Electrolyte Imbalance and Malabsorption in Diarrhoea
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Direct volume loss of water and electrolytes and malabsorption due to damage to intestinal lining occurs with
diarrhoea.
Decreased ECF causes shrinking of both interstitial space and blood volume.
Symptoms – thirst, muscle cramps, nausea, vomiting, postural dizziness. Severe depletion causes hypotension,
confusion and eventual coma.
Signs
 Loss of interstitial fluid – decreased skin turgor.
 Loss of circulating volume – decreased pressure in venous and atrial compartments. Loss up to 1L ECF in
adults compensated by venoconstriction. >1L loss leads to:
o Postural hypotension
o Low JVP
o Peripheral venoconstriction
o Tachycardia
Loss of water and electrolytes treated through oral (preferred) or IV fluid replacement.
 Oral - Water + sodium salts (6-12 slow sodium tablets/day + 2-3L water. Approx 10mmol Na+ and Cl- per
tablet). Sodium bicarbonate tablets may be used for very mild cased but are less effective.
 IV – 0.9%NaCl used for volume expansion.
Salt deficient hyponatreamia – due to excessive salt loss with decreased ECF. ADH secretion is intially supressed
(via hypothalamic osmoreceptors) but as more fluid volume is loss volume receptors override this stimulating
thirst and ADH secretion. Symptoms that of volume depletion. Treatment:
 Healthy patient – oral electrolyte + glucose and increase salt intake.
 Vomiting or severe volume depletion – IV 0.9% NaCl + potassium supplements.
Hypokalaemia – In severe cases from direct loss (<2.5mmol) may cause muscle weakness and symptomatic
hyponatreamia. Treatment is usually via underlying cause of fuid loss + slow release potassium replacements.
Hypomagnesaemia – Can occur is severe and chronic diarrhoea cases due to excessive urinary loss. Also occurs
due to defective gut absorption due to gut lining damage. Symptoms include irritability, tremor, ataxia,
hyperreflexia, confusion and hallucinations. ECG may show prolonged QT interval with broard flattened T waves
and ocassional shortening of ST segment. Rx is cause + parenteral infusion of 55mmol magnesium chlorise in 1L
5% dextrose over 12 – 24 hrs until normal plasma magnesium reached.
Hypophosphataemia – Due to increased loss, vomiting or malabsorption in gut. Symptoms – muscle weakness,
confusion, hallucinations and convulsions. If mild often resolves without treatment.