CRNI Fluid and Electrolyte Balance Questions and Answers — Questions and Answers
Question 1: A patient is admitted with severe dehydration secondary to gastroenteritis. The physician orders an intravenous solution to correct the fluid volume deficit. Which type of IV fluid is most appropriate for initial fluid resuscitation in this patient?
- 0.45% Sodium Chloride (1/2 NS)
- Dextrose 5% in Water (D5W)
- 3% Sodium Chloride
- 0.9% Sodium Chloride (Normal Saline) (Correct answer)
Correct answer: 0.9% Sodium Chloride (Normal Saline)
0.9% Sodium Chloride, also known as Normal Saline, is an isotonic solution, meaning it has the same concentration of solutes as blood plasma. This makes it the ideal choice for initial fluid resuscitation in cases of dehydration because it expands the extracellular fluid volume without causing a significant shift of fluid into or out of the cells. Hypotonic solutions like 0.45% NaCl would cause fluid to move into the cells, which is not the primary goal in correcting a fluid volume deficit. D5W is initially isotonic but becomes hypotonic as the dextrose is metabolized, and hypertonic solutions like 3% NaCl are reserved for severe, symptomatic hyponatremia.
Question 2: A CRNI is assessing a patient with a serum calcium level of 7.2 mg/dL. Which of the following physical examination findings would be most consistent with this laboratory value?
- Depressed deep tendon reflexes
- Positive Chvostek's sign (Correct answer)
- Peaked T waves on ECG
- Muscle flaccidity
Correct answer: Positive Chvostek's sign
A serum calcium level of 7.2 mg/dL indicates hypocalcemia. Hypocalcemia increases neuromuscular excitability. A positive Chvostek's sign, which is the twitching of facial muscles in response to tapping over the facial nerve, is a classic sign of this increased excitability. Depressed reflexes and muscle flaccidity are associated with hypercalcemia, while peaked T waves are characteristic of hyperkalemia.
Question 3: A post-operative patient who received large doses of opioid analgesia is noted to have a respiratory rate of 8 breaths per minute, is difficult to arouse, and has a PaCO2 of 55 mm Hg. The CRNI should recognize these findings as indicative of which acid-base imbalance?
- Metabolic Acidosis
- Respiratory Alkalosis
- Respiratory Acidosis (Correct answer)
- Metabolic Alkalosis
Correct answer: Respiratory Acidosis
The patient is demonstrating hypoventilation (RR of 8) likely due to the central nervous system depressant effects of opioids. Hypoventilation leads to the retention of carbon dioxide (evidenced by the high PaCO2 of 55 mm Hg). An excess of dissolved CO2 in the blood results in an increased concentration of hydrogen ions, causing the pH to drop and leading to respiratory acidosis.
Question 4: When developing a plan of care for a patient with a serum sodium level of 125 mEq/L and signs of euvolemic hyponatremia, which intervention is the priority for the CRNI to include?
- Administering intravenous 0.9% NaCl at a rapid rate.
- Encouraging a diet high in sodium-rich foods.
- Preparing for the administration of intravenous insulin.
- Implementing a fluid restriction of 1 L per day. (Correct answer)
Correct answer: Implementing a fluid restriction of 1 L per day.
For euvolemic hyponatremia, the primary issue is an excess of total body water relative to sodium. Therefore, the cornerstone of management is restricting free water intake to allow the kidneys to excrete excess water and the serum sodium to rise gradually. Administering isotonic saline may not be effective and could worsen the condition if the underlying cause is SIADH. A high-sodium diet may be helpful but is not the priority intervention. Insulin is used to treat hyperkalemia, not hyponatremia.
Question 5: A patient with end-stage renal disease has a serum potassium level of 6.8 mEq/L. Which of the following ECG changes should the CRNI anticipate and report immediately?
- Prominent U wave
- Shortened PR interval
- Tall, peaked T waves (Correct answer)
- Depressed ST segment
Correct answer: Tall, peaked T waves
Hyperkalemia, a serum potassium level above 5.0-5.5 mEq/L, alters cardiac membrane potential, leading to characteristic ECG changes. One of the earliest and most common findings is the appearance of tall, peaked T waves, especially as the level rises above 6.5 mEq/L. As hyperkalemia worsens, the PR interval becomes prolonged and the QRS complex widens. Prominent U waves and ST depression are associated with hypokalemia.
Question 6: A CRNI is caring for a patient receiving a continuous infusion of 3% Sodium Chloride for severe, symptomatic hyponatremia. Which assessment finding requires immediate intervention by the nurse?
- A gradual increase in serum sodium from 115 to 118 mEq/L over 6 hours.
- Patient report of a mild headache.
- Urine output of 40 mL/hour.
- New onset of confusion and signs of fluid overload. (Correct answer)
Correct answer: New onset of confusion and signs of fluid overload.
Rapid correction of chronic hyponatremia with hypertonic saline can lead to osmotic demyelination syndrome (ODS), a severe neurological complication. The development of new neurological symptoms like confusion, coupled with signs of fluid overload (e.g., crackles in the lungs, edema), indicates that the correction may be too rapid or the patient is experiencing fluid volume excess. This is a critical situation requiring immediate cessation or slowing of the infusion and notification of the provider. A gradual increase in sodium within safe limits is the therapeutic goal. A mild headache and adequate urine output are less immediately concerning.
CRNI Fluid and Electrolyte Balance Questions and Answers
A patient is admitted with severe dehydration secondary to gastroenteritis.
The physician orders an intravenous solution to correct the fluid volume deficit.
Which type of IV fluid is most appropriate for initial fluid resuscitation in this patient?