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Electrolyte Imbalance Flashcards

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1
Q

What timeline defines acute VS chronic hyponatremia?

A

Acute: <48 hours

Chronic: >48 hours OR duration unknown

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2
Q

Normal serum osmolality value

A

275-299 mOsm/kg

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3
Q

Renal causes for hypovolemic, hypotonic hyponatremia

A
  1. Diuretics
  2. Addison’s disease [aldosterone deficiency]
  3. Acute/chronic renal failure with high urinary output
  4. Recovery phase of ATN
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4
Q

Extrarenal causes for hypovolemic, hypotonic hyponatremia

A
  1. Diarrhea
  2. Vomiting
  3. Dermal fluid loss (sweating/burns)
  4. Bleeding/hemorrhage
  5. 3rd space fluid loss (peritonitis, ascites, heart failure)
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5
Q

Renal causes of euvolemic hypotonic hyponatremia

A
  1. SIADH
  2. Medications (SSRIs, opiates, barbiturates)
  3. Acute/chronic renal failure
  4. Adrenal insufficiency [mineralcorticioids, glucocorticoids, DHEA]
  5. Exercise-associated
  6. Severe hypothyroidism
  • 4) impaired renal free water excretion
  • *5) Effect of ADH & electrolyte loss in sweating
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6
Q

Extrarenal causes of euvolemic hypotonic hyponatremia

A
  1. Decreased salt intake “tea & bread diet” –> seen in elderly
  2. Water intoxication [chronic beer drinker, hypotonic saline solution 0.45% NaCl]
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7
Q

How would water intoxication affect sodium & EC volume status? What are the causes?

A

Euvolemic hypotonic, hyponatremia

CAUSES:

  • Excessive infusion of hypotonic (0.45% NaCl) or sodium-free isotonic IV fluids
  • Primary polydypsia
  • Beer potomania
  • Reset osmostat syndrome
  • Beer has a lot of calories, but no protein, thus you don’t have nitrates to form urea (which comes from protein breakdown)
  • *Chronic beer intake reduces urea, meaning there is no ability to concentrate the urine because there isn’t a gradient in the tubules to use
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8
Q

Renal causes of hypervolemic, hypotonic hyponatremia

A
  1. Acute/chronic renal failure with low urine output
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9
Q

Extrarenal causes of hypervolemic, hypotonic hyponatremia

A
  1. CHF
  2. Cirrhosis
  3. Severe hypoproteinemia (nephrotic syndrome)
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10
Q

Causes of hypertonic hyponatremia

A
  1. Hyperglycemia
  2. IV mannitol
  3. IV radiocontrast use
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11
Q

Definition of isotonic hyponatremia

A

Low serum Na+ levels, normal serum osmolality

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12
Q

Causes of isotonic hyponatremia

A

TURP syndrome
Pseudohyponatremia [hyperlipidemia or multiple myeloma]

  • Absorption of irrigant by the open prostatic blood vessels (not using saline)
  • *Very rare: <1%
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13
Q

Definition, causes & clinical symptoms of pseudohyponatremia

A

Asymptomatic laboratory artifact falsely indicating hyponatremia when sodium hasn’t been reduced or diluted

CAUSES:

  1. Hyperlipidemia
  2. Multiple myeloma (high protein)

CLINICAL FEATURES:

  • Pancreatitis
  • DKA
  • Obstructive jaundice
  • CRAB criteria of myeloma
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14
Q

What is the correlation to regarding the severity in a severely symptomatic hyponatremic patient?

A

Correlates with the extent of brain edema & occurs <48 hours

<120 mEq/L:

  • confusion/coma
  • seizures
  • ataxia
  • respiratory failure
  • headache/vomiting/nausea
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15
Q

In regards to hypovolemic, hyponatremia: extra renal & renal causes would produce what quantitative urine output? (ie: anuria, oliguria, polyuria)

A

Extrarenal: Oliguria [diarrhea, vomiting, hemorrhage]

Renal: Polyuria [Adrenal insufficiency, recovery phase in ATN]

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16
Q

Lab findings suggesting hypovolemia

A
  • Increased BUN/creatinine ratio
  • Increased hematocrit
  • Increased uric acid
  • Urinary sodium: <30 mEq/L
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17
Q

What lab tests would you order (outside of serum studies) in a patient with hypovolemia, hyponatremia

A

TSH [patient has myxedema]

Cortisol/ACTH [adrenal insufficiency]

MDMA [urine drug screening]

BNP [CHF]

Urine chloride

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18
Q

Rapid correction of acute or chronic hyponatremia would cause osmotic demyelination syndrome?

