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    Why would hypocapnia cause hypocalcemia, and then cause great flexion in wrists?
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    Hyperventilation > blows of CO2 > hypocapnia > respiratory alkalosis > increased binding of ionised calcium to serum proteins because of increased pH > less free ionised calcium available in the serum > hypocalcaemia > increased excitability of nerves > carpopedal spasm.

    Search Google images for "main d'accoucheur" (hand of the obstetrician) for the classical appearance of carpopedal spasm in hypocalcaemia. I remember seeing an otherwise-well patient on ITU whose only complaint was that both wrists were resting in this position. She was in ITU after a bleed following an elective operation and had subsequently received a massive blood transfusion - the citrate added to packed red cells sequesters calcium ions and so can lead to a similar set of signs as acute hypocapnia.
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    (Original post by kesun)
    Why would hypocapnia cause hypocalcemia, and then cause great flexion in wrists?
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    Something about large calcium ions being unavailable to block sodium ion entry to thus cause nerve depolarisation also rings a bell. Meh.
 
 
 
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