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Medicina Interna > 42. Alteraciones en el Sodio > Flashcards

42. Alteraciones en el Sodio Flashcards

1
Q

What is the most common electrolyte abnormlaity in the United States?

A

Hyponatremia

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2
Q

Epidemiology of sodium disorders in the US?

A
  • 3-6 miilion patients per year present to a clinical setting with hyponatremia
  • Between 12-20% of patients admitted to the emergency department have a sodium imbalance
  • Hypernatremia was found in 2% of patients and hyponatremia was found in 10% of patients presenting to the emergency department.
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3
Q

What is hyponatremia?

A

Serum sodium level of less than 135 mmol/L

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4
Q

What is hypernatremia?

A

Serum sodium level of greater than 145 mmol/L

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5
Q

Which is themost abundant cation in extracellular fluid?

A

Sodium

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6
Q

What is the primary determinant of plasma osmolality?

A

Sodium

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7
Q

T/F: “Any derangements in sodium can affect the balance of cations, anions and overall plasma osmolality”

A

True

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8
Q

The vast majority of dysnatremias originate from…?

A

A primary imbalance in electrolyte -free water intake and loss. The perturbation in water balance rather than the salt content is commonly the problem

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9
Q

What is plasma osmolality?

A

The concentration of osmoles dissolved per kilogram of plasma water.

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10
Q

What is plasma osmolarity?

A

The concentration of osmoles per liter of plasma water.

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11
Q

What is tonicity?

A

The concentration of osmoles- also known as effective osmoles- that do not freely cross cell membranes.

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12
Q

Tonicity can also be interpreted as…

A

The effective plasma osmolality.

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13
Q

What are some of the effects of antidiuretic hormone?

A
  • Increased expression of aquaporin 2 receptors
  • Decrease blood flow in the renal medulla through vasoconstriction
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14
Q

What factors can increase ADH release?

A
  • Hypovolemia
  • Drugs
  • Pain
  • Emotional stress
  • Nausea
  • Pregnancy
  • Menstruation
  • Hypoglicemia
  • Severe hypoxemia
  • Hypercapnia
  • Sepsis
  • Severe burns
  • Trauma
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15
Q

Which are the insensible losses of water?

A
  • Ventilation
  • Evaporation of sweat
  • Water lost in stool
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16
Q

How much water do we lose insensibly thoughout the day?

A

40 - 800 mL per day

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17
Q

What is the most common cause of hyponatremia?

A

Hemodilution, specifically, it is most commonly due to a failure to secrete free water.

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18
Q

What is the clinical presentation of hyponatremia:

A

It is a spectrum:

  • Asymptomatic
  • Neurologic dysfunction usually due to cerebral edema: sodium less than 125 mmol/L
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19
Q

What determines the severity of symptoms of hyponatremia?

A

It depends on the rate of reduction, rather than the serum sodium level.

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20
Q

What are some of the mild symptoms of hyponatremia?

A
  • Headache
  • Nausea
  • Vomiting
  • Lethargy
  • Fatigue
  • Dizziness
  • Gait disturbances
  • Forgetfulness
  • Muscle cramps
  • Confusion
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21
Q

What are some of the severe symptoms of hyponatremia?

A
  • Confusion
  • Seizure
  • Coma
  • Respiratory arrest
  • Death
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22
Q

¿Qué hacer ante la sospecha de hiponatremia?

A
  1. Confirmar la hiponatremia
  2. Determinar su causa
  3. Determinar el estado de volumen del paciente
  4. Calcular osmolalidad plasmática (Para ver si es hipertónica, isotónica o hipotónica)
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23
Q

What is hypertonic hyponatremia?

A

When serum osmolality exceeds 290 mOsm/kg

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24
Q

What is isotonic hyponatremia?

A

When serum osmolality is between 275 and 290 mOsm/Kg

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25
Q

What are some of the causes of hypertonic hyponatremia?

