Electrolytes

Question 1

Hyponatraemia (Na+<135) can be due to?

Answer 1

1. Gain of water in excess of Na.

2. Loss of Na in excess of water.

Question 2

What are treatment principles of hyponatraemia?

Answer 2

-Na deficit should be corrected over 48-72hrs.
Rate in asymptomatic children with Na>120: should be no more than 0.5mEq/l/hr.
-Rapid correction only if Na <120 with severe symptoms.
-Keep daily correction in the 6-8mEq/l per day range.
-Never correct Na>8mEq/l in a 24hr period.

Question 3

What are causes of SIADH?

Answer 3

Post-surgery, pain, CNS disorders

Pneumonia, malignancies, drugs and mechanical ventilation.

Question 4

State the Diagnostic criteria of SIADH

Answer 4

• Hypotonic hypernatraemia with (Posm <275mOsm/kg H2O) inappropriately elevated urinary osmolality (usually >200 mOsm/kg).
• Elevated urinary [Na+].

Question 5

Mx in SIADH?

Answer 5

• Treating the underlying cause.
• Free water restriction.
• lV Fluids with same tonicity as plasma.

Question 6

Causes of hypernatraemia (Na>145)?

Answer 6

It is associated with hyperosmolality (>295mOsm).

1. Loss of water
2. Gain of Na.

Question 7

Causes of free water loss (deficit) in hypernatraemia?

Answer 7

RENAL: diabetes insipidus, diuretics, recovering AKl, hyperglycemia, high soluble feeds, mannitol.
GI: vomiting, diarrhoea, lactulose, stoma losses, malabsorption.
INSENSIBLE: fever, Tachypnoea, high ambient temperature, burns.
⬇️ H2O INTAKE: neurological impairment, fluid restriction.

Question 8

Cause of gain in sodium?

Answer 8

Excess intake: hypertonic Saline, blood products, high solute feed, sodium ingestion, sea water drowning.

Question 9

Mx principles (hypernatraemia)?

Answer 9

• Correct slowly.
• Shock of severely dehydrated patient> bolus with isotonic solution is given until hemodynamic stability.
• Slow correction at a rate of 0.5mmol/l/hr with max 10mmol/24hrs.
• Free water replacement over 48-72hrs.

Question 10

What are treatment principles of hyponatraemia?

Answer 10

• Na+ deficit can be corrected over 48-72hrs.
• Rapid correction only if Na <120 with severe symptoms.
• Keep daily correction in the 6-8mEq

Question 11

What are clinical manifestations of hypokalaemia (K<3,5mmol/l)?

Answer 11

Skeletal muscle: weak or paralysis, decreased muscle tone, can manifest as failure to wean from the ventilator.
Smooth muscle: intestinal ileus, ureteric dilatation.
Cardiac muscle: Arrhythmias, myocardial cell necrosis.

Question 12

Treatment of hypokalaemia?

Answer 12

• Replacement: iv/ oral
• KCl preparation is the preferred choice.
• Potassium phosphate can be useful in concomitant low phosphate.
• Presence of severe symptoms: rapid correction iv is required.

Question 13

Causes of hyperkalaemia (K>5mmol/l)?

Answer 13

-Factitious-haemolysis of RBC (collecting difficulties, delayed processing as sample).
Leucocytosis or thrombocytosis
-Iatrogenic: large cell transfusion (massive transfusion).
-Shifting/release of intracellular stores:acidosis, rhambomyolysis, burns, tumor lysis, hyperthermia, crush injuries and drugs (scoline).
-Decreased excretion: AKl/CKI, adrenal insufficiency, aldosterone deficiency.

Question 14

Clinical manifestations of hypokalaemia?

Answer 14

Muscle weakness, paraesthesia
Muscle paralysis
Abdominal pain and distension
ECG changes
Cardiac conduction defects and Arrhythmias
Ventricular fibrillation : eventually asystole

Question 15

Treatment principles of hyperkalaemia?

Answer 15

Antagonise cardiac irritability-10% Ca gluconate
Shift K+ into cells - sodium bicarbonate, B2-agonists (salbutamol), insulin and glucose.
Decrease absorption - kayexalate
Increase elimination of K- dialysis