Electrolyte abnormalities Flashcards Preview

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Flashcards in Electrolyte abnormalities Deck (22):

Overview of causes of electrolyte imbalances

1. Renal
2. Endocrine
3. Gastrointestinal
4. Skin


Treatment priority

1. pH
2. Potassium
3. Calcium
4. Magnesium
5. Sodium
6. Chloride


Etiology of hypernatremia

1. Conn's syndrome
Hypokalemia, alkalosis,hypertensive
++loss of sodium:water
1. Fluid loss without water replacement
2. Incorrect IV replacement
3. Diabetes insipidus
4. Osmotic diuresis -> DKA


Management of hypernatremia

1. Oral fluid replacement - water if possible
2. If not, IV 5% dextrose, guide by urine
3. Do not decrease sodium by >0.5mmol/L / h or 10mmol/L / 24h
4. If hypovolemic->may use NS
5. Avoid hypertonic solutions


Calculating decrease in serum sodium/ L 5% glucose

][Serum sodium]/ TBW + 1

TBW= 0.6 in men, 0.4 in women


Etiology of hyponatremia

Check plasma osmolality
1. Factitious
->N osmolality= +lipids, proteins (MM)
->+Plasma osm= osmotic solutes drawing in= glucose, urea (hypertonic)
2. Hypoosmolar
a. Euvolemic
R: Drugs (lots of them….like NSAIDS, TCA’s, Carbamazepine)
E: ↓ Thyroid
G: H2O Intoxication (psychogenic polydipsia)
S: S.I.A.D.H. ( Nothing to do with skin this time)
b. Hypervolemic (+Na, +H20)
R: ARF, Nephrotic syndrome
E: ↑ Aldo (eg. CCF)
G: Cirrhosis (low albumin/protein)
S: I.V. Fluids (too much hypotonic stuff eg 5% Dextrose)
c. Hypovolemic (low sodium, low water)
R: diuretics, RTA, ARF, nephritis
E: Addisons, low aldosterone, osmotic diuresis
G: DV, fistula, NGT, pancreatitis
(3rd space occupation,)
S: sweat, burns


Clinical features

1. Anorexia, nausea, malaise initially
2. HA, irritability, confusion
3. Weak, -ve GCS, seizures
4. Determine if deH or not
5. Edema?


Iatrogenic hyponatremia

1. Infusion of 5% dextrose
2. Metabolised->hypotonic fluid
3. Hyponatremia
4. +Risk for those on diuretics, elderly, physiologic stress


Management of hyponatremia

1. Correct the underlying cause
2. If mild, chronic->fluid restriction
3. If severe seek expert help
IV 3% saline, target not >120 initially
4. Moderate
Fluid restriction 500ml-1L/24 h
Monitor serum/electrolytes/urine output daily
May consider demeclocycline (ADH antagonist)
5. Volume depletion
NS w/ potassium
6. If hypervolemic
Can consider vaptans->excretion of electrolyte free fluids


What is the concern with rapid correction of hypernatremia, risks, how to avoid

1. Permanent central nervous system injury due to osmotic demyelination
2. Those w. chronic +
10mmol (/L in first 24 hour
X +>18mmol/L in first 48 hours
Goal therapy +4-8mmol/L


When could more rapid correction in hypernatremia occur

1. Seizures or coma
2. Self induced acute water intoxication
3. Known hyponatremia for


Pathogenesis of CNS damage with rapid sodium correction

1. Cerebral shrinkage endothelial- +BBB permeable,
cytokines enter brain
2. Cell water shrinks, potassium and cations enter cells


Calculation infusion rate of NaCl 3%- use a 60kg woman, with serum sodium 110, want to be 118

1. calculate desired increase
in 24 hours. Say current = 110, want to
be 118 in 24 hours= 8mmol/L increase over 24 hours
2. Increase in Na/L of infused 3%= 513- Na serum mmol/L/
TBW + 1 (TBW= wt X 0.5 (female), 0.6 (male), elderly 0.45, 0.5
3. 13mmol/L of 3% increase over 24 hours
so 8/13 X 100= 615ml of 3% to +by 8mmol. 25ml/hour of solution If already given boluses need to deduct from total infusion amount


Etiology of hyperkalemia

1. Pseudo
From IV arm
2. Shift
Acidosis: decrease in Na/K pump= -ve IC K and +ECF K->low conc in tubular cell = reduced diffusion in tuular lumen = accumulation of K in body.
Low insulin
Digoxin toxicity
Hyperkalemic periodic paralysis
3. Load= +external K
Blood transfusion
4. Loss
Renal failure, burns
K sparing diuretics, ACEi
-ve aldosterone->Addisons


ECG changes in hyperkalemia

1. +K in ECF= MP less -ve, closer to threshold= +excitability but -ve Na channels open= -ve automaticity
2. Short QT interval
3. Tall T waves
4. Arrythmias
5. Wide QRS
6. P waves disappear
7. QRS sine wave and asystole/VFib


Management of hyperkalmeia (emergency)

1. Confirm diagnosis with secondary testing
2. Assess Acid base and fluid status/kidney function
3. ECG
4. IV access
5. Calcium gluconate
6. IVF replacement
7. Glucose + insulin (renal failure)-> 10u insulin + glucose 50% 50ml IV over 5 minutes
8. Nebulised salbutamol
9. Polyestyrene sulfonate resin orally
10. Consider bicarbonate if acidosis
11. Measure acid base, electrolytes, renal failure, fluid balance, glucose regularly
12. Dialysis
13. If due to adrenal insufficiency->hydrocortisone, avoid glucose


Most common 2 causes of hyperkalemia

1. Chronic renal failure
2. Loss of fluid


Etiology of hypokalemia

1. Shift
Catecholamine infusion
2. Loss
Renal: liquorice, renal tubular acidosis
Endorcine: +Aldosteone (primary), secondary due to CCF, cirrhosis, ascites
Low magnesium
3. Drugs
4. Other
Bartter's syndrome
Acute myeloid leukemia
Rectal villous adenoma
Pyloric stenosis
Poor nutrition


Clinical features of hypokalemia

1. Muscle weakness
2. Hypotonia
3. Hyporeflexia
4. Cramps
5. Tetany, palpitation


ECG changes in hypokalemia

1. Small, inverted T waves
2. Prominent U waves
3. Long PR
4. Depressed ST segments


When to suspect Conns

1. Hypertensive
2. Hypokalemic
3. Alkalosis
4. Not taking diuretics


Management of hypokalemia

1. Confirm
2. ECG
3. Assess kidney and fluid status, acid base
4. Potassium chloride SR
5. Consider IV if Xoral, severe