CRNI Exam Fluid and Electrolyte Balance 2

Question 1

Which electrolyte is the primary determinant of extracellular fluid osmolality?

Accepted Answer

Sodium

Answer

Sodium is the dominant cation in extracellular fluid and accounts for approximately 90% of extracellular osmolality, making it the principal regulator of ECF volume and tonicity.

Question 2

Antidiuretic hormone (ADH) is released in response to which of the following stimuli?

Accepted Answer

Increased serum osmolality

Answer

ADH is secreted by the posterior pituitary when osmoreceptors detect a rise in plasma osmolality. ADH promotes water reabsorption in the renal collecting ducts to dilute the plasma and restore normal osmolality.

Question 3

A patient has a serum potassium of 2.8 mEq/L. Which clinical finding would the nurse most expect to assess?

Accepted Answer

Muscle weakness and fatigue

Answer

Hypokalemia (serum K⁺ < 3.5 mEq/L) impairs neuromuscular conduction, leading to skeletal muscle weakness and fatigue. Peaked T waves and bradycardia are associated with hyperkalemia, not hypokalemia.

Question 4

Which fluid compartment contains the largest proportion of total body water in an adult?

Accepted Answer

Intracellular fluid

Answer

Intracellular fluid (ICF) accounts for approximately 40% of body weight, or about two-thirds of total body water — far exceeding any other single compartment. Extracellular fluid (interstitial + intravascular) makes up the remaining one-third.

Question 5

Which mechanism describes the movement of water across a semi-permeable membrane from an area of lower solute concentration to an area of higher solute concentration?

Accepted Answer

Osmosis

Answer

Osmosis is the passive movement of water across a semi-permeable membrane down its own concentration gradient — from a region of lower solute (higher water) concentration to higher solute (lower water) concentration — until equilibrium is reached.

CRNI Exam Practice Test

CRNI Exam Practice Test

CRNI Exam Fluid and Electrolyte Balance 2