Fluid & Electrolyte Balance

Vol. 7 •Issue 3 • Page 21
Fluid & Electrolyte Balance

Nurses’ early recognition of imbalances often can prevent complications

Balancing fluid and electrolytes can be challenging for healthy individuals, but maintaining this balance is harder for sick patients. Early recognition of imbalances and prompt intervention often prevents further complications.

Fluid Basics

Water helps bodies maintain temperature and cell shape and assists in transporting nutrients, wastes and gases. About 55-60 percent of a healthy, lean adult’s body weight is water, while about 75-80 percent of an infant’s body is water.1 Fluid amount and distribution within the body declines with age, increasing risk of an imbalance.

There are three types of body fluids: isotonic, hypotonic and hypertonic. Isotonic fluids have the same solute concentrations. Hypotonic solutions have the least solute concentrations, and hypertonic solutions have the most solute concentrations, which significantly impact fluid homeostasis.

Maintaining Fluid Homeostasis

Inside the body, fluid resides within or outside cells. Intracellular fluid (ICF) is found inside cells. Extracellular fluid (ECF) is found outside cells. Cell membranes and capillary walls separate ECF and ICF fluid compartments. A body strives for balance, or homeostasis, between the two compartments by shifting fluids.

Maintaining homeostasis of fluid volume is essential to healthy bodily functioning. Several regulatory mechanisms keep the body functioning near normal.

When a condition in the body changes, regulatory mechanisms in the body’s major organs start to work to regain a balance. Processes such as filtration, diffusion, osmosis, capillary pressure and activity-transport help move water to achieve this balance.

Hormonal Control

The hormones aldosterone, antidiuretic hormone (ADH) and atrial natriuretic peptide (ANP) regulate fluid and electrolyte balance. Aldosterone is secreted by the adrenal cortex in response to decreased sodium levels in the ECF or increased sodium in urine.1 Aldosterone prevents sodium loss and leads to water retention, resulting in increased fluid volume and sodium levels.1

ADH is produced in the brain and stored in the posterior pituitary gland. It is released in response to changes in blood osmolarity (normal body fluid osmolarity is 270-300 mOsm/L).2 ADH acts on kidney tubules, leading to increased water reabsorption and decreased osmolarity, producing dilute urine.

ANP is secreted by specific heart cells in response to increased blood pressure and volume.1 ANP inhibits reabsorption of sodium and increases the glomerular filtration rate. This results in urine production with high sodium concentration, leading to decreased circulatory volume and blood osmolarity.

Fluid Intake & Loss

Thirst is the primary driver of fluid intake. Increased plasma osmolarity or decreased plasma volume stimulates thirst. Adults drink about 1.5L of fluid daily and retain approximately 800 mL from foods.

Kidneys filter blood and expel excess water and waste from bodies. Several regulatory functions of kidneys control the volume of water excreted to maintain homeostasis.

Water loss also occurs through skin, lungs, gastrointestinal tract, salivation, other drainage of various fluids and gastrointestinal suctioning. Water lost through skin, lungs and stool cannot be controlled, is difficult to measure and termed “insensible” water loss. Insensible water loss increases with fever, trauma, thyroid crisis and burns.

Fluid Volume Deficit

Dehydration occurs when the body doesn’t have enough fluid, or a fluid volume deficit. Dehydration is a clinical state caused by factors such as excessive perspiration, decreased intake of fluids, hyperventilation, fever, diarrhea, ketoacidosis, diabetes and renal failure.3

Clinical manifestations of dehydration are multisystemic and include hypotension, increased heart rate, increased respiration, weakness, diminished pulse, lethargy, poor skin turgor, dry mouth with fissures, decreased bowel sounds, thirst and decreased urine output.1 Nursing interventions are listed in Table 1.

Fluid Volume Excess

Fluid overload occurs when intake and retention of fluid exceeds requirements. Causes can include renal failure, CHF, excessive sodium and fluid intake, syndrome of inappropriate antidiuretic hormone, prolonged corticosteroid therapy, polydipsia and rapid IV therapy.1

Clinical manifestations of fluid overload include increased or bounding pulse, elevated blood pressure, distended neck veins, increased respiratory rate, dyspnea, crackles, edema, headache, weakness, ascites and cool, pale skin. Nursing interventions are listed in Table 2.


Electrolytes are substances called ions that conduct an electrical current when dissolved in water. Electrolytes with a positive charge are called cations and include sodium, potassium, calcium and magnesium. Electrolytes with a negative charge are called anions and include chloride, bicarbonate and phosphorous. In all body fluids, anions and cations are present in equaling amounts, creating a state of electroneutrality (electrical balance).

Electrolyte imbalances can occur in healthy individuals with an imbalance of fluid intake and output. These imbalances are generally mild and corrected without medical intervention. Populations at risk include the young and old, patients with renal impairments, endocrine disorders, mental impairments and individuals using medications that affect fluid and electrolyte balance.


