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Arrhythmias of Cardiac Arrest |  |
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Asystole: |
| Asystole appears as a flat line on the ECG and suggests complete absence of electrical activity. Animals in asystole can be assumed to have hyperkalemia until proved otherwise. Regular insulin at 0.2 U/kg, followed by glucose at 2 g/U of insulin often starts the heart beating again. If it does not, the prognosis is grave. Atropine and epinephrine can be administered in an attempt to generate impulses. Many arrhythmias that appear to be asystole are, in fact, fine ventricular
fibrillation. For this reason, open-chest heart massage and direct observation of myocardial activity are warranted early with this arrhythmia. Administration of epinephrine and defibrillation may be indicated. |
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Ventricular Flutter: |
| This rhythm is more chaotic than ventricular tachycardia and is prefibrillatory. Lidocaine is the drug of choice to block the excited focus. If lidocaine is ineffective after 2 boluses and perfusion is absent, defibrillation may be required. |
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Ventricular Fibrillation: |
| This rhythm implies that multiple foci within the ventricles are firing rapidly and independently, resulting in no coordinated mechanical activity. There are no ventricular contractions and no cardiac output. The goal is to abruptly stop the electrical activity and allow one strong focus to take over. Defibrillation is more successful when there are few, strong foci (coarse fibrillation) than when there are multiple, weak foci (fine fibrillation). When the fibrillation is
fine, an attempt is made to convert it to coarse by use of epinephrine (if no effect, then lidocaine) before defibrillation. |
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Electromechanical Dissociation (EMD): |
| The ECG tracing can be normal or show an arrhythmia, but the heart has no muscular activity, ie, no contractions and no cardiac output. In this arrhythmia, it is vital that thoracic auscultation be performed in tandem with ECG evaluation. There are no heart sounds or pulse activity. However, severe hypovolemia, pericardial effusion, and significant accumulation of fluid or air in the pleural cavity can prevent detection of heart sounds in a beating heart. The ECG associated
with these conditions demonstrates tachyarrhythmias, in contrast to the usually normal or slow rate of EMD. EMD has a grave prognosis. Epinephrine and glucocorticoids may be given in an attempt to correct this arrhythmia. |
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Pulseless Idioventricular Rhythm: |
| This electrical activity originates from an ectopic ventricular focus that produces insufficient pressure to generate a peripheral pulse. Generally, this is a slow ventricular rhythm. Lidocaine should not be given because it can eliminate the single focus. Dexamethasone, vasopressors, or positive inotropes may help. Epinephrine may be given, one dose IV, followed by a constant rate infusion administered in the fluids. |
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