Question

QUESTION 8 BACKGROUND:
Mrs Yin, a 75-year-old female, who normally enjoys good health. She has been treated with digoxin for atrial fibrillation for the past 10 years and maintains an independent and socially active life. For the past 5 days she had been feeling unwell and had vomited frequently in the last 24 hours. On the morning preceding her hospital admission, Mrs Yin had called the retirement village nurse who visited her immediately and ascertained that she was feeling nauseous and had lost her appetite. She also noted that Mrs Yin was a little confused and agitated. The nurse took her pulse and had been immediately concerned about the bigeminal rhythm. Mrs Yin was subsequently taken to hospital where a venous blood sample was drawn for electrolyte analysis and digoxin plasma drug concentration.

QUESTIONS:

1. What is the most likely explanation for Mrs Yin’s gastrointestinal and CNS symptoms? (1 mark)

2. Discuss the mechanism of action of digoxin ; and what is expected to occur to the cardiovascular system at therapeutic plasma concentrations.

3. Explain what can occur to the cardiovascular system at higher than therapeutic and toxic concentrations of digoxin and why she has developed a bigeminal rhythm?

Answer 1

1 over dose of digoxin or digoxin toxicity causes the nausea ,vomiting, anorexia and also neurological symptoms. It can also cause trigger fatal arrhythmias.

2. Mechanism of action .

Digoxin inhibits yhe Na -K -ATPase membrane pump ,resulting in an increase in intracellular sodium and calcium Concentrations. Increased intracellular concentration of calcium may promote activation of contractile proteins. Digoxin act on the electrical activity of the heart,increasing the slope of phase4 depolarization, shortening the action potential duration ,and decreasing the maximal diastolic potential.

Serum digoxin concentration is .5to. 1.0 ng per ml.Digoxin is used only as a second line therapy for controlling the heart rates of patients with atrial fibrillation associated with heart failure.

3. Digoxin is commonly used for the treatment of atrial fibrillation ,especially with co- existing congestive heart failure.

Digoxin toxicity can cause hyperkalemia or life threatening dysarhythmias .if potassium is higher than 5 mEq/ml and any ECG changes of Av blocks, bradycardia, or ventricular dysrhythmias needs to monitor .Also check the signs of end organ hypo perfusion.cardiac arrhythmias are the common cause of death in digoxin toxicity.

Because of the narrow therapeutic index of digoxin ,patients can be digoxin toxic with therapeutic digoxin concentration.

Bigeminal rhythm or premature ventricular contraction. This is the beat that comes early after every routine beat.This happened because of hyperkalemia from the digoxin toxicity.