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Digoxin toxicity – don't break my heart

Serum digoxin levels can be used to assist diagnosis, but they do not correlate consistently with the clinical manifestations of toxicity. Patients are at an increased risk of digoxin toxicity when serum digoxin levels rise above 2.6 nmol/L (2 ng/mL). However, toxicity can also occur when serum levels are within the therapeutic range, especially in the presence of certain electrolyte disturbances (eg, hypokalaemia).

There are several risk factors for digoxin toxicity, and serum digoxin levels should be interpreted in conjunction with other clinical markers, such as serum potassium levels and renal and thyroid function tests.

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  Digoxin Toxicity: Van Gogh Vision

Hyperkalemia itself does not cause death. Temporizing measures to lower K levels do not reduce mortality. If fab fragments are given, hyperkalemia corrects itself. On the boards, do not treat hyperkalemia. In practice, we realize these are difficult patients to manage and the K level might return before the digoxin level, prompting the provider to urgently manage an electrolyte issue in the setting of new EKG findings. However, giving potassium-lowering therapy can actually cause hypokalemia if Fab is given as well which is not good either. In fact, hypokalemia exacerbates digoxin toxicity. Be judicious, do the best you can, and please don’t just “throw meds at the patient hoping something sticks”.

  Is calcium safe in hyperkalemic digoxin toxic patients?

Digoxin toxicity can cause almost any dysrhythmia except rapid atrial fibrillation... Chronic digoxin toxicity typically causes hypokalemia. If a chronic digoxin toxic patient is hyperkalemic it is likely due to acute renal failure and those patients giving calcium is likely safe (unlikely to cause ‘stone heart’). Acute digoxin toxicity typically causes hyperkalemia due to blockage of Na-K ATPase. These patients do not need anything to stabilize their cardiac membranes or shift potassium. These patients need DigiFab.

  Simplified Dosing Scheme for DigiFab® in Acute Digoxin Poisoning

Treatment of digoxin toxicity can be quite complex and generally involves the use of digoxin immune Fab (DigiFab®) for symptomatic patients. The dosing of DigiFab can vary depending on the amount ingested, serum concentration, and/or suspected chronicity of toxicity. Alternatively, for an acute ingested of an unknown amount where the serum concentration is not available, it is recommended that 10 vials of DigiFab be administered empirically.

 Unlike most overdoses we are used to, digoxin toxicity is usually unintentional

This is because digoxin (or dig, as we commonly refer to it) has a narrow therapeutic index and its toxicity can be life-threatening. Although it may also exhibit itself more acutely after an an overdose, it more commonly is seen as a chronically creeping digoxin levels, as is often seen in the elderly population.

Articles of Interest

DigiFab (Digibind) Dosing for Digoxin Poisoning

Therapeutic range for serum digoxin level is 0.8–2.0 ng/mL (1.0–2.6 nmol/L). If acute poisoning and serum digoxin confirmed >10 ng/mL, give empiric dose (10-20 vials).

Cardiac glycoside poisoning (including digoxin)

Most cases of digoxin intoxication are chronic and unintentional, due to gradual accumulation of digoxin over time. DSFabs is dosed in vials. Each vial contain 40mg of antibody fragments, which neutralize 0.5 mg of digoxin.

Cardiac Glycosides Overdose

Almost any type of atrial or ventricular dysrhythmia can be seen.

Digoxin monitoring and toxicity management

Sinus arrest, varying degrees of AV with dissociation or escape rhythms may occur, including paroxysmal atrial tachycardia with AV block, junctional tachycardia, frequent ventricular ectopics and bigeminy (alternation between a regular heartbeat and an extra, skipped heartbeat). In serious cases of toxicity, ventricular tachycardia and ventricular fibrillation may occur.

Digoxin Overdose

Digoxin toxicity is of critical importance to recognize. There are many subtleties to its management, which means that the concepts of digoxin toxicity are important to review. This case highlights some key features of chronic digoxin toxicity. In particular...

Digoxin Toxicity

Empiric therapy should be used in life-threatening cases instead of waiting for a serum level. Empiric therapy for acute poisoning: 10-20 vials. Empiric therapy for chronic poisoning: 3-6 vials. One potential side effect of antidigoxin-Fab is hypokalemia, as it will rapidly restore Na+-K+ ATPase activity. Potassium should be repleted in hypokalemia.

Digoxin Toxicity

There is often a reluctance to give the digibind antidote due to cost and underestimating the mortality associated with digoxin toxicity, however it is prudent to administer digibind based on a considered risk assessment and before the life-threatening manifestations of digoxin toxicity develop.

ED Management of Calcium-Channel Blocker, Beta Blocker, and Digoxin Toxicity

“Is there really any harm in administering calcium to the patient with digoxin toxicity?” Despite new evidence showing (potentially) no harm, treat these patients with digoxin-specific antibodies, and avoid the risk of calcium.

Emergency Department Management Of Calcium Channel Blocker, Beta Blocker, And Digoxin Toxicity

While it is relatively uncommon, an overdose of calcium-channel blockers, beta blockers, or digoxin has a significant morbidity and mortality rate, and its management can be complex. Digoxin toxicity can present with an acute overdose or as chronic toxicity while a patient is on therapeutic dosing, which has implications for diagnosis and management.

Management of Digoxin Toxicity

Although the overall prevalence of digoxin toxicity seems to be decreasing, one must think of this toxicity when facing a patient with bradycardia and “something else”. It does not have to be >2 to have toxic effects.

Pathophysiology

Beware drugs that raise plasma digoxin levels: Amiodarone, Ca++ channel blockers, quinine.

Tasty Morsels of EM 126 – #FRCEM Digoxin Toxicity

Traditionally people have talked about avoiding calcium for the hyper K given the mysterious “stone heart syndrome”. This is probably not a big risk and Toxbase agrees saying it’s fine to give the calcium.

The Diagnosis Digoxin Toxicity

Both acute and chronic toxicity can occur with digitalis medications. In acute toxicity, nausea, vomiting, and evidence of cardiotoxicity are prominent. Chronic toxicity can result in malaise, weakness, and nonspecific symptoms, though classic, rare visual disturbances (yellow halos around lights) have been described. Ventricular ectopy from increased automaticity is often the earliest electrocardiographic finding, often manifesting as frequent PVCs (unifocal and multifocal), and can result in bigeminy or trigeminy.

ToxCard: Digoxin Toxicity

Management focuses on ABCs, charcoal in acute ingestions, supportive care, and in some cases, reversal with DSFab.

Resources

UMEM Educational Pearls

Digoxin Toxicity Most common finding on ECG when digoxin toxic: PVCs Most classic ECG in digoxin toxicity: PAT with block Pathognomonic finding (RARE): Bidirectional ventricular tachycardia Easy formula for administration of digoxin specific Fab (Digibind?? or DigiFab?). Remember to round up even if its 2.3 vials, give 3. [(Dig Serum Concentration(ng/mL)) x wt(kg)] / 100 = # vials.

StatPearls

Treatment involves early recognition and the administration of antibodies specifically against digoxin also known as Fab fragments. Digoxin concentration does not necessarily correlate with clinical symptoms of toxicity however digoxin concentrations may be used for calculating the amount of antidote therapy. Although guidelines are unclear, treatment with digoxin immune Fab is also known by the trade name Digibind, is considered first-line therapy for dysrhythmias including AV block and ventricular tachycardia caused by suspected digoxin toxicity.