Volume Expansion and Hyponatremia

Question 1

Primary renal Na retention

Answer 1

AKI (decreased GFR)
ACKD (marked deceased GFR)
Could also be from neprhotic syndrome (decreased IV volume, decreased flow to MD, activation of RAAS)

Question 2

Secondary Renal Na retention

Answer 2

Reduced effective arterial BP (heart failure/nephrotic syndrome/liver cirrhosis)

Sympathetic, RAAS, and AVP activation

Renal vasoconstriction with decreased GFR

Resistance to natriuretic peptides

Question 3

Hx of ECF expansion

Answer 3

Alcohol intake

Heart dz

Liver/kidney dz

Sx of heart failure

Foamy urine

Question 4

Exam of ECF exapnsion

Answer 4

Edema, increased JVP, S3 heart sound, basilar crackles, pleural effusion, liver cirrhosis

Question 5

Therapy in ECV expansion

Answer 5

Tx underlying syndrome

Low sodium

Fluid restriction if hyponatremic

Avoid NSAIDS as they are salt retainers

Diuretics - enhance Na excretion

Aggressive tx if pulmonary edema or hypervolemia induced HTN

Question 6

Hyponatremia

Answer 6

Serum sodium reflects plasma water content

Thus hyponatermia often associated iwth high AVP levels

Question 7

Hypotonic hyponatremia

Answer 7

loss of sodium in excess of water or more commonly replacement of fluid losses with Na poor water

Non-osmotic stimulation of AVP despite hypotonicity (volume rules over tonicity)

Water rentention by kidney

Question 8

Non-osmotic release of AVP

Answer 8

Decreased effective arterial blood volume through carotid sinus baroreceptors

Pain

Nausea

Pregnancy…lowers osmoregulatory threshold

Drugs

Question 9

Renal hyponatremia (hypovolemic)

Non-renal

Answer 9

Diuretics (HCTZ) and mineralocorticoid def…over 20 U na

Non renal - GI loss or sweat…under 20 U Na

Question 10

Evaluation of ECF depletion key

Answer 10

Postural hypotension (over 20 mmHg)

Question 11

Tx of hypovolemic hyponatremia

Answer 11

Avoid rapid correction to avoid osmotic demyelination syndrome

Replace with isotonic saline to correct the hypovolemia

Question 12

Causes of hyponatremia with ECF expansion

Answer 12

Retention of water>Na with low AVP ——KIDNEY problem

Retention of water>Na with high AVP level…reduced effective arterial blood volume
Heart failure (not enough blood)
Nephrotic syndrome (fluid leaving the IV space)
Cirrhosis of the liver (aterial tree dilated)

Question 13

WHy is AVP increased in hypervolemic states

Answer 13

Decreased effective arterial blood volume (through carotid barorecpeotrs)

Approximately 15% of cirulating blood is in arterial tree

Question 14

Therapy of hypervolemic hyponatremia

Answer 14

Tx underlying dz

Loop diuretics (decrease response to AVP)

Fluid restriction

AVP-V2 receptor antagonis is Na<125

Question 15

Euvolemia with hypotonic hyponatremia

Answer 15

High AVP, high U osm - SIADH, hypothyroidism, GC def, pregnanyc

Low AVP, low U osm - Primary polydipsia or beer potomania

Question 16

Sx of hypotonic hyponatremia

Answer 16

Sx largely due to cerebral edema (movement of water from hypotonic ECF)

General sx

CNS sx

GI sx

Question 17

Tx of SIADH

Answer 17

Fluid striction

High solute intake plus loop diuretics (decrease osmolar gradient and render AVP less effective)

Hypertonic saline…ODS (not over 10)

Arginine vasopressin V2 receptor antagonists

Question 18

Hypertonic hyponatremia

Answer 18

Hypertonic plasma

Movement of water from ICF to ECF

Also called dilutional hyponatremia

Causes - large amouint of high-osmolality molecules (glucose or mannitol)

Question 19

Isotonic hyponatremia

Answer 19

Severe hyperlpipidemia

Multiple myeloma