Chloride, Blood

Synonym/acronym: Cl⁻.

Common use

To evaluate electrolytes, acid-base balance, and hydration level.

Specimen

Serum (1 mL) collected in a gold-, red-, or red/gray-top tube. Plasma (1 mL) collected in a green-top (heparin) tube is also acceptable.

Normal findings

(Method: Ion-selective electrode)

Age	Conventional & SI Units
Premature	95–110 mEq/L or mmol/L
0–1 mo	98–113 mEq/L or mmol/L
2 mo–older	adult 97–107 mEq/L or mmol/L

Description

Chloride is the most abundant anion in the extracellular fluid. Its most important function is in the maintenance of acid-base balance, in which it competes with bicarbonate for sodium. Chloride levels generally increase and decrease proportionally to sodium levels and inversely proportional to bicarbonate levels. Chloride also participates with sodium in the maintenance of water balance and aids in the regulation of osmotic pressure. Chloride contributes to gastric acid (hydrochloric acid) for digestion and activation of enzymes. The chloride content of venous blood is slightly higher than that of arterial blood because chloride ions enter red blood cells in response to absorption of carbon dioxide into the cell. As carbon dioxide enters the blood cell, bicarbonate leaves and chloride is absorbed in exchange to maintain electrical neutrality within the cell.

Chloride is provided by dietary intake, mostly in the form of sodium chloride. It is absorbed by the gastrointestinal system, filtered out by the glomeruli, and reabsorbed by the renal tubules. Excess chloride is excreted in the urine. Serum values normally remain fairly stable. A slight decrease may be detectable after meals because chloride is used to produce hydrochloric acid as part of the digestive process. Measurement of chloride levels is not as essential as measurement of other electrolytes such as sodium or potassium. Chloride is usually included in standard electrolyte panels to detect the presence of unmeasured anions via calculation of the anion gap. Chloride levels are usually not interpreted apart from sodium, potassium, carbon dioxide, and anion gap.

The patient’s clinical picture needs to be considered in the evaluation of electrolytes. Fluid and electrolyte imbalances are often seen in patients with serious illness or injury because in these cases the clinical situation has affected the normal homeostatic balance of the body. It is also possible that therapeutic treatments being administered are causing or contributing to the electrolyte imbalance. Children and adults are at high risk for fluid and electrolyte imbalances when chloride levels are depleted. Children are considered to be at high risk during chloride imbalance because a positive serum chloride balance is important for expansion of the extracellular fluid compartment. Anemia, the result of decreased hemoglobin levels, is a frequent issue for elderly patients. Because hemoglobin participates in a major buffer system in the body, depleted hemoglobin levels affect the efficiency of chloride ion exchange for bicarbonate in red blood cells, which in turn affects acid-base balance. Elderly patients are also at high risk because their renal response to change in pH is slower, resulting in a more rapid development of electrolyte imbalance.

This procedure is contraindicated for

N/A

Indications

Assist in confirming a diagnosis of disorders associated with abnormal chloride values, as seen in acid-base and fluid imbalances
Differentiate between types of acidosis (hyperchloremic versus anion gap)
Monitor effectiveness of drug therapy to increase or decrease serum chloride levels

Potential diagnosis

Increased in

Acute renal failure (related to decreased renal excretion)
Cushing’s disease (related to sodium retention as a result of increased levels of aldosterone; typically, chloride levels follow sodium levels)
Dehydration (related to hemoconcentration)
Diabetes insipidus (hemoconcentration related to excessive urine production)
Excessive infusion of normal saline (related to excessive intake)
Head trauma with hypothalamic stimulation or damage
Hyperparathyroidism (primary) (high chloride-to-phosphate ratio is used to assist in diagnosis)
Metabolic acidosis (associated with prolonged diarrhea)
Renal tubular acidosis (acidosis related to net retention of chloride ions)
Respiratory alkalosis (e.g., hyperventilation) (related to metabolic exchange of intracellular chloride replaced by bicarbonate; chloride levels increase)
Salicylate intoxication (related to acid-base imbalance resulting in a hyperchloremic acidosis)

