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Pharmacotherapy is an essential form of treatment in advanced cardiac life support (ACLS). Aimed at increasing cardiac contractility, increasing or decreasing cardiac chronotropy, and treating cardiac arrhythmias (especially ventricular tachycardia), the use and dosage of certain medications is key for ACLS clinicians to understand.
Procainamide is an important player in ACLS and several other medical scenarios. It acts as a sodium channel blocker that is administered intravenously for the treatment of:
To better understand Procainamide and its usage in ACLS, let’s break down the pharmacology, dosage, and side effects.
Procainamide is a Type IA antiarrhythmic according to the Vaughan-Williams (VW) classification system of antiarrhythmics. Originally approved by the FDA in 1950, Procainamide was only popular for a short time before other antiarrhythmic medications took precedence. However, it has since become more widely used to treat specific arrhythmias, particularly stable ventricular tachycardia. It is most often prescribed when other treatment options are not working, providing a backup approach to managing certain arrhythmias.
The drug acts on the sodium channel to block transmission, slowing conduction through the atrioventricular node. In ACLS, procainamide is indicated for the treatment of stable ventricular tachycardia. However, it can also be used in the treatment of AF with RVR including AF caused by WPW. The main side effect of procainamide is hypotension due to decreased inotropy.
As a sodium channel blocker, procainamide blocks the fast sodium channels in cardiac myocytes. This results in decreased firing of the myocyte cells. As a result, cardiac depolarization is slowed through the atrioventricular node and the bundle of His. Therefore, procainamide results in decreased chronotropy of the heart. Procainamide also has the unique property of slowing cardiac conductivity through accessory pathways in the heart as is found in WPW syndrome.
The main use of procainamide in ACLS treatment is for stable ventricular tachycardia, but it can also be used in the treatment of AF with RVR.
Treatment of ventricular tachycardia is crucial to prevent the arrhythmia from degenerating into ventricular fibrillation and subsequent cardiac arrest. In patients with acute coronary syndrome (ACS), premature ventricular contractions (PVCs) should not be treated unless they cause hemodynamic instability. PVCs are commonly seen in patients with ACS and after treatment for acute myocardial infarction with coronary stenting or thrombolytics therapy. PVCs may also be seen in patients with electrolyte abnormalities.
Patients, both those with ACS or other acute medical causes may have non-sustained ventricular tachycardia (NSVT), which is VT that lasts <30 seconds and does not cause hemodynamic instability or other systems (reference). Patients should not receive procainamide or other antiarrhythmic therapy for asymptomatic VT. Procainamide should only be administered for sustained VT.
Procainamide is indicated for the treatment of a wide variety of tachyarrhythmias. For instance, it can be used for the treatment of atrial fibrillation with RVR, atrioventricular node reentry tachycardias, and atrial fibrillation caused by WPW syndrome.
Procainamide can also be used in the treatment of stable monomorphic VT as well as polymorphic VT (other than torsades de pointes, for which magnesium sulfate is the medication of choice). Although Procainamide could be used for the treatment of pulseless VT or VF, its utility is limited by the need for a slow infusion of the medications.
As always, ACLS care should begin with basic life support. Address airway, breathing, and circulation prior to any additional interventions. If a patient is noted to have ventricular tachycardia and is in cardiac arrest, the ACLS provider should immediately defibrillate the patient rather than administering a medication like procainamide.
Procainamide should be used in patients with tachyarrhythmias who are deemed hemodynamically stable. Once the clinician has determined the cardiac rhythm by electrocardiogram, the clinician should begin treatment of the underlying arrhythmia with medication. Here is a dosage chart:
| INDICATION | ROUTE | DOSE | ADMINISTRATION |
|---|---|---|---|
| Atrial fibrillation with rapid ventricular response | Infusion IV or IO | 20-50mg/minute | Administer until arrhythmia suppressed or maximum dose of 17 mg/kg |
| Atrial fibrillation resulting from Wolff-Parkinson-White Syndrome | Infusion IV or IO | 20-50mg/minute | Administer until arrhythmia suppressed or maximum dose of 17 mg/kg |
| Other atrial tachyarrhythmia | Infusion IV or IO | 20-50mg/minute | Administer until arrhythmia suppressed or maximum dose of 17 mg/kg |
| Monomorphic ventricular tachycardia with a pulse | Infusion IV or IO | 20-50 mg/min until arrhythmia suppressed, then maintenance infusion: 1-4 mg/min. Avoid if prolonged QT or CHF | Administer until arrhythmia suppressed or maximum dose of 17 mg/kg |
| Polymorphic ventricular tachycardia with a pulse (not due to torsades de pointes) | Infusion IV or IO | 20-50 mg/min until arrhythmia suppressed, then maintenance infusion: 1-4 mg/min. Avoid if prolonged QT or CHF | Administer until arrhythmia suppressed or maximum dose of 17 mg/kg |
The infusion of procainamide should immediately be discontinued if one of the following four events occurs:
When administering procainamide, patients should have continuous cardiac monitoring and frequent blood pressure monitoring. Additionally, clinicians should avoid administering procainamide (or use it with caution) if the following conditions are present:
The ACLS practitioner must be prepared to stop the procainamide infusion and provide supportive care if the patient experiences side effects.
As procainamide works by slowing conduction through cardiac myocytes via sodium blockade, it can accentuate the effects of beta blockers and calcium channel blockers resulting in profound bradycardia. Procainamide can also interact with other sodium channel blockers and QT prolonging agents.
For a full list of QT prolonging agents, visit this article from U.S. Pharmacist.
There is no specific antidote for procainamide. Luckily, procainamide toxicity is rare when administered in an emergency setting. If any side effects occur such as bradycardia or hypotension, the infusion should be stopped immediately.
Hypotension should be managed with crystalloid fluids and vasopressors medications (such as norepinephrine) as needed. Although procainamide is a sodium channel blocker, there is no role for the administration of intravenous sodium bicarbonate.
Frequently Asked Questions (FAQs)
Q: Why is procainamide administered to patients with tachyarrhythmias?
A: Procainamide blocks sodium changes thereby slowing cardiac conduction through the atrioventricular node and myocytes, reducing heart rate and converting the heart to normal sinus rhythm.
Q: What is the protocol for procainamide?
A: Procainamide should be administered at a rate of 20-50 mg/minute administered as an infusion IV or IO until arrhythmia is suppressed or maximum dose of 17 mg/kg.
The infusion of procainamide should immediately be discontinued if one of the following four events occurs:
Q: How fast can I give IV procainamide?
A: For atrial fibrillation with rapid ventricular response, atrial fibrillation resulting from Wolff-Parkinson-White Syndrome, and other atrial tachyarrhythmias, procainamide should be administered at 20-50 mg/minute as an infusion IV. For monomorphic ventricular tachycardia with a pulse or polymorphic ventricular tachycardia with a pulse (not due to torsades de pointes), administer procainamide at 1-2 grams over 5-60 minutes. See the dosage table above for further details.
Procainamide is a versatile medication that can treat both atrial and ventricular tachyarrhythmia. The main side effects are hypotension, widening of the QRS interval, and prolongation of the QT interval.
While procainamide is quite effective at treating certain arrhythmias, it should be administered by a practitioner well-educated on ACLS protocols and related care. Knowledge and training are key, especially when administering life-saving drugs.
If you want to learn more about the drugs, clinical scenarios, and ECG rhythms associated with ACLS, AMRI has study materials to help you succeed. Having helped over one million professionals become certified or recertified in ACLS, BLS, or PALS, AMRI is well-qualified to help you prepare for any life support situation. Register for your exam today and gain access to study guides, practice tests, and more.
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