A 79-year-old man is brought to the hospital due to confusion for the past 2 days. The patient has had nausea, decreased appetite, and poor oral intake for several weeks. He has also mentioned that everything around him has "a yellow tint." He has no abdominal pain. Medical history includes long-standing heart failure with reduced ejection fraction and atrial fibrillation. Medications include metoprolol, digoxin, lisinopril, and apixaban. The patient is afebrile. Blood pressure is 130/80 mm Hg and pulse is 58/min. The abdomen is soft and nontender; there is no rigidity or rebound and no masses are present. Age-related changes in which of the following factors most likely accounts for this patient's symptoms?

Question

A 79-year-old man is brought to the hospital due to confusion for the past 2 days.  The patient has had nausea, decreased appetite, and poor oral intake for several weeks.  He has also mentioned that everything around him has "a yellow tint."  He has no abdominal pain.  Medical history includes long-standing heart failure with reduced ejection fraction and atrial fibrillation.  Medications include metoprolol, digoxin, lisinopril, and apixaban.  The patient is afebrile.  Blood pressure is 130/80 mm Hg and pulse is 58/min.  The abdomen is soft and nontender; there is no rigidity or rebound and no masses are present.  Age-related changes in which of the following factors most likely accounts for this patient's symptoms?

Quizplus · Accepted Answer

11ec160b_3b73_8360_9249_77c4bb89f5e5_MD0001_00 Digoxin is a cardiac glycoside that can be used to treat atrial fibrillation and systolic heart failure. This patient is experiencing symptoms classically associated with digoxin toxicity, which include visual changes (particularly yellow tinting of objects) and gastrointestinal disturbances. Digoxin is renally cleared and has a narrow therapeutic window, so toxicity frequently results from alterations in kidney function. As patients age, renal function decreases progressively. This decrease in renal function is often not accompanied by a concomitant rise in serum creatinine, as creatinine is derived from muscle tissue and lean body mass also decreases with age. Therefore, elderly patients (even those with a normal serum creatinine) should receive reduced doses of renally cleared medications to prevent toxicity. (Choice A) Intestinal absorption affects the dose of digoxin that reaches the bloodstream. Some preparations of digoxin may have a higher bioavailability than others, and some patients may carry gut bacteria that degrade digoxin before it has the ability to cross into the bloodstream. (Choice B) Liver enzyme activity plays a small role in the elimination of digoxin, as this agent is primarily excreted unchanged by the kidney. (Choice C) This patient's lean muscle mass is important to consider when dosing digoxin based on weight, as this serves as the primary site where digoxin is stored in the body. Lean body mass does tend to decrease in an age-related manner, but age-related renal insufficiency is more directly related to toxicity of digoxin in the elderly. (Choice D) Plasma protein binding of digoxin is not as significant as renal clearance when considering toxicity. Typically less than one-third of the digoxin that gains access to the bloodstream will be protein-bound; the remainder of the dose circulates unbound. Educational objective: Digoxin is a cardiac glycoside that is predominantly cleared by the kidneys. Elderly patients typically exhibit age-related renal insufficiency, even in the presence of normal creatinine levels. The dose of digoxin must be reduced in these patients to prevent toxicity. __________ References: Digoxin: clinical highlights: a review of digoxin and its use in contemporary medicine. (http://www.ncbi.nlm.nih.gov/pubmed/21988950)

A 79-Year-Old Man Is Brought to the Hospital Due to Confusion