A patient with type 1 Diabetes Mellitus is admitted to the medical unit with an acute exacerbation of chronic obstructive pulmonary disease. He is placed on IV piggyback antibiotics, nebulizer treatments with albuterol, and an IV corticosteroid, and he is also taking a proton pump inhibitor for gastroesophageal reflux disease. He takes a dose of glargine insulin every evening. This evening the nurse notes that his blood glucose level is 170 mg/dL. The next morning, his fasting glucose level is 202 mg/dL. What is the most likely cause of his elevated glucose levels?

Choice A rationale Albuterol, a short-acting beta-2 adrenergic agonist, can cause a transient increase in blood glucose levels by stimulating glycogenolysis in the liver and muscles. This effect is dose-dependent and typically short-lived. However, the continuous and sustained elevation from 170 to 202 mg/dL is more characteristic of a medication with a longer-acting metabolic effect. While possible, it is not the most likely cause. Choice B rationale Corticosteroids, such as prednisone or methylprednisolone, significantly increase blood glucose by promoting gluconeogenesis and inhibiting glucose uptake by peripheral tissues, leading to insulin resistance. This effect is prolonged and dose-dependent, making it a very common cause of hyperglycemia in patients, especially those with pre-existing conditions like Type 1 Diabetes Mellitus, who are already susceptible to glucose dysregulation. Choice C rationale Antibiotics, in general, are not known to directly cause a sustained increase in blood glucose levels. Some antibiotics like fluoroquinolones can affect glucose metabolism, but they are more commonly associated with hypoglycemia, although hyperglycemia can also occur. The effect is not as pronounced or as likely as that of corticosteroids in this clinical scenario. Choice D rationale Proton pump inhibitors (PPIs) work by inhibiting the H+/K+ ATPase pump in gastric parietal cells, reducing stomach acid production. There is no established direct physiological mechanism by which PPIs cause a sustained increase in blood glucose levels. Their primary effect is on the gastrointestinal system, and they do not significantly impact carbohydrate metabolism in the way that corticosteroids do.