Correct Answer: B

Rationale: In elderly patients, the clinical manifestations of fluid and electrolyte disturbances may be subtle or atypical. For example, fluid deficit may cause confusion or cognitive impairment in the elderly person.

Correct Answer: D

Rationale: The symptoms of hypokalemia include GI, cardiac, renal, respiratory, and neurologic disturbances. The use of potassium-wasting diuretics, such as hydrochlorothiazide, without potassium replacement therapy is a primary cause of hypokalemia.

Correct Answer: B

Rationale: Osmosis is the movement of fluid from a region of low solute concentration to a region of high solute concentration across a semipermeable membrane. The number of dissolved particles contained in a unit of fluid determines the osmolality of a solution, which influences the movement of fluid between the fluid compartments. Giving a patient who has a low blood pressure a hypertonic solution will increase the number of dissolved particles in the blood, creating pressure for fluids in the tissues to shift into the capillaries and increase the blood volume. Option A is incorrect; hydrostatic pressure refers to changes in water or volume related to water pressure. Option C is incorrect; diffusion is the movement of solutes from an area of greater concentration to lesser concentration. The solutes in an intact vascular system are unable to move, so diffusion should not normally take place. Option D is incorrect; active transport is the movement of molecules against the concentration gradient and requires ATP as an energy source. This process typically takes place at the cellular level and is not involved in vascular volume changes.

Correct Answer: D

Rationale: A low pH indicates acidosis (normal pH is 7.35 to 7.45). The PaCO3 is also low, which causes alkalosis. The bicarb is low, which causes acidosis. The pH bicarb more closely corresponds with a decrease in pH, making the metabolic component the primary problem.

Correct Answer: D

Rationale: Third-spacing fluid shift, which occurs when fluid moves out of the intravascular space but not into the intracellular space, can cause hypovolemia.