Hypocalcemia is when there are low levels of calcium in the blood. Calcium is an electrolyte that plays a vital role in many bodily functions, including muscle contraction, nerve transmission, and bone formation.
Various factors, including nutritional deficiencies, medications, and underlying medical conditions, can all lead to low calcium levels. As a nurse, it is essential to be familiar with the signs, symptoms, and treatment options for hypocalcemia to provide adequate and timely care to patients.
This article will discuss the importance of calcium in the body, the causes of hypocalcemia, nursing assessment and interventions, treatment options, and monitoring parameters for hypocalcemia.
WHY IS CALCIUM IMPORTANT IN THE BODY?
Calcium is an essential electrolyte that plays a critical role in maintaining the structure and function of our bones and teeth. It is also necessary for proper nerve function, muscle contraction (including the heart), blood clotting, and enzyme activity. In addition, calcium regulates the release of hormones and other chemicals in the body.
BONES AND TEETH
Calcium provides the structural support for strong and healthy bones and teeth.
Calcium helps regulate the transmission of nerve impulses, which is critical for communication between the brain and other body parts.
Calcium helps with muscle contraction and relaxation, including the muscles involved in breathing and the heart beating.
Calcium ions are necessary for the contraction of the heart muscles, but they also play a critical role in the generation and transmission of electrical impulses that coordinate the heart’s rhythm. These electrical impulses regulate the heart rate and ensure that the heart muscles contract in a coordinated manner. Without sufficient calcium, the heart may experience arrhythmias or other electrical disturbances.
Calcium is necessary to form blood clots, which help stop bleeding after an injury.
Calcium activates and regulates a wide range of enzymes, which are essential for the body to function as it’s supposed to!
HOW IS CALCIUM REGULATED IN THE BODY?
Calcium levels in the body are tightly regulated through a complex system involving hormones and their effects on the bones, intestines, and kidneys.
The regulation of calcium involves several hormones, including:
PARATHYROID HORMONE (PTH)
The parathyroid glands releases parathyroid hormone (PTH) in response to low calcium levels in the blood. It stimulates the release of calcium from bones and increases the reabsorption of calcium by the kidneys.
Vitamin D has similar effects to PTH, including increasing calcium absorption in the intestines and decreasing kidney excretion. It can also mobilize calcium from bones, but to a lesser extent than PTH.
The C-cells of the thyroid gland release calcitonin in response to high calcium levels in the blood. It inhibits calcium release from bones and promotes calcium excretion by the kidneys. This essentially has the opposite effect of PTH.
When calcium levels fall too low, PTH is released, which causes calcium to be released from bones and increases the reabsorption of calcium by the kidneys. In addition, PTH stimulates the production of vitamin D, which helps increase calcium absorption from the intestines. These actions work together to increase calcium levels in the blood.
When calcium levels are too high, calcitonin is released, inhibiting the release of calcium from bones and promoting the kidneys’ excretion of calcium. This helps reduce calcium levels in the blood.
Overall, regulating calcium in the body is a complex process involving multiple hormones and organs. Disrupting this process can lead to hypocalcemia or hypercalcemia, which can have serious consequences.
NORMAL CALCIUM LEVELS & HYPOCALCEMIA
Normal calcium levels can range from 8.5 – 10.5 mg/dL.
- Normal Levels: 8.5 – 10.5 mg/dL
- Hypocalcemia: < 8.5 mg/dL
- Critical Hypocalcemia: < 4.4 mg/dL
WHAT ARE IONIZED CALCIUM LEVELS?
When a patient has low calcium, you may have heard that an ionized calcium level is specifically checked.
Ionized calcium is ordered because it represents the blood’s physiologically active form of calcium.
Total calcium (checked on a BMP or CMP), includes both ionized and protein-bound calcium. Total calcium levels can be influenced by pH and albumin levels.
Ionized calcium is considered a more accurate reflection of the body’s calcium status.
Ionized Calcium Levels
- Normal Levels: 4.4 – 5.4 mg/dL
- Hypocalcemia: < 4.4 mg/dL
- Critical Hypocalcemia: < 3 mg/dL
ALBUMIN AND CALCIUM
Albumin is a protein in the blood that binds to calcium and other ions, reducing the amount of ionized calcium available for cellular processes.
As a result, total calcium levels may be affected by changes in albumin levels.
Ionized calcium levels are unaffected by changes in albumin levels and are considered a more accurate reflection of the body’s calcium status. This means if the calcium is low but the albumin level is also low, ionized calcium should definitely be checked. There is a correction calculator, but this isn’t always accurate so it’s best to check an ionized calcium level to verify.
