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发帖数: 143 | 1 I appreciate we bring the cardioversion technique on this forum because it
is so important that every clinician needs to know how to do it and how to do it right.
Cardioversion is a very safe life saving procedure no matter where in China
or States. I personally like the shit badly because of simplicity, safety,
and effectiveness. I used it in China before and have been using it in
States. I like it, my patient likes it, and I have nerve heard anyone get
sued about cardiversion .
Here i am going |
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发帖数: 143 | 2 Cardioversion is the application of DC (“shock”) across the chest or
directly across the ventricle to normalize the conduction pattern of a
rapidly beating heart. This shock is delivered during the absolute
refractory period of the ECG QRS—it is synchronized to the peak of the R-
wave. Defibrillation refers to application of electrical energy during the
nonvulnerable period to restore a fibrillating ventricle to normal sinus
rhythm.
The patient with a significant tachycardia may be asymptomatic |
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发帖数: 143 | 3 Background
The first successful defibrillation of the human heart was performed in 1947
by Beck and colleagues.[14] By the 1960s, electrical energy was being used
to treat dysrhythmias other than VF. AC remained in vogue until 1963, when
Lown and colleagues[71] advocated DC countershock as the method of choice
for terminating atrial fibrillation. The use of DC significantly decreased
the incidence of VF after countershock.
A brief burst of electrical current momentarily causes depolarization of |
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发帖数: 143 | 4 Indications and Contraindications
Cardioversion is indicated whenever there is a re-entrant tachycardia
causing chest pain, pulmonary edema, lightheadedness, or hypotension. This
excludes those tachydysrhythmias that are known to be caused by digitalis
toxicity as well as a known sinus tachycardia (i.e., known etiology). It
also is indicated in less urgent circumstances when medical therapy has
failed. In elderly patients, in whom a prolonged rapid heart beat can be
anticipated to cause complica |
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发帖数: 143 | 5 SVT with Aberrancy versus VT
Determining the rhythm is critical if the clinician is going to make the
appropriate clinical or pharmacologic intervention. However, at times, SVT
may manifest patterns on the electrocardiogram that look very similar to
those of VT. An incorrect assessment of the electrocardiogram can prompt the
clinician to implement a pharmacologic or therapeutic intervention that may
result in cardiovascular collapse. Although a comprehensive discussion of
SVT versus VT is beyond |
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发帖数: 143 | 6 Special Considerations: Wide-QRS-Complex Tachycardias
Wide-complex tachycardias (wide-complex SVT) are diagnostic challenges in
clinical medicine. The criterion often used to define wide-complex
supraventricular tachycardia (WCSVT) is a tachycardia with a QRS duration of
greater than 0.12 second. It is important to differentiate the rhythm as
one of the following: VT, SVT with aberrancy (left bundle branch block [LBBB
] or right bundle branch block [RBBB]), or an accessory AV pathway (“pre-
exci |
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发帖数: 143 | 7 Treatment
Therapy is dictated by the specific wide-complex tachycardia and the patient
's clinical presentation. The EC's initial approach must always be led, and
modified if necessary, by the patient's presentation and subsequent changes.
It is recommended in all cases of wide-complex tachycardias, and narrow-
complex tachycardias that are producing hemodynamic instability, such that
the clinician should immediately consider utilization of cardiovascular
electrical cardioversion. Synchronized m |
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发帖数: 143 | 8 Equipment and Setup
The critical components of preparation for cardioversion are IV access,
airway management equipment, drugs for sedation, and monitoring and DC
delivery equipment (cardioverter).
Secure IV access is essential for delivery of sedatives, antidysrhythmics,
fluids, and possibly, paralytic agents. Although many of these drugs are not
used routinely, if they are needed, timing is likely to be critical. A
large-bore IV catheter should be inserted and firmly taped to the patient's
ski |
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发帖数: 143 | 9 echnique
If time permits, metabolic abnormalities such as hypokalemia and
hypomagnesemia should be corrected before attempting cardioversion. At a
minimum, hypoxia should be corrected with supplemental oxygen. If a patient
has metabolic acidosis, compensatory hyperventilation after endotracheal
intubation may be indicated prior to cardioversion. Respiratory acidosis
should always be treated prior to the use of sedative drugs. |
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发帖数: 143 | 10 Sedation
Cardioversion may be extremely painful or terrifying, and patients must be
adequately sedated prior to its use. Patients who are not adequately sedated
may experience extreme anxieties and fear.[87] Several IV medications are
available for sedation of patients prior to cardioversion, including
etomidate (0.15 mg/kg), midazolam (0.15 mg/kg), methohexital (1 mg/kg),
propofol (1.5 mg/kg), and thiopental (3 mg/kg). In addition, fentanyl (1.5 &
#181;g/kg), a synthetic opioid analgesic, is so |
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发帖数: 143 | 11 Cardioverter Use
Selection of synchronized or nonsynchronized mode is the next critical step.
In the synchronized mode, the cardioverter searches for a large positive or
negative deflection, which it interprets as the R- or S-wave. It then
automatically discharges an electric current that lasts less than 4 msec,
avoiding the vulnerable period during repolarization when VF can be easily
induced. When the cardioverter is set to synchronize, a brief delay will
occur after the buttons are pushed for |
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发帖数: 143 | 12 Energy Requirements
The amount of energy required for cardioversion varies with the type of
dysrhythmia, the degree of metabolic derangement, and the configuration and
thickness of the chest wall. Obese patients may require a higher energy
level for cardioversion; the anteroposterior paddle position is sometimes
more effective in these patients. If patients are shocked while in the
expiratory phase of their respiratory cycle, energy requirements may also be
lower.
VT in a hemodynamically stable |
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发帖数: 143 | 13 Summary
In summary, cardioversion is performed on perfusing arrhythmias. The goal is
not to cause VF. Therefore, during cardioversion, the shock is administered
at the peak of the R-wave, during the absolute refractory period. Delivery
of the shock during the relative refractory period can cause the development
of a nonperfusing arrhythmia such as VF.
Cardioversion is performed to treat unstable SVT due to re-entry, unstable
atrial fibrillation, and unstable atrial flutter. These arrhythmias are |
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发帖数: 143 | 14 Caveats regarding Cardioversion*
• Electrical cardioversion is much less effective in
treating arrhythmias caused by increased automaticity (e.g., digitalis-
induced tachycardia, catecholamine-induced arrhythmia, multifocal AT).[5]
• Patients presenting with AF or atrial flutter lasting
longer than 36–48 hr are at risk for stroke from embolized thrombus
originating in the left atrium. Studies have shown that patients are often
unaware of the onset of AF, and |
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发帖数: 1745 | |
