"Balance" is a key consideration of normal bodily functioning. Continuing this series of articles related to fluid and electrolyte imbalances, readers should think about inverse and synergistic relationships, which can be recognized when certain imbalances occur. This article will focus on calcium imbalance. Possible causes of abnormal calcium levels, nursing assessment points, and interventions are discussed.

Calcium's role

Calcium plays a key role in many functions within the body in addition to being an essential component in the maintenance of fluid and electrolytes. Calcium helps to maintain acid-base balance, stabilizes cell membranes, affects the rate of nerve transmissions, blood coagulation, and heart rate, and plays an integral role in muscular contraction and relaxation. It's also a major building block for strong bones and teeth.1-4

Calcium is abundant within the body, with approximately 99% found in the skeletal system and the remaining 1% located in the extracellular fluid (ECF) compartments.2,3,5 Serum calcium, the total amount in the ECF, has a normal range from 8.5 to 10.5 mg/dL. (Note that all ranges are relative to measures used by the source lab.) The total measure of ECF calcium is comprised of three states: free (also called ionized), bound to protein (such as albumin), and complexed (mixed with small negatively charged nonprotein elements).1,3,6

Ionized calcium is the active form of calcium and is essential for the numerous bodily functions highlighted earlier. The normal ionized calcium falls within a range 4.0 to 5.0 mg/dL.1 This free-form availability is also measured by a serum blood test and is diagnostic for determining whether a patient has a true calcium deficiency (remember, the calcium may be present, but bound to proteins and unavailable for use). So, if you're really worried about your patient's calcium level, assess the serum ionized calcium.

Hormones released by the thyroid and parathyroid glands are controllers for the amount of calcium that is released from and absorbed into the bone.6,7 A decrease in serum calcium triggers the parathyroid glands to release parathyroid hormone, signaling the bones to release calcium into the blood. While an increase in serum calcium signals the thyroid gland to secrete calcitonin, stimulating absorption of calcium into the bone and reducing the total serum level.1,2,7 The body's calcium level, therefore, can be affected by the abnormal function of these glands. Additional factors must be considered as well, such as a phosphorus imbalance. An increase in serum phosphorus results in a decrease in calcium, and vice versa. This inverse relationship also presents the need to differentiate a synergistic cause for a calcium imbalance. A deficiency of magnesium is another factor, which can result in reduced calcium absorption.7

Many diagnostic studies are available to determine calcium levels within the body. While serum calcium levels and electrolyte panels are frequently an initial step, urine testing for calcium excretion is also used. Radiography (X-ray), nuclear medicine studies (bone scan), and even hair mineral analyses are useful methods for determining calcium utilization by the body.4

Hypocalcemia

Hypocalcemia exists when the calcium level falls less than 8.5 mg/dL. There are many potential causes of hypocalcemia, including: thyroid and parathyroid surgery, administration of large amounts of blood, pancreatitis, and renal failure. Remember, too, this can be determined by an ionized calcium level below 4.0 mg/dL.1

What to look for

Chronic hypocalcemia may be asymptomatic. Signs of chronic hypocalcemia include hyperactive bowel sounds, dry and brittle hair, and abnormal clotting. The patient with acute hypocalcemia can present with various signs and symptoms, including cardiac dysrhythmias, tetany, cognition changes, and hyperactive deep tendon reflexes.

Low calcium levels can lead to tetany, which causes involuntary and painful muscle contractions and can result in seizure activity and laryngospasm.5,6 Two distinctive signs of calcium deficiency include ipsilateral twitching of the circumoral muscles in response to gentle tapping of the facial nerve just anterior to the ear (Chvostek's sign) and carpal spasm upon inflation of a BP cuff to 20 mmHg above the patient's systolic blood pressure for three minutes (Trousseau's sign). ECG changes may include QT interval prolongation. It's important to note that a prolonged QT interval puts patients at risk for torsades de pointes.

Getting enough calcium

Calcium is necessary to maintain strong bones, and because vitamin D is needed for calcium absorption, both are essential dietary inclusions. Sunlight exposure naturally promotes the body to produce vitamin D, but when deficient, consumption of vitamin D through food or supplements is essential.

Many foods are excellent sources of calcium, especially dairy products (see Dietary sources of calcium). Some foods are fortified with calcium, and numerous over-the-counter calcium supplements are also available that include vitamin D. The recommended calcium intake for non-pregnant/non-lactating adults ranges from 1,000 to 1,200 mg daily. Additional calcium is required for a child related to growth and development phases.5,7

Patient education should include information about limiting alcohol and caffeine intake (these limit calcium absorption) and cigarette smoking, which increases urinary excretion of calcium. Patients should also be taught to avoid laxatives and antacids that contain phosphorous because these decrease calcium absorption. Nursing interventions for the calcium-deficient patient include monitoring serial lab values and continuous cardiac monitoring. Nurses must assess for signs of neuromuscular excitability including tetany and Chvostek's and Trousseau's signs. Close monitoring of the patient's respiratory status is critical. Calcium replacement may be prescribed as orally or I.V. If administered orally, vitamin D is also given to promote absorption. I.V. calcium can be caustic to the veins, and close monitoring is essential related to possible extravasation.3,7,9 A dietitian may be consulted to assist with meal planning and patient education.

