Hyperventilation tetany

After a delay of 4-12 hours, evidence of intoxication by metabolic products occurs, with anion gap acidosis, hyperventilation, convulsions, coma, cardiac conduction disturbances, and arrhythmias. Renal failure is corn-men but usually reversible. Pulmonary edema and cerebral edema may aisc cccur. Hypocalcemia with tetany has been reported. 

A low hydrogen ion concentration occurs as a result of hyperventilation, in which carbon dioxide is blown off in the lungs. The condition occurs in certain otherwise normal people who hyperventilate as a reaction to stress. A frequent result is a reduced concentration of ionized calcium in the extracellular fluid, the condition of hypocalcaemia. The effect is hypocalcaemic tetany, which consists of involuntary uncoordinated contractions of skeletal muscles and of bizarre subjective sensations and numbness. These symptoms and signs are due to hyperexcitability of peripheral nerve fibres, which fire action potentials spontaneously. The mechanism is that the reduced hydrogen ion concentration results in dissociation of complexes between plasma albumin and hydrogen ions, with a binding of plasma calcium to the albumin sites which are vacated by the hydrogen ions. Hence there is a fall in the concentration of ionized calcium in the extracellular fluid and this results in the nervous hyperexcitability. 

Indicate why hyperventilation may result in hypocalcaemic tetany include the importance of extracellular [H ] variation. 

Tetany is a rare complication of salicylate poisoning, and is probably due to the combination of hypocalcaemia and alkalosis caused by hyperventilation and forced alkaline diuresis. In one recently reported case prolonged tetany was followed by a bilateral... 

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