A normal serum sodium level ranges from 136 mE/L to 145 mEq/L. Sodium is the major anion of the ECF. Sodium enables skeletal muscle and cardiac contractions, nerve impulse transmission, ECF balance and concentration of urine.2

Imbalances in plasma sodium levels impact fluid volume and distribution of electrolytes. The sodium-potassium pump, or active transport mechanism, maintains normal sodium levels in the body. Despite the actions of sodium-potassium pumps, imbalances in sodium levels can occur (Table 3).


A normal serum potassium level ranges from 3.5 mEq/L to 5 mEq/L. Potassium is the major cation of the ICF and helps regulate protein synthesis, cellular electrical neutrality and osmolality nerve impulse transmission, acid-base balance and muscle contractility.2

Potassium balance is controlled by the sodium-potassium pump and renal excretion. Minor potassium imbalances affect physiologic functions within the body (Table 3).


The normal range for a serum calcium level is 9-10.5 mg/dL. Calcium is bound to proteins, such as albumin, and also present in blood or ECF. The majority of calcium is in bones and teeth, which it helps form. Calcium impacts enzymes, skeletal and cardiac contractions, nerve impulse transmission and blood clotting.1

The body gets most of its calcium from dietary intake and absorption through the intestinal tract. Absorption of calcium requires active vitamin D. Imbalances in calcium increase or limit secretion of parathyroid hormone (PTH) to achieve homeostasis. Despite this regulatory process, imbalances in calcium levels occur (Table 3).


Normal serum phosphorus levels range from 3 mg/dL to 4.5 mg/dL. Phosphorus is the major anion in ICF. Most phosphorus in is in bones. It plays a role activating B-complex vitamins, cell division and membrane integrity, and metabolism of carbohydrates, proteins and fats.1

Phosphorus and calcium have a reciprocal relationship; a change in phosphorus results in an opposite change in calcium levels.2 Phosphorus imbalances should be promptly managed, due to the impact on calcium levels (Table 3).


The acceptable reference range for serum magnesium levels is 1.2-2 mg/dL. Magnesium helps muscle contraction, carbohydrate metabolism, cellular energy activity, blood coagulation and protein synthesis.1 Magnesium is absorbed from the intestinal tract. Phosphorus and PTH levels also impact the balance of magnesium (Table 3).


Normal chloride levels fall between 90 mEq/L and 110 mEq/L. Chloride is the major anion of ECF and travels with positively charged sodium. Together, sodium and chloride maintain ECF osmotic pressure, form cerebral spinal fluid, assist in digestive processes and enzyme activation, and maintain acid-base balance.1 Chloride enters the body through dietary intake, but imbalances can occur (Table 3).

Prompt Recognition Important

Nurses in all areas of practice have patients with fluid and electrolyte imbalances. Prompt recognition of symptoms, laboratory values and ECG changes indicative of an imbalance enable immediate interventions. Nurses should monitor all patients for actual or potential fluid and electrolyte imbalances.


1. Ignatavicius, D.D., & Workman, M.L.(2002). Medical-surgical nursing: Critical thinking for collaborative care (4th ed.). Philadelphia: W.B. Saunders.

2. Springhouse Corp. Staff. (2002). Fluids & electrolytes made incredibly easy! (2nd ed.). Philadelphia: Lippincott Williams & Wilkins.

3. Metheny, N.M. (2000). Fluid and electrolyte balance: Nursing Considerations (4th ed.). Philadelphia: Lippincott Williams & Wilkins.

Tamara Kear is a nursing instructor at Gwynedd-Mercy College School of Nursing, Gwynedd Valley, PA.

ADVANCE provides the latest information on nursing certification and recertification in med/surg nursing. For those nurses interested in obtaining certification or recertification, ADVANCE provides highlights of what you’ll need to get started. Here is a glimpse of two certification organizations — the American Nurses Credentialing Center (ANCC) and the Academy of Medical-Surgical Nurses (AMSN).


For more information or to request an application, you can:

• Visit ANCC online at www.nursecredentialing.org;

• Call 800-284-2378; or E-mail [email protected].


In an effort to help nurses preparing to take certification exams, the ANCC is now offering immediate access to materials and test content outlines (TCOs) on its Web site.

This also offers ANCC the ability to quickly update and disseminate information regarding TCOs and reference lists to candidates. TCOs summarize subject matter covered on particular exams. Nurses preparing to take a certification exam can use the TCOs, along with the accompanying reference list, to study. Sample questions for each exam currently are being added to the site, according to the ANCC.

Beginning Sept. 1, 2004, candidates taking ANCC exams began receiving new test booklets. The General Testing Information booklet replaced the previously titled Candidate Handbook and Reference Materials and contains key information for candidates, including timelines for receiving credentialing information and how to schedule computer-based exams.

