Calcium Levels

Serum Electrolytes

• Serum electrolyte levels are important for monitoring fluid and electrolyte status, acid-base balance, and hematology.
• Normal value ranges can vary depending on lab techniques.

Calcium (Ca2+)

• Normal range: 8.5-10.5 mg/dL

Hypocalcemia

• Signs and symptoms include seizures, neuromuscular irritability/tetany (paresthesia, bronchospasm, laryngospasm, carpopedal spasm [Trousseau's sign], Chvostek's sign [facial muscle contractions elicited by tapping facial nerve on ipsilateral side]), tingling sensations of the fingers, mouth/feet, increased deep tendon reflexes, and bleeding abnormalities.
• ECG changes can include prolonged QT interval and arrhythmias.
• Implement seizure precautions and closely monitor respiratory status.

Hypercalcemia

• Signs and symptoms include lethargy, confusion, nausea, vomiting, anorexia, constipation, muscle weakness, and depressed DTRs
• Monitor cardiac rate and rhythm.
• Increase mobilization and ensure adequate hydration with IV fluids or encourage oral intake.
• Watch for digitalis toxicity.

Chloride (Cl)

• Normal range- 97-107 mEq/L

Hypochloremia

• Signs and symptoms include muscle spasms, alkalosis, and depressed respirations.
• It may be precipitated or exacerbated by GI losses such as vomiting and diarrhea.

Hyperchloremia

• Monitor for acidosis
• It is associated with large volume 0.9% normal saline resuscitation.

Magnesium (Mg2+)

• Normal Range: 1.8-3 mg/dL

Hypomagnesemia

• Signs and symptoms include cardiac/ventricular arrhythmias, laryngeal stridor/spasm, seizures, and neuromuscular disturbances.
• Risk factors include chronic diarrhea, PPI use, alcoholism, and diuretic use.
• Monitor cardiac rate and rhythm.
• Monitor for digitalis toxicity.

Hypermagnesemia

• Earlier symptoms include nausea, vomiting, and flushing.
• Cardiac symptoms include hypotension, bradycardia, and complete heart block/cardiac arrest.
• Neurologic symptoms include lethargy/somnolence, decreased DTRs, paralysis, coma, and respiratory muscle weakness (shallow respirations, apnea).
• Avoid Mg-containing medications with compromised renal function.
• Monitor cardiac rate and rhythm and neurologic status, including DTRs.

Phosphate (PO4)

• Normal Range: 2.5-4.5 mg/dL

Hypophosphatemia

• Symptoms are rare unless PO4 is less than 1mg/dL, and may include muscle weakness, rhabdomyolysis
• Treatment is indicated when PO4 is less than 2mg/dL.
• Oral replacement is preferred.
• IV is indicated if PO4 < 1mg/dL; administer slowly.
• When administering IV phosphate products, measure serum phosphate levels every 6-8 hours.
• Monitor for hypocalcemia, renal failure, arrhythmias, and diarrhea (with oral replacement).

Hyperphosphatemia

• Symptoms are typically asymptomatic.
• Clinical features are due to accompanying hypocalcemia.
• Severe hyperphosphatemia can be life-threatening.
• Risk factors include advanced renal insufficiency, rhabdomyolysis, tumor-lysis syndrome, and overingestion of phosphate containing laxatives.
• Soft tissue calcification can be a long-term complication.

Potassium (K+)

• Normal Range: 3.5-5 mEq/L

Hypokalemia

• Signs and symptoms include muscle cramps/weakness, rhabdomyolysis, respiratory muscle weakness, decreased bowel motility, cardiac arrhythmias, hypotension, mental status changes, and speech changes.
• Characteristic ECG findings include ST segment depression, flattened T wave, and U wave.
• Monitor cardiac rate and rhythm.
• Common causes include GI losses (diarrhea/vomiting) and diuretic therapy.
• Educate patients on using laxatives and diuretics only as prescribed.
• Monitor potassium levels in patients on digoxin; hypokalemia will potentiate its effects.

Hyperkalemia

• Signs and symptoms include irritability/anxiety, paresthesias, ascending muscle weakness, cardiac arrhythmias/conduction abnormalities, lethargy, GI symptoms (nausea and intestinal colic).
• Characteristic ECG findings include tall, peaked T waves with shortened QT interval, prolonged PR interval, wide QRS complex and in severe cases, ventricular standstill.
• Monitor cardiac rate and rhythm.
• Avoid potassium-sparing diuretics, potassium supplements, or salt substitutes in patients with renal insufficiency.
• Use ACE inhibitors cautiously, as they cause K+ retention.

Sodium (Na+)

• Normal Range: 135-145 mEq/L

Hyponatremia

• Signs and symptoms:
  • Neurologic symptoms include lethargy, weakness, irritability, confusion, tremors, myoclonus, and seizure.
  • Other symptoms include hypotension, GI symptoms (anorexia, nausea, vomiting, abdominal cramping).
• Correction should be slow (4 to 6 mEq/L in first 24 hours) to avoid osmotic demyelination syndrome; monitor serum Na⁺ levels and neurologic status frequently.
• Avoid large water supplements to patients receiving isotonic tube feedings.
• Implement seizure precautions in severe cases.

Hypernatremia

• Signs and symptoms include excessive thirst, dehydration, dry mucous membranes, oliguria, mental status changes including lethargy, disorientation, restlessness, and elevated body temperature
• Monitor fluid losses and gains; urine and plasma osmolality may assist in establishing etiology.
• Give sufficient free water with tube feedings or salt-free IV fluids to keep serum Na⁺ and BUN within normal limits.