CAUSES OF HYPOCALCEMIA:
There are multiple causes of hypocalcemia, including:
Hypoparathyroidism is when the parathyroid glands produce insufficient amounts of PTH, leading to decreased calcium levels in the blood. This is usually caused by surgery or radiation.
VITAMIN D DEFICIENCY
As stated above, vitamin D is essential for calcium absorption from the intestines. This means a lack of vitamin D can lead to hypocalcemia.
CHRONIC KIDNEY DISEASE
The kidneys play a critical role in regulating calcium levels in the blood. Chronic kidney disease can cause decreased vitamin D production, as well as too much calcium excretion.
High phosphate levels lead to depositing calcium outside the blood, such as in skeletal muscle or bones.
ABNORMAL MAGNESIUM LEVELS
Hypomagnesemia can cause parathyroid hormone resistance or decrease PTH secretion in severe cases. Severe hypermagnesemia can also induce hypocalcemia.
Acute pancreatitis can lead to calcium deposition in the pancreatic tissue, leading to decreased calcium levels in the blood.
Certain medications can cause low calcium levels, including:
- Chemos (cisplatin)
- Anticonvulsants (Dilantin, Phenobarbital)
Anxiety and hyperventilation can lead to a decrease CO2 in the blood, which can result in respiratory alkalosis.
Alkalosis can cause calcium ions to bind more readily to proteins like albumin, resulting in decreased levels of ionized calcium in the blood. This is often why patient’s having panic attacks experience numbness, tingling, and even muscle spasms.
Having the patient breathe into a non-rebreather not hooked up to oxygen (or a good ole paper bag) can help them retain more CO2 and decrease symptoms.
NURSING ASSESSMENT OF HYPOCALCEMIA
Hypocalcemia can cause many symptoms, with tetany being the most common and hallmark sign.
Tetany is when there is hyper-irritability of the peripheral neurons and their control over muscles. This can range from mild symptoms to more severe symptoms. This is unlikely to occur until calcium levels below 7-7.5 mg/dL.
Symptoms of tetany include:
Numbness and/or tingling around the mouth and lips.
MUSCLE CRAMPS AND SPASMS
Hypocalcemia can cause muscle cramps, carpopedal spasms, and even laryngospasms which can cause hypoxia and respiratory distress.
The patient may have numbness or tingling of their hands or their feet.
Other generalized symptoms of hypocalcemia include:
Low calcium can cause generalized weakness and fatigue.
Hypocalcemia can lead to anxiety, irritability, and even depression.
Severe hypocalcemia can cause focal or generalized seizures.
When performing a physical exam for a patient suspected of having hypocalcemia, the nurse should assess for the following:
- HR: May be irregular (indicating an arrhythmia)
- BP: May be decreased
Chvostek’s sign is positive when tapping the facial nerve in front of the ear causing twitching of the facial muscles on that side in patients with hypocalcemia.
- Sensitivity: 10-64%
- Specificity: 69-92%
This means that it is not always present in hypocalcemia, but if it is present, then hypocalcemia is a good possibility.
Trousseau’s sign is positive when spasms of the hand and wrist occur after inflating a blood pressure cuff above the patient’s systolic BP for 3-5 minutes.
- Sensitivity: 30-94%
- Specificity: 29-63%
This means it is likely more commonly present in hypocalcemia than Chvostek’s sign, but its presence doesn’t necessarily mean it is from hypocalcemia.
There are no other specific physical findings for low calcium, but you should observe for weakness, irregular heart rhythms, and possibly painful muscles to palpation.
Also check out: “The Cranial Nerve Assessment for Nurses”
TREATMENT FOR HYPOCALCEMIA
The treatment of hypocalcemia depends on the severity of the condition and the underlying cause. When you get a low calcium level back on the blood work of your patient, as the nurse you should:
Step 1: Assess the Patient
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Ensure they don’t have any symptoms and are stable, including recent vital signs.
Step 2: Cardiac Monitor
Make sure your patient is on the cardiac monitor. Obtain an ECG if it still needs to be done. Close cardiac monitoring is essential when infusing electrolytes through the IV as well.
Step 3: Notify the Provider
Notify the provider of the calcium levels, your assessment, and their cardiac rhythm (and if any QT prolongation is present)..
Step 4: Ensure IV Access
Make sure there is at least one IV site, but place a second line if the hypocalcemia is severe.
