Question

Mr FG is a 69-year-old retired school teacher who was admitted to the emergencydepartment complaining of severe chest pain after climbing stairs at hisdaughter’s house. In the ambulance he is administered aspirin 300 mg. Onarrival at hospital and subsequent examination and review by the admittingdoctor the following information is obtained.

Previous medical history

Hypertension (10 years). Type 2 diabetes mellitus (recently diagnosed, currentlydiet controlled). The patient is a regular cigarette smoker (>40 per day) anddrinks approximately 10 units of alcohol per week. He has osteoarthritis of theknee.

Family history

Father died following a myocardial infarction at 60 years of age. No maternal

history of cardiovascular disease.

Drug history

Allergies: Trimethoprim. Mr FG has been taking diclofenac MR tablets 75 mg

(twice daily) and nifedipine (Adalat Retard) MR tablets 20 mg (twice daily). Both

were stopped on admission.

Signs and symptoms on examination

▪ Temperature 36.4°C

▪ Blood pressure 160/80 mmHg

▪ Heart rate 75 b/m, regular

▪ Respiratory rate 15 breaths per minute

▪ No basal crackles in the lungs.

▪ An ECG taken immediately on arrival reveals ST elevation of 3 mm in the inferior

▪ leads.

Diagnosis

A preliminary diagnosis of myocardial infarction is made.

Relevant test results

Full blood counts, liver function tests, electrolytes and renal function, CXR,total cholesterol, full blood count and blood glucose were taken at admission.

The following tests taken at admission are reported:

Na+ 134 mmol/L (135–145 mmol/L)

K+ 4.3 mmol/L (3.5–4.0 mmol/L)

Urea 5.2 mmol/L (0–7.5 mmol/L)

Creatinine 81 micromol/L (35–125 micromol/L)

Total cholesterol 5.9 mmol/L (<4 mmol/L)

Blood glucose 4.4 mmol/L (4–10 mmol/L)

Initial treatment

About 45 minutes after the onset of chest pain the patient received the following

treatment in the emergency department:

▪ Heparin 5000 units stat

▪ Reteplase 10 units i.v. bolus followed by a further 10 unit i.v. bolus after 30minutes

▪ Diamorphine 2.5 mg IV stat

▪ Metoclopramide 10 mg stat.

▪ A sliding scale insulin infusion of Actrapid 50 units made up to 50 mL with

sodium chloride 0.9% was initiated and titrated against blood glucose.

The patient is subsequently transferred 2 hours later to the coronary care unit as he is pain-free. As the ward cli

nical pharmacist, you are responsible for dailyreview of drug charts and advice to medical and nursing staff on all aspects ofdrug treatment for patients on the ward.

6. What effect may occur if this client has decreased renal function and the physician order to give him digoxin? What actions could be taken to minimize this effect?

Answer 1

DIGOXIN TOXICITY

Digoxin is a cardiac glycoside which has positive inotropic activity characterized by an increase in the force of myocardial infarction . It also reduces the conductivity of the heart through the atrioventricular ( AV ) node.It is indicated in CHF ( Congestive heart failure ) , atrial fibrillation etc .

Digoxin is primarily eliminated by the kidney . Patients with renal impairement may be at increased risk for digoxin toxicity , including ventricular arrhythmias and AV conduction disturbances , due to decreased drug clearance . Therapy with digoxin should be administered cautiously in patients with impaired renal function . Dosage adjusments should be made according to product package labeling and patient attributes such as age , body weight , and other concomitant disease states and medication usage .Dosage increments should be made very gradually , since the elimination half - life may be prlonged in these patients and a longer period of time is required to establish steady - state serum concentrations than normal . These patients should be monitored closely for manifestations of toxicity , and dosage further adjusted as necessary .

Signs of digoxin toxicity ;

• Gastrointestinal disturbances ( nausea , vomiting , constipation , diarrhoea , anorexia ) .
• Visual disturbances ( blurred vision or a yellow halo ) .
• CNS disturbances ( confusion , weakness , dizziness , apathy , fatigue , malaise , headache , depression and even psychosis ) .
• Cardiac ( irregular heart beat , ventricular tachycardia , ventricular fibrillation ) .

Management of digoxin toxicity ;

• Breathing assistance

The first priority in treatment is ensuring the patient has an adequate airway and breathing . If the patient has breathing difficulty intubate and ventillate the patient .

• Activated charcoal ; Activated charcoal may be used if it can be given within 2 hours of the person taking the medication .
• Atropine ; It may be used if the heartrate is slow while magnesium sulphate may be used in those with premature ventricular contractions .
• Antidote ( Digoxin immune fab or digibind ) ; In case of severe digoxin intoxication antidote digibind is available . It binds and inactivates digoxin . Its use is recommended in those who have a serious dysrhythmia , are in cardiac arrest , or have a pottasium of greater than 5 mmol/ L . Low blood potassium or magnesium should also be corrected . Cardiac glycoside - induced hyperkalemia should be treated with digoxin specific fab fragments . These antibodies will effectively reduce the hyperkalemia due to cardiac glycosides .Patients with underlying renal dysfunction who are hyperkalemic from their underlying renal failure , however may need traditional treatments for hyperkalemia .
• Hemodialysis ; If the condition is extreme , hemodialysis ( blood filtering ) can be done . This will remove digitalis from the blood .

NURSING CONSIDERATIONS ;

Assessment

• Assess any allergy to digitalis preparations
• Monitor apical pulse for 1 minute before administering ; hold dose if pulse rate less than 60 in adult ; recheck pulse in 1 hour . If pulse rate remains less than 60 hold drug and notify physician .
• Check dosage and preparation carefully .
• Avoid IM injections , which may be very painful.
• Follow diluting instructions carefully , and use diluted solution promptly .
• Avoid giving with meals ; this will delay absorption .
• Have emergency equipment ready ; have potassium salts , lidocaine , phenytoin , atropine , and cardiac monitor .
• Monitor for therapeutic drug levels ; 0.5 - 2 ng/ml . The toxic level is greater than 2.4 ng/mL .