VF ventricular fibrillation VT ventricular tachycardia

Drugs used for the termination of hemodynamically stable VT are presented in Table 9-14. IV drug administration is required. A decision algorithm for management of hemodynamically stable VT is presented in Figure 9-10. The initial choice of drug is dependent on whether the patient's VT is occurring in the setting of acute myocardial ischemia or infarction; if this is the case the initial drug of choice is lidocaine, followed by procainamide and amiodarone. However, if the patient's VT is not associated with myocardial ischemia or infarction, there is evidence that procainamide may be more effective for termination of VT; choice in this situation.45

therefore, procainamide is the drug of

Nonpharmacologic Therapy: Prevention of Sudden Cardiac Death

In patients who have experienced VT and are at risk for sudden cardiac death, implantation of an implantable cardioverter-defibrillator (ICD) is the treatment of choice.47 An ICD is a device that provides internal electrical cardioversion of VT or defibrillation of VF; the ICD does not prevent the patient from developing the arrhythmia, but it reduces the risk that the patient will die of sudden cardiac death as a result of the arrhythmia. Whereas early versions of ICDs required a thoracotomy for implantation, these devices now may be implanted transvenously, similarly to pacemakers, markedly reducing the incidence of complications.

ICDs have been found to be significantly more effective than antiarrhythmic agents such as amiodarone or sotalol for reducing the risk of sudden cardiac death 8,49

therefore, ICDs are preferred therapy. However, many patients with ICDs receive concurrent antiarrhythmic drug therapy to reduce the frequency with which patients experience the discomfort of shocks and to prolong battery life of the devices. Combined pharmacotherapy with amiodarone and a P-blocker is more effective than monotherapy with sotalol or P-blockers for reduction in the frequency of ICD shocks.50

Outcome Evaluation

• Monitor patients for termination of VT and restoration of normal sinus rhythm.

• Monitor patients for adverse effects of antiarrhythmic drugs administered (Table 9-7).

Ventricular Fibrillation

VF is irregular, disorganized, chaotic electrical activity in the ventricles resulting in absence of ventricular depolarizations, and, consequently, lack of pulse, cardiac output, and blood pressure.

Epidemiology and Etiology

Approximately 400,000 people die of sudden cardiac death annually in the United States. While some of these deaths occur as a result of asystole, the majority occur as a result of VT that degenerates into VF or primary VF. Etiologies of VF are presented in Table 9-13 and are similar to those of VT.

Table 9-14 Drugs for Termination of VT

Dru-g

trading Doip

Maintenance

friQcuiamide

U-\'f mgvfcg IV, nnf#s<H than JD mg/nnln

1-4 ring/mln eofitwuKHis inliijlon

Lutociuie

0.5-0.?$ mgvig IV bolus

1-4 mqAnin ooniruoui inrtusbn

r*--|hML lOruinuh't m 1 l> l.il ill 1

Amodarone

iiO mg IV over lOminules

1 mcj'min continuous infusion hx 6 hours, 0.5 mg/him for IE hours

Vlwntrcular lachyicardia.

Vlwntrcular lachyicardia.

FIGURE 9-10. Decision algorithm for termination of hemodynamically stable ventricular tachycardia. (MI, myocardial infarction; VT, ventricular tachycardia.)

Treatment Desired Outcomes

The desired outcomes for treatment are to: (a) terminate VF, (b) achieve return of spontaneous circulation, and (c) achieve patient survival to hospital admission (in those with out-of-hospital cardiac arrest) and to hospital discharge.

Pharmacologic and Nonpharmacologic Therapy

VF is by definition hemodynamically unstable, due to the absence of a pulse and blood pressure. Initial management includes provision of basic life support, including calling for help and initiation of cardiopulmonary resuscitation (CPR).51 Oxygen should be administered as soon as it is available. Most importantly, defibrillation should be performed as soon as possible. It is critically important to understand that the only means of successfully terminating VF and restoring sinus rhythm is electrical defibrillation. Defibrillation should be attempted using 200 J, after which CPR should be resumed immediately while the defibrillator charges; if the first shock was unsuccessful, subsequent defibrillation shocks should be 360 J.51

Clinical Presentation and Diagnosis of VF Symptoms

• VF results in immediate loss of pulse and blood pressure. Patients who are in the standing position at the onset of VF suddenly and immediately collapse to the ground

Diagnosis

• The absence of a pulse does not guarantee VF, as the pulse may also be absent in patients with asystole, VT, or pulseless electrical activity

• Confirmation of the diagnosis with an ECG is necessary in order to determine appropriate treatment. ECG reveals no organized, recognizable QRS complexes. If treatment is not initiated within a few minutes, death will occur, or at best, resuscitation of the patient with permanent anoxic brain injury

If VF persists following one or two defibrillation shocks, drug therapy may be administered. The purpose of drug administration for treatment of VF is to facilitate successful defibrillation. Drug therapy alone will not result in termination of VF. Drugs that are used for facilitation of defibrillation in patients with VF are listed in Table 9-15. Drug administration should occur during CPR, before or after delivery of a defibrillation shock. The vasopressor agents epinephrine or vasopressin are administered initially because it has been shown that a critical factor in successful de-fibrillation is maintenance of coronary perfusion pressure, which is achieved via the vasoconstricting effects of these drugs. A decision algorithm for the treatment of VF is presented in Figure 9-11. Epinephrine and vasopressin are equally effective for fa-

cilitation of defibrillation leading to survival to hospital admission in patients with out-of-hospital cardiac arrest due to VF. Amiodarone is more effective than lidocaine for facilitation of defibrillation leading to survival to hospital admission in patients with VF, which is the reason that amiodarone administration is recommended earlier than lidocaine administration in the decision algorithm.51 Note that the amiodarone doses recommended for administration during a resuscitation attempt for VF (Table 9-15) are different than those recommended for administration for termination of VT (Table 9-14).

Table 9-15 Drugs for Facilitation of Defibrillation in Patients with VF

Drug

Dose

Fpinephrine

1 m g J V every 3-5 minutes

Vasopressin

40 units IV single doso

Amiodarone

30Q mg IV diluted in 20-30 mL D5W. One

subsequent dose of 150 mg IV m ay be

administered

Lidocaine

1 1,5 rng/kg IV bolus, Follow with additional IV

bonuses of 0:5-0.75 mg/ky up to total of

3 my/kg

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