Transcutaneous Pacing
The video below demonstrates transcutaneous cardiac pacing using a defibrillator.
In nonemergent situations, sedate the patient and administer pain medication. Record the baseline rhythm and vital signs, if this has not already been done.
Prepare and apply the pads as described earlier (see Positioning). Although transcutaneous pacing has been used continuously for as long as 4-5 days, [22, 23] the sites at which the pads are applied should be changed every 4-5 hours to reduce skin burn and discomfort. There are case reports of thermal burns at sites where transcutaneous gel pads have been placed for prolonged periods (eg, for prophylaxis or for maintenance until temporary pacemakes are placed). [24, 25] For patients who require longer-term pacing, a more appropriate mode of pacing should be considered.
Turn the pacemaker on, and choose the pacing mode. Most pacing units are capable of pacing on either a demand mode or a fixed mode. The demand mode is usually preferable and should be used initially. If capture cannot be obtained on that mode, then the fixed mode should be tried. In the demand mode, the pacemaker senses the intrinsic impulses and delivers current only if necessary.
Capture the heart rate. If the patient is in cardiac arrest with bradycardia or an asystolic rhythm, the pacing should be initiated at the maximum current output to ensure that capture is achieved as soon as possible, after which time the current can be gradually reduced to 5-10 mA above the threshold.
The presence of one QRS complex after each pacing stimulus suggests but does not confirm the capture. Cardiac capture should be confirmed by detecting the pulse (see the image below). However, pulse detection can be difficult, particularly in bradyasystolic arrest; in these cases, detecting ventricular capture by means of two-dimensional echocardiography is a good alternative if the echocardiography system is available. [26, 27]
Transcutaneous Cardiac Pacing. A rhythm strip showing failure to capture in the first four pacing stimuli that did not produce any pulse. When capture occurred, each pacing artifact was followed by a QRS complex (albeit bizarrely shaped) and pulse.
A small polarization artifact that is usually noted after each pacing artifact should not be confused with a QRS complex. In a healthy individual, the pacing threshold is usually less than 80 mA.
Many factors (eg, obesity, myocardial ischemia, metabolic derangement, pneumothorax, poor skin-to-electrode contact) can increase the pacing threshold, and some of those conditions are correctable. Reevaluate the patient.
It has been shown that walkie-talkies and cellular digital phones can cause various disturbances in the function of external pacing units, including pacing inhibition and asynchronous pacing, [28] even when these devices are as far as 200 cm from the pacing units. Therefore, an appropriate warning against using such communication equipment near patients undergoing transcutaneous cardiac pacing should be issued.
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Transcutaneous Cardiac Pacing. Normal action potential of myocyte and main ion channels that play major roles in different phases of action potential.
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Transcutaneous Cardiac Pacing. A defibrillator with pacing capability.
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Transcutaneous Cardiac Pacing. The pacing electrode pads of an external pacing unit and locations in which each pad should be placed.
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Transcutaneous Cardiac Pacing. A rhythm strip showing failure to capture in the first four pacing stimuli that did not produce any pulse. When capture occurred, each pacing artifact was followed by a QRS complex (albeit bizarrely shaped) and pulse.
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Transcutaneous Cardiac Pacing. Transcutaneous cardiac pacing in a patient with third-degree heart block. Video courtesy of Therese Canares, MD; Marleny Franco, MD; and Jonathan Valente, MD (Rhode Island Hospital, Brown University).
