Hypercalcemia

Some points about Hypercalcemia

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. When we are correcting calcium it is not because of a lab error, but rather to help us put the measured lab value into proper physiologic context in terms of possible causes, associated symptoms and need for treatment

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) - basically means that for every decrease of albumin by 10, add 0.2 to the total calcium.

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.

DIFFERENTIAL DIAGNOSIS:
Most commonly either HyperPTH or Malignancy related. Malignancy related often presents with higher calcium levels, more symptoms and a more acute rise in calcium level (if previous values are known.
Other causes are out there - look them up if in doubt

Treatment:
TREATMENT
FLUIDS!!!!!!!!

Infusion rate depends on volume status, heart function, etc, but should target 100-150 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 - 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. Trying to get tissue before giving steroids if hypercalcemia not overly severe/symptomatic is a good idea.

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. If Lasix is need for pulmonary edema etc., it can certainly be given, just monitor lytes and volume status.

Dialysis should be considered if the above fail/can't be done because of renal failure or heart failure.

RENAL CELL CARCINOMA and PARANEOPLASTIC SYNDROMES

Hypercalcemia - from lytic bone mets, PTHrP or increased production of prostaglandins that promote bone resorption.

Polycythemia - from EPO overproduction

Hepaitc Dysfunction - "Stauffer syndrome" - in the abscence of mets, increased ALP (+/- fever, wt.loss, fatigue), often improves after nephrectomy

Fever, cacheixa