Patient Applications
Samantha’s story doesn’t end here. While walking down the street, Samantha is approached and offered an Amazon gift card to receive an infusion of Normal Saline-286 mOsm/L NaCl. Describe the changes to the following: ECF volume, ECF osmolality, ICF volume, ICF osmolality.
increase, no change, no change, no change
This term describes the concentration of solute particles per liter of solution.
Osmolality
5% Dextrose in 0.9% saline is an example of what type of solution?
Hypotonic Solution
What are the clinical signs and symptoms of mild hyponatremia?
headache, generalized weakness, fatigue, nausea, and lightheadedness
What is the first step in a physical exam?
Vital signs
As a competitive eater for MLE (Major League Eating), Samantha tours the world engaging in food and beverage contests. Today, she is attempting to chug as much water as possible. Describe the changes to the following: ECF volume, ECF osmolality, ICF volume, ICF osmolality.
increases, decreases, increases, decreases
What is the plasma volume of someone who weighs 85 kg.
TBW = 85 x 0.6 = 51 L; ECF 51 x 0.2 = 10.2 L; Plasma Volume = 10.2 x 0.25 = 2.55 L
Why is 3% saline preferred over normal saline in treating severe hyponatremia?
Raises sodium faster than normal saline would
What are the clinical signs and symptoms of severe hyponatremia?
altered mental status, vomiting, collapse, or seizures
What are the components of a H&P?
Past medical history, surgical history, family history, allergies and medications, subjective symptoms (ROS), and the physical exam
As a prize for winning the water-chugging competition, Samantha is awarded an all-inclusive vacation at a Tahitian resort. Unfortunately, her ship sunk and she was marooned on a different island in the South Pacific. She begins consuming large quantities of seawater to avoid dehydration. Describe the changes to the following: ECF volume, ECF osmolality, ICF volume, ICF osmolality.
increases, increases, decreases, increases
How can overhydration lead to exercise-associated hyponatremia (EAH)?
water is hypotonic so it is diluting the ECF, ECF volume increases, ECF osmolality decreases, water flows into the cells, ICF volume increases, ICF osmolality decreases
How does the administration of hypertonic saline correct hyponatremia at the cellular level?
ECF volume increases, ECF Osmolality increases, water flows from low osmolality to high osmolality, ICF volume decreases, ICF osmolality increases
What would happen if Samantha received normal saline instead of 3% saline?
her sodium would correct much slower, would not correct fast enough
What lab test would you order for Samantha?
Basic Metabolic Panel
Thankfully Samantha is rescued a few days later. As an apology for the unfortunate incident, the MLE has gifted her a relaxing trip to Mexico. When she arrives she orders a margarita and tap water. A few hours later she begins experiencing severe diarrhea. It continued for a few days and she is now also vomiting. Samantha is bedridden. She is nauseous and has little desire for food or water. Describe the changes to the following: ECF volume, ECF osmolality, ICF volume, ICF osmolality.
decreased, increasing, decreasing, increasing
In the case of Aldosterone deficiency, what type of volume contraction occurs, and what is the tonicity of the fluid lost compared to the ECF?
hyposmotic volume contraction/depletion, loss of hypertonic fluid compared to the ECF → aldosterone promotes reabsorption of Na+ in the kidneys, when absent there is a loss of Na+ and water but Na+ loss is greater (fluid is hypertonic to the ECF), ECF osmolality decreases
What are the potential complications of untreated severe hyponatremia?
Rhabdomyolysis (life threatening muscle breakdown), altered mental status, seizures, coma, in extreme cases death
What is the body's natural reaction to a decreased ECF volume?
Renin-Angiotensin-Aldosterone System (RAAS)
What are the components of the BMP?
Sodium, Potassium, Chloride, Bicarb, BUN, Creatine, Glucose
Samantha’s flight home is not ideal. She is stuck in the middle seat, between two morbidly obese sisters, who also happen to be reality television stars. The plane’s air conditioning is broken and it is an unseasonably hot summer day. She starts sweating profusely. Luckily, the stewardess provides several Dr. Pepper’s for her enjoyment. Explain which organ and brain structure are releasing Aldosterone and ADH, as well as what these hormones do.
Sweating and drinking soda (a diuretic) decrease ECF volume. The extracellular fluid becomes a hypertonic solution, which we define as dehydration. To correct this, Samantha’s adrenal glands release aldosterone to stimulate sodium reuptake, while her posterior pituitary gland will release ADH to stimulate water uptake.
What is the difference between hypovolemia and dehydration?
Dehydration - only losing water, free water loss, water would need to leave ICF to balance ECF osmolality; Hypovolemia - isotonic fluid loss mostly from ECF (no net water movement)
This condition can occur if hyponatremia is corrected too rapidly, leading to damage in the brain.
Osmotic demyelination syndrome (central pontine myelinolysis)?
What would happen to Samantha if D5W was given instead of 3% saline?
ECF volume would increase, ECF osmolality would decrease, causing more water to flow into the cells, ICF volume would increase, ICF osmolality would decrease. Influx of water into brain cells would lead to swelling of the brain (cerebral edema) → confusion, seizures, induced coma
The normal range for this electrolyte in the BMP is typically 135-145 mEq/L.
Sodium