L1 and L2 - ECF vol and Hyponatremia

Question 1

How much volume is in ECF and what comparments? How much in ICF? What are the barriers between compartments?

Answer 1

60% volume in ECF made up of 1/4 Intravascular and 3/4 Interstitial

~barrier between not permeable to proteins!~

40% volume in ICF and barrier between ECF/ICF not permeable to electrolytes

Question 2

what is effective arterial blood volume? How does kidney react to it?

Answer 2

The intravascular volume that the kidney sees

if its low, despite high interstitial volumes, then the kidney will conserve Na!! try to maintain BP

Question 3

what are the two main regulators of ADH?

Answer 3

PLasma Osmolality - as that goes up, ADH and thirst goes up as monitored by hypothalamus

Blood Volume!!!! 20% drop in blood volume will override any signals from Posm and ADH will increase to maintain BP

Question 4

if you have too much ECF volume or too much Na intake, what regulators kick in?

Answer 4

Volume receptpors and Atrial Stretch receptors detect volume expansion and TURN OFF symptathetic, RAAS system and increase GFR and Flow rate to decrease Na reapsorption and increase Na excretion

Question 5

what is Hyponatremia? What is serum sodium?

What must you know in order to treat patients w/ hyponatremia?

Answer 5

Hyponatremia: RELATIVE increase in plasma water to Na but total body Na cannot be determined from am examination of the concentration term

Serum Sodium is a concentration and not an absolute

MUST DETERMINE VOLUME STATUS to know how to treat patients!!!

Question 6

Problems w/ any of these 4 variables can lead to hyponatremia which is, overall, a problem of what?

What are the 4 main ways that the Kidney Dilutes urine?

Answer 6

Hyponatremia = Problem w/ Urinary Dilution Disorder!!!! If you could dilute your urine, you would not get hyponatremic.

_Problems w/ any of the 4 following variables can lead to hyponatremia: _

1) GFR (normal 100- 120 ml/min) –> Low GFR means you can’t dilute urine - reduces delivery to diluting sites
2) Distal Delivery to TAL–> if you increase reabsorption in PCT (hypovolemic states from 80% reabs to 95% reabs) then decrease delivery to distal diluting sites (from 20% to 5%)
3) TAL NaCl pumped out of filtrate into interstitium: –> Loop diuretics inhibit NaCl removal and so lose ions and get hyponatremia and impair diluting mechanism
4) Suppress ADH! --> do NOT want CD permeable to water if trying to excrete it

Question 7

you’re Euvolemic and drink a big glass of water, what happens?

Answer 7

plasma osmolality falls, ADH suppressed, and bc have normal GFR and are euvolemic you make dilute urine

(Uosm<100)

An abnomally high Uosm > 100 denotes failure to suppress ADH

Question 8

What is the ideal pOsm value? what happens to ADH when it rises? and lowers?

Answer 8

Ideal pOsm is 285

when Posm increases, Adh increase

when Posm drops, ADH should be inhibited

(pOsm <270 mOsm)

Question 9

What is the first step in assessing Hyponatremia?

Answer 9

First Calculate Posm and make sure not pseudohyponatremia

THEN:

Assess ECF Volume status w/ the following:

JVP - venous

Postural BP - arterial

Edema - Interstitial

Decide if Hypo, Eu, or Hypervolemic

Question 10

What does Hypovolemic Hyponatremia mean? What are the causes?

Answer 10

Low arterial BV and low ECF volume

Renal Loss: Diuretics, Na wasting nephropathy

Mineralcorticoid deficiency - ex. Addison’s or lact of aldosterone

Non-Renal Loss - Vomitting or skin

Question 11

What should the Urine values be for the different causes of Hypovolemic Hyponatremia?

Answer 11

Renal Causes: Una > 20 (high) and Uosm Isotonic

Non-Renal Causes: Una <20 (low) and Uosm high

Question 12

What does Hypervolemic Hyponatremia mean? What are the causes? What should the urine values be?

Answer 12

Hypervolemic - high ECF - edema etc

Hyponatremia - low effective circulating volume

Cuases - CHF, Cirrhosis, Nephrosis, Post-op 3rd spacing

Una Low (

Uosm high (>300)

Question 13

What is Euvolemic Hyponatremia? Causes? Urine Values?

Answer 13

Euvolemic - no clinical detection of volume change (although really slightly larger)

Causes: SIADH, psychogenic water, hypothyroidism, drugs

Urine:

Una High >20

Uosm high >300

Question 14

treatment of acute vs chronic hyponatremia?

Answer 14

Acute- treat rapidly to reverse w/ hypertonic saline

Risk of over rapid correctoin can lead to Osmotic Demyelination!!

Chronic- correct SLOWLY

• restore volume if total body volume low (hypovolemic)

Water restriction and V2 receptor antagonists

Question 15

Treatments for the 3 hyponatremic conditions?

Answer 15

Hypovolemia: ECF volume repletion w/ saline

Euvolemia: Water restriction and/or V2 receptor Antagonists to block ADH receptor

Hypervolemic: Underlying Dx treatment, Water restriction, V2 receptor antagonists, Diuretics to get rid of massive volume

Question 16

How do you raise serum Na concentration in first 24 hours? Meaning at what rate?

What happens if correct too rapidly?

Answer 16

Raise Serum [Na] by 4-6 mEq/L in the first 24 hours and should never exceed 8

Correct too rapidly and get **cerebral pontine myelinolysis **

Question 17

What is pseudohyponatreima?

Answer 17

Na content is actually the same but bc some relative volume displaced from either hyperlipidemia or hyperproteinemia then Na content appears lower than it actually is

Question 18

How does Addison’s Present?

Answer 18

Cant make steroid hormones - Aldosterone

Mineralcorticoids stimulate K secretion and deficiency results in hyperkalemia

+ Uosm higher than Posm but not very high bc adrenal hormones are required co-factors for MAXIMAL ADH action

Hypoosmotic hypovolemic hyponatremia