HYPOCALCEMIA 1. Correct for hypoalbuminemia: for every 1 mg/dL decrease in albumin, increase the Ca++ level by 0.8 mg/dL. If albumin is < 2, check ionized Ca++. Note that alkalosis augments Ca++ binding to albumin, decreasing the amount of ionized (effective) Ca++ and increasing severity of symptoms at a given level. 2. Signs: paresthesias, tetany (especially carpopedal spasm), lethargy, confusion, seizures, Trousseau’s sign (carpal spasm occurring after the occlusion of the brachial artery with a blood pressure cuff for 3 minutes), Chvostek’s sign (contraction of the facial muscle in response to tapping the facial nerve anterior to the ear), QT prolongation. 3. Causes: • Insufficient GI absorption: hypoparathyroidism or pseudohypoparathyroidism (PTH resistance), vitamin D deficiency, renal failure (1,25(OH)2-vitamin D deficiency), critically ill patients, hypomagnesemia (inhibits PTH release and action). • Intra-corporeal shifts: acute pancreatitis, rhabdomyolysis, tumor lysis syndrome, hungry bones s/p parathyroidectomy. • Meds: e.g. loop diuretics • HIPOCAL pneumonic - H Hypoparathyroidism, hypo/hypermagnesemia - I Infection, especially gram negative sepsis - P Pancreatitis - O Overload (rapid intravascular volume expansion) - C Chronic renal failure-most common cause (or other vitamin D deficient states): decreased formation of active vitamin D; decreased intestinal Ca++ absorption. - A Absorption abnormalities: - L Loop diuretics occasionally cause enhanced renal excretion of Ca++ 4. Treatment: • PO: CaCO3 500-1000 mg TID between meals (to maximize absorption). Also consider vitamin D (give 1,25(OH)2-vit. D in patients with renal failure). • IV: max 10 mEq/hour. CaCl2 has 14mEq/amp, Ca gluconate only 4.65 mEq/amp (one amp = one gram). Give 5-15 mEq at a time, more if necessary. • Correct hypomagnesemia. • Beware that treatment of concomitant metabolic acidosis may further reduce ionized calcium level because both hydrogen ions and calcium are bound to albumin. As acidosis is corrected, hydrogen ions dissociate from albumin, allowing calcium to bind to albumin and further reducing the ionized calcium level.
Posted on: Sun, 23 Mar 2014 13:18:16 +0000
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