The booklet will not contain the test content outline, reference list or sample questions, according to the ANCC. Candidates who have received the Candidate Handbook and Reference Materials are encouraged to go online and review the TCO, reference list and sample questions to ensure they have the most accurate information.


The ANCC currently offers certifications in more than 40 specialty areas of nursing practice, including three in med/surg: RN,C; RN,BC; and APRN,BC. Paper exams cost $180 for members of an ANA Constituent Member Association (CMA), which includes the Federal Nurses Association (FedNA) and the former State Nurses Associations (SNAs); the Hospice and Palliative Nurses Association; and the American Association of Diabetes Educators.

A $250 rate is available for active members of select organizations. This list can be found on the ANCC Web site. The fee for non-members is $320.

Computer-based exams for CMA, FedNA, SNA and American Association of Diabetes Educators members cost $230, while a select group of collaborating organizations (see list online) are charged $300 and non-members are charged $370. Exam dates and locations are available online.


To obtain RN,C and RN,BC certification, candidates must meet all of the following basic eligibility requirements at the time of application:

• hold an active RN license in the United States or its territories;

• have practiced as an RN for the equivalent of 2 years full-time in the United States or its territories;

• hold a baccalaureate or higher degree in nursing;

• have a minimum of 2,000 hours of clinical practice within the last 3 years, unless specified in criteria specific to specialty areas (see list online); and

• have earned 30 contact hours within the last 3 years.

To obtain APRN,BC certification, candidates must:

• hold an active RN license in the United States or its territories;

• hold a master’s or higher degree in nursing (Candidates seeking certification as a clinical nurse specialist in community health nursing may have a master’s or higher degree in community health nursing or a baccalaureate degree in nursing and a master’s or higher degree in public health with a specialization in community and/or public health nursing.);

• have preparation in the area of practice for which they have applied for certification through a master’s program or a formal postgraduate master’s program in nursing (APRNs seeking certification as clinical specialists can apply for initial certification upon graduation, provided they have received 500 hours of supervised clinical practicum within their academic program. Candidates whose academic program did not include 500 hours of supervised clinical practicum must complete the difference, after conferral of master’s degree, 12 months prior to applying for certification);

• have graduated from a program offered by an accredited institution granting graduate-level academic credit for all course work that includes both didactic and clinical components, and a minimum of 500 hours of supervised clinical practice in the specialty area and role.


For more complete information or to request an application, you can:

• Visit AMSN online at www.medsurgnurse.org;

• Call 856-256-2676; or

• E-mail [email protected].


A record number of nurses are seeking and earning certification through the AMSN, according to the Medical-Surgical Nursing Certification Board (MSNCB), the certification arm of the AMSN.

AMSN reports that nearly 750 nurses sat for the MSNCB certification exam Oct. 16, 2004 at various locations around the country, reportedly the highest number to date. According to the AMSN, 2,100 nurses have taken the test since it began offering its certification exam.

“I think the spark has been increased recognition by the entire healthcare profession that medical/surgical nursing is a cornerstone practice,” said MSNCB President Marlene Roman, MSN, ARNP, CMSRN. “Taking that a step further, nurses know that certification validates their expertise, and that has direct benefits for them, their employer and their patients.”

MSNCB works with the Center for Nursing Education and Testing, a testing company, to administer the exam, which is designed and written by med/surge nurses. Those who meet exam requirements and pass the test, given each year at AMSN’s annual convention in May and October, receive the Certified Medical-Surgical Registered Nurse (CMSRN) credential.

AMSN Executive Director Cynthia Nowicki, EdD, RN, CAE, said another appealing aspect of CMSRN certification is the “examination exemption.”

“Not everyone has to take the test,” she related in the news release. “We have developed the program so nurses who are already certified in med/surg by another certification board are eligible for the credential through MSNCB without having to sit for the exam if they meet all of the other criteria.”

Visit the AMSN Web site for a list of exemptions.


CMSRN certification is valid for 5 years. Renewal is available by:

• meeting the stated eligibility requirements for certification;

• submitting the completed application form for renewal and all applicable fees; and

• successfully passing the certification exam or meeting stated requirements for continuing education.


To obtain CMSRN certification, candidates must:

• hold an active, unrestricted RN license in the United States or its territories; or

• hold an active, full and unrestricted license to practice as a first-level general nurse in the country in which one’s general nursing education was completed, and meet the eligibility criteria for licensure as an RN in the United States in accordance with requirements of the Commission on Graduates of Foreign Nursing Schools;

• have practiced at least 2 full years as an RN in an adult med/surg clinical setting within the last 5 years; and

• have a minimum of 3,000 hours clinical practice as a staff nurse, clinical nurse specialist, clinical educator, faculty, manager or supervisor.