Everything You Need to Know for Fluid and Electrolyte Questions on the NCLEX!

  • 15 April, 2022

Fluid and electrolytes always seemed like such a big, complicated beast to me when I was a nursing student. Does it ever feel that way to you? If so, just know you're not alone! It's so challenging for most people that thankfully many smart people along the way have created some great ways to remember and understand fluid and electrolyte imbalances!

Everything You Need to Know for Fluid and Electrolyte Questions on the NCLEX

1. Assess

What's the first thing we do as nurses? We assess! As part of your nursing assessment, you evaluate aspects of the client's fluid volume status: skin turgor, mucus membranes, thirst, vomiting or diarrhea, bleeding, capillary refill, heart rate, pulse quality, vein appearance, blood pressure, and more. So, you should begin with a basic idea of whether the client is adequately hydrated, dehydrated (hypovolemia), or experiencing hypervolemia (or fluid overload).

2. Fluid Imbalance

Hypovolemia, or a bodily fluid deficiency, can occur from bleeding, severe dehydration, or vomiting and diarrhea. If not addressed promptly, the fluid deficiency can lead to hypovolemic shock, multisystem organ failure, and death. To address hypovolemia, the cause of the volume deficit should first be addressed along with intravenous rehydration and/or plasma expanders and blood products. For example, the client who is dehydrated from vomiting and diarrhea is best treated by stopping the continued loss through antiemetics and antidiarrheals as well as intravenous fluids. The client who is hypovolemic from bleeding or hemorrhage needs the cause of the bleeding addressed while simultaneously receiving blood products or plasma expanders.

A client can experience fluid overload (hypervolemia) from increased plasma sodium, fluid overcorrection, or organ failure (heart, renal, or hepatic). The client in a state of hypervolemia will present with hypertension, dyspnea, crackles or rales, shortness of breath, bulging veins, tachycardia, edema, or ascites. The cause of hypervolemia should be addressed, when possible, and the client will need diuretics and a sodium restriction.

3. Electrolytes

When it comes to electrolytes, you first need to memorize the normal values. Yes, I said MEMORIZATION - plain and simple. You just have to know the normal values because you will be referencing them for the rest of your career as a nurse. (Each laboratory/facility may have slight variations in norms, but it's just important to know the expectations.)

The main labs you will be considering are:

Sodium: Adults: 135 to 145 mEq/L (SI, 135 to 145 mmol/L).
Potassium: Adults: 3.5 to 5.2 mEq/L (SI, 3.5 to 5.2 mmol/L)
Calcium: Adults: 8.2 and 10.2 mg/dL (SI, 2.05 to 2.54 mmol/L).
Magnesium: Adults: 1.8 to 2.6 mg/dL (SI, 0.74 to 1.07 mmol/L).
Phosphate: Adults: 2.7 to 4.5 mg/dL (SI, 0.87 to 1.45 mmol/L).

Once you know the normal value expected, you will be able to distinguish an abnormal value. (Here's a little secret: the most common values tested are sodium and potassium! But there's no guarantee you won't see a question on Calcium, Magnesium, or Phosphate.) Typically, if you see issues with Calcium, Magnesium, or Phosphate, the value will be significantly out of the normal range, which will make it more recognizable. But with Potassium, for example, you might see a result of 3.2 mEq/L and need to recognize HYPOkalemia.

If you are still struggling with understanding electrolytes and don't know the normal ranges yet, I suggest you stop here for now and spend time learning those. Repeat them out loud. Tell your family, your roommate, your co-workers "The normal range for serum magnesium is 1.8 to 2.6mg/dL!" Write them out and put them on your bathroom mirror and your refrigerator so you can see them. It's really that important that you know them. Once you feel good about recognizing a value that is abnormal, come back here and review the signs, symptoms, and causes of electrolyte imbalances.

4. Signs, Symptoms, and Causes

Aside from memorizing the normal ranges for each of these, you need to be able to recognize the symptoms of a client who may be suffering from complications of a fluid/electrolyte imbalance. Here are a few mnemonics you can use to remember the causes and symptoms.

First, let's look at sodium. Sodium (normal range 135 to 145 mEq/L) is one of the body's primary electrolytes and most abundant in the blood plasma. For reviewing a client's symptoms, think FRIED or SALT.

Symptoms of HYPERnatremia:

F: Flushed skin
R: Restlessness
I: Increased fluid retention and blood pressure
E: Edema
D: Decreased urine output and Dry Mouth

Symptoms of HYPOnatremia

S: Stupor/Coma
A: Anorexia, Nausea & vomiting
L: Lethargy
T: Tendon reflexes decreased, poor skin Turgor

L: Limp muscles
O: Orthostatic hypotension
S: Seizures
S: Stomach cramps

Once you know if the client has hypo or hypernatremia, you need to assess for possible causes. For those we remember MODEL and SALT LOSS. (This is the easiest one for me because the mnemonic makes sense with the problem!)

