A salty tale: What EMS personnel need to know about electrolyte disorders

You may have wondered what the emergency department physician is looking for when she orders lab tests on a patient's electrolyte levels. The answer is fairly straightforward; without an adequate balance of electrolytes, the body is unable to perform many mission-critical functions. In fact, certain electrolyte imbalances can quickly become life-threatening.

While EMS providers generally are unable to determine electrolyte levels in the field, a careful analysis of the patient's presentation, coupled with a well-conducted history taking, can bring an electrolyte disorder to light.

Chemically, electrolytes are salts. They dissolve (or disassociate) in water to form electrically-charged ions. An ion that is positively (+) charged is called a cation; an ion that is negatively (-) charged is called an anion. For example, sodium chloride (NaCL) becomes sodium ions (Na⁺) and chloride anions (Cl^-) when dissolved in water.

Electrolytes are essential to the conduction of the electrical pulses needed to control all living functions within the body. It is the amount and location of the cations and anions that allows energy to be conducted. Other essential life functions include the regulation of water within and outside the cells, muscle contraction and maintaining the general balance of the cell's operating environment.

Here are the key electrolytes for homeostasis, along with associated signs and symptoms when their levels are too high or too low.

Sodium
Why sodium is important: Sodium (Na⁺) is found mostly outside of cells. Its major role is to regulate the amount of water inside the body. As the kidney excretes sodium, water follows it, creating urine. Sodium is also a key electrolyte in creating electrical impulses both within and across cells, which allow a wide variety of functions to occur. This is critical for the brain, nervous system and muscles.

A normal lab value for sodium is 135–145 mEq/L.

When sodium levels get too high: Kidney disease, excessive water loss from massive diarrhea and vomiting, or too little water intake are the major causes of hypernatremia. Patients complain of excessive thirst. Tachycardia, anxiety and fatigue are other pertinent signs and symptoms. In severe cases of hypernatremia, altered mental status and seizures may occur.

When sodium levels get too low: Liver disease, some forms of kidney disease, congestive heart failure, burns and rarely overhydration can cause hyponatremia. Signs and symptoms include fatigue, nausea, vomiting, muscle spasms and weakness. Seizures may also occur in severe circumstances.

Potassium
Why potassium is important: Potassium (K⁺) is found mostly inside cells. It works in conjunction with sodium to propagate electrical signals in cells. Sodium-potassium pumps are embedded into the cell membrane, and work like pumps to keep levels of potassium high in the cell and sodium levels high in the surrounding interstitial space.

This creates a polarized electrical state across the cell's membrane. An electrical stimulus from a nearby cell triggers sodium and potassium channels to quickly open in sequence. This allows sodium to rush into the cell first, changing the cell's polarized state. Potassium then rushes out, dampening the effect.

This creates a depolarization of the cell, creating an electrical signal that triggers a wide range of effects, such as muscle contraction, hormones released from glands, and contraction of the heart. The sodium-potassium pumps then push the electrolytes back across the membrane, allowing the polarized state to exist again.

Normal lab values for potassium are 3.5–5.0 mEq/L.

When potassium levels are too high: Similar to sodium, the potassium levels are regulated by excretion through the kidneys. Patients with renal disease are at risk for developing hyperkalemia. Certain medications can also cause potassium levels to rise, such as potassium-sparing diuretics — spironolactone, triamterene), NSAIDs, ACE inhibitors and heparin.

Hyperkalemia is a potentially lethal condition that can manifest itself quickly. As levels rise, patients complain of muscle weakness, fatigue, numbness or tingling and nausea and vomiting. At high doses, bradycardia, hypotension and respiratory arrest. On an EKG, wide QRS complexes and unusually tall, peaked T waves can be seen.

When potassium levels are too low: Kidney disease, excessive vomiting or diarrhea, overuse of laxatives, excessive sweating, medications such as diuretics related to furosemide, beta-2 agonists such as albuterol, and certain antimicrobials such as penicillin can cause hypokalemia. Patients with hypokalemia may have symptoms similar to hyperkalemia, including weakness, fatigue, cramping and constipation. Lethal dysrhythmias appear as levels drop to dangerously low levels.

Chloride
Why chloride is important: Chloride (Cl^-) is the major anion found mostly outside of the cell. Its major functions are to help keep fluid levels in balance and help to balance acidity levels.

Normal lab values for chloride are 98 - 108 mmol/L.

When chloride levels are too high: Hyperchloremia is more rare than hypernatremia and hyperkalemia. It usually results from major diarrhea, certain kidney diseases and occasionally from parathyroid gland disease. Patients may complain of headaches, nausea and fatigue. They may be tachypneic in order to compensate for the corresponding metabolic acidosis. In severe cases of hyperchloremia, hypotension and ventricular fibrillation may occur.

