Regulation and Disorders of Salt and Water Flashcards Preview

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Flashcards in Regulation and Disorders of Salt and Water Deck (22)
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1

What is the cause of disorders of extracellular volume?

Alteration in SODIUM BALANCE
***Remember Sodium in the main determinant of ECFV)

2

What effect does ADH have on urine sodium and osmolality?

• LOW urine sodium
• HIGH urine osmolality

3

What is ECV?
• what does it tell you?
• How does it relate to ECFV?

ECV = Effective Circulating Volume

Relates to the FULLNESS and TENSION within the arterial tree (this is only 15% of total blood volume)

ECV relates the Extra Cellular Fluid Volume almost all the time with the exception of a few diseases (CHF, Liver Disease, Sepsis, Nephrotic Syndrome, Pregnancy, Anaphylaxis)

4

What are the 2 most important disorders where ECV does not relate to Extra Cellular Fluid Volume?
• why do these two values not line up?

Heart Failure:
• Veins are distended (high ECFV)
• Arteries are Relatively Empty (Low ECV)

Liver Disease:
• Splanchic Ciruculation is Taking all the Blood (low ECFV)
• Renal Arteries don't get blood flow (Low ECV)

5

What is TRUE volume depletion?
• general cause?

Decreased:
• ECV and ECFV
• Low Total BODY Na+

6

What occurs in TRUE volume depletion due to Extra Renal Losses?
• examples of causes.
• Labs?

Low Na+ and Low ECV and ECFV

Examples of Causes:
• Diarrhea, Burns

Labs:
• URINE should be HIGHLY CONCENTRATED
• URINE should also be SALT POOR

7

What occurs in TRUE volume depletion due to Renal Losses?
• examples of causes.
• Labs?

Low Na+ and Low ECV and ECFV

Examples of Causes:
• Diuretics, reconvery phase of ATN

Labs:
• URINE will not be that concentrated
• URINE could also be salt rich

8

What clinical features will you see in someone with TRUE volume depletion?

• Reduction in Blood Pressure
• Poor skin turgor
• ABSENCE OF DEPENDENT EDEMA
• ***Disproportionate increase in BUN relative to serum creatinine:Reduced Urine Na except in cases with renal losses of Na***
• Decline in mental status and cool extremities

9

When does volume expansion occur?
• common underlying disturbance?

• When salt and water intake exceeds renal and extrarenal losses.

• Common underlying disturbance - sodium and water retention by the kidney

10

What are some common causes of volume excess?
• Primary and Secondary?
• Net Result of both of these diseases?

Primary:
• Chronic Kidney Disease
***Results in increased ECV

Secondary:
• Liver Disease and Heart Failure
***ECV is not increased despite increases in ECFV

Net Result:
• Starling Forces (increased capillary hydrostatic pressure, reduction in osmolarity) SHIFTS FLUID TO INTERSTITIAL SPACE

11

What are some clinical features of Excessive Volume?

• Edema
• Elevated JVD
• Crackles, Ascites, Pleural Effusion

12

What should your plasma osmolality be?
• what happens if you get above this range (in healthy individuals)?

280-290 mOsm/L

Above Range:
• Hypothalamic Receptors are Stimulated triggering… 1) Thirst 2) ADH release

13

T or F: Sodium balance is regulated by both osmolality and volume.

FALSE, sodium balance is ONLY regulated by VOLUME STATUS

water balance is controlled by BOTH osmolarity and volume

14

What value of plasma Na+ defines Hyponatremia (low plasma Na+)?

Less than 135 mEq/L

15

How is serum sodium calculated?
• why is that important to Remember?

Serum Na is NOT the same as total body Na, SERUM SODIUM IS DEPENDENT ON VOLUME OF WATER in the body

Formula:
Serum Na Conc. = Amount of Na(TBNa) / (Volume of water (TBW))

16

What is a hyperosmolar hyponatremia?
• what causes it?

• Low Sodium concentration due to other osmotically active molecules in the periphery

Causes:
• Mannitol
• Hyperglycemia

17

What is the most common type of Hyponatremia?

Hypoosmolar Hyponatremia

18

Is hypernatremia typically due to water loss or sodium gain?
• who is most susceptible?

Water Loss is the cause of Hypernatremia

Ppl with Primary Defects:
• Don't make ADH
• Resistant to ADH

Ppl. with Secondary Defects:
• Diseases of Brain
• Paralyzed people

19

Hypoosmolar Hyponatremia
• HYPOVOLUMERIC
• Lab Values
• Associated Diseases

Lab Values:
• Low TBW
• EVEN LOWER Na+

Associated Diseases:
EXTRA renal Sodium Loss:
• Vomiting
• Burns
• Hemorrhage

Renal Sodium Loss:
• Defective Renal Handling of Na
• Mineral Corticoid Deficiency
• Diuretic Therapy

20

Hypoosmolar Hyponatremia
• EUVOLUMERIC
• Lab Values
• Associated Diseases

Lab Values:
• Low TBW
• Na+ is normal

Associated Diseases:
• Pulmonary disorders, CNS disorders and malignancy
• Pain/ nausea
• Glucocorticoid deficiency
• Hypothyroidism
• Drug-induced water retention
Vasopressin analogues or drugs that enhance vasopressin action i.e chlorpropamide, clofibrate, narcotics, antipsychotics, carbemezepine

21

Hypoosmolar Hyponatremia
• HYPERVOLUMERIC
• Lab Values
• Associated Diseases

Lab Values:
• HIGH TBW
• Na+ increased but not enough

Associated Diseases:
• Congestive heart failure
• Hepatic cirrhosis
• Nephrotic Syndrome
• Renal disease

22

How can lab values help you to distinguish Renal Sodium Loss from Extrarenal Sodium Loss in hypovolemic hyponatremia?
• explain this finding

RENAL
Una will be GREATER than 20 mEq/L

Extra Renal
Una will be LESS THAN 20 mEq/L

***Having a high Urinary concentration of Na+ implies that your kidney is not responding appropriately to the hypovolemic state. In most people you should resorb lots of Na+***