Margaret Lewis, a 74-year-old patient with chronic heart fai…

Mаrgаret Lewis, а 74-year-оld patient with chrоnic heart failure, is admitted fоr increasing fatigue and weakness. Her home medications include: Digoxin 0.125 mg PO daily Furosemide 40 mg PO twice daily Lisinopril 10 mg PO daily During morning assessment, Margaret tells the nurse: “I haven't felt like eating for the last couple of days. This morning I started feeling nauseated, and I threw up twice. Everything also looks a little blurry and yellow to me.” Assessment findings: HR: 52 beats/min, irregular BP: 98/60 mmHg RR: 18 breaths/min SpO₂: 95% on room air Mild bilateral ankle edema Urine output: adequate Patient appears fatigued and mildly confused Morning laboratory results: Potassium: 2.9 mEq/L BUN: 32 mg/dL Creatinine: 1.7 mg/dL Previous creatinine: 1.0 mg/dL Which finding should cause the nurse the greatest concern before administering the patient's scheduled digoxin?