Electrolyte abnormalities Flashcards Preview

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Flashcards in Electrolyte abnormalities Deck (22):
1

Overview of causes of electrolyte imbalances

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

2

Treatment priority

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

3

Etiology of hypernatremia

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

4

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

5

Calculating decrease in serum sodium/ L 5% glucose

][Serum sodium]/ TBW + 1

TBW= 0.6 in men, 0.4 in women

6

Etiology of hyponatremia

Check plasma osmolality
1. Factitious
->N osmolality= +lipids, proteins (MM)
->+Plasma osm= osmotic solutes drawing in= glucose, urea (hypertonic)
->Pseudohyponatremia
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

7

Clinical features

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

8

Iatrogenic hyponatremia

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

9

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

10

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

11

When could more rapid correction in hypernatremia occur

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

12

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

13

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

14

Etiology of hyperkalemia

1. Pseudo
Hemolysed
From IV arm
+WCC
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.
Exercise
Low insulin
Digoxin toxicity
Hyperkalemic periodic paralysis
3. Load= +external K
Supplements
Blood transfusion
Rhabdomyolysis
Hemolysis
Suxamethonium
4. Loss
Renal failure, burns
K sparing diuretics, ACEi
-ve aldosterone->Addisons

15

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

16

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

17

Most common 2 causes of hyperkalemia

1. Chronic renal failure
2. Loss of fluid

18

Etiology of hypokalemia

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

19

Clinical features of hypokalemia

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

20

ECG changes in hypokalemia

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

21

When to suspect Conns

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

22

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