A

It is most often due to another solute increasing:

  • Severe hyperglicemia (Diabetic ketoacidosis, hyperosmolar hyperglycemia)
  • Administration of hypertonic agents (Mannitol, hypertonic saline)
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26
Q

What are some of the causes of isotonic hyponatremia?

A

Pseudohyponatremia:
- Severely elevated cholesterol
- Hypertrygliceridemia
- Obstructive jaundice
- Mieloma

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27
Q

What is hypotonic hyponatremia?

A

When serum osmolality is less than 275 mOsm/Kg

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28
Q

Whic hyponatremia is most common: hyper, iso or hypotonic?

A

Hypotonic

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29
Q

What are the subtypes of hypotonic hyponatremia?

A
  • Hypervolemic
  • Euvolemic
  • Hypovolemic
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30
Q

What are some common causes of hypervolemic hyponatremia? (4)

A
  1. Heart failure
  2. Hepatic failure
  3. Renal Failure
  4. Nephrotic Syndrome
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31
Q

What are some common causes of euvolemic hyponatremia? (9)

A
  1. Syndome of inappropiate antidiuretic hormone excretion (Malignancy, CNS disorders, HIV, tuberculosis, pneumonia)
  2. Drugs
  3. Primary polydipsia
  4. Beer potomania
  5. Hyperglicemia
  6. Hypothirodism
  7. Adrenal insufficiencyy
  8. Hypokalemia
  9. Diet
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32
Q

What are some common causes of hypovolemic hyponatremia? (5)

A
  1. Vomiting
  2. Diarrhea
  3. Exercise induced
  4. Diuretics (Thiazides most commonly)
  5. Cerebral salt wasting syndrome
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33
Q

If we have a patient with hypotonic hyponatremia, and his urine sodium is greater than 20 mEq/L, what is the likely culprit?

A

Neprogenic in etiology

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34
Q

What are some of the lab tests we should order in the initial workup of a patient with hyponatremia?

A
  • Comprehensive metabolic panel
  • TSH
  • Cortisol
  • Urine sodium
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35
Q

What do we suspect in a patient who seems dry or “volume down” on examination, they lack edema, skin tugor is poor, serum sodium is decreased and urine sodium is elevated?

A

This may be due to renal losses in cases of diuretic use, salt wasting or adrenal insufficiency.

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36
Q

What do we suspect in a patient who seems dry or “volume down” on examination, they lack edema, skin tugor is poor, serum sodium is decreased and urine sodium is decreased?

A

One should suspect extrarenal losses, as in cases of gastroenteritis.

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37
Q

What are the diagnostic criteria for Syndome of inappropiate antidiuretic hormone excretion ?

A
  • Hypoosmolality (Less than 275 mOsm/Kg)
  • Hyperosmolar urine (Greater than 100 mOsm/Kg)
  • Euvolemia
  • Increased urine sodium (Greater than 20 mEq/L)
  • NO diuretic use or evidence of thyroid or adrenal disease
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38
Q

What is acute hyponatremia?

A

Sodium level of less than 135 mmol/L that develops during a period of 48 hours; which may result in cerebral edema.

39
Q

What is chronic hyponatremia?

A

If it is known that the hyponatremia has been present longer than 48 hours. It is oftentimes asymptomatic.

40
Q

What is mild hyponatremia?

A

Concentrations between 130 and 134 mEq/L

41
Q

What is moderate hyponatremia?

A

Concentrations between 120 and 129 mEq/L

42
Q

What is severe hyponatremia?

A

Concentrations less than 120 mEq/L

43
Q

Which patients warrant emergent management?

A

Patients withnsevere symptoms.

44
Q

What is the goal during the management of hyponatremia?

A

Increase te serum sodium by 2-4 mEq/L until symptoms abate as rapidly as possible.

45
Q

How to manage hyponatremia?

A

Infusion of 100 ml bolues (or 5 mL/kg in children) of 3% hypertonic solution, up to a maximum of 3 boluses.

46
Q

How to manage hyponatremia if hypertonic solution is NOT readily available?

A

8.4% sodium bicarbonate ampules from the code cart can be used as an acceptable alternative.