Step 5: Administer Treatment
Administer medications that are ordered (discussed below).
TREATMENT FOR HYPOCALCEMIA:
Treatment for hypocalcemia will depend on the severity, as well as any symptoms the patient is having. Severe symptoms that require immediate and likely IV repletion include tetany, arrhythmias, or seizures.
IV calcium is given for patients with severe symptomatic hypocalcemia. This includes patients with:
- Carpopedal spasms
- Prolonged QT interval on ECG
- Levels < 7.5 mg/dL who are at higher risk for serious complications
Calcium Gluconate 1-2g (90 – 180mg elemental calcium) in 50mL of 5% dextrose or NS infused over 10-20 minutes. This can be repeated after 10-60 minutes if needed. This is expected to raise serum calcium levels for only 2-3 hours.
After the bolus is given, a solution of 10% calcium gluconate can be used for a continuous infusion, started at 50ml/hr (11g calcium gluconate diluted in 1000ml of NS or D5W).
ORAL CALCIUM SUPPLEMENTATION
Oral calcium supplementation is started with mild symptoms or levels above 7.5 – 8.0 mg/dL, or for chronic hypocalcemia. Patients should be given 1-2g of elemental calcium in divided doses.
- Calcium carbonate 1250mg, Take 1 tablet PO TID
- Calcium citrate 950mg, Take 2 tablets PO BID
VITAMIN D SUPPLEMENTATION
Vitamin D should be started if the patient has low vitamin D levels. This is because low vitamin D levels can decrease calcium absorption in the intestines.
- Ergocalciferol (D2) 50,000 iU PO weekly x 6-8 weeks
- Cholecalciferol (D3) 50,000 iU PO weekly x 6-8 weeks
Calcitriol is a vitamin D metabolite that is preferred in patients with severe hypocalcemia, or in those with chronic kidney or liver disease. This effectively skips the need for the kidney and/or liver to process the vitamin D, leading to more rapid correction.
- Calcitriol 0.25mcg PO BID
MONITORING OF HYPOCALCEMIA
As a nurse, it is essential to monitor patients with hypocalcemia closely to identify and manage any potential complications. The following parameters should be observed:
Serum calcium levels should be monitored regularly to assess treatment response and to identify potential complications such as hypercalcemia. This may include ionized calcium for a more accurate reflection of calcium status. Initially may need to be checked every 4-6 hours.
Other important tests that may be ordered with a patient with hypocalcemia includes:
- PTH levels
- Vitamin D levels
Foods High in Calcium
- Fortified soy, almond, and/or oat milk
- Fortified orange juice
HYPOCALCEMIA AND CARDIAC ARRHYTHMIAS
- Torsades de Pointes: Torsades de Pointes is a type of ventricular tachycardia characterized by twisting the QRS complex around the isoelectric line.
- Atrial fibrillation: Hypocalcemia can increase the risk of atrial fibrillation, due to impaired atrial and AV nodal conduction.
- Ventricular Tachycardia: Hypocalcemia-induced VTACH can occur due to increased automaticity of the ventricular myocardium.
- Premature ventricular contractions (PVCs): Hypocalcemia can increase the risk of PVCs, which are abnormal contractions that originate from the ventricles rather than the atria.
- Atrioventricular (AV) blocks: Hypocalcemia can cause AV blocks, which occur when there is impaired conduction between the atria and ventricles.
- QT interval: Hypocalcemia can prolong the QT interval on ECG, increasing the risk of arrhythmias such as torsades de pointes.
- ST-Segment: Hypocalcemia can also prolong the ST-segment. This is because low calcium levels can delay the repolarization of the heart muscle, leading to a prolonged ST segment.
Hypocalcemia can also cause Torsades de Pointes, a type of polymorphic ventricular tachycardia that is deadly and quickly degenerates into Ventricular fibrillation if not treated ASAP. This does not happen as commonly as with hypomagnesemia.
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Hypocalcemia is an important electrolyte abnormality that must be recognized and treated quickly in the inpatient and ER settings. This is often caused by hypoparathyroidism, vitamin D deficiency, chronic kidney disease, or certain medications. It can cause symptoms such as tetany, evidenced sometimes by positive Chvostek or Trusseau signs.
Treatment involves oral or IV calcium and supplementation of Vitamin D and/or magnesium if applicable. Monitoring involves checking electrolytes, labs like PTH and Vitamin D, and montioring the ECG and continuous cardiac monitor.
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