Hypernatremia causes:

M: Medications/meals (foods they are eating)
O: Osmotic diuretics
D: Diabetes insipidus
E: Excessive water loss
L: Low water intake

Hyponatremia causes:

No Na+
Na+: sodium (Na+) excretion is increased (vomiting, diarrhea, diuretics, NG suctioning), renal problems, sweating, or decreased secretion of aldosterone
O: Overload of fluid
A: Antidiuretic hormone oversecreted (SIADH)

In evaluating potassium issues, remember MURDER (yikes! Sounds ominous, but it is easily fatal if not addressed quickly!) or all the "L's".

Symptoms of HYPERkalemia:

M: Muscle cramps
U: Urine abnormalities
R: Respiratory distress
D: Decreased cardiac contractility
E: EKG (peaked T wave)
R: Reflexes

Symptoms of HYPOkalemia:

L: Lethargy, Leg cramps, Limp muscles, Low/shallow respirations, Lots of urine, Lethal dysrhythmias

And again, once hypo or hyperkalemia has been determined, begin the assessment for possible causes.

For causes of hyperkalemia, think MACHINE:

M: Medications (ACE inhibitors, NSAIDS, potassium-sparring diuretics)
A: Acidosis (both metabolic and respiratory)
C: Cellular destruction from burns, injury, or hemolysis
H: Hypoaldosteronism (Addisons)
I: Impaired excretion
N: Nephrons (renal failure)
E: Excess intake

For symptoms of magnesium imbalance, remember PIN or the "D's":

Symptoms of HYPOmagnesemia:

P: Positive signs for Chvostek or Trousseau
I: Increased reflexes
N: Neuromuscular irritability

Symptoms of HYPERmagnesemia:

D: Dysphagia, decreased pulse, decreased blood pressure, diminished deep tendon reflexes

To assess possible causes of magnesium imbalance, remember BALL and RAM.

Causes of HYPOmagnesemia

B: Burns
A: alcoholism
L: loss from gastrointestinal tract
L: long term diuretic use

Causes of HYPERmagnesemia

R: Renal failure
A: Adrenal insufficiency
M: magnesium salts

Yes, that's a lot of mnemonics to remember! But most of us are able to remember some of these without a mnemonic with a little practice and critical thinking. And then you only need to use the mnemonic for the most challenging concepts for YOU! For instance, when I was in nursing school, I had worked on a med-surg floor and saw lots of patients with sodium and potassium imbalances and had a pretty good grasp on those, but magnesium was a little more challenging at first.

5. Correcting Fluid Imbalance

For the client with a fluid and electrolyte imbalance, it's important to understand your IV solutions that may be used. There are three types of solutions: isotonic, hypotonic, and hypertonic.

Isotonic solutions (the solution is equal to osmotic pressure) are used for dehydration and metabolic acidosis. These are probably the most common IV solutions utilized. Examples are Lactated Ringers solution, 0.9% sodium chloride (also known as Normal Saline), and 5% dextrose in water (D5W).

Hypertonic solutions (have a high osmotic pressure) will be used in cases of high blood loss, hyponatremia, and hypovolemia. Examples include 5% dextrose in normal saline (D5NS) and 10% dextrose in water (D10W).

Hypotonic solutions (have a low osmotic pressure) are used in clients with edema. Examples of hypotonic solutions are 0.45% normal saline (1/2 NS) and 5% dextrose in half normal saline (D51/2NS). The client with edema typically has a high sodium level, so you don't want to give them any extra sodium than is required, so 1/2 NS is the better option.

I won't lie and say I had this all figured out when I took the NCLEX-RN - I didn't! But I knew my normal ranges and had an entry-level understanding of the imbalances that grew quickly once I was a nurse working med-surg! I would suggest taking each electrolyte individually and focusing on it for a few days - print out or write out the mnemonics and do the same thing that was said about learning normal ranges. Put them wherever you will see them frequently and repeat them to anyone who will listen (or even people who won't listen!). Spend a few days on sodium, a few on potassium, a few on magnesium, and then take a practice test and see how you do! You just might surprise yourself! But it's also important to understand that fluid and electrolyte imbalances are not an isolated concept. Continuing to grow in your knowledge of the disorders that can lead to these issues will only improve your understanding of them and your ability to recognize the signs, symptoms, and causes of them.

Maybe you find yourself still struggling with discerning the difference between client presentations or knowing what your nursing actions should be? Fluid and electrolyte imbalances (and so much more) are covered in the review course offered through EduMind! Be sure to get registered for it today!

About the Author: Lana Wilkins, MSN, BSN, RN

Lana Wilkins is a Registered Nurse with over 16 years of professional nursing. She is a nursing educator, consultant, Subject Matter Expert, and writer with a passion for helping students and new nurses. She holds a B.S. in Nursing from the University of Oklahoma and a M.S. in Nursing Education from Western Governors University. Outside of the world of nursing she can be found managing the chaos of 2 kids, a husband, and a cat, being crafty, or spending time with friends.

Blogs you might also like