An elderly diabetic woman with chronic steroid-dependent bronchospasm has an ileocolectomy for a perforated cecum. She is taken to the ICU intubated and is maintained on broad-spectrum antibiotics, renal dose dopamine, and a rapid steroid taper. On postoperative day 2, she develops a fever of 39.2degC (102.5degF), hypotension, lethargy, and laboratory values remarkable for hypoglycemia and hyperkalemia. Which of the following is the most likely explanation for her deterioration?