47
Q

How fast should you correct hyponatremia?

A

Both US and european guidelines recommend a correction limit of 10 mmol/L per day, regardlesss of chronicity and advise frequent monitoring response to treatment.

48
Q

How to manage overcorrection?

A

Vasopressin anhd free water.

49
Q

How to manage mild symptoms of hyponatremia?

A

3% hypertonic solution bilus 150 mL over 20 minutes once.

50
Q

What is the first-line therapy for management of chronic euvolemic and hypervolemic hyponatremia?

A

Fluid restriction.

51
Q

What are Vaptans?

A

They block vasopressin type 2 receptors, to cause free water loss. And are the second-line therapy for euvolemic and hypervolemic hyponatremia in the US.

However they can cause liver toxicity and overcorrection, so the European guidelines do not recommend them.

52
Q

What does the European society recommend as second-line therapy for SIADH?

A

Loop diuretics.

53
Q

What is the mainstay of treatment in hypovolemic hyponatremia?

A

Volume expansion. The initial fluid used is 0.9% fluid saline.

54
Q

What are the 2 main complications of hyponatremia?

A
  1. Cerebral edema
  2. Osmotic demyelination syndrome
55
Q

Which patients are particularly at risk for developing cerebral edema post hyponatremia?

A
  • Post menopausal women
  • Women on thiazide diuretics
  • Children
  • Psychiatric patients with polydipsia
  • Hypoxemic patients
56
Q

What should you do once treatment of hyponatremia has commenced?

A
  • Watch electrolyte levels closely, checking every 2 hours
  • Urine output should be monitored hourly
57
Q

What is Osmotic Demyelination syndrome?

A

It is the iatrogenic irreversible clinical syndrome of neurologic symptoms that occurs after too rapid a correction of serum sodium.

58
Q

What are the symptoms of osmotic demyelination syndrome?

A
  • Fluctuating levels of conciousness or confusion.
  • Behavioural changes
  • Dysarthria
  • Dysphagia
  • Seizures
  • “Locked-in syndrome”
  • Death
59
Q

What is the most common cause of hypernatremia?

A

Most commonly due to excess water loss.

60
Q

What are other less common causes of hypernatremia?

A
  • Intake of salt without water
  • Administration of HTS solutions.
61
Q

What are the most common symptoms of hypernatremia?

A

Initially:
- Thrist
- Dry mucous membranes
- Decreased urine output

As it progresses:
- Restlessness
- Irritability
- Confusion
- Lethargy
- Muscle twitching
- Seizures

62
Q

What are some of the symptoms of severe hypernatremia?

A
  • Altered mental status
  • Hallucinations
  • Coma
  • Death
63
Q

What consequence can the shrinking of brain cells have, in cases of hypernatremia?

A

Intracerebral hemorrhage, because of tearing of cerebral blood vessels.

64
Q

When are the severe manifestations of hypernatremia present?

A

When the sodium levels increase more than 158 mEq/L and values greater than 180 mEq/L are associated with a very high mortality rate.

65
Q

What are some of the common causes of hypovolemic hypernatremia? (5)

A
  1. Dehydration due to decreased water intake
  2. Prolonged hyperglycemia
  3. Hyperglicemic hyperosmolar syndrome
  4. Osmotic diarrhea
  5. Hyperaldosteronism
66
Q

What is the main cause of euvolemic hypernatremia?

A

Diabetes insipidus (The body does not respond to ADH either centrally or peripherally)

67
Q

What are some of the common causes of hypervolemic hypernatremia? (2)

A
  • Hypertonic solution administration
  • Improper preparation of solutions for enteral or parenteral feeding or peritoneal dialysis.
68
Q

What are the two subtypes of diabetes insipidus?

A

Central and nephrogenic

69
Q

What is central diabetes insipidus?

A

Arginine vasopressin deficiency. It can be caused by trauma, pituitary surgery and malignnacies. It is most commonly idiopathic.

