Most common cause of hyponatremia in surgical practice

Ans. a (Small intestinal obstruction) (Ref. Bailey and Love Short textbook of surgery 24th ed., p 56)The most frequent cause of sodium depletion in surgical practice is obstruction of the small intestine.SODIUM BALANCE# Sodium is the principal cation content of the extracellular fluid.# On average it is 1 mmol/kg sodium chloride or 500 mL of isotonic 0.9 % saline solution. An equivalent amount is excreted daily, mainly in the urine and some in the faeces.Sodium Depletion (syn.Hyponatremia)Etiology# Small intestinal obstruction (most frequent cause in surgical practice).# Duodenal, total biliary, pancreatic and high intestinal external fistulae.# Severe diarrhea will cause hyponatremia with acidosis.# Hyponatremia with elevated potassium would suggest adrenocortical insufficiency.# SIADH.Potassium Depletion# It occurs most frequently in diabetic coma treated by insulin and prolonged infusion of saline solution.# Diuretics.# The diarrhoea from ulcerative colitis, villous tumours of the rectum and the loss from external fistulae of the alimentary tract are also common causes (e.g., duodenal fistula, ileostomy);Clinical features# risk of cardiac arrhythmias.# Symptoms of severe hypokalemia include listlessness and slurred speech, muscular hypotonia, depressed reflexes and abdominal distension as a result of a paralytic ileus.# ECG:Prolonged QT interval, depression of ST segment and flattening or inversion of the T-wave.Rx# Oral potassium. Potassium can be given in the form of milk, meat extracts, fruit juices and honey. However, in hospital practice, effervescent tablets of potassium chloride 2 g can be given by mouth 6-hourly.# IV potassium. Rapid IV supplementation (especially when renal function is impaired) carries the risk of dysrhythmias and cardiac arrest if the serum concentration rises to a dangerous level.# When there is no associated alkalosis, potassium deficit can be restored by adding 40 mmol KCL to each litre of 5% glucose, glucose-saline or 0.9 % saline solution, given 6-8-hrly.Sodium Excess (syn. Hypernatremia)Etiology# excessive amount of 0.9% saline solution given intravenously during the early postoperative period.Clinical Features# Slight puffiness of the face is the only early sign.POTASSIUM BALANCE# Potassium is almost entirely intracellular.# No less than 98% is intracellular, and only 2% is present in the extracellular fluid.# Three-quarters of the total body potassium (approximately 3500 mmol) is found in skeletal muscles.