Decreased in

(related to insufficient production of aldosterone; potassium is retained while sodium and chloride are lost)

(dilutional effect related to sequestration of extracellular fluid)

(related to dilutional effect of fluid buildup)

(related to acid-base imbalance with accumulation of ketone bodies and increased chloride)

(related to excessive loss of chloride without replacement)

(related to homeostatic response in which intracellular chloride increases to reduce alkalinity of extracellular fluid)

(related to dilutional effect)

(related to excessive loss)

(related to dilutional effect)

Critical findings

Less than 80 mEq/L or mmol/L (SI: Less than 80 mmol/L)
Greater than 115 mEq/L or mmol/L (SI: Greater than 115 mEq/L or mmol/L)
Note and immediately report to the health-care provider (HCP) any critically increased or decreased values and related symptoms.
It is essential that a critical finding be communicated immediately to the requesting health-care provider (HCP). A listing of these findings varies among facilities.
Timely notification of a critical finding for lab or diagnostic studies is a role expectation of the professional nurse. Notification processes will vary among facilities. Upon receipt of the critical value the information should be read back to the caller to verify accuracy. Most policies require immediate notification of the primary HCP, Hospitalist, or on-call HCP. Reported information includes the patient’s name, unique identifiers, critical value, name of the person giving the report, and name of the person receiving the report. Documentation of notification should be made in the medical record with the name of the HCP notified, time and date of notification, and any orders received. Any delay in a timely report of a critical finding may require completion of a notification form with review by Risk Management.
The following may be seen in hypochloremia: twitching or tremors, which may indicate excitability of the nervous system; slow and shallow breathing; and decreased blood pressure as a result of fluid loss. Possible interventions relate to treatment of the underlying cause.
Signs and symptoms associated with hyperchloremia are weakness; lethargy; and deep, rapid breathing. Proper interventions include treatments that correct the underlying cause.

Interfering factors

Drugs that may cause an increase in chloride levels include acetazolamide, acetylsalicylic acid, ammonium chloride, androgens, bromide, chlorothiazide, cholestyramine, cyclosporine, estrogens, guanethidine, hydrochlorothiazide, lithium, methyldopa, NSAIDs, oxyphenbutazone, phenylbutazone, and triamterene.
Drugs that may cause a decrease in chloride levels include aldosterone, bicarbonate, corticosteroids, corticotropin, cortisone, diuretics, ethacrynic acid, furosemide, hydroflumethiazide, laxatives (if chronic abuse occurs), mannitol, meralluride, mersalyl, methyclothiazide, metolazone, and triamterene. Many of these drugs can cause a diuretic action that inhibits the tubular reabsorption of chloride. Note: Triamterene has nephrotoxic and azotemic effects, and when organ damage has occurred, increased serum chloride levels result. Potassium chloride (found in salt substitutes) can lower blood chloride levels and raise urine chloride levels.
Elevated triglyceride or protein levels may cause a volume-displacement error in the specimen, reflecting falsely decreased chloride values when chloride measurement methods employing predilution specimens are used (e.g., indirect ion-selective electrode, flame photometry).
Specimens should never be collected above an IV line because of the potential for dilution when the specimen and the IV solution combine in the collection container, falsely decreasing the result. There is also the potential of contaminating the sample with the normal saline contained in the IV solution, falsely increasing the result.