When chloride levels are too low: Hypochloremia can result from excessive sweating or urination. Vomiting can also cause chloride levels to fall, as well as adrenal gland disease. Patients may experience tetany (muscle spasms), muscle weakness, difficulty breathing and fever.

Calcium
Why calcium is important: Calcium (Ca²⁺) is the most common cation in the body, with most of it found in bone and teeth. It also has a critical function in conducting electrical signals, as well as muscle contraction and blood clotting.

Normal lab values for calcium are 9–11 mg/dL or (4.5–5.5 mEq/L).

When calcium levels are too high: Hypercalcemia primarily results from noncancerous tumors that cause parathyroid glands to over secrete their hormones. Cancer, certain medications like lithium, or ingesting excessive calcium supplements are other potential causes.

Signs of hypercalcemia can be organized according to the following mnemonic:

• Moans: abdominal pain, nausea, constipation
• Groans: lethargy, weakness, confusion and coma
• Stones: polyuria, kidney stones, renal failure
• Bones: bone aches and pains, fractures).

In severe cases, changes in the patient's EKG include a shortened QT interval associated with a shortened ST segment, flattened T waves and the presence of Osborn waves.

When calcium levels are too low: Hypocalcemia tends to occur most commonly in chronic and acute renal failure. Deficiencies in magnesium or vitamin D can also cause a drop in calcium levels, as well as hypoparathyroidism and acute pancreatitis. Severe cases of hypocalcemia include confusion, lethargy, muscle cramping or weakness and paresthesia.

Phosphate
Why phosphate is important: Phosphorous is the second most abundant mineral in the body. The anion phosphate (HPO^4-) is found mostly in the skeleton, along with calcium. However, it is a major component in adenosine triphosphate (ATP) production, the primary energy source for cells. It is also involved in cell reproduction and repair.

Normal lab values for phosphate are 2.4–4.7 mg/dL.

When phosphate levels are too high: Like other electrolytes, most cases of hyperphosphatemia result from some form of kidney disease. Excessive intake of phosphate is a less common cause. Hypoparathyroidism and metabolic or respiratory acidosis can cause phosphate levels to rise as well. Signs of hyperphosphatemia are similar to hypocalcemia, as the two conditions are often correlated.

When phosphate levels are too low: Hyperparathyroidism prevents the kidneys from retaining adequate levels of phosphate, as well as calcium, causing hypophosphatemia. Poor diet, especially related to alcoholism, can cause phosphate levels to drop. Hypophosphatemia can also be seen in patients being treated for diabetic ketoacidosis, or patients with respiratory alkalosis. Weakness, bone pain, rhabdomyolysis and altered mental status are the most common presenting features of persons with symptomatic hypophosphatemia.

Magnesium
Why is magnesium important: Magnesium (Mg²⁺) plays a major role in maintaining normal function in the nervous system, muscle contraction, and cardiac physiology. It also is a major component of DNA and RNA synthesis as well as bone formation.

Normal lab values for magnesium are 1.8–3.0 mg/dL (1.5–2.5 mEq/L).

When magnesium levels are too high: Hypermagnesemia is usually due to kidney disease. Excessive intake, lithium therapy, hypothyroidism and Addison's disease are other less common causes. Severe cases of hypermagnesemia may be lethal, resulting in respiratory depression, failure or arrest, hypotension and cardiac arrest. Milder cases may result in lethargy, poor deep tendon reflexes, nausea or vomiting and skin flushing.

When magnesium levels are too low: Hypomagnesemia is often associated with alcoholism. Chronic diarrhea, burns, polyuria (excessive urination) and hypercalcemia can cause magnesium levels to fall. Patients may experience generalized weakness, muscle tremors, tetany parathesia and heart palpitations.

Electrolyte disorders: 4 Take home points
Differentiating electrolyte disturbances can be difficult in the field, with many overlapping signs and symptoms. Here are a couple of key points for patient assessment and treatment:

1. Of the different disorders, hyperkalemia is the most significant one to be aware of. Patients with kidney disease, especially those requiring dialysis are at significant risk for hyperkalemia.
2. Suspect an electrolyte disorder if the patient has had a period of prolonged nausea, vomiting and or diarrhea. Suspicions should rise if there is a history of renal disease.
3. Unexplained weakness, muscle spasms and numbness or tingling may point to an electrolyte disturbance.
4. An electrolyte imbalance may be the underlying cause in patients with altered mental status or reduced level of consciousness.

Finally, it is not the field provider's primary responsibility to identify the specific electrolyte disturbance. However, by paying attention to the history of the illness and some of the more subtle signs and symptoms, EMS providers can provide a more detailed report to emergency department personnel, alerting them to the possibility of an electrolyte imbalance emergency. Perhaps more importantly, recognizing that a severe electrolyte imbalance may exist can better prepare you to respond quickly if the patient suddenly takes a turn for the worse while in your care.

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