Electrolytes

Question 1

Hyponatremia
Diagnosed by Na level of less than 135 mol/L
Severe hyponatremia: less than 120mmol/L

Hyponatremia is a primarily disorder of H20 homeostasis

Answer 1

Urine Na less than 20meqs/L is consistent with hypovolemic hyponatremia

Urine osmolality <100 mosmol/kg is suggestive of polydipsia

Urine osmolality >400momol/kg suggest of AVP excess

Question 2

Hyponatremia + hyperkalemia = suggest adrenal insufficiency or hypoaldosteronism

Answer 2

Cause of pseudo hyponatremia: hyperlipidemia or hyperproteinemia

Serum Na decreases 1.4mM for every 100mg/dL increase in glucose

Question 3

Treatment for acute hypovolemic hyponatremia : fluid resuscitation with 0.9NaCL

Answer 3

Treatment for chronic hyponatremia: more than 48 hours

Desmopressin

Question 4

Hypervolemic Hypernatremia

1. CHF
2. Hepatic cirrhosis
3. Nephrotic syndrome

Answer 4

Associated with moderate decrease in hyponatremia: 125-135mmol/L

However severe CHF or cirrhosis may present with Na <120mmol/L

Treatment: after load reduction, large volume paracenthesis, immunomodulatory therapy , Na restriction, diuretic therapy, H20 restriction

Vasopressin antagonist; tolvaptan, conivaptan ( cirrhosis and CHF)

Question 5

Euvolemic Hyponatremia
SIADH: syndrome of inappropriate antiduretic hormone- most cases
Others:
Hypothyroidism
Secondary adrenal insufficiency (pituitary disease)

Answer 5

Treatment
Treat underlying disorder
H20 restriction to <1L/d cornerstone of therapy (ineffective of poorly tolerated)
Alternatives: loop diuretics 
Salt tablets

Question 6

Acute Symptomatic hyponatremia
-medical emergency

Polydipsia with associated cause

Risk: women in premenopausal

Answer 6

Polydipsia: associated with increase AVP
Drug: MDMA ,

Question 7

Osmotic demyelination syndrome: such as central pontine myelinolysis

Answer 7

Na is corrected corrected >10-12mM within the first 24

Or >18 within with the first 48

Question 8

Treatment for acute symptomatic hyponatremia

Hypertonic solution: increase Na 1-2mM/L to a total increase of 4-6mM

Na should be monitored 2-4 hours

Answer 8

Treatment for chronic hyponatremia

<10-12mM within the first 24/h
And <18 in 48 hours

Question 9

Hypernatremia
Mostly hypervolemic
Iatrogenic; Na bicarbonate infusion

Answer 9

Treatment:
1. Hypotonic solution

Central DI: intranasal DDAVP
Nephrogenic DI: hydrochlorothiazide (12.5-50mg/dl)
Lithium associated nephrogenic DI: amiloride 2.5-10mg/d

Question 10

Potassium: major intracellular cation

Extracellular K: <20% of total body content

Answer 10

Promote uptake by cells:
1. Insulin, B2 adrenergic agonist, alkalosis

Promote effluent by cells:
1. Acidosis, insulinopenia, acute hyperosmolality

Question 11

TTKG: transtubular K gradient
Formula

K (urine) x OSM serum over K (serum) x OSM (urine)

Answer 11

Urinary K to creatinine ratio:: >13mmol/g creatinine ( >1.5mmol/mol creatinine)
Compatible with excessive K excretion

Central line correction should not be more than 20mmol/h

Question 12

Expected TTKG value

Answer 12

<3 in the presence of hypokalemia

>7-8 in the presence of hyperkalemia