Symptoms of Digitalis Toxicity

The most commonly reported cardiac signs of toxicity are dysrhythmias, such as ventricular ectopic depolarization, second- and third-degree heart block, junctional tachycardia, atrial tachycardia with block, ventricular tachycardia, sinoatrial block, and sinus arrest. 

---

Quinidine can increase the plasma concentrations of digoxin, which may in turn lead to signs and symptoms of digitalis toxicity. Gastrointestinal, central nervous system (CNS), or cardiac toxicity associated with elevated digoxin concentrations may occur. Quinidine and digoxin can be administered concurrently however, a downward adjustment in the digoxin dose may be required. 

Hyperkalemia may occur as a result of digitalis toxicity. Signs and symptoms of hyperkalemia include diarrhea, paresthesia of extremities, heaviness of legs, decreased BP, cold skin, grayish pallor, hypotension, mental confusion, irritability, flaccid paralysis, tented T waves, widening QRS interval, and ST depression. 

Assess for signs of digitalis toxicity which include anorexia, nausea, vomiting, bradycardia, cardiac dysrhythmias, and visual disturbances. Report symptoms immediately. 

If a patient is over-digitalised, signs of toxicity will occur, which may include loss of appetite, nausea and vomiting, and bradycardia. These symptoms are often used as clinical indicators of toxicity, and a pulse rate of less than 60 bpm is usually considered to be an indication of over-treatment. Note that paroxysmal atrial tachycardia with AV block and junctional tachycardia can also occur as a result of digitalis toxicity. Other symptoms inelude visual disturbances, headache, drowsiness and occasionally diarrhoea. Death may result from cardiac arrhythmias. Patients treated for eardiac arrhythmias can therefore demonstrate arrhythmias when they are both under- as well as over-digitalised. 

Digitalis toxicity can occur even when normal doses are being administered or when the patient has been receiving a maintenance dose Many symptoms of toxicity are similar to tiie symptoms of the heart conditions for which tiie patient is receiving the cardiotonic. This makes careful assessment of the patient by the nurse a critical aspect of care... 

All antiarrhythmic dra are used cautiously in patients with renal or hepatic disease. When renal or hepatic dysfunction is present, a dosage reduction may be necessary. All patients should be observed for renal and hepatic dysfunction. Quinidine and procainamide are used cautiously in patients with CHF. Disopyramide is used cautiously in patients with CHF, myasthenia gravis, or glaucoma, and in men with prostate enlargement. Bretylium is used cautiously in patients with digitalis toxicity because the initial release of norepinephrine with digitalis toxicity may exacerbate arrhythmias and symptoms of toxicity. Verapamil is used cautiously in patients with a history of serious ventricular arrhythmias or CHF. Electrolyte disturbances such as hypokalemia, hyperkalemia, or hypomagnesemia may alter the effects of the antiarrhythmic dru . Electrolytes are monitored frequently and imbalances corrected as soon as possible... 

The prevalence of digitalis intoxication is from 16% to 20%. Color vision disturbances are especially common and may occur before, simultaneously with, or after the onset of cardiac toxicity. Although color vision disturbances are associated with cardiac glycoside toxicity decreased visual acuity without the accompanying classic symptom of xanthopsia is also common. 

Visual symptoms may occur as soon as 1 day after drug administration, but often occur within 2 weeks of initial therapy. Occasionally, ocular toxicity does not appear imtil after several years of treatment. Once the serum level is decreased or digitalis therapy is discontinued, however, visual symptoms quickly subside, usually within several weeks. 

Digitalis can be used to control congestive heart failure, but the dose must be carefully determined and monitored because the therapeutic dose is close to the dose that causes toxicity. The symptoms that result from high body levels of cardiotonic steroids include vomiting, blurred vision and lightheadedness, increased water loss, convulsions, and death. Only a physician can determine the inihal dose and maintenance schedule for an individual to control congestive heart failure and yet avoid the toxic side effects. 

---