Acid-Base Status

• Arterial Blood Gas (ABG) components are used to assess acid-base status.

pH

• Normal range: 7.35-7.45
• Identification of the specific acid-base disturbance is important in identifying the underlying cause of the disorder and determining appropriate treatment.
• A pH less than 7.35 indicates acidosis, and a pH greater than 7.45 indicates alkalosis.

PaCO2

• Normal range: 35-45 mmHg
• PaCO2 is influenced almost entirely by respiratory activity.
• When the PaCO2 is low, carbonic acid leaves the body in excessive amounts; when the PaCO2 is high, there are excessive amounts of carbonic acid in the body.

HCO3

• Normal range: 22-26 mEq/L
• The bicarbonate level of the ABG reflects the bicarbonate level of the body.
• The kidneys are involved in either reabsorbing or excreting bicarbonate to maintain acid-base balance.

Renal Function

Blood Urea Nitrogen (BUN)

• Normal range: 10-20 mg/dL
• Increased BUN may be seen in patients with impaired renal function.
• Increased BUN may be caused by hypotension/shock, heart failure, salt and water depletion, dehydration, diabetic ketoacidosis, GI hemorrhage, and burns.

Creatinine

• Normal range: 0.7-1.4 mg/dL
• Increased creatinine levels may be seen in patients with impaired renal function due to decreased blood flow to the kidney (heart failure, shock, liver disease, dehydration), urinary tract obstruction, intrinsic kidney disease (i.e., glomerulonephritis), or certain medications.
• Acute kidney injury (AKI) is diagnosed when baseline creatinine increases abruptly by ≥ 0.3 mg/dL, even if creatinine remains in the normal range.

Hematologic Studies

Hemoglobin

• Males: 13-18 g/dL
• Females: 12-16 g/dL
• Increased hemoglobin levels may be caused by hypoxia, high altitude living, or hemoconcentration of the blood from dehydration.
• Decreased hemoglobin levels (anemia) may be due to hemorrhage/blood loss, hemodilution, nutritional deficiencies, chronic kidney disease, underlying malignancy, hereditary disorders, or a hemolytic reaction.

Hematocrit

• Males: 42-52%
• Females: 35-47%
• Increased hematocrit values are seen in severe fluid volume deficit and shock (when hemoconcentration rises considerably).
• Decreased hematocrit values are seen with blood loss and hemolytic reactions, after transfusion of incompatible blood, and fluid overload, and in other similar conditions where hemoglobin levels are also decreased.

Platelet Count

• Normal range: 150,000-450,000/mm³
• Increased platelet levels (thrombocythemia or thrombocytosis) may be caused by a bone marrow disorder or malignancy, infection or inflammation, anemia, splenectomy, or certain medications.
• Decreased platelet levels (thrombocytopenia) may result from bone marrow suppression, sequestration from an enlarged spleen, increased platelet destruction, or decreased platelet production. Liver disease, renal disorders, and pregnancy can also cause thrombocytopenia.

Coagulation Studies

Prothrombin Time (PT)

• Normal range: 9.5-12 seconds
• Measures the activity of the extrinsic pathway of the clotting cascade.
• Prothrombin is a protein made by the liver.
• Elevated PT may indicate liver dysfunction, Vitamin K deficiency, or coagulation factor deficiency (e.g. factor VII).

Partial Thromboplastin Time (PTT)

• Normal range: 20-39 seconds
• Tests the activity of the intrinsic pathway of the clotting cascade.
• Used to monitor the effects of unfractionated heparin.

International Normalized Ratio (INR)

• Normal value : 1.0
• For patients taking warfarin sodium normal range is 2-3.5 (varies based on diagnosis)
• Used to monitor the effectiveness of warfarin therapy.
• As INR increases, time for blood to clot increases.

Protein

Total Protein

• Normal range: 6-8 g/100 mL
• Proteins influence the colloid osmotic pressure.
• Includes both albumin and globulin.

Albumin

• Normal range: 3.5-5 g/100 mL
• Makes up 60% of total protein.
• Keeps fluid from leaking out of blood vessels.
• Changes in serum albumin affect total serum calcium levels.
• Decreased albumin can be due to malnutrition or liver disease and lead to edema, ascites, and pulmonary edema.

Serum Osmolality

• Normal range: 280-300 mOsm/L water
• Increased osmolality may be caused by severe dehydration, free water loss, diabetes insipidus, hypernatremia, hyperglycemia, stroke or head injury, renal tubular necrosis, or ingestion of methanol or ethylene glycol (antifreeze).
• Decreased osmolality may be caused by volume excess, SIADH, renal failure, diuretic use, adrenal insufficiency, hyponatremia, overhydration, or paraneoplastic syndrome associated with lung cancer.

Urine Tests

pH (urine)

• Normal range: 4.6-8.2
• Decreased urine pH may be caused by metabolic acidosis, diabetic ketoacidosis, or diarrhea.
• Increased urine pH may be caused by respiratory alkalosis, potassium depletion, or chronic renal failure.

Specific Gravity (urine)

• Normal range: 1.010-1.025
• Depends on the patient's state of hydration and varies with urine volume and the load of solutes to be excreted.
• Increased urine specific gravity may be seen with dehydration, vomiting, diarrhea, infection, and heart failure.
• Decreased urine specific gravity can occur with renal damage.