Nursing Implications and Procedure

Pretest

Positively identify the patient using at least two unique identifiers before providing care, treatment, or services.
Patient Teaching: Inform the patient this test can assist in evaluating the amount of chloride in the blood.
Obtain a history of the patient’s complaints, including a list of known allergens, especially allergies or sensitivities to latex.
Obtain a history of the patient’s cardiovascular, endocrine, gastrointestinal, genitourinary, and respiratory systems, as well as results of previously performed laboratory tests and diagnostic and surgical procedures.
Specimens should not be collected during hemodialysis.
Obtain a list of the patient’s current medications, including herbs, nutritional supplements, and nutraceuticals (see Effects of Natural Products on Laboratory Values online at DavisPlus).
Review the procedure with the patient. Inform the patient that specimen collection takes approximately 5 to 10 min. Address concerns about pain and explain that there may be some discomfort during the venipuncture.
Sensitivity to social and cultural issues, as well as concern for modesty, is important in providing psychological support before, during, and after the procedure.
Note that there are no food, fluid, or medication restrictions unless by medical direction.

Intratest

Potential complications: N/A
Avoid the use of equipment containing latex if the patient has a history of allergic reaction to latex.
Instruct the patient to cooperate fully and to follow directions. Direct the patient to breathe normally and to avoid unnecessary movement. Instruct the patient not to clench and unclench fist immediately before or during specimen collection.
Observe standard precautions, and follow the general guidelines in Patient Preparation and Specimen Collection. Positively identify the patient, and label the appropriate specimen container with the corresponding patient demographics, initials of the person collecting the specimen, date, and time of collection. Perform a venipuncture.
Remove the needle and apply direct pressure with dry gauze to stop bleeding. Observe/assess venipuncture site for bleeding or hematoma formation and secure gauze with adhesive bandage.
Promptly transport the specimen to the laboratory for processing and analysis.

Post-Test

Inform the patient that a report of the results will be made available to the requesting HCP, who will discuss the results with the patient.
Observe the patient on saline IV fluid replacement therapy for signs of overhydration, especially in cases in which there is a history of cardiac or renal disease. Signs of overhydration include constant, irritable cough; chest rales; dyspnea; or engorgement of neck and hand veins.
Evaluate the patient for signs and symptoms of dehydration. Check the patient’s skin turgor, mucous membrane moisture, and ability to produce tears. Dehydration is a significant and common finding in geriatric and other patients in whom renal function has deteriorated.
Monitor daily weights as well as intake and output to determine whether fluid retention is occurring because of sodium and chloride excess. Patients at risk for or with a history of fluid imbalance are also at risk for electrolyte imbalance.
Nutritional Considerations: Careful observation of the patient on IV fluid replacement therapy is important. A patient receiving a continuous 5% dextrose solution (D₅W) may not be taking in an adequate amount of chloride to meet the body’s needs. The patient, if allowed, should be encouraged to drink fluids such as broths, tomato juice, or colas and to eat foods such as meats, seafood, or eggs, which contain sodium and chloride. The use of table salt may also be appropriate.
Nutritional Considerations: Instruct patients with elevated chloride levels to avoid eating or drinking anything containing sodium chloride salt. The patient or caregiver should also be encouraged to read food labels to determine which products are suitable for a low-sodium diet.
Nutritional Considerations: Instruct patients with low chloride levels that a decrease in iron absorption may occur as a result of less chloride available to form gastric acid, which is essential for iron absorption. In prolonged periods of chloride deficit, iron-deficiency anemia could develop.
Reinforce information given by the patient’s HCP regarding further testing, treatment, or referral to another HCP. Answer any questions or address any concerns voiced by the patient or family. Educate the patient regarding access to nutritional counseling services. Provide contact information, if desired, for the Institute of Medicine of the National Academies (www.iom.edu).
Depending on the results of this procedure, additional testing may be performed to evaluate or monitor progression of the disease process and determine the need for a change in therapy. Evaluate test results in relation to the patient’s symptoms and other tests performed.

Related Monographs

Related tests include ACTH, anion gap, blood gases, carbon dioxide, CBC hematocrit, CBC hemoglobin, osmolality, potassium, protein total and fractions, sodium, and US abdomen.
Refer to the Cardiovascular, Endocrine, Gastrointestinal, Genitourinary, and Respiratory systems tables at the end of the book for related test by body system.