Corrected Calcium:
The physiologically important calcium (Ca2+) is ionized calcium. This can be measured in the lab, however, total calcium is the value most commonly reported.
Calcium is bound to serum proteins, most importantly albumin. Therefore, in patients with low serum albumin concentration, the fraction of total serum Ca2+ that exists as ionized Ca2+ will be higher.
It is important to know the serum albumin when interpreting total serum calcium levels. A correction for total serum calcium can be made using the following formula (alternatively ionized Ca2+ could be measured):
Ca = SerumCa + 0.02 * (NormalAlbumin - PatientAlbumin) (SI UNITS)
Pseudohypercalcemia can occur when patients are hyperalbuminemic or have a multiple myeloma with a paraprotein that binds calcium (rare) - in these cases total CA2+ will be high, but ionized CA2+ will be normal.
TREATMENT
FLUIDS!!!!!!!!
Infusion rate depends on volume status, heart function, etc, but should target 100-1500 cc urine output/hr - do not need to hydrate beyond euvolemia
If severe/symptomatic consider: Bisphosphonates (IV) - will not take effect for 48-72 hrs, but will help maintain normal calcium when achieved.
Calcitonin by nasal spray or subQ is also very effective.
If hyperCa2+ is from sarcoid or lymphoma consider steroids (20-40 mg/day) - this works by decreasing calcitriol production from activated mononuclear cells in the lung and lymph nodes.
AVOID LASIX since most patients are profoundly volume depleted initially and once replete can cause hypokalemia, hypomagnesemia, and lead to recurrence of volume depletion. A recent Annals of Internal Medicine article reviews the use/concerns regarding Lasix in hypercalcemia.
Dialysis should be consider if the above fail/can't be done because of renal failure or heart failure.
