrosis
36
What treatment is both diagnostic and therapeutic for central DI induced hypernatremia?
dDAVP (1-desamino-8d-arginine vasopressin)
37
What is the rate at which hypernatremia should be corrected?
no faster 0.5 - 1mEq/L per hour -if pt is experiencing seizure activity give free water to reduce to level before sz began, or reduce by ~6mmol/L
38
How do you calculate free water deficit?
water deficit = total body water x {1-(serum Na/140)}
39
What is the amount of potassium typically found in the human body?
-intracellular = 40 - 50mmol/kg body weight -only 2% of total body potassium is found extracellular
40
What are the typical extrarenal causes of hypokalemia in a surgical patient?
-GI losses (emesis, NGT) -diarrhea -burns -profuse perspiration
41
What are the typical renal causes of hypokalemia in a surgical patient?
-diuretic therapy -tubular disorders (type 1 renal tubular acidosis) -meds (cisplatin, amphotericin B)
42
What can cause hypokalemia due to an intracellular influx of K+?
-metabolic alkalosis -insulin -beta2-adrenergic stimulation
43
What are some disorders that can cause hypokalemia?
-primary hyperaldosteronism -renal artery stenosis -Cushing syndrome
44
How does vomiting lead to hypokalemia when gastric secretions only ave about 10mEq/L of K?
-ECV contraction leads to elevated levels of aldosterone -elevated aldosterone causes enhanced renal Na reabsorption and increased K secretion
45
What is the most serious consequence of hypokalemia?
cardiac arrhythmias
46
What are some factors that can exacerbate the potential for arrhythmias in hypokalemia?
-metabolic alkalosis -digoxin -hypercalcemia
47
What EKG changes are seen in hypokalemia?
-flattened T waves -T wave inversion -depressed ST segments -U waves -prolonged QTc
48
At what level does weakness typically manifest in hypokalemia?
K < 2.5
49
What is the total K deficiency when the plasma value drops from 4 to 3?
100 - 400mmol^3
50
What can cause hyperkalemia due to an extracellular flux of K+?
-severe metabolic acidosis -insulin deficiency (DM) -rhabdomyolysis -succinylcholine (transient) - most commonly seen following paralysis or prolonged bed rest
51
What EKG changes are seen in hyperkalemia?
-peaked T-waves -reduced P-wave amplitude -QRS widening -sinusoidal complex -Vfib
52
What are the approximate total body stores of calcium?
1000gm w/ almost 99% in the bones
53
Why does hyperventilation cause hypocalcemia?
-acid-base alterations effect the binding of calcium to albumin -respiratory alkalosis increases the binding affinity of calcium for albumin -causes reduction in the serum ionized calcium
54
Which patient populations are prone to alternations in calcium homeostasis?
-major fluid shifts -prolonged immobilization -alterations in GI absorption -post-op from thyroid or parathyroid cases
55
What is the most frequent cause of hypocalcemia?
low serum albumin
56
What are causes of hypocalcemia not due to hypoalbuminemia?
-acute pancreatitis -massive soft tissue infection -small bowel fistulae -hypoparathyroidism -MTP d/t chelation of calcium w/ citrate
57
Approximately how much citrate does each unit of blood contain? How fast can the liver metabolize citrate?
-3gm per unit of blood -metabolizes 3gm every 5 minutes
58
What are the s/s of hypocalcemia?
-circumoral numbness or tingling -numbness or tingling at the finger tips -tetany -carpopedal spasm -seizures -EKG changes = bradycardia, prolonged QTc
59
What is the most common cause of hypercalcemia?
hyperparathyroidism -primary HPT and malignant causes account for 90% of hypercalcemia
60
What are the s/s of hypercalcemia?
-confusion, lethargy, come -muscle weakness -anorexia, nausea, vomiting -constipation -pancreatitis -renal stones (in prolonged cases) -polyuria (d/t induced nephrogenic DI) -EKG changes (shortened QT)
61
What medication can exacerbate arrhythmias due to hypercalcemia?
digitalis
62
When is treatment for hypercalcemia considered urgent?
Ca > 15 or EKG changes
63
What is the treatment protocol for hypercalcemia?
-large volume hydration w/ NS -once hydrated --> furosemide -if severe may need diphosphonates, calcitonin, or mithramycin
64
What is the MOA for diphosphonates and calcitonin in treating severe hypercalcemia?
-diphosphonates = inhibits osteoclast resorption and reduces Ca levels by forming Ca-phosphate complexes -calcitonin = inhibits osteoclast resorption
65
What is the principal intracellular divalent cation?