It is characterized by a decrease in the release od ADH resulting in a variable degree of polyuria.

70
Q

What is nephrogenic diabetes insipidus?

A

Arginine vasopressin resistance, is commonly caused by renal disease, medications and genetic disorders.

71
Q

What is acute hypernatremia?

A

Serum sodium level greater thank 145 mEq/L, which develops during a period of less than 48 hours.

72
Q

What is chronic hypernatremia?

A

Hypernatremia that developed during a period greater than 48 hours or if duration unknown.

73
Q

How fast should you correct hypernatremia in unstable patients?

A

Minimum of 48 hours to decrease the likelihood of seizures, permanent brain damage, or even death.

74
Q

What is the correction limit for hypernatremia?

A

Sodium should NOT decrease by more than 8-15 mEq/L in a given 8 hour period.

75
Q

Where is ADH synthetized?

A

Hypothalamus

76
Q

Where is ADH stored?

A

Posterior pituitary gland

77
Q

Where does ADH act?

A

On the collecting duct of the nephron to increase water reabsorption and decrease serum tonicity

78
Q

What is pseudohyponatremia?

A

Not true hyponatremia, but rather a laboratory artifact.

It happens when there is a high plasma lipid or protein concentration that lowers the aqueous contribution to plasma volume (normally 93%), leading to a falsely decreased calculated sodium value.

79
Q

Which liquids do you use to correct hypernatremia?

A

Isotonic fluids like:
- 0.9% normal saline
- Lactated Ringer´s

80
Q

How to correct hypernatremia in an asymptomatic patient?

A

At a rate no greater than 0.5 mEq/L/h and no more than 8-15 mEq/L/per day.

81
Q

What to do if the patient is asymptomatic and has nornal renal function?

A

Wait for natural excretion

82
Q

What are the 4 main complications of hypernatremia?

A
  1. Cerebral edema (If correction too fast)
  2. Osmotic demyelination syndrome (If correction too fast)
  3. Fluid overload
  4. Electrolyte imbalances (Potassium, magnesium)
83
Q

What are some of the causes of hypovolemic hypotonic hyponatremia? (4)

A
  1. Hemorrhage
  2. Gastrointestinal fluid loss
  3. Diuretics
  4. Aalt wasting due to mineralocorticoid deficiency in Addisonian crisis
84
Q

What is SIADH?

A

Persistent vasopressin secretion in the abscense of an osmotic or hemodynamic stimulus.

85
Q

In which patients are we meassuring urine sodium concentration?

A

Because the differentiation of subtle hypovolemia from euvolemia is difficult, we will measure it in any patient not plainly hypervolemic due to congestive heart failure or cirrhosis.

86
Q

Hyponatremia secondary to hyperglycemia should improve with…

A

Lowering of blood glucose level.

87
Q

What are the risk factors for osmotic demyelination syndrome?

A
  • Patients with chronic hypotonic hyponatremia
  • Presenting Na less than 105 mEq/L
  • Alcoholism
  • Advanced liver disease
  • Malnutrition
  • Hypokalemia
88
Q

What is the first-line therapy for hyponatremia attributed to heart failure?

A

Loop diuretics

89
Q

When fluid restriction and loop diuretics fail a __________ can be used to promote aquaresis.

A

Vasopressin antagonist (Vaptan) like tolvaptan or conivaptan.

90
Q

What should i calculate if overcorrection occurs?

A

Urine electrolyte-free water excretion

91
Q

What to do if i overcorrect, and want to prevent a further increase in sodium?

A

Administer enteral water or IV 5% dextrose in wanter in an amount equal to urinary electrolyte-free water loss + estimated extrarenal and insensible water losses.

92
Q

What to do if i over correct and i want to relower the concentration of sodium?

A

Increase the calculated rate or enteral water or IV 5% dextrose in water administration by 3 ml/kg/h

93
Q

What to do if urine output id high and urine is very dilute, to overturn any further urine electrolyte-free water loss and simplify fluid management?

A

Administer desmopressin

Medicina Interna (42 decks)

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