Jan8 M1-Disorders of Water Balance

Question 1

cause and consequence of water imbalance ultimately

Answer 1

ADH is cause. Hypo and hyperNa is consequence

Question 2

what controls plasma Na conc

Answer 2

water balance

Question 3

consequence of too much Na and too little Na (not related to water balance)

Answer 3

too much = edema

not enough = volume depletion

Question 4

main worry in Na imbalances

Answer 4

neuron swelling in the brain (cerebral edema)

Question 5

what can cause cerebral edema (swelling of neurons)

Answer 5

HYPOTONIC hyponatremia

Question 6

cause of central pontine myelinolysis

Answer 6

too rapid correction of hypoNa or hyperNa

Question 7

4 types of water excretion impairment hyponatremias and volume state in each

Answer 7

• circulating volume depletion (low IV volume. can have high ECF volume though bc high ISF volume)
• SIADH (euvolemic)
• advanced renal failure (hypervolemia)
• hormonal changes (euvolemia)

Question 8

conditions where appropriate ADH release with high ECF volume but low IV volume and ones with low ECF

Answer 8

CHF, cirrhosis, nephrotic syndrome
diarrhea, vomiting: high ECF low IV volumes
low ECF: diarrhea, vomiting, volume depletion with thiazides

Question 9

causes of SIADH and mechanisms

Answer 9

• neuropsychiatric disorder (any CNS disorder) or severe pain or nausea (signaling to hypothalamus)
• lung tumor (making ADH)
• pulmonary diseases (unknown)
• drugs

Question 10

volume state, Na and osms in SIADH

Answer 10

euvolemic, hypoosmolar, hypoNa

Question 11

hormonal changes that can cause water excretion impairment hypoNa and mechansims

Answer 11

• hypothyroidism (thyroid contributes to water excretion)
• cortisol deficiency (adrenal problem and low BP, perceived as low volume)
• pregnancy

Question 12

4 questions in hypoNa history

Answer 12

• why hospitalized?
• concurrent illnesses (renal disease, thyroid, low cortisol=Addison’s)
• medications (diuretics**)
• pain and nausea

Question 13

how to assess volume status in general

Answer 13

intravascular: BP, HR, urine output, JVP, postural hypotension BP
extravascular: edema and where

Question 14

what’s a postural hypotension BP

Answer 14

check BP diff when seat after lying down and if ­­>10, hypovolemia

Question 15

how to approach hypoNa and determine the cause

Answer 15

depending on volumee status

Question 16

hypoNa causes in hypovolemia

Answer 16

water loss (dehydration, diarrhea, vomiting), meds like diuretics

Question 17

hypoNa causes in euvolemia

Answer 17

SIADH, thyroid, adrenal insufficiency

Question 18

hypoNa causes in hypervolemia

Answer 18

CHF, liver disease, nephrotic syndrome, advanced renal failure

Question 19

most common causes of severe hypoNa

Answer 19

• SIADH,
• thiazide diuretics
• postoperative state (pain and nausea)
• GI fluid loss
• polydipsia in psychiatric patients (rare)

Question 20

formula for plasma osmolality

Answer 20

2 x Na + glucose + urea + (alcohol)

Question 21

4 criteria to diagnose SIADH

Answer 21

U Na>40
U osms>100
Na<125
serum osms<275

Question 22

why do you not retain volume or develop edema in SIADH (and stay euvolemic)

Answer 22

when sense excess volume, aldo and AT2 turned off so Na excreted

Question 23

hypoNa that is not a water excretion impairment

Answer 23

reset osmostat (hypothalamus is reset to be thirsty at a lower osmolality during pregnancy)

Question 24

ADH turned on or off in reset osmostat

Answer 24

turned off

Question 25

fluid treatment in hypoNa with peripheral edema + ADH before and after

Answer 25

fluid restrict to limit water reabso and return Na back up | ADH turned on initially and still turned on after

Question 26

fluid treatment in hypovolemia due to GI loss + ADH before and after

Answer 26

isotonic saline. ADH on before and turned off after

Question 27

fluid treatment in SIADH + ADH before and after

Answer 27

hypertonic saline (ADH on before and after, it's constitutively active..)

Question 28

D5W composition + what are we giving

Answer 28

water with 300 mosms of dextrose (is like giving pure water)

Question 29

normal saline composition

Answer 29

0.9% (0.9g per 100 mL NaCl): 154 mEq Na and 154 mEq Cl

Question 30

half NS composition and used when

Answer 30

77 mmol of Na. maintenance when not drinking or eating before surgery

Question 31

d5w + 3 ampules of NaHCO3 composition + used when

Answer 31

145 meq or Na and 145 meq of HCO3 per L (used in acid base disorder when need bicarb)

Question 32

3% saline composition and used when

Answer 32

513 mmol Na per L. SIADH

Question 33

Adrogue formula for Na correction

Answer 33

change = (infusate Na - serum Na)/(TBW + 1)

Question 34

long term treatment in SIADH

Answer 34

water restriction, dietary Na, loop diuretic to wipe out medullary interstitium osmotic gradient

Question 35

goal for speed of Na correction

Answer 35

5 mM per 12 hours

Question 36

why NS doesn't work in SIADH hypoNa

Answer 36

patient is euvolemic so extra Na seen is secreted

Question 37

2 categories of causes of hyperNa

Answer 37

1. increased water losses unreplaced due to impairment of thirst 2. administration of hypertonic NaCl or NaHCO3

Question 38

hyperNa due to increased water losses unreplaced due to impairment of thirst: 4 types

Answer 38

- insensible and sweat losses (fever, resp infections) (hypotonic) - urinary losses (central or nephrogenic DI: ADH not working, or osmotic diuresis with glucose or mannitol) - GI loss (hypotonic) - lesion to hypothalamic thirst center

Question 39

hyperNa is usually caused by what 2 things

Answer 39

fluid deficit (volume contraction) and inability/failure to drink

Question 40

first formula to estimate water deficit

Answer 40

TBW x (Na/140 - 1) = water deficit in L

Question 41

2nd formula to estimate water deficit

Answer 41

C1V1 = C2V2 | V1 and V2 being TBW

Question 42

treatment to hyperNa

Answer 42

give water (d5w)

Question 43

why NS doesn't work for hyperNa

Answer 43

NS outplaced by the ongoing hypotonic losses of water (sweat, GI, etc.) would have to give too much saline to retrieve normal Na

Question 44

ADH turned on or off in hypernatremia

Answer 44

on (osmotic receptors in the hypothalamus)