A client with diabetic ketoacidosis (DKA) is receiving an IV infusion of 0.9% sodium chloride and insulin.
Two hours later, the client’s serum laboratory results show a decrease in the serum blood glucose from 580 to 430 mg/dL (32.2 to 23.86 mmol/L). What additional laboratory result is most important for the nurse to monitor?

Choice A rationale
Administering IV fluids is a potential nursing intervention for several body systems. For example, the circulatory system may require IV fluids to maintain blood volume and pressure. The renal system may need IV fluids to ensure adequate urine output. The digestive system might need IV fluids to compensate for losses from vomiting or diarrhea.
Choice B rationale
Assessing a rash is a potential nursing intervention for the integumentary system. Rashes can be a sign of many different conditions, including allergic reactions, infections, autoimmune diseases, and more. By assessing the rash, the nurse can gather information to help determine its cause and appropriate treatment.
Choice C rationale
Administering an antihistamine is a potential nursing intervention for the immune system. Antihistamines are often used to treat allergic reactions, which involve the immune system.

They can also be used to treat symptoms of the common cold, which is caused by a viral infection.
Choice D rationale
Administering a steroid is a potential nursing intervention for several body systems. Steroids can be used to reduce inflammation, which can benefit the musculoskeletal, integumentary, respiratory, and other systems. They can also be used to treat certain endocrine disorders.

Clinical Rationale

Choice B (Correct): To ensure a proper seal and maintain the prescribed $FiO_2$, the mask must be secured over the bridge of the nose first, then pulled down to cover the mouth and chin. A snug fit prevents oxygen from leaking toward the eyes, which can cause irritation, and ensures the client receives the full benefit of the oxygen therapy.

Choice A (Incorrect): Simple face masks used in acute care are generally disposable, single-patient-use items. Cleaning them with soap and water is not standard practice and could introduce contaminants or moisture that compromises the equipment.

Choice C (Incorrect): A client with an oxygen saturation of 89% is hypoxic and requires continuous supplemental oxygen. Taking frequent "breaks" would cause the saturation to drop further, potentially leading to respiratory distress or cardiac strain.

Choice D (Incorrect): For an oxygen mask to be effective, it must cover both the nose and the mouth. Leaving the nose exposed allows the client to inhale room air (21% oxygen), which dilutes the supplemental oxygen and fails to reach the desired therapeutic level.

Choice E (Incorrect): Oxygen is a medication that requires a provider's order. While a nurse may titrate oxygen based on specific standing orders (e.g., "titrate to keep $SpO_2$ > 92%"), a nurse cannot unilaterally "adjust" levels without a protocol or direct order in place.