Lidocaine

In this lesson, we'll go over the medication lidocaine and all of its effects, including indications, precautions and contraindications, and adult dosages. And at the end of the lesson, you'll find a Word about STEMI.

Lidocaine works by bringing about negative inotropic (meaning, modifying the force or speed of the contraction of muscles) effects and antiarrhythmic actions in the heart which weaken the force of muscular contractions and can calm erratic and uncoordinated electro myocardial activity.

In other words, lidocaine decreases automaticity and suppresses ventricular arrhythmias.

Lidocaine Indications

Now let's take a look at lidocaine indications.

Due to lidocaine's antiarrhythmic properties, the primary use of lidocaine is for cardiac arrest from ventricular fibrillation (VFib) and pulseless ventricular tachycardia.

Lidocaine is also an effective medication for treating the following conditions:

• Stable monomorphic ventricular tachycardia (V-tach) with preserved ventricular function
• Stable polymorphic V-tach with normal baseline
• A QT interval and preserved lower ventricular function when ischemia is treated, and electrolyte balance is corrected
• Stable polymorphic V-tach with baseline and QT interval prolongation when torsade's is suspected

Lidocaine Precautions and Contraindications

Now let's go over the precautions and contraindications for lidocaine.

Lidocaine should not be used a prophylactic treatment in patients with acute myocardial infarction. It has also been suggested that you should reduce the maintenance dose in the presence of impaired liver function or lower ventricular dysfunction. And you should discontinue the infusion immediately if signs of toxicity develop.

Lidocaine would be contraindicated if the patient has a known hypersensitivity to lidocaine or its derivatives, such as xylocaine, Novocain (also known as procaine), and similar drugs. And also in patients with sinus bradycardia and atrioventricular blocks.

Adult Dosage of Lidocaine

Now let's look at the adult dosage of lidocaine.

For adult dosages when treating for cardiac arrest from VFib or pulseless V-tach, the initial dose is 1 to 1.5 mg per kg via IV or IO. And remember, lidocaine is one of those drugs that can also be administered via an endotracheal tube.

For refractory VFib, an additional 0.5 to 0.75 mg per kg may be given via IV push. This can be repeated after 5 to 10 minutes. And the maximum number of lidocaine doses should not exceed 3 and the total amount should not exceed 3 mg per kg.

For perfusing arrhythmias like stable V-tach, wide complex tachycardia, or uncertain type or significant ectopy, doses range from 0.5 to 0.75 mg per kg, up to 1 to 1.5 mg per kg.

This can also be repeated at 0.5 to 0.75mg per kg every 5 to 10 minutes, up to that maximum dose of 3 mg per kg.

For a maintenance infusion, give 1 to 4 mg per minute equal to 30 to 50 mcg per kg per minute. And remember, a micro drip infusion set is needed in order to deliver the appropriate dose.

A Word About STEMI

ST-Elevation Myocardial Infarction (STEMI) is a very serious type of heart attack during which one of the heart's major arteries is blocked.

Patients with STEMI usually have complete occlusion of an epicardial coronary artery. The mainstay of treatment for STEMI is early reperfusion therapy achieved with primary PCI or fibrinolytics.

Reperfusion therapy for STEMI is probably the most important advancement in the treatment of cardiovascular disease in recent years. Early fibrinolytic therapy has been established as the standard of care for patients with STEMI who present within 12 hours after the onset of symptoms with no contraindications.

Reperfusion therapy reduces mortality and saves heart muscle – the shorter the time to reperfusion, the greater the benefit. A 47 percent reduction in mortality has been noted when fibrinolytic therapy is provided in the first hour after the onset of symptoms.

Delay of Therapy can be Critical

It's important that routine consultation with a cardiologist or another physician does not delay the diagnosis and treatment except in equivocal or uncertain cases. Consultation can delay therapy and is associated with an increase in hospital mortality rates.

Potential delays during the pivotal in-hospital evaluation period can occur in several key areas: from door to data (ECG), from data to decision, and from decision to drug (or PCI). These four major points of in-hospital therapy – Door, Data, Decision, and Drug – are commonly referred to as the 4 D's.

All healthcare providers should focus on minimizing these delays at each of these points. Out-of-hospital transport time accounts for only 5 percent of delays to treatment time, while ED evaluation accounts for between 25 and 33 percent of these delays.

In the next lesson – Magnesium Sulfate – we'll continue our Word on STEMI, specifically – early reperfusion therapy.