A

Chronic!

Maximum correction rate limit in high risk patients is 8mEq/L in 24 hours

Minimum correction rate in high risk patients is 4-6 mEq/L in 24 hours

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19
Q

Should we treat acute/severely symptomatic hyponatremia patients rapidly or slowly?

A

Rapid!

  • Want to prevent neurologic symptoms & brain herniation due to the hyponatremia
  • 4-6 mEq/L within the first 6 hours of therapy
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20
Q

How to determine if a patient with hyponatremia is euvolemic or hypovolemic

A

Give isotonic saline infusion (0.9% NaCl)

  • If serum sodium increases: Hypovolemic
  • If serum sodium decreases: SIADH [euvolemic]
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21
Q

How to treat euvolemic hyponatremia

A

Fluid restriction: Only 500-1000 mL/day allowed

Pharmacological intervention if there is high urine osmolality (>500 mOsm/kg)

Use urea or vaptans

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22
Q

How to treat hypervolemic hyponatremia

A

Fluid restriction with or without loops diuretics

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23
Q

Managing sodium overcorrection

A

**Overcorrection not necessary in patient who initially started with >120 mEq/L

  • *In patient who started with <120 mEq/L:
  • Replace free water loss with 5% dextrose in water
  • Desmopressin
  • Glucocorticoid therapy (dexamethasone)
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24
Q

Correcting hyponatremia too rapidly causes two complications:

A

from low to HIGH, your pons will DIE (ODS)

from high to LOW, your brain will BLOW (cerebral edema)

