Elective Cardioversion
Cardioversion is used to convert supraventricular and ventricular
arrhythmias to sinus rhythm by delivery of synchronized direct-current electric shock.
Current evidence indicates that biphasic shock delivery is superior to the former
damped sinusoidal current delivery.[135]
When these
arrhythmias are not causing hemodynamic instability or when the arrhythmia is of
long-standing duration and has not responded to drug therapy, cardioversion can be
performed on an elective and possibly an outpatient basis. The patient's cardiovascular
status and medical therapy are optimized before elective cardioversion. In contrast,
emergency cardioversion is often required when the arrhythmia causes hemodynamic
instability and when time pressure and the patient's condition may not allow for
full evaluation or administration of anesthesia.
Elective cardioversion is uncomfortable, and general anesthesia
is required. Many medications have been used, including barbiturates, propofol,
etomidate, and benzodiazepines.[136]
[137]
[138]
[139]
In
the
case of chronic atrial fibrillation, echocardiography is performed before cardioversion
to rule out the presence of left atrial thrombus, which could cause stroke. Our
practice is to perform transesophageal echocardiography under sedation/analgesia
with topical anesthesia and to then proceed directly to cardioversion under general
anesthesia if no intra-atrial thrombus is found. Standard monitoring is used, and
standards for the availability of equipment must be observed. When all is in readiness
for cardioversion, the patient is preoxygenated and then given small incremental
doses of anesthetic until the eyelid reflex is abolished. Immediately before the
countershock, the mask is removed, and it is confirmed that no person is touching
the patient. More than one shock may be required to restore sinus rhythm, and it
is important to keep the patient anesthetized until the procedure is successful or
the attempt is terminated. After cardioversion, the patient is ventilated with 100%
oxygen until consciousness is regained and the patient is able to maintain the airway.
It should be noted that muscle relaxants are not
typically needed for this procedure. If cardioversion is required on an urgent basis,
it must be remembered that the patient may not have been fasting before the procedure.
To prevent aspiration during anesthesia in this situation, it is appropriate to
intubate the trachea with a rapidsequence induction technique using cricoid pressure.
 |
