Sodium Disorders Flashcards Preview

CRRAB II - Medicine > Sodium Disorders > Flashcards

Flashcards in Sodium Disorders Deck (31)
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0
Q

What equation can be used to estimate serum osmolality?

A

[Na]x2 + [Glucose]/18 + [BUN]/2.8

1
Q

What is normal sodium serum concentration?

A

135-145 mEq/L

2
Q

What are the symptoms of sodium concentration below 125 mEq? 120-115? <115?

A

120-125: Nausea/malaise
115-120: Headache/lethargy
<115: Seizures, obtundation, coma

3
Q

What is the main pathophysiological effect of hyponatremia?

A

Decreased extracellular osmolality results in brain cell swelling

4
Q

What are the symptoms of hypernatremia?

A

Lethargy, weakness, irritability, twitching, seizures, coma, death

5
Q

What is the key pathophysiological finding to hypernatremia?

A

Shrinkage of brain cells, leading to rupture of cerebral vasculature due to decreased volume

6
Q

What are the nonosmotic stimuli to increasing levels of ADH?

A

Baroreceptors (hypovolemia)
Pain (post-operative for instance)
Esophageal stimuli
Various medications

7
Q

If ADH is present, is serum osmolality increased or decreased?

A

decreased

8
Q

If plasma osmolality is high, is urine osmolality supposed to be high or low?

A

high

9
Q

If urine sodium is high, what does the body think about the body’s volume status?

A

Body thinks serum volume is expanded, wants to get rid of excess sodium

10
Q

What level of urine osmolality usually means ADH is involved in the system?

A

> 100 mOsm/L

11
Q

Given osmoles taken in per day and amount of urine osmolality, how can you calculate amount liquid excreted per day?

A

(Osm/day)/(urine osmolarity in Osm/day)

12
Q

In the nephron, what percentage of sodium is reabsorbed by each of the tubules?

A

Proximal tubule: 65%
LOH: 25-35%
Distal tubule: 5%
Collecting duct: 4% (dependent upon aldosterone, ANP)

13
Q

If the urine sodium concentration is <10 meq/L, then what is the body sensing the circulating volume to be?

A

low circulating volume

leads to increased water and sodium resorption

14
Q

If the urine sodium concentration is >10 mEq/L, then what does the body think is going on?

A

Increased volume of ECV
Kidney unable to retain Na
Na is leaving with something else (as an obligate cation)

15
Q

What is pseudohyponatremia with regular osmolality usually due to?

A

Hyperlipidemia, hyperproteinemia

16
Q

What is pseudohyponatremia with elevated osmolality due to?

A

Increased Glucose levels

Increased mannitol levels

17
Q

When evaluating Hyponatremia in the clinic, what steps should you follow?

A

Check serum osmolality (True or pseudo hyponatremia?)
Check urine osmolality (Is ADH acting?)
Check urine Na osmolality (What do kidneys think of ECV?)
Check H&P

18
Q

What are primary and secondary causes of hyponatremia with Uosm <100?

A
  1. Increased water consumption
  2. Alcohol
  3. Tea and toast syndrome
19
Q

How do you treat primary polydipsia?

A

Let the kidneys do their thang

20
Q

If you have hyponatremia with Uosm >100, and UNa is <10 with volume depletion, what is the cause?

A

Normal kidney response to add fluid back into the depleted ECV.

From: Burns, diuretics, GI losses (vomiting, diarrhea), cortisol deficiency

21
Q

If you have hyponatremia with Uosm >100, and UNa <10 with expanded volume but ECV depletion, what is likely the cause?

A

Kidney is confused because of edema (CHF, cirrhosis, nephrosis)

22
Q

If you have hyponatremia with Uosm >100, and UNa >10 with depleted volume, what is likely the cause?

A

Salt-wasting (kidney is failing)

Causes:
Diuretics (early), renal diseases, adrenal insufficiency, hypokalemia/metabolic alkylosis after vomiting, hypothyroidism

23
Q

If you have hyponatremia with Uosm >100, and UNa >10 with expanded volume, what is likely the cause?

A

Brain or kidney confused (inappropriate ADH secretion)

24
Q

What are some causes of inappropriate ADH secretion?

A
Tumor
Pulmonary process
Drugs (oxytocin, cytoxan, tegretol, chlorpropramide)
Esophageal process
Pain
Neuropsychiatric disorders
25
Q

What should you give patients with volume depleted hyponatremia?

A

Normal saline

26
Q

What should you give patients with volume expanded hyponatremia?

A

Nothing. Restrict free water intake.

27
Q

What should you give patients with hyponatremia causing neurologic symptoms?

A

Hypertonic saline

28
Q

What is the oral ADH antagonist?

A

Tolvaptan

29
Q

What is the IV ADH antagonist?

A

Conivaptan

30
Q

What drug can cause Nephrogenic diabetes insipidus after long term use?

A

Lithium