Help with true calcium level!

getoverit, BSN, RN, EMT-P · Jul 21, 2009

Total calcium test is generally a good reflection of the amount of free calcium involved in metabolism, since the balance between free and bound calcium is fairly predictable in most patients.

Some critically ill patients, major surgery, some receiving IVF or blood products and also some patients with protein abnomalities, like hypoalbuminemia, may have an imbalance between free (total) and bound (ionized). Which is why in those patients it's important to get an ionized calcium level.

It's the ionized calcium that can cause serious arrythmias, muscle tetany and even coma/death if the level fluctuates widely.

Hope this helps somewhat. I'm sure someone will come along and give a much better explanation than this.

KellyCCRN · Jul 21, 2009

here is the formula we use.... (4-albumin)X0.8+CA++= true CA++ From my understanding it is a rough estimate

Trishalishus, PhD, CNS · Jul 21, 2009

normal ionised (aka free – not attached to proteins) ca2+ value for adults: 4.4 - 5.3 mg/dl

normal serum calcium (includes free ca2+) values range from 8.5 to 10.2 mg/dl

changes in serum protein concentrations alter the total serum ca2+ level but do not affect the unbound fraction. ca2+ level reported by the laboratory usually represents the bound and unbound ca2+.

to calculate the actual level of calcium:

corrected total calcium (mg/dl) = (measured total calcium mg/dl) + 0.8 (4.4 - measured albumin g/dl)

your patient = (14.4) + 0.8 (4.4 – 2) = 16.32

your pt is hypercalcaemic (see below)

normal serum albumin values range from 3.4 - 5.4 g/dl (your pt is hypoalbuminaemic)

hypoalbuminaemia can be caused by various conditions, including nephrotic syndrome, hepatic cirrhosis, heart failure, and malnutrition; however, most cases are caused by acute and chronic inflammatory responses. among hospitalized patients, lower serum albumin levels correlate with an increased risk of morbidity and mortality. the presentation, physical examination findings, and laboratory results associated with hypoalbuminaemia depend on the underlying disease process.

hypercalcaemia can be due to excessive skeletal ca2+ release, increased intestinal ca2+ absorption, or decreased renal ca2+ excretion. s&s include fatigue, depression, confusion, anorexia, nausea, vomiting, constipation, pancreatitis or increased urination. if chronic, it can result in urinary calculi. abnormal heart rhythms can result, and ecg findings of a short qt interval and a widened t wave suggest hypercalcaemia. peptic ulcers may also occur.

symptoms are more common at high calcium blood values (12.0 mg/dl). severe hypercalcaemia (above 15-16 mg/dl) is considered a medical emergency: at these levels, coma and cardiac arrest can result.

true calcium absorption is defined as the quantitative, unidirectional flux of calcium from the intestinal lumen into the blood (heaney rp, dowell, ms & wolf, rl, 2002, clinical chemistry 48: 786-788)

total calcium would include the plasma + icf + ecf (it is the major cation after na+) + skeleton which holds 99% of the total.

best wishes and good luck to your poor sick patient!