Hypercalcemia

Hypercalcemia occurs when the serum total calcium level rises greater than 10.5 mg/dL or an ionized level rises above 5.0 mg/dL. Hyperparathyroidism and malignancies account for most cases of hypercalcemia. High serum calcium levels can be related to excess ingestion of dietary calcium, through vitamin D and calcium supplements, and through calcium-containing antacids. Diseases that affect the skeletal system, such as Paget's disease, can have a direct impact on calcium levels.5 Dehydration can cause the kidneys to block excretion of calcium, leading to increased calcium levels. Hormonal imbalances related to the parathyroid and thyroid glands may affect the body's calcium availability and, of course, medications that affect gastrointestinal absorption must be considered. Interestingly, patients who have diminished mobility or who are on bed rest may have increased calcium levels. Inactivity for extended periods can result in bone loss, thus causing an increase in serum calcium levels.2,5

Additional points

I.V. therapy and loop diuretics are commonly prescribed, requiring close monitoring of the patient's fluid status. Strict intake and output and serial lab values are important assessment tools. Monitor for ECG changes, such as bradycardia, atrioventricular blocks, and shortening of the QT interval.3,5,7,8 Assess the patient for muscle weakness and lethargy. Concurrent medications must be considered as well. For example, thiazide diuretics cause a decrease in renal calcium excretion, and digitalis effectiveness can be increased.7,10 Dialysis may be required for severe calcium elevations.

Calcium needs of the older population

The calcium needs of the aging population require special consideration. Bone loss is a normal part of the aging process. The normal aging process also results in alterations in gastrointestinal absorption, which may result in vitamin D and calcium deficiency.11 Malabsorption also may be related to disease processes and medications. Calcium deficits directly contribute to additional bone loss and may lead to osteoporosis.

Falls are of particular concern for the older population as injuries related to falls and bone fractures can be devastating. Nurses can educate patients and family members regarding the importance of adequate calcium intake, whether via dietary intake or supplements; the need for exercise; and strategies to prevent falls.11 Provide additional resources that may be helpful, such as the National Osteoporosis Foundation (mailto:[email protected]) or the National Institutes of Health (http://nih.gov). Fall prevention measures must always be a priority. While not all falls can be prevented, fewer fractures may occur as a result of stronger bone mass.

Case study

A 70-year-old woman presents with a left ankle fracture resulting from a fall. She states that she has not been feeling well for the past few days, complaining of fatigue and lightheadedness. She believes that her fall occurred from losing her balance after standing up too quickly. Her medical history includes hypertension, hypercholesterolemia, chronic kidney disease, and bilateral cataract surgery. Current medications include: atenolol, pravastatin, and an over-the-counter calcium plus vitamin D supplement once daily. She denies any recent changes in weight, urinary problems, or pain (with the exception of current left ankle pain), and states she has an occasional alcoholic drink, declining having done so in several months. Further assessment reveals the following: BP, 186/88 mm Hg; pulse, 92 beats/minute; respirations, 20/minute; temperature, 97.2[degrees] F. Additional assessment findings include intact cognition with irritability, lethargy, and slight abdominal tenderness. ECG findings include shortening of the QT interval. Her respiratory system is unremarkable. She also complains of having increased nausea over the past 2 hours. Blood work results include a complete blood cell count and serum electrolytes within normal limits; Additional results include a serum ionized calcium level of 6.2 mg/dL, a blood urea nitrogen (BUN) of 30 mg/dL, and a serum creatinine of 2.6 mg/dL.

During a subsequent conversation, the patient informs the nurse that she is sad to be missing the final day of a 4-day family reunion. She describes the food and fun she had been having, disclosing that she had eaten too much and had taken "numerous antacid tablets" over the past 2 to 3 days to combat heartburn. The additional information provided clarity, and a determination was made that the patient's condition stemmed from excessive calcium ingestion. Not only had she been taking daily calcium and vitamin D supplements, but she had also ingested far too many calcium carbonate tablets. Renal dysfunction also contributed to the inability of the patient's kidneys to clear excess calcium from her system. The combination resulted in signs and symptoms associated with hypercalcemia.

In a case such as this, immediate interventions can readily be recognized: discontinue the calcium supplements, provide an appropriate diet, and provide adequate hydration, both oral and I.V. The nurse would assess the patient's cardiac status via continuous monitoring and monitor serial serum electrolyte results. Because the patient has a history of renal disease, the nurse would also monitor the patient's BUN and serum creatinine levels and I & O. Patient education regarding the use of prescribed medications, daily calcium supplements, and the use of calcium carbonate for heartburn would be paramount.

Dietary sources of calcium4,6

Milk

Cheese

Yogurt

Kefir

Sardines

Yeast

Egg yolks

Green leafy vegetables

Fresh oysters

Canned salmon

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