Mg2+
66
Where is 50% of the body's Mg found?
in bone
67
Where does Mg absorption occur?
small intestine -reabsorbed by the renal tubules
68
What are the s/s of hypomagnesemia?
similar to hypocalcemia w/ neuromuscular and CNS excitability -tremor -tetany -fasciculations -Chvostek and Trousseau signs -impaired parathyroid hormone excretion -can induce hypocalcemia that is refractory to Ca supplementation
69
What are the s/s of hypermagnesemia?
rare to see outside of renal failure or iatrogenic -flaccid paralysis -hypotension -confusion -EKG changes similar to hyperkalemia
70
What is the treatment for severe hypermagnesemia?
-emergently = administration of calcium as calcium gluconate or calcium chloride -definitive = hydration and diuresis to increase renal excretion, dialysis if there is renal impairment
71
What are common causes of hypophosphatemia?
-impaired intestinal absorption -increased renal excretion -hyperparathyroidism (d/t increased renal excretion) -s/p major liver resection d/t rapid phosphate utilization of regenerating hepatocytes -refeeding syndrome
72
What are some adverse effects of severe hypophosphatemia?
-impaired tissue oxygen delivery d/t decreased 2,3-DPG -muscle weakness -rhabdomyolysis
73
How is Na transported out of the nephron?
ENaC (epithelial sodium channels) = specialized Na-K ATPase -these are stimulated by aldosterone -their activation is triggered by hypovolemia, hypotension, and ANP d/t atrial overdistention
74
Which ion channel in the nephron does furosemide act on?
inhibits Na reabsorption via Na-K-Cl cotransporter in the loop of Henle
75
Which part of the nephron does furosemide act on?
loop of Henle
76
Which channels in the nephron specialize in water reabsorption?
aquaporins -open in response to ADH -results in movement of water into the medullary interstitium
77
Where in the nephron do you first find aquapornins?
collecting ducts
78
What is DI?
inadequate or absent effect of ADH leading to closed aquaporins and excessive free water excretion but not Na d/t: -injury of pituitary (central) -desensitization of the collecting ducts (nephrogenic), usually d/t toxic effects (ie. lithium)
79
What are the s/s of DI?
-very dilute polyuria -hypernatremia -hypovolemia
80
What cardiac specific symptoms are seen w/ hypocalcemia?
-bradycardia -CHF -cardiomyopathy
81
What hematologic specific symptoms are seen w/ hypophosphatemia?
-hemolytic anemia -impaired leukocyte function -impaired platelet function
82
What are some of the etiologies of hyperkalemia (surgery and trauma specific)?
-crush injuries -reperfusion syndrome -AKI -severe metabolic acidosis -succinylcholine -hypoaldosteronism
83
What are some of the etiologies of hypermagnesemia (surgery and trauma specific)?
rare in the absence of renal failure -large vol. tissue necrosis (large burns, large crush injuries) -medication induced (laxative abuse, antacids, lithium)
84
What are some of the etiologies of hyperphosphatemia in critically ill patients?
-exogenous = phosphate-based laxatives/enemas or high dose fosphenytoin -endogenous = rhabdomyolysis or tumor lysis -extracellular shifts
85
How do the T-waves in hyperkalemia differ from those in hypercalcemia
both are peaked -hyperkalemia = narrow based -hypercalcemia = broad based
86
What is the goal UOP in a patient being hydrated for hypercalcemia?
100-150mL/hr
87
What two electrolyte derrangements can lead to hypocalcemia?
-hypomagnesemia -hyperkalemia
88
What is the fastest rate at which you should correct hypernatremia?
0.5mEq/L/hr
89
What are the principal regulators of serum osmolarity?
all determined on the kidneys ability to excrete urine, so: -intact renal function -appropriate ADH secretion
90
When both low plasm osmolarity and low blood volume/pressure are present what effects dominates the renal response?
low blood volume/pressure -this can lead to hypovolemic hyponatremia
91
For every 100mg/dL rise in glucose by how much does sodium fall?
1.3mEq/L
92
How much will the drop of albumin by 1g/dL reduce the baseline anion gap?
by 2.5mEq
93
What are typical serum osmolality, urine osmolality, urine sodium, and volume status of SIADH?
-serum osm < 280mOsm/kg -Uosm > 100mOsm/kg -UNa > 30mEq/L -euvolemic

Acid/base/electrolytes/fluids (3 decks)

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