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.
Normal values: Total Calcium: 8.4-10.2 mg/dl (2.1-2.6 mmol/L). Ionized Calcium: 3.8-5.3 mg/dl (0.95-1.35 mmol/L). Protein binding: Moderate, approximately 45% in plasma.
1. Correct for hypoalbuminemia: 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. Determine Ca x PO4 product in mg/dl before administering calcium. If product is greater than 60 mg/dl, there is an increased risk of calcium phosphate precipitation in the cornea, lung, kidney, cardiac conduction system, and blood vessels. 3. Other: a) Correct hypomagnesemia. Determine potassium, phosphorus and magnesium levels. If the magnesium concentration is low, it should be corrected, otherwise it will be difficult to normalize potassium and calcium.Hyperkalemia and hypomagnesemia potentiate the cardiac neuromuscular irritability produced by hypocalcemia. Hypokalemia and hypermagnesemia protect against the effects of hypocalcemia. b) 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.
4. Treatment:
Oral: CaCO3 500-1000 mg TID between (after) meals (to maximize absorption). Also consider vitamin D in patients with renal failure.
IV: max 10 mEq/hour. Symptomatic hypocalcemia (See signs above) — Patients should be treated immediately. Many patients have symptoms when their serum ionized calcium conc is < 2.8 mg/dL (0.7 mmol/L), or their serum total calcium conc (corrected) is ~ 7 to 7.5 mg/dL (1.8 mmol/L).
The most appropriate treatment, unless hypomagnesemia is documented, is intravenous calcium, in the form of 100 to 200 mg (2.5 to 5 mmol) of elemental calcium (1 to 2 grams of calcium gluconate) in 10 to 20 minutes. The calcium should not be given more rapidly, because of the risk of serious cardiac dysfunction, including systolic arrest. Such infusions do not raise the serum calcium concentration for more than two to three hours, and therefore should be followed by a slow infusion of calcium. The dose should be 0.5 to 1.5 mg/kg per hour. Either 10% CaGluc (93 mg [2.25 mmol] elemental Ca++/ 10 ml amp) or 10% CaCL (272 mg [6.75 mmol] elemental Ca++/ 10 ml amp) can be used, with the following recommendations: The calcium should be diluted in dextrose and water or saline, because concentrated calcium solutions are irritating to veins. Calcium gluconate is usually preferred to calcium chloride because it is less likely to cause tissue necrosis if extravasated.
Add 5 to 10 grams of Calcium gluconate to 1 liter of D5W. |
Weight (kg) |
0.5 mg/kg/hr |
1 mg/kg/hr |
1.5 mg/kg/hr |
Elemental Ca++/hr converted to amt CaGluc/hr. Example: 70kg patient (1 mg/kg/hr = 70 mg/hr. 70mg/(93 mg Ca++/gram CaGluc) = 0.753 grams CaGluc/hr |
50 |
0.27 g CaGluc/hr |
0.54 g CaGluc/hr |
0.8 g CaGluc/hr |
60 |
0.32 g CaGluc/hr |
0.65 g CaGluc/hr |
0.97 g CaGluc/hr |
70 |
0.38 g CaGluc/hr |
0.75 g CaGluc/hr |
1.1 g CaGluc/hr |
80 |
0.43 g CaGluc/hr |
0.86 g CaGluc/hr |
1.3 g CaGluc/hr |
90 |
0.48 g CaGluc/hr |
0.97 g CaGluc/hr |
1.45 g CaGluc/hr |
100 |
0.54 g CaGluc/hr |
1.1 g CaGluc/hr |
1.6 g CaGluc/hr |
Continue calcium infusion until serum calcium level reaches 8 to 9 mg/dl. As a guideline, the total calcium will increase by 0.5 mg/dl for every gram of calcium gluconate given intravenously.
MAXIMUM CONCENTRATIONS: Calcium gluconate: 1 gm in 50 ml D5W or NS.
Calcium chloride*: 1 gm in 100 ml D5W or NS *Calcium chloride should not be given IM or SC because severe tissue necrosis may occur.
INFUSION RATE: Infuse over 30-60 minutes. Rapid administration may cause bradycardia, hypotension and vasodilation. Infiltration of IV calcium may cause severe tissue necrosis and sloughing. |
Summary: Calcium: (hypocalcemia): Oral: ~1-2 grams/day (elemental Ca++) in 2-4 divided doses with food. Example: CaCO3 500mg (200mg Ca++): 1-2 tabs qid. IV: Symptomatic + corrected total < ~ 7 to 7.5 mg/dL. 1-2 grams CaGluc over 10-20 min x 1, then 0.5 to 1.5 mg/kg/hr elemental calcium. 70kg patient (1 mg/kg/hr) = 0.75g CaGluc/hour. Total calcium will increase ~ 0.5 mg/dl /gram of CaGluc given. Target level: 8 mg/dl.
|