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25
Severe hypokalemia definition
serum potassium level < 2.5 mEq/L
26
GI causes of hypokalemia
Vomiting Diarrhea Laxatives
27
Renal causes of hypokalemia
Rental tubular acidosis (type 1 & 2) Cushing syndrome Renin-secreting tumors Fanconi Syndrome ``` Diuretics (thiazides, loops, osmotic) Beta 2 agonists (albuterol/terbutaline) Glucocorticoids Licorice (aldosterone like) Hyperaldosteronism/cortisolism Hypomagnesmia ```
28
Causes of hypokalemia, forcing potassium into the cell (intracellular shift)
Alkalosis Insulin Hypo-osmolality
29
Explain how alkalosis leads to hypokalemia
- Decreased extracellular H+ - Causes stimulation of Na/H+ anti porter - Increases H+ out of the cell & Na+ in - Increased Na+ in cell stimulates Na/K+ ATPase - More K+ gets placed into cells - Hypokalemia occurs -Decreased extracellular K+ inhibits Na/K+ ATPase -Decreased extracellular Na+, inhibits Na/H+ antiporter -Decreases extracellular H+ =ALKALOSIS
30
Explain how hypomagnesemia causes hypokalemia
* Mg is a cofactor for Na/K+ ATPase, thus low levels will disrupt it in the proximal portion of the distal convoluted tubule * Causes increases luminal Na+, thus increasing Na+ reabsorption & K+ secretion by principal cells distally * Apical ROMK channels in principal cells are normally inhibited by Mg++, but low levels of magnesium allows uninhibited K+ secretion
31
Symptoms of hypokalemia
Cardiac arrhythmias (can cause v.fib!) Muscle weakness/paralysis Decreased deep tendon reflexes Constipation
32
EKG of hypokalemia
"No POT, no TEA" T-wave flattening, ST depression Presence of U waves (severe hypokalemia)
33
Treatment of hypokalemia
IV KCl *Administer slowly to prevent cardiac arrhythmias! 10 mEq/hr peripheral line or 40 mEq/hr central line
34
Explain how acidosis causes hyperkalemia
- Increased extracellular H+ inhibits the Na/H+ anti porter - Decreases intracellular Na+, thus inhibiting the Na/K ATPase - Increases extracellular K+ causing hyperkalemia -Increased extracellular K+ activates Na/K+ ATPase -Increased extracellular Na+ activates Na/H+ antiporter -Increased H+ extracellular =ACIDOSIS
35
Cause of pseudohyperkalemia
Release of potassium from RBC lysis Examples: - Blood drawn form the side of IV infusion or central line without previous flushing - Prolonged tourniquet use - Fist clenching during blood withdrawal - Delayed sample analysis
36
Causes of hyperkalemia
DO LABSS: ``` Digoxin HyperOSMOLARITY Lysis of cells Acidosis Succinylcholine Sugar (high) ```
37
What level of potassium is considered severely elevated?
>8 mEq/L
38
Routine labs for hyperkalemia
BMP (basic metabolic panel) CBC (hemolytic anemia present) Liver chemistry (hemolysis or tumor lysis syndrome) Blood gas (metabolic acidosis)
39
Aside from routine labs for hyperkalemia, what specific investigation would you do? (labs wise, what would you want to measure)
Creatine kinase (Increased in rhabdomyolysis) LDH (increased in hemolysis) RAAS Cortisol (decreased in adrenal insufficiency)
40
EKG changes in hyperkalemia
Peaking t waves QRS widening Flattening p wave (absent >8 mEq/L)
41
Treatment of hyperkalemia
Acute, not chronic treatment: ``` Calcium gluconate Short acting insulin w/ glucose Dialysis/diuretics Bicarbonate (treat acidosis) Beta agonists ```
42
Definition of hypercalcemia
total serum calcium > 10.5 mg/dL (>2.62 mmol/L) ionized (free) calcium >5.25 mg/dL (>1.31 mol/L)
43
Reasons for PTH mediated hypercalcemia
Primary hyperthyroidism: Adenoma (sporadic or MEN syndrome) Secondary hyperthyroidism: Renal insufficiency or vitamins D deficiency
44
Reasons for non-PTH mediated hypercalcemia
Malignancy (SSC of lung) Osteolytic metastases (multiple myeloma) Sarcoidosis (activates hydroxylase activity, increasing calcitriol) Thiazide diuretics Pagets disease Hyperthyroidism (Increased thyroid hormone increases osteoclast activity)
45
Hypercalcemic crisis definition
Total calcium: > 14 mg/dL (3.5 mmol/L) Free calcium: > 10 mg/dL (2.5 mmol/L)
46
Equation for corrected calcium (mg/dL)
=measured total Ca + [0.8 x (4-albumin concentration in g/dL)]
47
EKG changes in hypercalcemia
``` QT interval shortening J waves (in severe) ```
48
Treatment of severe hypercalcemia
IMMEDIATE THERAPY: IV hydration with isotonic saline Calcitonin CAUSE-BASED THERAPY: Biphosphonates (malignancy) Loop diuretics (Renal insufficiency, CHF) Dialysis (>18 mg/dL; 4.5 mmol/L --> renal failure)
49
Definition of severe hypocalcemia
Total serum: <7.5 mg/dL (<1.9 mmol/L) | Total free: <3.6 mg/dL (<0.9 mmol/L)
50
What percent of total serum calcium is bound to albumin?
40% & is inactive
51
How does PTH respond to pH changes?
Increased pH = Increased PTH Decreased pH = decreased PTH *Because ie) Decreased H+ means less are binding to proteins, so Ca+ binds to those proteins, thus decreasing ionized calcium levels and increasing PTH
52
What effect does PTH have on serum calcium and phosphate?
Increase calcium, decrease phosphate
53
What effect does calcitriol (D3) have on serum calcium and phosphate?
Increase calcium & phosphate
54
What effect does calcitonin have on serum calcium and phosphate?
Decrease calcium & phosphate
55
What effect does magnesium have on PTH
Mild hypomagnesium: Increase PTH Severe hypomagnesium: Decreased PTH
56
Top 2 causes of hypocalcemia
Hypoparathyroidism & vitamin D deficiency ``` OTHERS: Loop diuretics Biphosphonates Osteoblastic metastasis RTA type 1 Blood transfusions (citrate in blood products chelates serum calcium) ```
57
What ion does DiGeorge syndrome effect
Calcium (because no parathyroid)
58
Causes of secondary hyperparathyroidism
Vitamin D deficiency CKD Hyperphosphatemia (decreased excretion or increased tissue breakdown) Acute necrotizing pancreatitis (calcium soap)
59
Cause of pseudohypocalcemia
Gadolinium contrast | Hypoalbuminemia
60
Chvostek sign
Twitching of facial muscle after tapping on facial nerve (below & in front of ear) *Due to hypocalcemia
61
Trousseau sign
Carpopedal spasm several minutes after inflation of blood pressure cuff at pressures above systolic *Due to hypocalcemia
62
Labs to order in case of hypocalcemia
PTH Amylase (pancreatitis) Calcidiol
63
Lab findings in vitamin D deficiency
Low calcium, phosphate | High PTH
64
EKG changes in hypocalcemia
Prolonged QT interval
65
Treatment of hypocalcemia
Calcium gluconate (IV if severe, oral if moderate/chronic)
66
What medication combined with IV calcium can cause life threatening arrhythmias
Digoxin/Digitoxin *cardiac glycosides

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