Mrs. G. had iatrogenic digoxin toxicity.

When Mrs. G. presented in congestive heart failure with chronic atrial fibrillation, the dose of furosemide was increased, and the dyspnea improved. Then she got 1.25 mg of digoxin within 24 hours. It's likely that the nausea and other symptoms were due to toxicity to this medication.

Further doses were stopped and a trough digoxin level showed the concentration was markedly elevated -- 5.6 ng/mL. Even though she hadn't developed junctional rhythm, she was treated with digoxin-specific antibody Fab fragment (Digibind), and luckily her symptoms improved within a few hours.

The dose prescribed was higher than required, based on Mrs. G.'s renal function and age -- a reduction of at least 50% would have been warranted. This case highlights the importance of appropriate dosing of medications, especially with a narrow therapeutic index and drugs that are excreted by the kidneys. Older age should always be taken into consideration.

There's also another teaching point here, and that's the importance of non-pharmacologic therapy -- especially dietary education. The patient should have been informed about a low potassium diet, and this should have been reinforced at periodic visits to check for adherence. Instead, the medications that likely were helpful for her underlying heart failure, i.e. enalapril and spironolactone, were stopped and NOT resumed after correction of hyperkalemia, even though she was tolerating them well for over 3 years.

It's essential to resume cardiac medications that have been tolerated by the patient and that appear to be beneficial at keeping the individual stable. Of course, these should be restarted one at a time, with careful monitoring of electrolytes and renal function, all the while reinforcing dietary modifications to control the serum potassium. The discontinuation of these drugs and not resuming them later likely resulted in her present condition -- and that, by definition, is also iatrogenic in origin.