Tonicity & Cellular Shifts
What type of fluid shift occurs when a hypotonic solution (like 0.45% Normal Saline) is infused into the intravascular space?
Fluid shifts out of the blood vessels and into the intracellular space, causing the cells to swell.
What is the absolute safety rule that a nurse must always obey regarding the speed and method of administering Intravenous Potassium Chloride (KCl)?
Never give potassium IV push (bolus); it must always be diluted and infused slowly via an electronic infusion pump.
Because sodium dictates serum osmolality, a nurse assessing a patient with severe hypernatremia or hyponatremia must prioritize monitoring which body system?
The Central Nervous System (Neurological system).
A nurse elicits a twitch of the facial muscles by tapping on the patient's facial nerve. What is the name of this sign, and what electrolyte imbalance does it indicate?
Chvostek's sign; it indicates hypocalcemia (or hypomagnesemia).
What direct cellular effect does a hypertonic solution (like 3% Sodium Chloride) have on human cells, and what is a primary clinical indication for its use?
It draws fluid out of the cells, causing them to shrink (crenate); it is primarily used to treat severe, symptomatic hyponatremia or cerebral edema.
A nurse notes a patient's serum potassium level is 6.5 mEq/L. What classic, sequential changes will the nurse observe on the patient's ECG monitor?
Tall, peaked T-waves, a prolonged PR interval, widening of the QRS complex, and a flat P-wave.
What hormonal mechanisms trigger the body to retain sodium and water when blood pressure drops?
Activation of the Renin-Angiotensin-Aldosterone System (RAAS) and the release of Aldosterone.
While inflating a blood pressure cuff on a patient's arm, the nurse notes carpal spasms (the wrist and fingers flex inward). What is this sign called, and what does it signify?
Trousseau's sign; it signifies hypocalcemia (or hypomagnesemia).
Question: Why is 5% Dextrose in Water (D5W) considered isotonic in the bag but hypotonic in the body?
Once infused, the body rapidly metabolizes the dextrose, leaving behind pure, free water.
What are three common clinical manifestations a nurse should look for in a patient suffering from hypokalemia (Potassium < 3.5 mEq/L)?
Muscle weakness/cramps, cardiac dysrhythmias (U-waves), and decreased bowel sounds/paralytic ileus.
What dangerous neurological condition can occur if a nurse corrects a patient's chronic hyponatremia too quickly with hypertonic saline?
Central Pontine Myelinolysis (also known as Osmotic Demyelination Syndrome).
What medication is considered the antidote for a patient experiencing dangerous toxicity from an intravenous Magnesium Sulfate infusion?
Calcium Gluconate.
Which fluid is the crystalloid of choice for acute fluid resuscitation (e.g., severe hemorrhage or hypovolemic shock), and why?
0.9% Normal Saline (or Lactated Ringer's); because they are isotonic and expand only the extracellular/intravascular volume without causing cellular shifts.
While infusing peripheral IV Potassium Chloride, the patient complains of a severe burning sensation at the site. What action should the nurse take?
Assess the site for infiltration/phlebitis, and if intact, slow the infusion rate or ask the provider to dilute the solution further.
A patient with fluid volume overload develops dilutional hyponatremia. What is the primary, non-pharmacological nursing intervention for this condition?
Strict fluid restriction.
A patient with severe preeclampsia is receiving IV Magnesium Sulfate. Which three critical nursing assessments must be performed frequently to monitor for toxicity?
Deep tendon reflexes (DTRs), respiratory rate, and hourly urine output.
A nurse is administering Lactated Ringer's (LR) to a patient. In which two specific patient populations is LR generally contraindicated due to its composition?
Patients with severe liver failure (who cannot metabolize lactate) and patients with hyperkalemia/renal failure (LR contains potassium).
Name three medications commonly administered to a patient with severe hyperkalemia to temporarily protect the heart or shift potassium back into the cells.
Calcium Gluconate (protects the heart), Regular Insulin + D50 (shifts K+ into cells), and Sodium Bicarbonate or Albuterol (shifts K+ into cells).
What are three hallmark signs and symptoms of Hypernatremia caused by severe dehydration?
Extreme thirst, dry/sticky mucous membranes, flushed skin, and altered mental status (agitation/lethargy).
How does hypercalcemia affect a patient's neuromuscular activity and GI tract, and what are two classic symptoms?
It depresses neuromuscular activity; symptoms include muscle weakness, constipation, lethargy, and decreased deep tendon reflexes.